(F3) Clinical Pathology Dr Kits

(F3) Clinical Pathology LectureDr. Ayochok :)) Feb 11-12,17-18,20 2014

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Cases: Clinical Pathology

CASE 1

A 10 year old boy, who recently recovered from a streptococcal infection, was taken to the doctor with symptoms including, fever, nausea, and malaise. Physical examination reveals edema around the eyes and the knees. Blood test reveals a decrease in serum concentration. A routine urinalysis reveals the following results:

Chemical and physical analysis:o Color: Yellowo Blood: Moderateo Clarity: hazyo pH: 6.5o Glucose: Negativeo Protein: 300 mg/dL (increased)o Bilirubin: Negativeo Urobilinogen: Normalo Ketones: Negativeo Leukocyte Esterase: Smallo Specific Gravity: 1.015o Nitrite: Negative

Microscopic Analysis:o 20-50 RBC/hpfo 10-20 WBC/hpfo 2-5 RBC casts/lpfo 2-5 Granular casts/lpf

What is the significance of a Positive leukocyte esterase?o A positive leukocyte esterase indicates the presence of

WBCs. These are present due to an inflammation or infection.

o Leukocyte esterase is used to screen patients with UTI

How could there be a positive leukocyte esterase and a negative nitrite?

a) Non Gram (-) enteric bacteria presentb) Yeastc) Inflammationd) A and Ce) A, B and Co Usually if LE is positive nitritewould alsoincreaseo Yeast (Candida) and non-gram negative enteric does not have nitrate reductase

What is the significance of the presence of blood along with protein in the urine?

o If the glomerulus was in some way damaged, its efficacy as a filter may be compromised. As a result, RBCs, protein, and other large particles could get into the urine.

o It gives you a clue as to where the damage is, there is a definite glomerular damageo If your glomerulus is compromised expect proteins to leak out (+ proteinuria)

What disease are the results indicative of?o ACUTE GLOMERULONEPHRITIS (AGN)(one sequela of strep throat).

The recent streptococcal infection is a cause of glomerulonephritis. The physical examination of the patient also indicates an inflammatory disease. This is further supported by the presence of WBCs in the urine without any bacteria. The presence of blood along with protein in the urine suggests that the problem is occuring at the glomerulus itself.

Correlate the formed element present with the diagnosed disease.

o Swelling of the interstitium due to edema and inflammation obstructs capillaries and tubules. This may decrease urine flow which may lead to the formation of casts. Since there is an abundance of RBCs present in the tubules due to the infection in the glomerulus, there is a possibility that these RBCs may become trapped in the cast resulting in a RBC cellular cast.

o The longer urine stays in the kidney the higher the chance of cast formation

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CASE 2

A 33-year old woman complains of lower abdominal pain which she has had for the past day. She left her job as a nurse’s aide (her second day on the job) because the pain was so bad. She says the pain began after she had fallen off a stepstool while getting a bedpan off a top shelf. No one saw her fall, but she convinced her supervisor that she had an industrial accident and needed medical attention because of blood in her urine. To prove it, she brings in a urine specimen.

Physical/chemical analysis:o Color: redo Appearance : Clearo Leukocyte Esterase:negativeo Nitrite: Negativeo pH: 7.0o Protein: Negativeo Blood: Negativeo Specific Gravity: 1.015o Ketones, Glucose, Bilirubin: Negative

Microscopic Urinalysis:o WBC/hpf: <2/hpfo RBC/hpf: Noneo Casts: Occasional hyaline casts (normal)o Others: few squamous epithelial cells (most commonly seen

but least significant)

How do you correlate the macroscopic and microscopic findings?o The macroscopic appearance is red, but the test for blood is

negative and there are no RBCs microscopically. It is unlikely to be rhabdomyolysis. This specimen could be factitious. It would be a simple matter to have the patient produce another sample (though she might still be carrying the same bottle of red food coloring with her). Remember that various drugs can also produce colored urine. Eating fresh beets can color the urine red temporarily.

What do you thiink is happening?o Although cae and concern should be the immediate

response of health care workers to a patient, and historical


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findings should be duly noted, remember that patients may not always be telling you everything, or telling you correctly, particularly when compensation is being sought.

What kind of variables are pH and protein?o These measurements represent a quantitative (measured)

variable that is discrete, with a finite number of possible measurements in the range of 5 to 8 for pH and from 0 to 4+ for protein.

o The other form of quatitative variable is continuous with an infinite number of possible measurements within a range, as would be typical for a serum chemistry test such as urea nitrogen or creatinine. Categorical variables could be nominal or ordinal. A nominal variable is assigned (not measured) and could be a demographic characteristic such as sex or race. An ordinal variable is a ranking, such as mild, moderate, or severe.

Further history:A week later she faints on the job and is taken to the emergency

department. No external sign of trauma are noted. Laboratory studies show negative drugs of abuse screen, normal electrolytes, but serum glucose of only 24 mg/dL(low). The ER physician orders a plasma C-peptide, which is low. She is given an intravenous solution containing glucose (D5050) and she is fine within an hour.

How do you explain this episode?o If insulin is secreted from islets of Langerhans, C-peptide is

released simultaneously. Thus, the findings suggest exogenous insulin administration.

Further history:A week later she comes to the emergency department

complaining of severe abdominal pain for the past 3 days. She also reports weakness beginning in her hands and feet and moving toward her torso. On examination she has tachycardia and hypertension. She then experiences a tonic-clonic seizure. Laboratory studies shownegative drugs of abuse screen. Her serum glucose is 65 mg/dL. Her urine has a reddish color, but the person transporting the specimen to the lab noted that it glowed while passing under an ultraviolet light. The pathologist stated that she can tie these findings together with an in born error of metabolism, confirmed by additional testing on the urine.

What is this patient’s underlying disease, and what abnormal metabolites were present in her urine?

o Acute intermittent porphyria (AIP) is caused by porphobilinogen-deaminase gene mutations that have an autosomal dominant mode of inheritance. Porphyrin precursors , porphobilinogen (PBG) and amine-levulinic acid (ALA), accumulate and are excessively excreted in urine. They are neurotoxins to the CNS and PNS (explains seizure and weakness).

o Pain and other signs and symptoms are most often mediated by neuropathy. Autonomic neuropathy can lead to colicky abdominal pain, vomiting, and constipation. Cardiovascular effects include hypertension and tachycardia. Peripheral neuropathy is most often motor, leading to weakness, often ascending from limbs. CNS problems include psychiatric manifestations, such as depression, seizures, and focal neurologic deficits.

o Ingestion of drugs that increase hepatic cytochrome P450 activity includesphenobarbital, sulfonamides, estrogens,

and alcohol. Decreased caloric intake with hypoglycemia will also induce hepatic ALA synthase activity to increase PBG and ALA. Increased excretion of porphyrin compounds leads to dark or even reddish urine (and porphyrins fluoresce under ultraviolet light).

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CASE 3

A 57 year old man has a routine urinalysis as part of his company’s yearly required physical examination. He has a chronic cough (50 pack/year smoking history). His only complaints referable to the urinary tract are some mild dysuria and hesitancy, but he otherwise feels fine. On physical examination there are no abnormal findings.

Physical anf chemical analysis:o Color: ambero Appearance: Hazyo Leukocyte esterase: Negativeo Nitrite: Negativeo pH: 5.0o Protein: traceo Blood: 2+o Specific Gravity: 1.020o Ketones: traceo Glucose, Bilirubin: Negative

Microscopic analysis:o WBC/hpf: <2/hpfo RBC/hpf: 10-30/hpfo Casts: Occasional hyaline castso Others: Atypical Urothelial cells present

(urothelial- refers to transitional cells)

What do these findings suggest?o The atypical urothelial cells suggest the possibility of a

carcinoma. The presence of the RBC's is consistent with that.

o Might be bladder CA because patient is a smoker

What furhter studies are indicated?o He should be referred to a urologist, who performs

cystoscopy to look at the bladder urothelium, collect urine for cytology, and biopsy any suspicious areas. For lesions that could be higher (ureter, renal pelvis), an IVP and CT scan can be of use. In this case, a lesion is found in the urinary bladder and biopsy shows urothelial carcinoma.

What social and environmental history would be important?o Smokers have an increased risk for urothelial malignancies.

A history of exposure to beta-naphthylamine and analine dye is also a risk. Persons with chronic schistosomahaematobiuminfection (Egypt is one endemic area) may develop squamous cell cancers of the bladder.

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CASE 4

A 48-year-old man has noted increased thirst and urine output, even getting him up at night, along with mild back pain. On physical examination he is afebrile, but his blood pressure is 160/100 mmHg. There is right costovertebral angle tenderness. Family history reveals that his father died in his early 50’s of “kidney” disease. An abdominal ultrasound


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examination shows no hydronephrosis or filling defects, but both his kidneys are markedly enlarged from numerous large cysts.

Physical/chemical analysiso Color: Yellowo Appearnce: Slightly Cloudyo Leukocyte Esterase: Negativeo Nitrite: Negativeo pH: 6.5o Protein: 1+o Blood: 1+o Specific Gravity: 1.010o Ketones: Neagiveo Glucose, Bilirubin: Negative

Microscopic Analysis:o WBC/hpf: <2/hpfo RBC/hpf: 5-10/hpfo Casts: noneo Others: Many oxalate crystals

What do the historical findings suggest?o There is a possible genetic problem in the family. The most

likely diagnosis is Autosomal Dominant polycystic kidney disease (ADPKD)/ Adult type.

What laboratory tests would be useful?o Tests for renal function: serum creatinine and BUN,

creatinine clearance can be obtained to determine the level of renal function that is remaining.

o Main concern is to know if the patients kidney is functioning

If you were to give the patient anti-diuretic hormone (ADH) or if he didn’t drink any water for 12 hours, and then the urinalysis was repeated and the specific gravity was still measured at 1.010, what would this suggest?

o The lack of change to a higher specific gravity suggests that the kidneys have lost their concentrating ability- from renal failure- though this is still at a stage at which some function remains, so he has polyuria and nocturia. The fixed specific gravity at 1.010 results from lack of tubular modification of the glomerular ultrafiltrate of plasma. His back pain and his CVA tenderness are likely due to rupture of a cyst or bleeding into a cyst.

o Isosthenuric- the patient's specific gravity has the same specific gravity as the glomerulusAs the cysts would enlarge, it will have much thinner forms, making it prone to rupture.

Why do you think the kidneys are enlarged?o ADPKD leads to massive bilateral enlargement of the kidneys

with multiple cysts. The liver may also be cystic. Affected persons have an increased incidence of intracranial berry aneurysms.

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CASE 5

Two construction workers manage to dislodge a large boulder from the path of a new water pipe installation. As the boulder begins rolling, they suddenly become aware of a pick up truck parked below them at the bottom of the hill. The boulder smashes through the side window and lands on the driver’s lap. The injured 44-year-old man has multiple contusions from

the blunt trauma to his thighs and lower abdomen. Radiographs reveal no bony fractures. A paracenthesis yields no blood (no internal bleeding). That evening in hospital, the injured man’s urine output begins to drop.

Physical/chenmical analysiso Color: yellow-browno Appearance: slightly Cloudyo Leukocyte Esterase: Negativeo Nitrite: Negativeo pH: 7.0o Protein: traceo Blood: 3+o Specific Gravity: 1.010o Ketones: Negativeo Glucose, Bilirubin: Negative

Microscopic anlaysis:o WBC/hpf: <2/hpfo RBC/hpf: 0-1/hpfo Casts: Occasional hyaline, granular castso Other: Squamous andrenal tubular epithelial cells.

How do you explain the macroscopic findings in view of the microscopic findings in view of the microscopic findings? How does the history fit with this?

o The urine is brownish and the test for blood is markedly positive, but there are no RBCs visualized. Perhaps this is hemoglobinuria or myoglobinuria (the dipstick test for blood is even more sensitive for myoglobin). The history suggests a crush injury to soft tissue, including muscle ( lower abdomen and thigh).

What other studies would be of help?o Laboratory test for serum and urine myoglobin are available

(confirm myoglobinuria). More likely, the patient had serum chemistries ordered on admission, one of which should have been creatine kinase (CK) in view of the history (should be increased).

Explain the appearance of the casts and epithelial cells.o The damage to the kidney from the excessive myoglobin

excretion leads to acute tubular necrosis.

What are some other causes for this condition?o Muscle ischemia from lying in one position for a long time

(comatose patient or alcoholic “found down”), hyperthermia, cocaine or phencyclidine intoxication.

o May also be due to strenuous exercise

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CASE 6

A 22-year-oldAfrican-American woman is admitted to hospital because of swelling, of the legs and a weight gain of 4kg (10lbs) over the past week. She has felt extremely tired for the past month. On physical examination she is afebrile. Her blood pressure is 145/95 mmHg. A chest radiograph shows marked pleural effusions.

Physical/ chemical analysis:o Color: yellow


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o Appearance: Cloudyo Leukocyte esterase: negativeo Nitrite: Negativeo pH: 6.0o Protein: 3+o Blood: 2+o Specific gravity: 1.020o Ketones: Negativeo Glucose, Bilirubin: Negative

Microscopic analysis:o WBC/hpf: <5/hpfo RBC/hpf: 5-10/hpfo Casts: Many hyaline, WBC, RBC, granular castso Other: Mucus, Renal tubular cells

What is suggested by these findings?o The presence of RBCs, WBCs, and numerous casts suggests

nephritis. The presence of so many elements suggests severe renal disease from glomerulonephritis.

What are possible underlying disease processes?o Systemic Lupus Erythematosus should be high on the list.

Other diseases such as membranoproliferatve glomerulonephritis can give a similar picture.

Serologies:o Her ANA and anti-dsDNA serologies are positive. Her serum

C4 and C1qcomplement components are decreased. Renal biopsy can be considered to determine the extent of renal disease for therapy.

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CASE 7

A 45-year-old man comes to his physician after spending a second sleepless night with excruciating lower abdominal pain. The pain seemed to come in waves and was unrelieved by aspirin, tylenol, a six-pack of beer, or lying or standing in any position. He has not experienced any similar pain before. When asked to rate the pain on a scale of 0 (no pain at all) to 10 (worst pain ever) he replies, “11”. On physical examination there are no abnormal findings.

His serum creatinine is 1mg/dL, urea nitrogen 12mg/dL, calcium 9mg/dL(high), phosphorus 3 mg/dL (low), and uric acid 5mg/dL. He is instructed to strain urine over the next 24 hours and collect it into a container. The urine sample collected has a volume of 1440 mL, with creatinine of 1440 mg. There are 140 mg of protein. There are 800 mg of calcium (high). His urine osmolality is 300 mOsm/mLand his plasma osmolality is 300 mOsm/mL. His serum cystatin C is 1mg/L (one way of determining GFR).

Physical/chemical analysis:o Color: Dark Yellowo Appearance: Cloudyo Leukocyte Esterase: Negativeo Nitrite: Negativeo pH: 6.0o Protein: Negativeo Blood: 3+o Specific gravity: 1.015

o Ketones: Negativeo Glucose, Bilirubin: Neagative

Microscopic analysis:o WBC/hpf: 2-5/hpfo RBC/hpf: >100/hpfo Casts: Noneo Other: occasional squamous epithelial cells

There is cloudiness with microscopic hematuriao Hematuria can be due to numerous causes: inflammation,

trauma, glomerulonephritis, calculi, instrumentation, neoplasms, etc.

What diagnosis do you suspect?o The severe pain suggests a renal calculus.

What other studies could be done?o Radiographic studies. A plain film will demonstrate about

80% of stones (those with calcium). An IVP may show a filling defect. The urine could be strained to catch a passed stone so that it could be sent for analysis. Uric acid stones suggest gout, magnesium, ammonium phosphate stones suggest urinary tract infection

What is his creatinine clearance, free water clearance, and calcium/creatinine ratio?

o His creatinine clearance is 100 mL/min, which is normal.Cr Cl = (urine Cr x urine volume) / (serum Cr x 1440 min)

Cr Cl = (100 mg/dL x 1440 mL) / (1 mg/dL x 1440 min)Cr Cl = (100/1) mL/min = 100 mL/min

o Another estimate of glomerular filtration rate (GFR) in ml/min is 100/ serum cystatin C, yielding the same value: 100 ml/min

o Free water clearance is 0o His calcium/creatinine ratio (normal 20-240 mg/g) is 555.o Urine Ca/Cr 800 mg/1.44g = 555 mg/g

o Normally, if the serum (plasma) osmolality increases (as with dehydration), the free water clearance decreases, the ADH increases, and the urine flow decreases. Drinking a lot of water ill diminish serum osmolality, increasing free water clearance through a decrease in ADH with increase in urine flow. If his urine osmolality is high (>300 mosm/mL) then excretion of a solute pulling the water with it is likely, such as glucosuria or hypercalciuria. His high excretion of calcium with normal serum calcium is consistent with idiopathic hypercalciuria with calcium-containing urinary calculi.

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CASE 8

A 5 year old boy usually drove his mother crazy by running around the house all day long, but he has been lethargic for the past 2 weeks. On physical examination he is afebrile, but there is puffiness around his eyes.

Physical/chemical analysis:o Color: Yellowo Appearance:Hazyo Leukocyte Esterase: Negativeo Nitrite: Negativeo pH: 6.0


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o Protein: 4+o Blood: Negativeo Specific gravity: 1.020o Ketones: Negativeo Glucose, Bilirubin: Negative

Microscopic analysis:o WBC/hpf: 1-2/hpfo RBC/hpf: Noneo Casts: Noneo Other: occasional oval fat bodies

• What key abnormal finding is present? Just what does the dipstick measure here, and what other test could be done on the urine?

o The protein is markedly positive. The dipstick protein test uses bromphenol blue, which is more sensitive to albumin than to globulin. Thus, a semiquantitativesulfosalicylic acid test, which precipitates all proteins, would be helpful if one suspected globulins (such as Bence-Jones protein with myeloma) were present. The presence of proteins other than albumin would make this a 'non-selective' proteinuria less likely to be minimal change disease.

What is suggested by the child’s physical findings?o The loosest skin in a child is periorbital, so this is the first

place that edema is often noticed.

What other laboratory test(s) would be helpful?o A 24 hour urine proteintest would help establish a diagnosis

of nephrotic syndrome. One could get a serum creatinine to establish that the child's "renal function" is normal. In reality, obtaining a reliable 24 hour urine sample on a child is difficult, and depends in large measure on how compulsive his mother is. Since the amount of creatinine excreted in the urine is relatively constant for body size ,one could do a protein/creatinine ratio on what sample was obtained, and a ratio of 0 to 0.2 is likely to be normal, 0.2 to 2.0 is pathologic proteinuria, and >2 is nephrotic.

o Hypoalbuminemia (serum albumin) below 2.5 g/dL is often present with childhood nephrotic syndrome. Hyperlipidemia with increased serum cholesterol may be present. This lipid can be taken up into renal tubular cells, which slough and degenerate to form the oval fat bodies seen microscopically.

o Of course, a blood pressure measurement is part of the physical examination and an elevated blood pressure would cast some doubt on presumed diagnosis of nephrotic syndrome from minimal change disease in a child, as would an increasing blood urea nitrogen or creatinine, and would suggest a more serious renal disease.

o Nephrotic syndrome is always secondary to something

What is the diagnosis?o Nephrotic syndrome. The most likely etiology in this setting

is minimal change disease leading to nephrotic syndrome.o Minimal change disease- one of the spectrums of disease that would lead to a

nephritic or nephrotic syndrome. It is diagnosed through biopsy of the kidney and counting the number of glomeruli affected as well as inspecting each glomerulus to determine the percentage of damage to that particular glomerulus.

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CASE 9

A 23 year old woman has noted an increase in her appetite and thirst over the past six months, although she has lost 2 kg (5 pounds)/ she also has had considerable frequency of urine output, without associated dysuria. On physical examination her vital signs included T: 37 C; PR: 77/min; RR: 26/min; and BP 120/70 mmHg. A midstream clean catch urine sample is obtained.

Physical/chemical analysis:

o Color: Yellowo Appearance: Clearo Leukocyte Esterase: Negativeo Nitrite: Negativeo pH: 5.5o Protein: Negativeo Blood: Negativeo Specific gravity: 1.025o Ketones: 4+o Glucose: 4+o Bilirubin: Negative

Microscopic analysis:o WBC/hpf: Noneo RBC/hpf: 1-2/hpfo Casts: Noneo Other: None

What disease is suggested by these findings?o Diabetes mellitus, Type 1

Will all sugars be detected by the reagent test strip for glucose? Why?o Only glucose will be detected, because the reagent strip

uses glucose oxidase. Other sugars must be detected by a test for reducing substances (Benedict’s copper reduction method) which will pick up such sugars as fructose. Sucrose will NOT be present unless you are a member of the plant kingdom. Deliberately putting table sugar, which is sucrose, into urine to make it appear as diabetic urine will NOT work because it will not be detected by the dipstick.

What is the significance of the positive test for ketones? What would you suspect if the ketones were positive and everything else was normal?

o The ketones suggest that insulin is lacking and that in the diabetic catabolic state adipose tissue is being metabolized with utilization of fatty acids to produce ketone bodies, typical of type 1 diabetes mellitus. In the absence of glucosuria, ketone bodies suggest starvation.

What other test would be helpful?o Serum glucose. Persons with diabetes mellitus do not use

urine dipsticks to monitor their urine, but use fingerstick measurements of blood glucose obtained with a portable meter, and they become very adept at getting accurate results. Measuring haemoglobin A1C would give an indication of glucose control over a longer time frame.


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I. Renal Function Test Categories:

I. Tests predominantly of glomerular function.- Clearance test

II. Tests reflecting glomerular damage, tubular damage, or both- BUN- creatinine

III. Tests of predominantly tubular function(absorption test and secretion test)

- Specific gravity- Osmolality- PSP excretion- Free water clearance test

_______________________________________________________________I. Tests predominantly of glomerular function

CLEARANCE TESTS:

- Measures the rate at which the kidneys are able to remove (clear) a filterable substance from the blood

- Estimate of mild to moderate diffuse glomerular damage (AGN)- UV/P

U: urine conc. of substance cleared (mg/dL)V: Urine flow rate (mL/min)P: Plasma/serum conc. of substance being cleared (mg/dL)

Features of a good Clearance test (CT):o Substance neither reabsorbed or secreted by the kidneyo Consistency of its plasma levelo Substance availability in the body

-it is better to use endogenous substanceso Stability of the substance in urine during a 24-hour

collection period/ timed urine specimeno Availability of the test

A. UREA CTo Earliesto Product of Protein Metabolismo 40% reabsorbed back

o Via passive back diffusiono Values parallel true GFR at 60%o Dependent on Urine flow

o <2mL/min: inaccurate valueso Concentration affected by:

diet diurnal change

B. INULIN CTo NOT routinely usedo Polymer of fructoseo Stable(consistent in plasma): NOT reabsorbed nor secreted by the

tubuleso Healthy adults:

MEN: 127 mL/min/1.73 m2

WOMEN: 118 mL/min/1.73 m2

o Exogenous procedureo IV infusion, timed urine collection

o Availability, cost

C. RADIONUCLEOTIDE CTo NO need for urine collection (convenient)

o NOT as accurate as those with urine collectiono Measured plasma disappearance of radioactive material

o I-iothalamateo Tc-DTPA (diethylenetriaminepenta-acetic acid)

o Allows visualization of filtrationo Exogenous, expensive

D. B2 MACROGLOBULIN CTo More sensitive and specific than CCTo Endogenous CTo Dissociates from human leukocyte Ags at a constant rateo Rapidly removed from plasma by glomerular filtrationo NOT reliable for patients with immunologic problems,

malignancies(Crea clearance result is expected to be abnormal).

E. CREATININE CTo Routinely usedo Endogenous, inexpensiveo Relatively constant level in blood

More constant production rate than ureao Excretion: by GF (70-80%) and tubular secretiono Secretion increases as blood levels rise(high serumcrea=high

secretion)Chromogens in plasma false increase

Disintegration of creatinine by bacteria if kept at room temperature-long standing urine would cause proliferation of

bacteria

false decrease

Heavy meat diet false increaseo Not reliable in muscle wasting disorders(affected by muscle mass)

o Incomplete urine collection

Reference value: 90-120 mL/minMen: 107-139 mL/minWomen: 87-107mL/min

o C=UV/P U:urine creatinine in mg/dL V: urine volume in mL/min(if per 24 hours- 1440mins)

P: Plasma creatinine in mg/dL

FORMULAS TO ESTIMATE CCT AS ESTIMATE OF GFR:1. Cockroft and Gault formula (mL/min)

(140-age) x (IBW)/(72 x SCr), x 0.85 if female

- IBW=50kg+2.3Kg for each inch over 5 ft (males)- IBW=45.5Kg+2.3Kg for each inch over 5 ft (females)

o Decreases variability of serum creatinine estimates of GFR due to difference in creatinine production

Differences in muscle mass based on sex and ageo Use in adults

Drawback:o Does not consider differences in creatinine production due

to variation in muscle mass due to disease Overestimation of GFR: obese, debilitated

o Does not consider variations due to extrarenal elimination and tubular secretion.

2. MDRD formula (mL/min/1.73m 3 ) o 6 variables:

Age Race Sex BUN


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Serum creatinine Albumin

GFR=170x Cr-0.999x age-0.176x (0.762 if female)x(1.180 if black)x BUN-0.170 x alb0.318

o Simplified formula: 4 variables Creatinine Age Race Sex

GFR=186.3xCr-1.164 x age-0.203x1.212 (for black) x 0.742 (for women)-Does not include body weight

3. Creatinine clearance in Children: a. Schwartz formula:o GFR=0.55xheight (cm)/SCr (mg/dL)o GFR=43xheight (cm)/SCr (umol/L)

b. Modified Counahan Barrett formulao GFR=40xheight (cm)/SCr (umol/L)

DETERMINE EXTENT OF NEPHRON DAMAGE IN A KNOWN CASE OF RENAL DISEASE (CCT)

Mild: 60-80% of NVModerate: 40-60% of NVSever: 20-40% of NV

In AGN: - Follow clinical course and monitor effectiveness of treatment- Determine feasibility of administering medications- Measurement of overall renal function impairment.

______________________________________________________________II. Tests reflecting glomerular damage, tubular damage, or both

BLOOD UREA NITROGEN- Main waste product of nitrogen-containing chemicals- Serum, urine- Produced in liver (ammonia, amino acid)- Excreted by the kidney- Elevation: Azotemia

o High BUN + severe renal damage (s/s) = UREMIA (clinical azotemia)

- Not specific for intrinsic kidney disease- Decreased: severe liver disease; late pregnancy- Widely used as measure of renal dysfunction

Limitations in its use to measure GFR:1. Conc. in serum depends on renal function and rate of urea production: depends on CHON intake2. Freely filtered by glomerulus, but reabsorbed in PCT and inner medullary collecting ducts (CD).

Amount reabsorbed in PCT: depends on status of effective vascular volume

Amount reabsorbed in inner medullary CD: depends on urine flow rate.

For GFR it is better to use CCT than BUN alone; remember that not all elevations of BUN are reflective of a renal disease

When will you suspect a renal disease? If the creatinine is high, with high BUN

DISEASES:A. PRERENALAZOTEMIA:

- Anything that causes decrease blood flow or perfusion to kidneys/ factors that would overwhelm the kidneys

- Traumatic shock (head injuries; postsurgical hypotension)- Hemorrhagic shock (varices, ulcer, postpartum hemorrhage)- Severe dehydration or electrolyte loss (vomiting, diarrhea, DKA,

Addison’s dse)- Acute cardiac decomposition- Infections, toxemia- Excess intake of protein, extensive protein breakdown.

Etiology of prerenalazotemia:

1. Decreased blood volume/blood flow Blood volume deficit, heart failure to pump enough

blood, toxic effects on blood vessels Structural renal damage not necessary

2. Increased CHON intake or endogenous CHON catabolism High: CHON tube feedings, GIT hemorrhage, low

calorie diet, adrenocortical steroid therapy.

B. RENAL AZOTEMIA- Intrinsic damage to the kidneys

a. Chronic diffuse bilateral kidney disease (Chronic GN, bilateral chronic Pyelonephritis)b. ATN (Acute tubularnecrosis)

Due to hypotension/shock Rhabdomyolysis transfusion reactions Precipitation of uric acid/sulfa crystals in tubules

c. Severe Acute glomerular damage (AGN)

C. POSTRENALAZOTEMIA- Ureteral /Urethral obstruction

Strictures stones, pelvic tumors

- Obstructing tumors of UB; congenital defects in UB or Urethra- Prostatic Obstruction

Tumor BPH

CREATININE- Muscle metabolism- Standard clearance test- Synthesized from creatine and creatinePO4 via non-enzymatic

dehydration process.- Rate of production dependent on body muscle mass- Increase after meals; diurnal variation (lowest at 7am, peak at

7pm)true value of Creatinine: test should be done in am

- Significant increase: suggest chronicity of renal damage (but must be interpreted in conjunction with an elevated BUN value)

- In a renal patient: BUN increases earlier than creatinine

- Increase: some significance with BUN, but rises later- BUN/crea ratio: 10:1(20:1)

Most widely used marker of GFR: (CT >BUN)1. Endogenous substance of fairly constant rate of

production(amount in plasma is stable)2. Not bound to plasma CHONs, thereby freely filtered by

glomerulus-approximate GFR: 80%; BUN GFR: 60%

3. Not reabsorbed by renal tubules; only a small amount is secreted by tubules.

DRAWBACKS OF CREATININE AS A MEASURE OF GFR:- Substantial individual variation, depending mainly on muscle

mass.o Severe muscle wasting: creatinine decreased to 25%

of value predicted from body weight- Also derived from dietary meat- Assayed MC by alkaline picrate method

o Endogenous and exogenous chromogens: interfere with results(false elevation)

o Ketones, glucose, fructose, CHON, urea, ascorbic acid(false elevation)

- Partial tubular secretion blocked by certain drugs: (false elevation)

Cimetidine Pyrimethamine Trimethoprim Salicylate

TUBULAR REABSORPTION TEST:- 1ST FUNCTION affected by renal disease- LAST function to be lost


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- Important in differentiating prerenalazotemia from renal failureo When will the test be abnormal? Prerenal or renal failure?o If pt is in shock vs blood transfusion reaction- the latter would have an abnormal result___________________________________________________________________________________

III. Tests of predominantly tubular function

CONCENTRATION TESTS:- Determine the ability of the tubules to reabsorb essential salts

and water filtered by the glomerulus

URINE SPECIFIC GRAVITY:- determines the concentrating ability of tubules

After GF: 1.010 After TR: higher, more concentrated

-Initial filtrate SG 1.010 (iso) after tubular reabsorption the Sp Gravity of filtrate should increase due to reabsorption-NV: 1.015-1.025

a) Fishberg concentration test:- Sp. Gravity after 24-hr H2O deprivation -N: expect it to increase

b) Mosenthal concentration test:- Compares volume and specific gravity of day and night urine samples-urine sample taken at night should have a higher SG-Higher volume -during the day

- Normally: sp. Gravity of 1.025 after water deprivation of 16 hours.

FREE WATER CLEARANCE TEST:- Assesses reabsorption of fluid and electrolytes with formation of

free water- Measures osmolar clearance

Amount of water to be cleared each minute to produce urine with same osmolarity as plasma

- Determines ability of tubules to respond to state of hydration -2: dehydration 0: no renal concentration/ dilution

Free water clearance:Clearance (osm)=U(osm) x V/P(osm)

Subtract Clearance (osm) from urine volume [V-Cosm]- Reference range: -20 to -100- ATN/CRF (Acute tubular necrosis or chronic renal failure):

near 0 or (+)- Needs accurately timed urine collection- Interference by diuretics

Loop diuretics: block reabsorption of NaCl: urine isotonic with little free water or negative free water

Mask a sick kidney? Will it worsen a truly normal kidney?

SPECIFIC GRAVITY- Simple, readily available- NV: 1.025 (1.015 to 1.035)- Does not measure dissolved substances- Early chronic diffused bilateral kidney disease- Monitor course of illnessuseful in pts with known renal disease

- Monitor electrolyte and fluid therapy To be accurate: deprive patient of H2O (16-17 hours)

10 gm CHON: rise in sp g by 0.003 1% glucose: rise in spg by 0.004 Contrast media for IVP: increase sp g Urine at ref temp (2-8^c): decrease in sp g

Isosthenuric (1.010)urine has the same specific gravity as initial filtrate

- Occurs in advance of final renal decompensation

Fixation of sp g:- Manifested by nocturiafrequent urination during the night

- Reversal or decrease in day/ night urine excretion ratio to 1:1 (N 3:1 or 4:1)

Other causes to be considered: - Diabetes insipidus- Diuretic phase of ATN

- Hyperthyroidism- Severe salt restricted diets- Sickle cell anemia

OSMOLALITY- Best quantitative measurement of renal concentratingability- Urea, Na, Cl

Plasma Osmolality = 2 x [ Na + K ] + Urea24 hr.Urine Osmolality: Osmol excreted/day

V (liters)- Osmometers: based on freezing point

- NV: 800-1300 m0sm/L (after 14 hr period of dehydration); 275-300 m0sm/L (serum); 24 hour: 500-800 m0sm/kg water; Random: 50- 1400 m0sm/Kg water

- Normal urine: serum osm; 1:1 to 3:1

Uses of osmolality- Initial evaluation of renal concentrating ability- Monitor course of renal disease- Monitor fluid and electrolyte therapy- Secretion and renal response to ADH:

Failure to respond: renal defect Response: production defectpositive response:defect in higher center

Hyperosmolality- Excessive water loss- Inadequate water replacement

Hypoosmolality- Increased water intake with or without an increased solute load- Plasma osmolality:

Osmolality (calc)= 2 x Na + glucose + urea**if all measurement in mmol/L (SI)

Osmolality (calc)= 2 x Na + glucose/18 + urea/2.8**if measurements are in mg/dL(MC used for conventional units)Given:

- Plasma Na= 123 mEq/L- Glucose = 98 mg/dL- Urea= 22 mg/dL- Compute for plasma osmolality

Answer: 259.301 mosm/Kg(Below reference range: 275-300 m0sm/L)

-Effective osmolality:refers to overall effect of sodium to ECF tonicity, which is primarily influenced by sodium

EO (calc)= 2 x Na + glucose**if all measurements in mmol/L (SI)

Osmolality (calc)= 2 x Na + glucose /18**if measurements are in mg/dL

<275: hyponatremiatrue hypo vs artifactualhyponatremia

Given:- Plasma Na= 123 mEq/L- Glucose= 98 mg/dL- Urea= 22 mg/dL

Osmolality= 2(123) + (98/18)Answer: Osmolality= 251.44

TUBULAR SECRETION TESTS:Important: use a substance completely removed from the blood

(plasma) by peritubular capillaries (located in the cortex of the kidneys- similar to vasa recta in medulla of kidney)

- Measures blood flow (q) through the nephron- Abnormal result

Impaired tubular secretory activity Decreased renal blood flow (q)

P-AMINOHIPPURIC TEST- Non-toxic, high MW substance, exogenous substance

- Does not bind strongly to plasma proteins


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- Permits complete removal- NV: 600-700 mL/min

Average renal q: 1200 mL/min

TITRATABLE ACIDITY AND URINARY AMMONIA- Measure PCT (H+ secretion) and DCT (NH4+) functions- NV: 70 mEq/day

Alkaline tides: after rising, postprandial (2pm. 8pm)

Lowest pH: night time- Significance:

RTA/ renatubular acidosis: inability to produce an acid urine in the presence of metabolic acidosis

•Patient:o Primed with an acid load (oral NH4+Cl)o Fresh urine collected (2hr intervals)o [NH4+]= total acidity – titratable acidity

Titratable acidity: [H+]______________________________________________________________

II. Water Balance: - Body has an influence on the Extracellular fluid

Which Part of the body has an influence in ECF and tonicity?1. Thirst center2. ADH effect on collecting tubules3. RAA system

2 Disorders regarding water content:

1. Dehydration - decreased amounto Causes:

Diarrhea Vomiting Fever Diuretic use if not monitored could lead

to DHN Excessive sweating/ profuse sweating

2. Overhydration - excessive

2 Renal function test: BUN and creatinine Not all elevation would indicate a renal disease BUN = creatinine: parallel elevation may be indicative of a

kidney disease BUN > creatinine : Lab abnormality could lead you to

investigate dehydration

How would you diagnose DHN?It is a clinical diagnosis NEVER a laboratory diagnosis

Urine: serum osmolality ratio is usually more than 1 (n 1:1, 3:1) Addison's disease: Problem: Dehydration

Volume overload: - There is an increased in total body tonicity specifically sodium

Seen in the ff conditions:o SIADHo CHFo Nephrotic Conn's diseaseo syndrome ( + edema)o Cirrhosis

- Elevated aldosterone or ADH and elevation of total body watero SIADHo Pleural effusiono Ascites

Diagnosis of volume overload: clinical diagnosis ;))_______________________________________________________________

III. Electrolytes ECF and ICF

ECF: o Sodium - major cationo Chloride - major aniono bicarbonate

ICF: o potassium- major cation

*Express electrolytes: either in mmol/ L or mEq/L_______________________________________________________________EXTRACELLULAR FLUIDSodium

- Principal osmotic particle outside the cell

- Major ECF cation

- In the Kidney- it is reabsorbed up to 70%

- Reference range: 135-145 mmol/L

Abnormalities:A.HYPONATREMIA

1. Sodium loss with water excess: Sodium (solute) and water (solvent) Serum Osmolality: decreased

2 Subdivisions: a) Renal:

Adrenal insufficiency Ketonuria with accompanying hyponatremia Urinary sodium: Below 20 mmol/L

b) Extrarenal: Vomiting/ diarrhea Peritonitis- third space loses Burns Urinary sodium: less than 10 mmol/L

**Measure urinary sodium to differentiate renal form extrarenal

Symptoms of hyponatremia: o Ex. History of prolonged diuretic use: patient would

present with: Musculoskeletal: muscle cramps, weakness

and fatigue, slow to movement and thinking Neurologic: Changes in behavior, change in

mentation, may not be oriented/ disoriented

Rate of decrease: Gradual or sudden fall of sodium is said to be directly proportional to the severity of symptoms

Ex: Over days and weeks- gradual

increase in Fatigue, muscle cramps, lassitude etc.

With in Hours- severe disorientation, confusion, convulsions and coma

2. Hyponatremia with excessive total body water

Example: Nephrotic syndrome Cirrhosis CHF renal failure (both acute and chronic)

o Actual body sodium is increasedo Hyponatremia- because there is greater excess fluid

(water is even greater)o Urinary sodium

Low: less than 10 mmol/ L except for renal failure, which may be above 20 mmOl/L

3. Hyponatremia with euvolemia


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o Euvolemia: No visible increase in ECF volume Ex:Inhyponatremia with glucocorticoid

deficiency Free water excretion tends to be

inhibited No apparent increase in ECF volume

o Endocrine disorder: Hypothyroidism - High level ADH secretion;

inability to dilute urine maximally SIADH

Continuously secreting ADH despite a decrease plasma osmolality (more of a condition rather than a disease)

usually accompanying a disease Pt in extreme pain may have SIADH?

Yes. Such as in Appendicitis or emotional stress

Delt as a Paraneoplastic Metabolic CNS disorder Such as

after trauma to head if with seizure disorder

Brain abscess COPD Decreased plasma osmolality - more

of a condition4. Artifactualhyponatremia

Cause: Hyperglycemia-there is an increase serum osmolality that

causes a shift of whatever is in ICF to ECF Relative decrease in serum sodium Each 100mg increase in blood glucose would cause a 1.6

mmol decrease in serum sodiumOther causes:o High / increase protein o Lipemic blood or increased CHON: sodium

concentration will be restricted to water space (Or where water is available) which is proportionately decreased by lipid or protein volume

Serum sodium is low Plasma volume is low

o Displaced or occupied by fat and protein that is why there is low serum sodium

o We have to be careful because we may treat it as a true hyponatremia

Treatment: treat underlying cause, if caused by hyperglycemia, treat the increased sugar, because the sodium is normal

Psuedohyponatremiao Serum osmolality: normal

True sodium value for specimen that is lipemic

Ask pt to fast then come back For re-extraction If Lipemic again -> Centrifuge the specimen

Among the four categories, which will present with a decreased anion gap secondary to decrease in unmeasured anion?

- Hyponatremia with increased ECF volume- Mechanism of low anion gap :Kidneyalso excretes unmeasured

anions

High serum sodium/ hypernatremiaCauses:Excessive loss of water relative to sodiumReally increased amount of body sodium

Hypotonic fluid loss: Etiology

o Renal o Extrarenal

Hypotonic fluid loss renal etiology:

Osmotic diuresis - urine osmolality could be low or normal Urine sodium is above 20 mmoL/L

Extra renal etiology:

Diarrhea Profuse sweating Febrile child Urine osmolality: increased Urine sodium: Less than 10 mmol/L

B.HYPERNATREMIA

1. Hypernatremia due to water loss ONLYa. Renal

DI (nephrogenic and Central)o Central- above the kidneyo Nephrogenic- in the kidney (Insensitive to ADH)

** medulla- responds to ADH Drugs

o Lithium Urine osmolality is either normal or low

b. Extrarenal Urine osmolality- increased

Ex: Cushings - too much aldosteronism leading

to elevation of sodium that is reabsorbed Excessive sodium intake - such as sodium

bicarbonate urinary osmolality is normal or increased

_______________________________________________________________ INTRACELLULAR FLUIDPotassium

- Major intracellular cation- Total body potassium: 2% extracellular- Reference range: 3.8-5-5 mmol/L- Average diet - consume 50-150 mmol of K/ day

Majority Excreted: 90% via kidneys- Daily urinary excretion:25-125 mmol of K

Abnormalities

A. HYPOKALEMIA2 forms:1. Hypokalemia with normal body potassium

- Hypokalemia is secondary to the shift of potassium from ICF to ECF

Example: Seen in(Unmonitored) insulin therapy Periodic paralysis (this is also true for hyperkalemia)

Hypokalemia with periods of hyperkalemia(intermittent attack "waxing and waning")

Familial disease: AD pattern Clinically how will you distinguish

hypokalemia or hyperkalemia? No difference in clinical

manifestation Measure serum potassium

2. Hypokalemia with low body potassium GIT losses: Vomiting and diarrhea Renal loss of potassium: Diuretics(*except k sparing diuretics)

Metabolic disorders: RTA (Renal Tubularacidosis) Metabolic acidosis


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Mineralocorticoid excess ** For both type Urinary potassium is above 20 mmol/ L

**Exception: if the loss of potassium is gradual and the etiology is extrarenal the urinary potassium is below 20 mmol/L

B. HYPERKALEMIAo Due to shifts or increase in body potassium o Mineralocorticoid deficiencyo Acute and Chronic Renal failureo Shifting from ICF to ECF:

Rhabdomyolysis hemolysis

1. Artifactual hyperkalemiaReasons:

a) High platelet count- The k present in platelet is also releasedb) Prolonged tourniquet application during

venipuncture-Maximum of 2 minutes- beyond: leakage due to venular injury causing false

elevation c) making a fist during venipuncture tomake the vein prominentd) Hemolyzed specimen

- 105 mmol/L k in RBCe) Contaminate sample with potassium EDTA

Avoided by: Using plain or yellow topVacutainer technique:-This avoided by rearranging the order of draw, K specimen first before CBC

_______________________________________________________________

Chloride- Major extracellular fluid anion - Referencerange: 98-106 mmol/L- With normal daily urinary output 110-250mmol/L

Disorders:A. HYPOCHLORIDEMIA

- Diarrhea and vomiting- Mineralocorticoid excess- Chronic salt losing renal disease with hyponatremia- Hypochloridemia with high serum bicarbonate

- Common in metabolic alkalosis or decompensated form of renal acidosis due to Intracellular shift of bicarbonate with increased renal excretion

B. HYPERCHLORIDEMIA- Mineralocorticoid deficiency- hyperparathyroidism: indirect effect of PTH to Cl, influencing the reabsorption of bicarbonate: decreasingPCT reabsorption of bicarbonate secondarily augment the Cl reabsorption- Metabolic acidosis from bicarbonate loss: diarrhea, renal tubularacidosis- Ammonium chloride administration - Exocrine glandular disorder: cystic fibrosis

- Measure chloride in sweat: NV:5-45 mmol/LChildren with CF: above 60 mmol/LAdults with CF: above 70 mmol/ L

*How do we measure this? We induce sweating by : iontophoresis Administer Pilocarpine ID

Ensure Quality control: check chloride and sodium in sweat *How will you know that the test is right?

- The diff between the sodium and cl should be10 mmol/L of each other, if it exceeds REPEAT test

Bicarbonate (HCO3-)- Second most important anion- Dissociation of carbonic acid (H2C03)- Anion that is freely filtered by the glomerulus- 85% reabsorbed by proximal tubules- 15% reabsorbed by distal tubules- Measured as total C02- Range of bicarbonate:

Venous-23-30mmol/LArterial: 19-25mmol/L

- Excess and deficiency are more appreciated in ascitic disorder_______________________________________________________________Anion gap

- Gap: diff between anion and cationRoutine calculation

Cation: na and kAnion: cl and bicarbonate

Formula: sodium - (chloride + HCO3)= anion gap

Normal: less than 17 mmol/LConsider unmeasured:

Unmeasured Cation: calcium and mg:7 mmol/lUnmeasured Anions: phosphate, sulfate, chon, anions of organic

acids:24 mmol/L Abnormalities:HIGH ANION GAP

Value: more than 17 mmol/LExample:

- DKA- Starvation- Too much dieting- Shock secondary to lactic acidosis

*Anything that would increase the amount of unmeasured anion will lead to an elevation of anion gap

- Uremia: retention of phosphate and sulfate - Dehydration: increased plasma protein

LOW ANION GAP

Value: less than 10 mmol/LDisorders:

A. Decreased unmeasured cations:1. Multiple myeloma2. Hypermagnesemia- Increased unmeasured cation: Mg and Calcium3. Polyclonalgammopathy- cause a decreased in anion gap

-The gammaglobulins will have a net positive charge at physiologic PH thus decreasing anion gap- Proteins are negatively charged therefore an increase protein would yield a high anion gap BUT this is an exception

B. Decreased unmeasured anions:Value: less than 10 mmol/L

1. Hypoalbuminemia- low amount of albumin in the body leading to decrease in anion

gap ______________________________________________________________

CalciumMore on extracellular 10^4:1Measure: ECFCalciumReference range: 2.25- 2.5 mmol/L

4.5-5 mEq/L *For K, Na and Cl: mmol/L = mEq/L

Calcium in ECF1. Bound calcium- bound to albumin or globulin: 45% of ECF2. Ionized or free calcium- 50%,- physiologically active form3. Complexed form- either with phosphate or citrate: 5%

Body: 98% in skeleton


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Remaining ca is 50:50 ;ECF: tissue PTH on calcium

Stimulation: Low calciumVitamin D on calcium

Absorption- Increase blood calciumCalcitonin

Decrease serum calcium Inhibitosteoclastic activity

Conditions associated with excess PTH secretion:Hyperparathyroidism:

- High calcium- MC common: Parathyroid Adenoma

Other test:PTH measurement: highSerum phosphorus: lowPhosphate excreted: increased

Malignancy associated hypercalcemia2 types:1. Local osteolytichypercalcemia

- due to CA with bone metastasis- leukemia (primary hematologic malignancy)- Multiple myeloma

2. Humoralhypercalcemia of malignancy

- tumor producing a PTH related protein that is causing the hypercalcemia- Can also influence thereby promoting bone resorption - Usually a solid tumor such as sarcoma - No bone metastasis

______________________________________________________________Magnesium

- Mainly in ICF- ICF: ECF; 10:1- 4th most abundant cation- 50% in bone and 50% tissue- Less than 1% in blood- Reference range: 0.7-1.1 mEq/L; 1.3-2.1 mmol/L - Function:

1. Activates enzymes ex. phosphatase, hexokinase, carboxylase

2. Preservation of macromolecular structure for DNA, RNA, and ribosomes

Disorder:A. HYPOMAGNESIMIA:

Symptoms similar to hypocalcemia and hypokalemia- Weakness- Seizure- Agitation- Arrhythmia

B. HYPERMAGNESIMIALess clinically significant compared to hypomagnesimiaSymptoms:

- Flaccid paralysis- hypotension


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Acid Base Balance:

Arterial blood gases (ABG)

Parameters:1. Blood pH- is the concentration of H ions in the blood

NV: 7.35-7.45 Blood pH

Less than 6.8 or more than 7.8 not compatible with lifeBuffers in the body regulate Blood pH by:

a. Binding to H ions without causing marked changes in pH: these buffers are weak acids with its conjugate base containing solution or other weaker acids

o Buffers: descending order base on buffering capacity Bicarbonate/ carbonic acid buffer Hemoglobin Plasma proteins Erythrocytes Plasma Phosphate

o Henderson hasselbach equation:

o Bicarbonate: Formation of HCO3 from the kidneys by:

a. Hydrogen phosphate to dihydrogen phosphate release bicarbonate

b. Ammonia formation via amino acid deamination

c. Resident bicarb inside tubular cellso Carbonic acid:

Formed in the lungs: Carbonic acid Is converted to

water and CO2In interpreting ABG check ratio of bicarbonate and carbonic acid:

Bicarbonate/ Carbonic acid

b/a Ratio pH

Increase bicarbonate Increase Increase/alkalosisIncrease carbonic acid decrease Decrease/Acidosis

Normal Bicarbonate to carbonic acid ratio: 20:1

_______________________________________________________________ Lab determination of pH and CO2

1. Carbon dioxide combining power

Specimen: Venous blood drawn aerobically

serum equilibrated to normal alveolar levels of 40 mmHg

Blow air into the specimen via a tube arrangement

Adjusts amount of dissolved C02 to normal amount found in arterial blood

HCO3 converted to CO2 by acid hydrolysis in a vacuum: released gas measured

Released CO2: dissolved CO2+ specimen + converted HCO3

HCO3 alone: subtract know amount of dissolved CO2 and H2CO3 in normal blood; combining power

2. CO2 content: From heparinized arterial or venous blood drawn

anaerobically Vacuum tube, quickly capped

syringe Blood centrifuged, plasma removed

Plasma analyzed for CO2 Method: convert HCO3 and

H2CO3 to gas form Measures sum of HCO3 + H2CO3 + dissolved CO2 Result: more accurate than that obtained from

CO2 combining power

3. Serum HCO3o Venous blood drawn aerobicallyo Assayed for HCO3 without equilibriumo Less accurate than CO2 combining power

o Serum frequently exposed to air for longer periods

o Underfilling of tubes: decreased HCO3 values

4. Partial P of CO2 (PCO2)- In mmHg or Torr- Proportional to amount of dissolved CO2- Proportional to the denominator of Henderson-

hasselbach equationo Denominator: represents dissolved CO2

- Whole blood collected anaerobically- Direct measurement via PCO2 electrode

o HCO3 calculated (from the HH equation)o PCO2: used with pH to differentiate acid

base disorders - Measured together with pH

5. pH measurment- Before: difference in electric charge between 2

electrodes placed in solution (plasma, WB)- Now: direct- reading pH electrode - Room temperature:

o Plasma PH decrease at a rate of 0.015 pH unit every 30 minutes

o Refrigerate immediately: viable up to 4 hours

pH determination:CO2 combining power (HCO3) 24 meq/L (20-28)

CO2 content 25 meq/L (22-28)PCO2 40 mmHg (35-45)PO2 80-100 mmHg

_______________________________________________________________pH DisturbacncesI. Metabolic pH disturbances:

Metabolic AcidosisAcid gainingBase losingRenal Type


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Metabolic AlkalosisII. Respiratory pH disturbances:

Respiratory Acidosis_______________________________________________________________

Metabolic pH disturbances

Metabolic Acidosis:1. Acid gaining

- Lactic acidosis- Diabetic ketoacidosis- Severe starvation- Severe dehydration- Iatrogenic: thru administration of ammonium chloride- Aspirin toxicity (late phase)

o Bicarbonate: decreasedo pH: decreasedo Carbon dioxide: decreaseRule: if the primary disorder is metabolic compensation is respiratory

2. Base losing- Severe diarrhea - No bicarbonate- Serum bicarbonate: decrease- Ratio: decrease

o pH: decreaseo Carbon dioxide: decrease

3. Renal acidosis- Both acute and chronic type- Retaining hydrogen ions in bloodstream- ratio: decreases

o CO2: decreases

Metabolic alkalosis:1. Alkali administration:

o Sodium bicarbonate administrationo numerator: increaseso pH: increaseo carbon dioxide: increases

2. Acid losing:o Retching or vomitngo HH: increasedo pH: increasedo CO2: increased

3. Hypokalemic typeo Diuretic useo HH: Numerator: increasedo pH: increasedo Compensatory CO2: increased

_______________________________________________________________Respiratory pH disturbances

Respiratory acidosis- Retention of carbon dioxide: emphysema, CHF, encephalitis- Basic problem: excess of denominator (carbonic acid excess)- HH equation: decrease in pH

o Carbon dioxide: increased or normal

Respiratory alkalosis- Early phase of aspirin toxicity

- MC: Hyperventilation

- Carbonic acid: decreased

- pH: Increased

- Decreased CO2 in blood_______________________________________________________________ Compensation:

Parameter: Degree of PCO2 change1. Uncompensated

o Metabolic: pH abnormal; PCO2 normalo Respiratory: pH, PCO2 abnormal or outside their

reference ranges (severe)

2. Partially compensated:o M and R: pH, PCO2: outside reference range

3. Compensated:o M and R: PCO2 out of range; pH within range

_______________________________________________________________Interpret ABG:

I. 1. Look at PH: 2. Check PCO2:

-if pH and PCO2: same direction = primary metabolic disorder-if pH is high and PCO2 is low = primary respiratory disorder

II. 1. Look at PCO2:

-if decreased =either respiratory alkalosis or metabolic acidosis-if increased = respiratory acidosis or metabolic alkalosis

2. Look at pH:LOW PCO2

a.Respiratory Alkalosis:Uncompensated and partially compensated:pH =highCompensated: pH=normal or above 7.4

b.Metabolic Acidosis: Partially compensated: pH=lowCompensated: pH= normal or below 7.4

HIGH pCO2a. Respiratory Acidosis:

Uncompensated and partially compensated: pH= lowCompensated: pH= normal or below 7.4

b. Metabolic alkalosisUncompensated or partially compensated: pH= highCompensated: pH= normal or above 7.4

_______________________________________________________________

Case1

A 44 year old moderately dehydrated man was admitted with a two day history of acute severe diarrhea. Electrolyte results: Na+: 134, K+:2.9 (low), Cl- 108, HCO3-:16, BUN: 31, Cr: 1.5.

ABG: pH: 7.31HCO3: 16pCO2: 33 mmHg (RR: 35-45)pO2 : 93 mmHg

Interpretation: (Primary)Metabolic Acidosis

Calculate the anion gap:sodium - (chloride + HCO3)= anion gap

134 - (108 + 16) = 10Answer: 10 (normal)

Based on the clinical scenario, likely acid base diorders in this patient are:o Normal anion gap acidosis from diarrhea or,o Elevated anion gap acidosis secondary to lactic acidosis as a result

of hypovolemia and poor perfusion

Look at the pH:- The pH is low, (less than 7.35) therefore by definition,

patient is acidemic.

Look at the PCO2, HCO3:- PCO2 and HCO3 are abnormal in the same direction, therefore

less likely a mixed acid base diorder. Need to distinguish the initial change from the compensatory response. A low PCO2 represents alkalosis and is not consistent with the pH. A low HCO3 represents acidosis and is consistent with the pH, therefore it must be the initial change. The low PCO2 must be the compensatory response. Since the primary change involves HCO3, this is a metabolic process, i.e. Metabolic Acidosis.


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Is compensation adequate?- Since the actual PCO2 falls within the estimated range, we can

deduce that the compensation is adequate and there is no separate respiratory disorder present.

Assessment: Normal anion gap metabolic acidosis with adequate compensation most likely secondary to severe diarrhea_______________________________________________________________

Case 2

A 22 year old female with type 1 Diabetes Mellitus, presents to the emergency department with one day history of nausea, vomiting, polyuria, polydipsia and vague abdominal pain. PE noted for deep sighing breathing, orthostatic hypotension, and dry mucous membranes.

Laboratory:- Sodium: 132 - Potassium: 6.0- Cl: 93- HCO3: 11- Glucose: 720 mg/dL- BUN: 38- Crea: 2.6- UA: pH- 5.0, sg- 1.010, ketones- negative, glucose-+- plasma ketones: trace- ABG: pH- 7.27, HCO3- 10, PCO2-23

What is the acid base disorder?Based on the clinical scenario, likely acid base disorders in this patient are:

a) Elevated anion gap acidosis secondary to DKA; orb) Elevated anion gap acidosis secondary to lactic acidosis in the

setting of vomiting and polyuria which may lead to hypovolemia; or

c) Metabolic alkalosis in the setting of vomiting

Look at the pH:The pH is low, (less than 7.35)therefore by definition, patient is

acidemic

Look at the PCO2, HCO3:PCO2 and HCO3- are abnormal in the same direction, therefore

less likely a mixed acid base disorder but not yet ruled out. (it is a pure metabolic disorder.)

Again, need to distinguish the initial change from the compensatory response. A low HCO3- represents acidosis and is consistent with the pH, therefore it must be the initial change. To maintain the PCO2/HCO3, the PCO2 is reduced in response (compensatory).The low PCO2 must be the compensatory response. Since the primary change involves HCO3, this is a metabolic process. Ex metabolic acidosis

Calculate the anion gap:The anion gap is Na- (Cl + HCO3)= 132- (93 +11)= 28Since gap is greater than 17, it is therefore abnormal.

Is compensation adequate?Since the actual PCO2 falls within the estimated range we can

deduce that the compensation is adequate and there is no separate respiratory disorder present.

Assessment: compensated elevated anion gap metabolic acidosis most likely secondary to DKA, note the absence of ketones in the urine. This is sometimes seen in early DKA due to the predominance of beta-hydroxybutyrate. The dipstick test for ketones detect acetoacetate but not beta-hydroxybutyrate_______________________________________________________________

Case 3

A previously wel 55 year old woman is admitted with a complaint of severe vomiting for 5 days. PE reveals postural hypotension, tachycardia and diminished skin turgor. The laboratory finding include the ff:

Electrolytes: Na-140; K- 3.4; Cl-77; HCO3-9; Crea-2.1; ABG: pH-7.23, PCO2- 22 mmHg

What is the acid base disorder?Based on the clinical scenario, the likely acid base disorders in this patient are:

Elevated anion gap acidosis secondary to lactic acidosis in the setting of severe persistent vomiting which may lead to hypovolemia and/or

Metabolic alkalosis in the setting of persistent vomiting

Look at the pH:The pH is low (less than 7.35) therefore by definition patient is

acidemic

Look at the PCO2, HCO3.PCO2 and HCO3 are abnormal in the same direction, therefore

less likely a mixed acid base disorder but not yet ruled out.

Again, need to distinguish the initial change from the compensatory response. A low HCO3 represents acidosis and is consistent with the pH, therefore it must be the initial change. The low PCO2 must be the compensatory response. Since the primary change involve HCO3, this a metabolic process, i.e. metabolic acidosis.

Calculate the anion gap:sodium - (chloride + HCO3)= anion gap

140- (77+9) = 54

Since the actual PCO2 falls within the estimated range, we can deduce that the compensation is adequate and there is no separate respiratory disorder present.

Since anion gap is elevated, calculate the delta ratio to rule out concurrent metabolic alkalosis:

DELTA RATIO:Measured anion gap – normal anion gap

Normal HCO3 – Measured HCO3

=AG-12/ 24-HCO3=54-12/24-9

= 2.8

Delta ratio interpretations:


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<0.4 hyperchloremic normal anion gap acidosis<1 High AG and Normal AG acidosis1-2 pure anion gap acidosis, lactic acidosis (Average: 1.6), DKA (Closer to

1 due to urine ketones>2 High AG acidosis and concurrent metabolic alkalosis or pre-existing

compensated respiratory acidosis.

Since the delta ratio is greater than 2, we can deduce that there is a concurrent metabolic alkalosis. This is likely due to vomiting.

Another possibility is a pre-existent high HCO3 level due to compensated respiratory acidosis. But we have no reason to suspect respiratory acidosis base on history.

Assessment: mixed elevated AG metabolic acidosis and metabolic alkalosis likely due to lactic acidosis and vomiting.

(F3) Clinical Pathology Dr Kits

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