APPROACH TO A PATIENT WITH SUSPECTED KIDNEY DISEASEELIZABETH ROMANO-SEBASTIAN MD FPCP FPSN

A 28 yo female came to your clinic for bi pedal edema of 2 weeks duration. PE showed puffy eyelids, pale conjunctiva, + friction rub, decrease breath sounds and Gr 2 pedal edema. She denies any intake of any meds.

Creatinine

2.4 mg/dl

ELECTROLYTES

Na – 138

K – 5.5

iCal – 4.8

Phos – 3

URINALYSIS

ColorNormal:

pale to dark depending on the concentration of the urine.

Pathologic conditions:

gross hematuria

hemoglobinuria

myoglobinuria (pink, red, brown or black) ;

jaundice (dark yellow to brown);

chyluria (white,milky)

massive uric acid crystalluria (pink)

Drugs:

rifampin (yellow-orange to red; phenytoin (red), nitrofurantoin (brown);

metronidazole, imipinem, methyldopa (darkening on standing)

Odor

Pungent UTI due to production of ammonia)

Sweet ketones

Musty pku

Turbidity

Usually transparent but can be due to inc concentration of any particle

FOAM

Indicates the amount of protein in the urine

Chemical Analysis Dipstick

pH

Hemoglobin

Glucose

Albumin

Leukocyte esterase

Nitrates

Bilirubin

Specific gravity

pH

presence of H+ ions due to the secretion of acid in the collecting ductlow ph:

metabolic acidosis, high protein meals, (generate more acid and ammonia) and with volume depletion- aldosterone is stimulated resulting in acidic urine)

high ph:RTA, vegetable diets, infection with urease + like proteus)

Range: 5-8.5

Hemoglobin

Pseudoperoxidase activity of the heme moiety of Hgb, which catalyzes peroxide and chromagen ---colored product

False positive: hemoglobinuria from intravascular hemolysismyoglobinuria from rhabdomyolysishigh concentration of bacteria with enterobacter staphylococci, strep

False negative: ascorbic acid

RBC- Hematuria – blood in the urineDifferentiated by centrifugation

Glycosuria

Used for testingMultistix – glucose oxodase reaction

Clinitest – modified Benedict’s test for reducing substances

Types of glycosuriaOverflow glycosuria – above 180mg/dl

Renal glycosuria – associated with Fanconi Syndrome

ProteinPhysiologic

Daily production – 40-150 mg/day40% albumin, 40% tissue, 15% Ig and fragments, 5% other plasma proteins 150 mg/24 hrs adults, 140 mg/m2 in childrenMethod is sensitive to albumin

First morning Random protein crea ratio (same time for follow-up)

Types of ProteinuriaOverflow – contains Bence-Jones proteins, myoglobin, HgbGlomerular permeability

Selective - albuminNon-selective

Tubular – decrease reabsorption of filtered protein; caused by antibiotics, heavy metalsHemodynamic – caused by CHF, heat, seizures, exercise

Parameter False Positive False Negative

Specific Gravity Reduced when in the presence of glucose, urine pH>6.5

Increased when in the presence of keto acids,

protein >7g/L

pH Reduced when in the presence of formaldehyde

Hemoglobin Ascorbic acid, delayed examination, high density of

urine, formaldehyde (>0.5 g/L)

Myoglobin, microbial peroxidise, oxidizing agent,

HCl

Glucose Ascorbic acid, bacteria Oxidizing detergents, HCl

Albumin Ig light chains, tubular proteinuria, globulins,

abnormally colored urine, HCl

Urine pH >9, quaternary ammonium detergents,

chlorhexidines, polyvinylpyrolidone

Leukocyte esterase High density of urine, high Vitamin C intake, protein >5g/L , glucose >20g/L,

cephalosporin,

Oxidizing detergents, formaldehyde (>0.4 g/L), sodium azide, abnormally colored urine due to beet

Nitrites No vegetables in diet, short bladder incubation time,

vitamin C, bacteria that do not reduce nitrates to nitrites

Abnormally colored urine

Microscopic Examination

Sediment OverviewTechnique for preparation and examinationMorning specimen is the most concentratedCentrifugation done in a conical tube for 3 to 5 minutes at 3000-5000 rpm Pipetting

Decant supernatant liquidPipette while invertedAspirate buttonMay resuspend if too thick

Cover slip: avoid bubbles, examine periphery for formed elements

ExaminationScan entire entire field at low power

Magnify selected areas

Stop down diaphragm or move light source for contrast

Stain if necessary

Microscopic Formed elementsCellular elements

WBC- easiest to find due to granular cytoplasm and lobulated nucleus

Marker for upper or lower tract infections

In women may be found as contaminant

May also be GN, Interstitial nephritis

RBCChanging the focus, causes red cells to appear as black tires, appear concave

NormalDysmorphic RBC’sCrenated RBC- occurs in hypertonic urineAcanthocytes- doughnut-like with blebs (mickey mouse ears)Discocyte→echinocytes→stomatocyte- transition inducible in changes in pH, osmolality and protein concentrations

Casts

Can only come from the tubules

Primarily Tamm- Horsfall mucoprotein

Secreted in TAL as monomers

Polymerized into casts in distal tubules and collecting ducts

Incorpotate material that is within the tubules

Favored by low flow rates, low pH, high luminal Na

Larger casts from larger tubules especially with decreased flows

Hyaline cast

Fine granular cast

Broad coarsely granular cast

Fatty cast

Waxy cast

Acute Tubular Necrosis

RBC Cast-

indicative of Glomerular injury

White Blood cell castAcute interstitial nephritis,

acute pyelonephritis, proliferative glomerulonephritis

Casts Main Clinical association

Hyaline Normal subject and renal disease

Hyaline granule Normal subject and renal disease

Granular Renal disease

Waxy Renal insufficiency and rapidly progressing renal disease

Fatty Marked proteinuria, nephritic syndrome

Erythrocyte Glomerular bleeding, proliferating/ necrotizing glomerulonephritis

Hemoglobin Same as erythrocytic cast + hemoglobinuria

Leukocyte Acute interstitial nephritis, acute pyelonephritis, proliferative glomerulonephritis

Epithelial Acute tubular necrosis, acute interstitial nephritis, glomerulonephritis

Myoglobin Rhabdomyolysis

Bacteria/ Fungi Bacterial/ fungal infection in kidney

pH 6

Sg 1.02

Protein ++++

RBC 8/hpf

WBC 9/hpf

Epithelial cells many

RBC casts, fine granular casts

USG

Size

Cortical thickness

Echogenicity

Calyxes

Ureter

Normal sized kidneys with hypoechoic parenchyma

54 yo male known hypertensive, known diabetic admitted for decreasing urine output

A 32 yo male known to have a solitary functioning R kidney came in for R flank pain radiating to the R testicle with no urine output for the past 8 hours

TAKE HOME MESSAGESHistory and PE will determine the type of exams to be requested

In approaching a patient with elevated creatinine, the first step is to differentiate acute from chronic kidney disease

Trend of creatinine more important than a single determination

Proper collection of urine must be emphasized to a patient

Be systematic in interpreting laboratory results.