Urinalysis

Belinda Jim, MD

July 17, 2009

Urinalysis

• Major noninvasive tool

• Provide information about disease severity, though not always a direct relationship

• Specimen should be examined about 30-60 minutes of voiding

• Sample centrifuged at 3000 rpm for 3-5 minutes, supernatant be tested by dipstick

Color

• Normal color is clear and light yellow

• White- pyuria or phosphate crystals

• Green- administration of methylene blue, amitriptyline, propofol

• Red or Brown- due to blood

Turbidity

Normal urine should be clearTurbidity indicates:•cellular material•bacteria•protein•lipids•crystals•salt precipitation

Odor

• Normal odor is urinoid

• Ammonia- related to UTI, prolonged urinary retention

• Sweetish- diabetic ketoacidosis due to acetone

• Sulfuric- cysteine decomposition

• Drugs/Foods- e.g. antibiotics, asparagus

Test Reagent Strip

Protein

• Detects primarily albumin

• Highly specific, but not sensitive

• Positive only when protein excretion > 300-500 mg/day

• Not good to detect microalbuminuria or immunoglobulin light chains

Sulfosalicylic acid test (SSA)

• SSA detects all proteins in the urine• Especially useful if suspects multiple myeloma in

which immunogloblin light chains form casts that obstruct the tubules

• A positive SSA test in conjunction with a negative dipstick indicates presence of non-albumin proteins in urine

• Mix 1 part urine supernatant with 3 parts SSA (3%), grade its turbidity

pH

• Reflects degree of acidification of urine• Urine pH ranges from 4.5 to 8.0• Major clinical use for patient with metabolic

acidosis• Appropriate response to increase urinary acid

excretion, with urine pH falling below 5.3• A higher value indicate presence of RTA or

infection

Ketones

• Detects acetone and acetoacetate using nitroprusside reaction

• Does not detect -hydroxybutyrate

• Presence in the urine indicates diabetic ketoacidosis, starvation ketosis, low carb diet

Bilirubin/Urobilinogen

• Normal bilirubin not detected in urine

• If increased conjugated bilirubin in urine, indicates liver dysfunction

• Bilirubin metabolized by bacteria in the intestines to form urobilins

• Small % absorbed in intestine and appears in urine

Osmolality and specific gravity

• Osmolality- number of solute particles per unit volume

• Specific gravity- weight of solution compared with weight of water– Generally varies with osmolality, though

presence of large molecules in urine, such as glucose or radiocontrast media can produce large changes in specific gravity with little changes in osmolality

Glucose

• Presence of glucose indicates inability to reabsorb filtered glucose in the proximal tubule despite normal plasma levels

• OR urinary spillage due to abnormally high plasma concentrations

• Generally glucosuria does not occur until plasma glucose exceeds 180 mg/dL

Hematuria and Pyuria

• Dipsticks very sensitive in detecting rbc’s, as few as 1 to 2 rbc’s per high power field

• Detect leukocyte esterase (pyuria) and nitrite (enterobacteriaceae converts nitrate to nitrite)

• Sterile pyuria: interstitial nephritis, renal tuberculosis, and nephrolithiasis

Urine sediment

• Crystals

• Bacteria

• Red blood cells (0-2 rbc’s in normal)

• White blood cells (0-4 wbc’s)

• Casts

• Artifact

Crystals

• Calcium phosphate or calcium oxalate crystals

• Uric acid crystals

• Magnesium ammonium phosphate crystals

• Cystine crystals

Bacteria

• Significance depends on quality of collection

• More significant in presence of wbc’s and other elements

• Urine in the bladder should be sterile, but becomes contaminated as it passes through bladder

Hematuria

• Transient hematuria - relatively common in young subjects, not indicative of disease

• Persistant hematuria- gross or microscopic– Morphology is important, usually uniform and

round with extrarenal bleeding– Dysmorphic appearance with renal lesions, I.e.

blebs, budding, segmental loss of membrane

Pyuria• White cells are larger than red cells, granular

cytoplasm and multilobed nuclei• Pyuria alone usually indicated infection• Less diagnostic value when seen with other

elements such as cellular casts, and/or proteinuria• Eosinophils may indicate allergic interstitial

nephritis, cholesterol emboli disease• Lymphocytes seen in disorders associated with

infiltration of kidney by lymphocytes, such as chronic tubulointerstitial disease

Epithelial Cells

• May be shed anywhere within the GU tract

• Only renal tubular cells are significant

• Generally 1.5 to 3 times larger than white cells, contain a round, large nucleus

• May be normal or indicative of ATN, pyelonephritis, nephrotic syndrome

Casts

• Conform to the shape of the renal tubule in which they form

• Organic matrix composed mostly of Tamm-Horsfall mucoprotein

• Types of casts: hyaline, red cell, white cell, epithelial, granular, waxy, broad

Theory of Casts Genesis

•

Key:A = Cellular castsB = Coarsely granular castC = Finely granular castD = Waxy cast

RBC cast

                                                                                                                                        

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Miscellaneous Findings

Trichomonas Vaginalis

Sperm

Talc

Fiber

Case 1

• A 46 y.o. man with HTN presents with acute right flank pain that moves around. He is slightly febrile to 100.4 C. Exam unremarkable. UA shows hematuria.

Case 2

• A 22 y.o. woman with no significant past medical history presents with dysuria, ammonia-smelling urine and increased urinary frequency for 3 days.

• What will her UA show?

• What do you expect on the urine sediment?

Case 3

• A 57 y.o. woman with h/o poorly controlled HTN and DM, diabetic retinopathy presents with creatinine of 1.8 and lower extremity edema.

• What would you expect your UA to show?

• What would you do next?

Case 4

• A 3-year old boy brought to pediatrician for increasing facial and peripheral edema of eight days duration. Urine- 4.2 grams protein/24 hours, cholesterol 450 mg/dl, albumin 3.0 g/dl

Case 5

• A 45-year old man hospitalized for peripheral edema and proteinuria. Urine-6 g protein/24 hours, albumin 1.6 g/dl. Cholesterol 380 mg/dl. Creatinine 1.6. Review of medical records showed he had 1+ proteinuria four years previously.

Case 6

• A 52-year old woman with sudden onset of edema, “dark urine”, headaches, malaise. BP: 150/105, urine 900 cc/24 hr, 1.7g protein/24 hours, creatinine 4.5 mg/dl, BUN 68 mg/dl. Review of records show that she had normal renal function 1 month ago.