Chapter 4 Urine tests and renal function tests

Sample’s collection and sending: A first morning voided urine specimen obtained by a clean catch technique yields the most information. Other collections of urine might have their specific usage ( random urine, postcibal urine, 12 hours urine, 24 hours urine, etc.) The urine should be examined promptly by both chemical and microscopic means.

Contents and clinical significance of URT

General property:

•Urine volume: Normal volume of urine in 24 hours should be 1000 -2000 ml .

•Polyuria: > 2500ml/ 24 hrs: chronic nephritis , diabetes insipdus, diabetes mellitus

•Oliguria: < 400 ml/ 24 hrs: acute nephritis ,sereve shock, urinary tract obstruction

•Anuria: < 100 ml/ 24 hrs: acute renal failure

Color • Hematuria: microscopic hematuria is defined as more than 3 RBCs/HP on a centrifuged urine specimen. Naked-eye hematuria is defined as more than 1 ml blood in one liter urine.

• Hemoglobinuria: the color looks like strong tea or wine because of the existing of free hemoglobin

• Pyuria or becteriuria : presence of more than 5 WBCs /HP or germs with cloudy-looking

• Bilirubinuria : presence of direct bilirubin with dark-yellow color

• Crystoluria: presence of salts crystal with cloudy-looking

PH: 6.5

• aciduria: acid: acidosis

• alkaluria : alkalosis , renal tubular acidosis

•Specific gravity: 1.015-1.025

• lower SG: chronic renal failure, diabetes insipdus

• high SG: acute nephritis, diabetes mellitus, heart failure

Chemical tests: include detection the presence of protein, occult blood, glucose and ketone in the urine.

Urine protein: normal : (-) or 20-80 mg/24 hrs,

abnormal: (+ ) or > 150 mg / 24 hrs

Urine glucose: normal : (-) or 0.56- 5.6mmol/L, diabetic urine ( glucosuria): (+-++++)

•Urine ketone : normal : (-),ketonuria : (+-+++)

Microscopic examination: ( urine sediment tests)

•Cells : In normal urine, RBC and WBC are rare ( RBC 0-1 / HP , WBC < 5 / HP ) . Epithelial cells ( oval fat bodies ) are commonly found in urinary sediment and may derive from any site along the urinary tract from the renal pelvis to the urethra. When renal tubular epithedlial cells or renal cells appears in the urine, it is pathological change.

Casts

•cellular casts (erythrocyte casts, leukocyte casts, renal tubular cell casts )

•granular casts( coarse and fine granule)

•hyaline casts

•waxy casts

•renal failure casts

Crystal bodies:

Pathogen:

Microscopic examination of the urine

finding associations

casts

red blood cell glomerulonephritis, vasculitis

white blood cell interstitial nephritis, pyelonephritis

epithelial cell acute tubular necrosis,interstitial

nephritis, glomerulonephritis

granular renal parenchymal disease (non-specific)

waxy ,broad advanced renal failure

hyaline normal finding in concentrated urine

fatty heavy proteinuria

cells

red blood cell urinary tract infection or inflammation

white blood cell urinary tract infection or inflammation

Renal function tests

Tests of glomerular function:

•Endogenous creatinine clearance rate (Ccr): Determination of the clearance of endogenous creatinine is a more convenient test and provides a reasonable estimate of the GFR.

The creatinine clearance is calculated as Ccr (ml/min)=Ucr(mg/dl)xV(volume of urine in 24 hours, ml/min) / Pcr (mg/dl). Normal range is 80-120 ml/min/1.73m2.

•Blood concentration of creatinine (Cr) and urea nitrogen (BUN): Creatinine is a metabolite of creatine, a major muscle constituent. In a given individual, the daily rate of production of creatinine is constant and is determined by the mass of skeletal muscle. Urea is the major product of protein metabolism, and its productoin reflects the dietary intake protein as well as the protein catabolic rate. BUN is often used in conjunction with the Cr as a measure of renal function.

•Cr : 53-106 umol/L (M), 44-97 umol/L (F)

BUN: 3.2-7.1 mmol/ L (adult) , 1.8-6.5 mmol/ L (children)

Tests of renal tubule function Renal tubular function is evaluated by tests that examine the ability of the kidney to maintain salt and water balance as well as acid-base balance.

a. •Urine specific gravity (3 hours urine) test :

Day uine (2/3-3/4) should be more than night urine (1/3-1/4), hightest SG > 1.025 ,lowest SG < 1.003

• Phenolsulfonphthalein excretion test (PSP):

excretion rate: 15 min > 25%, 2 hrs (total) > 55%

•Carbon dioxide combining power ( CO2CP):normal: 22-31 mmol / L, elevated CO2CP : metabolic acidosis, respiratory alkalosis, declined CO2CP: respiratory acidosis, metabolic alkalosis

•Automatic urine analyzer (10 items) :

•GLU(-), BIL(-~+), UBG(3.2umol/L),

•NIT(-), KET(-), PRO(-), PH(6.5),

•BLD(-), LEU(-), SG(1.025)

Case analysisHistory and physical examination : A 48-year- old female patient was admitted with the complains of severe headache with a fever, edema in her face and eyelids for 3 days. From yesterday, she found her amount of urine was decrease once a day . The color of her urine is reddish and cloudy. Physical examination her blood pressure is 180/100 mm Hg , there is severe pitting edema in her face and legs.

Question• After physical examination, what laboratory test do you plan to do?

• How do you think or judge this case?

• What urinary abnormalities and renal function test results do you probably find?

• Teacher give laboratory results of this case and discuss the case .