URINALYSIS – The ‘cornerstone’ of Clinical Nephrology

N.Gopalakrishnan,

MD, MRCP, DM

‘Sick Lady and Doctor’

16 th century painting by Caspar Netscher

(AJKD,2007)

Urinalysis - Aims

• Physical characteristics

• Chemical composition

• Cellular elements

• Microorganisms

Abnormal Colour of urine

• White Chyle,pus

• Yellow Bilirubin

• Pink / reddish brown RBCs, haemoglobin,myoglobin

• Brown / black Methaemoglobin, homogentisic acid

• Green Pseudomonas

Dipstick

• pH• Protein• Blood• Specific gravity• Glucose

• Leucocytes• Nitrite• Bilirubin• Urobilinogen• Ketones

pH

pH

• Dipstick – pH 4.5 to 8.5; less accurate when pH is < 5 or >8

• For accurate estimation, pH meter with glass electrode is mandatory

Specific gravity

• Denotes weight of solutes• Inaccurate surrogate of osmolality• Methods: Hydrometer

Refractometer

Dipstick

Range: 1.001 – 1.035

Assesses concentrating ability

Differentiation between pre renal azotemia & ATN

Protein

• Heat coagulation

• Sulphosalicylic acid

• Dipstick

Dipstick - protein

• Protein indicator strips – tetrabromophenol blue or bromocresol blue

• Colour change according to protein concentration

• Trace to 4+

trace 5 – 20 mg/dl

1+ - 30, 2+ - 100,

3+ - 300, 4+ - > 2000 mg/dl

Dipstick - protein

• Highly alkaline urine - false positive reaction • Quantification – influenced by urinary

concentration• Less sensitive to globulin,haemoglobin & light

chain

Urine negative by dipstick but positive with sulphosalicylic acid – highly suspicious for light chains

Henry Bence Jones

Light chains

• Myeloma• Precipitate 40- 60 C• Dissolves 100 C• Reappears on cooling

Preparation of sample for microscopy

• Second urine of the morning after discarding initial few millilitres

• Analysis within 2 – 4 hrs

• Centrifuge (10 ml) at 2000 rpm for 10 min

• Remove 9.5 ml of supernatant

• Resuspend sediment with pipette in the in remaining 0.5 ml

• Transfer 50 ul with pipette on to a slide

Microscopy

Phase contrast microscope – ideal

• High sensitivity for hyaline casts & RBCs with low Hb content

• For RBC morphology

• Filters to polarize light – for lipids & unusual crystals

Erythrocytes

• > 2 -3 / HPF --- Haematuria

• Isomorphic haematuria – from collecting system

• Dysmorphic haematuria – from renal parenchyma

Dysmorphic RBCS

• Glomerular origin

• Acanthocytes – sensitive indicator

Leucocytes

• Indicate urinary tract inflammation

• ‘Glitter cells’ – swollen polymorphs with prominent granules

• UTI, interstitial nephritis, glomerulonephritis

Sterile pyuria

• Tuberculosis

• Partially treated UTI

• Steroids

• Calculi

• Prostatitis

• Bladder tumour

• Papillary necrosis

Eosinophiluria

• Acute allergic interstitial nephritis

• Atheroembolism

• Rapidly progressive glomerulonephritis

• Schistosomiasis

Hansel’s stain

Renal tubular epithelial cells(RTECs)

• Larger than WBCs

• Few cells are normal

• Indicate tubular damage or inflammation

ATN, interstitial nephritis

Casts in the urine

• Tubular moulds

• Tamm Horsfall protein

forms the matrix

Hyaline casts – base for other casts

RBC cast

Hyaline cast

+

RBC

Always pathological

RBC cast

Hallmark of Nephritic sediment

WBC cast

• Pyelonephritis

• Glomerulonephritis

‘Dirty brown’ cast

Acute Tubular Necrosis

Fine granular cast

• Derived from altered serum proteins

• Usually, pathological

Coarse granular cast

• Result from degeneration of embedded cells

• Usually pathological

Broad casts (Waxy cast)

• Form in dilated, atrophic tubules

• More refractile than hyaline casts

• Usual in chronic renal insufficiency

Telescoped urine sediment

Plethora of findings

RBCs, RBC casts, WBCs, granular casts, broad casts,etc

Classically seen in SLE

Crystals in urine

• Common crystals

• Pathological crystals

• Crystals due to drugs

Pathological crystals

• Cystine - Cystinuria

• Cholesterol – massive proteinuria

• 2,8 dihydroxyadenine – Adeninie phosphoribosyl transferase deficiency

Drugs causing crystalluria

• Drug overdose• Dehydration• Hypoalbuminemia• Urine pH

• Acyclovir• Indinavir• Sulphadiazine• Amoxycillin• Vitamin C (oxalate)

Cystine crystals

• Always pathological

• Pathognomonic of cystinuria

Uric acid crystals

Rhomboid

Hyperuricosuric conditions

Acute uric acid nephropathy

Calcium Oxalate

• Monohydrate:’dumb bell’

• Byhydrate: ‘envelope’

Triple phosphate crystals

• ‘Coffin lid’shaped

• Rectangular with beveled ends

Blood

• Depends on peroxidase activity of haemoglobin

• Blood, haemoglobin & myoglobin test positive

• Dipstick positive for blood, but no RBCs in microscopy – haemoglobin or myoglobin

Microorganisms

• Bacteria

• Yeasts

• Trichomonas

Nitrite screening test

• For detection of bacteriuria

• Bacteria convert urinary nitrate to nitrite which activates a chromogen

• False negative – Enterococcus

Oval fat bodies

• Macrophages filled with fat droplets

• Proteinuric conditions

Microalbumin dipsticks

• For screening for microalbuminuria

• Colorimetric detection of albumin bound to gold – conjugated antibody

Let us uphold the ancient tradition!

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