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
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