MLT GlobeUrinalysis & Body Fluids: Urine microscopy (casts, crystals) – page 2
54 Urinalysis & Body Fluids MCQs on Urine microscopy (casts, crystals) with answers and explanations.
Waxy casts with cracked edges are associated with:
Waxy casts form as granular casts degenerate during long stasis in the tubules. Broad waxy casts suggest dilated tubules in end-stage kidney disease ('renal failure casts').
Many 'picket fence' (monohydrate) calcium oxalate crystals in a comatose patient with a high osmolal gap suggest poisoning with:
Ethylene glycol is metabolised to oxalic acid, which forms calcium oxalate crystals, often monohydrate, in urine. Methanol does not produce oxalate crystals.
A woman with fever, flank pain and pyuria has white blood cell casts in her urine. This finding helps distinguish:
WBC casts form inside renal tubules, showing that the inflammation involves the kidney (pyelonephritis or interstitial nephritis). Cystitis produces WBCs without casts.
How is a mucus thread best distinguished from a hyaline cast in urine sediment?
Hyaline casts have parallel sides and rounded ends reflecting the tubule shape; mucus forms long, wavy, irregular strands. Both have low refractive index, so shape is the key feature.
A patient with heavy proteinuria has casts containing highly refractile droplets that show 'Maltese cross' patterns under polarized light. These are:
Fatty casts contain cholesterol-rich lipid droplets that form Maltese crosses under polarized light, typical of nephrotic syndrome. Waxy casts are homogeneous and do not polarize this way.
Broad casts, several times wider than ordinary casts, are most significant because they indicate:
Broad casts form in widened distal or collecting tubules where flow is very slow, often in advanced chronic kidney disease, hence the old name 'renal failure casts'.
A hospitalized patient develops acute kidney injury after hypotension. Urine sediment shows many 'muddy brown' coarse granular casts and renal tubular epithelial cells. This suggests:
Muddy brown granular casts and tubular cells reflect injured, sloughing tubular epithelium in acute tubular necrosis. Prerenal azotemia usually has a bland sediment with only hyaline casts.
Colourless hexagonal plates are seen in acidic urine from a child with kidney stones. Which test confirms their identity?
Hexagonal crystals suggest cystine (cystinuria); the cyanide–nitroprusside test turns red-purple with cystine. Uric acid can form similar-looking plates, so confirmation is important.
A pink precipitate ('brick dust') forms in a refrigerated acidic urine and obscures the sediment. What will dissolve it?
Amorphous urates form in cooled acid urine and dissolve when warmed to about 60 °C or on alkalinization. Amorphous phosphates, found in alkaline urine, dissolve in dilute acetic acid.
A patient with severe liver failure has fine, colourless-to-yellow needle crystals in sheaves in an acidic urine. These are most likely:
Tyrosine crystals (needles in clusters or sheaves) and leucine spheres appear in severe liver disease or inherited amino acid disorders. They are abnormal crystals of clinical significance.
Large, flat, colourless plates with a notched corner are seen in urine of a patient with nephrotic syndrome. They are:
Cholesterol crystals are flat plates with notched corners, often seen with lipiduria in nephrotic syndrome. They are best seen in refrigerated samples.
Yellow-brown clumped needles are seen in urine with a positive dipstick bilirubin in a patient with hepatitis. These crystals are:
Bilirubin crystals appear as clumped yellow-brown needles or granules and match a positive bilirubin pad. Sulfonamide crystals are usually linked to drug therapy and a negative bilirubin test.
Phase-contrast examination shows that most urinary red cells are small with blebs, ring forms and budding (acanthocytes). This mainly suggests:
Dysmorphic red cells, especially acanthocytes (G1 cells), are damaged as they pass through the glomerulus and tubules, pointing to glomerular disease. Lower tract bleeding gives mostly normal-shaped red cells.
Round structures in urine sediment could be red cells or yeast. Which simple step helps distinguish them?
Dilute acetic acid lyses red cells; yeast remain and may show budding or hyphae. Red cells are also more uniform in size and do not bud.
When preparing urine sediment by a standardized method, a typical procedure is:
Standardized procedures centrifuge a fixed volume (about 10–15 mL) at around 400 RCF for 5 minutes so results are comparable. High forces can damage casts and cells.
A urine sample with low specific gravity (1.003) and pH 8.0 was left at room temperature for 4 hours. What is most likely to be underestimated on microscopy?
Casts dissolve in dilute, alkaline urine, and delay makes this worse. Bacteria multiply rather than decrease at room temperature.
Small colourless dumbbell-shaped crystals in alkaline urine produce gas bubbles when acetic acid is added. They are:
Calcium carbonate crystals release CO2 (effervescence) in acetic acid. Calcium oxalate monohydrate may also be dumbbell-shaped but does not dissolve or bubble in acetic acid.
Yellow-brown spheres with concentric circles and radial striations are seen in the urine of a patient with severe liver disease. They are most likely:
Leucine forms oily yellow spheres with concentric and radial lines, seen with tyrosine in severe liver disease. Ammonium biurate spheres have spiky projections and occur in alkaline urine.
A patient receiving high-dose trimethoprim-sulfamethoxazole has brown sheaves of needles and fan-like crystals in acidic urine. They are most likely:
Sulfonamide crystals form sheaves, fans or rosettes in acidic urine of patients on sulfa drugs, especially when poorly hydrated. Medication history helps separate them from tyrosine in liver disease.
Three days after a haemolytic transfusion reaction, yellow-brown granules are seen free and inside cells in the urine sediment. Which stain confirms they are haemosiderin?
Haemosiderin (iron) stains blue with Prussian blue and appears in urine 2–3 days after intravascular haemolysis. Sudan III is used for fat.