MLT GlobeUrinalysis & Body Fluids: Urine microscopy (casts, crystals) – page 3
54 Urinalysis & Body Fluids MCQs on Urine microscopy (casts, crystals) with answers and explanations.
Which epithelial cell, when seen in increased numbers in urine sediment, is the most clinically significant sign of kidney damage?
Renal tubular epithelial cells come from the nephron, so increased numbers indicate tubular injury such as ATN or toxicity. Squamous cells usually reflect contamination.
A cellular cast slowly degenerates as it stays in the tubule. Which sequence of cast appearance is expected?
Cells in a cast break down into coarse, then fine granules, and long stasis gives a homogeneous waxy cast. Waxy casts therefore imply prolonged urine stasis.
Which condition favours the formation of urinary casts in the tubules?
Uromodulin precipitates more readily in acidic, concentrated urine with slow flow. Casts dissolve in dilute alkaline urine.
After a crush injury, a patient has red-brown urine with a positive blood pad and no RBCs. The sediment shows reddish-brown granular casts. These casts most likely contain:
Pigmented granular casts in rhabdomyolysis are formed from myoglobin, which is toxic to tubules. Bilirubin-stained casts are yellow and occur with jaundice.
Highly refractile round structures with a central dimple show a 'Maltese cross' under polarised light. The patient's urine was collected by a nurse wearing powdered gloves. These are most likely:
Starch granules from glove powder also show a Maltese cross but have a dimpled centre and are irregular. Fat droplets are smooth, variable in size and stain with Sudan III.
The Sternheimer-Malbin stain used on urine sediment contains:
This supravital stain of crystal violet and safranin improves detail of nuclei, cells and casts. Oil Red O is used to identify lipids.
In a dilute hypotonic urine, neutrophils swell and their granules show Brownian movement. These cells are called:
Glitter cells are swollen neutrophils in hypotonic urine whose granules sparkle as they move; they stain pale with Sternheimer-Malbin. They have no special diagnostic meaning.
For a standardised sediment, 12 mL of urine is centrifuged, and the supernatant is removed leaving 0.5 mL to resuspend the sediment. The concentration factor is:
The concentration factor is 12 mL ÷ 0.5 mL = 24. Standardising volumes makes results comparable between specimens and laboratories.
A woman has dysuria and frequency without fever or flank pain. Urine shows many white cells and bacteria but no casts. This is most consistent with:
Pyuria and bacteriuria without white cell casts or systemic signs suggest infection of the bladder. White cell casts would point to kidney involvement (pyelonephritis).
A boy from an endemic area has blood at the end of urination. Urine microscopy shows large oval eggs with a terminal spine. The parasite is:
Schistosoma haematobium lives in the veins of the bladder and passes terminal-spined eggs in urine, causing terminal hematuria. S. mansoni eggs have a lateral spine and are found in stool.
A patient has 50 red cells per HPF with normal, uniform shape and no red cell casts or protein. The bleeding most likely comes from:
Uniform (isomorphic) red cells without red cell casts or proteinuria suggest non-glomerular bleeding, for example from stones, infection or tumour anywhere from the renal pelvis to the urethra. Glomerular bleeding gives dysmorphic red cells, red cell casts and often proteinuria.
Yellow-brown spheres with spiky projections ('thorny apples') are seen in an old, alkaline urine specimen. They are most likely:
Ammonium biurate crystals form in alkaline, often old specimens and look like thorny apples. They convert to uric acid when acetic acid is added. Leucine spheres have concentric rings and no spikes.
Refractile droplets in the urine of a nephrotic patient stain orange-red with Sudan III, but some droplets do not stain and show a 'Maltese cross' under polarised light. The non-staining droplets are:
Sudan III and Oil Red O stain triglycerides and neutral fats but not cholesterol, which is identified by Maltese cross patterns under polarised light. Using both methods detects all lipid types.
A patient with fever and flank pain has casts that appear granular under bright-field microscopy. A Gram stain of the sediment shows these casts are packed with bacilli. These are:
Bacterial casts look like granular casts but contain bacteria, confirmed by Gram stain; they indicate pyelonephritis. They are often accompanied by white cell casts.