MLT GlobeUrinalysis & Body Fluids: Urine microscopy (casts, crystals)
54 Urinalysis & Body Fluids MCQs on Urine microscopy (casts, crystals) with answers and explanations.
A urine report shows many white cells (pus cells). This is termed:
Pyuria means leucocytes in urine, often from infection. Haematuria is blood; oliguria and anuria describe reduced output.
Red blood cell casts in urine sediment indicate:
Casts form in the tubules, so red cells inside a cast must come from the nephron. RBC casts point to glomerular disease such as post-streptococcal glomerulonephritis.
The protein matrix of all urinary casts is uromodulin (Tamm–Horsfall protein). Where is it produced?
Uromodulin is secreted by cells of the thick ascending limb and distal tubule; casts form in distal and collecting tubules where urine is concentrated. It is not a glomerular protein.
A healthy student gives a urine sample after a football match. The sediment shows 0–2 hyaline casts/LPF and nothing else abnormal. This finding is:
A few hyaline casts can be seen in normal urine, and numbers rise after strenuous exercise, dehydration or heat. Cellular casts, not hyaline casts, point to renal disease.
Yellow-brown, rhombic or rosette-shaped crystals that polarize strongly are seen in a urine with pH 5.5. They are most likely:
Uric acid crystals form in acidic urine, are yellow to red-brown, take rhombic, barrel or rosette shapes, and are strongly birefringent. Triple phosphate and calcium carbonate form in alkaline urine.
Colourless, prism-shaped 'coffin-lid' crystals in alkaline urine from a patient with a Proteus infection are:
Urease-producing bacteria such as Proteus make urine alkaline and promote struvite (triple phosphate) crystals and stones. Cystine forms hexagonal plates in acidic urine.
A pear-shaped flagellate with a jerky, rapid movement is seen in a fresh urine from a woman with vaginal discharge. It is:
Trichomonas vaginalis is identified in urine or vaginal fluid by its pear shape and jerky motility; non-motile forms can be confused with WBCs. Schistosoma is seen as terminal-spined eggs.
Colourless, octahedral 'envelope' crystals are seen in a normal acidic urine. They are:
Calcium oxalate dihydrate forms envelope-shaped crystals, common in acidic and neutral urine and often diet related. Triple phosphate forms 'coffin-lid' prisms in alkaline urine.
A refrigerated alkaline urine has a heavy white precipitate. Microscopy shows granular amorphous material. This precipitate will dissolve after adding:
White amorphous phosphates form in alkaline urine and dissolve in dilute acid. Warming dissolves amorphous urates (pink, acidic urine), not phosphates.
Many round urothelial (transitional) epithelial cells with normal morphology are seen in a urine collected just after bladder catheterisation. This finding is most likely:
Catheterisation scrapes cells from the urothelium, so increased normal transitional cells are expected. Malignancy is suspected only when cells show abnormal nuclear features.
Large, flat urinary epithelial cells with abundant cytoplasm and a small central nucleus are most often:
These are squamous cells, the largest cells in sediment, and in large numbers suggest a poorly collected specimen. Renal tubular cells are smaller with an eccentric nucleus.
Urinary casts are best screened and reported under:
Casts are scanned under low power with subdued light, because hyaline casts have a low refractive index and are easily missed in bright light. They are reported as the average per LPF.
Budding yeast with branching pseudohyphae is seen in urine from a woman with poorly controlled diabetes. The organism is most likely:
Candida produces budding yeast and pseudohyphae and is common in diabetic urine, where glucose supports growth. Cryptococcus does not form pseudohyphae.
Urinary casts are formed mainly in the:
Casts are moulds of the tubular lumen formed when uromodulin gels in the distal tubules and collecting ducts, so they come only from the kidney.
Why is urine pH useful when identifying crystals in urine sediment?
Crystal formation depends on pH; for example, uric acid crystals form in acidic urine and triple phosphate in alkaline urine, so pH helps narrow the identification.
In a normal urine sediment, red blood cells are usually seen at about:
A few red cells (roughly 0–2 or 0–3 per HPF) can be normal. Higher numbers indicate hematuria and need investigation.
In a normal urine sediment, white blood cells are usually seen at about:
Up to about 5 white cells per HPF is generally regarded as normal; higher counts indicate pyuria, often due to infection or inflammation.
Many squamous epithelial cells in a urine sediment most often indicate:
Squamous cells line the vagina and distal urethra, so large numbers usually mean the sample was not a proper midstream clean-catch collection.
Many bacteria are seen in a urine that stood unrefrigerated for 6 hours, with no white cells. The bacteria are most likely due to:
Bacteria double rapidly in urine at room temperature, so an old unpreserved sample can show many bacteria without true infection. Urine should be tested within 2 hours or refrigerated.
Transitional (urothelial) epithelial cells in urine come from which part of the urinary tract?
Urothelium lines the renal pelvis, ureters, bladder and upper urethra. Renal tubular cells come from the tubules and squamous cells from the vagina and distal urethra.