Urine, CSF, body fluids and calculi

27 Kerala MSc MLT Entrance practice questions on Urine, CSF, body fluids and calculi, part of Biochemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   CSF lactate helps to separate bacterial from viral meningitis because it:

   1. ARises from anaerobic glycolysis in the infected meninges
   2. BCrosses freely from blood and mirrors plasma lactate
   3. CIs produced only by viruses replicating in the brain
   4. DFalls in bacterial meningitis as bacteria consume it

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   Answer: A · Rises from anaerobic glycolysis in the infected meninges

   In bacterial meningitis, neutrophils, bacteria and hypoxic brain tissue metabolise glucose anaerobically, so CSF lactate rises (often above about 35 mg/dL) while CSF glucose falls. Lactate crosses the blood-brain barrier poorly, so CSF lactate reflects events in the CNS rather than blood levels. In viral meningitis it usually stays normal. It remains raised for a time after antibiotics are started, which helps in partly treated cases.

   • B: Lactate crosses the blood-brain barrier slowly, so CSF levels are largely independent of plasma.
   • C: Lactate comes from host cell and bacterial metabolism; viral meningitis leaves it normal.
   • D: CSF lactate rises, not falls, in bacterial meningitis.

2. Question 2 · Easy

   Which substance gives normal joint fluid its stringy, highly viscous nature?

   1. AHyaluronic acid
   2. BFibrinogen
   3. CAlbumin
   4. DChondroitin sulphate

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   Answer: A · Hyaluronic acid

   Synoviocytes secrete hyaluronic acid, a large polymer of glucuronic acid and N-acetylglucosamine that makes normal synovial fluid viscous and lubricating. A drop of normal fluid forms a string of 4-6 cm from a syringe. In inflammatory and septic arthritis, enzymes from neutrophils break down hyaluronate, so viscosity falls. Hyaluronidase is used to reduce viscosity before a cell count.

   • B: Normal synovial fluid has no fibrinogen and does not clot.
   • C: Albumin is present at a low level and adds little viscosity.
   • D: Chondroitin sulphate is a component of cartilage, not the source of fluid viscosity.

3. Question 3 · Easy

   What is the usual total protein of lumbar CSF in a healthy adult?

   1. A150-450 mg/dL
   2. B6.0-8.0 g/dL
   3. C1.5-4.5 g/dL
   4. D15-45 mg/dL

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   Answer: D · 15-45 mg/dL

   Normal lumbar CSF contains only about 15-45 mg/dL of protein, less than 1% of the plasma level, because the blood-brain barrier keeps most plasma proteins out. Most of it is albumin. Ventricular CSF has even less protein, and neonates have more. Raised CSF protein is seen in meningitis, especially tuberculous, in Guillain-Barre syndrome and below a spinal block.

   • A: 150-450 mg/dL would be markedly raised, as in tuberculous meningitis or a spinal block.
   • B: 6.0-8.0 g/dL is the normal serum total protein.
   • C: 1.5-4.5 g/dL is in the range of a serous fluid exudate, not CSF.

4. Question 4 · Hard

   A 38-year-old man has passed three calcium oxalate stones in 2 years. Serum calcium 9.4 mg/dL (8.5-10.5), phosphate 3.4 mg/dL, PTH normal. 24-hour urine: volume 2.1 L; calcium 390 mg (below 300); oxalate 34 mg (below 45); citrate 560 mg (above 320); uric acid 610 mg (below 800). Which abnormality best explains his stones?

   1. AHypocitraturia
   2. BIdiopathic hypercalciuria
   3. CEnteric hyperoxaluria
   4. DPrimary hyperparathyroidism

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   Answer: B · Idiopathic hypercalciuria

   The only abnormal stone-risk result is a urine calcium of 390 mg/day, with normal serum calcium and PTH. That is idiopathic hypercalciuria, the commonest metabolic finding in calcium stone formers. Primary hyperparathyroidism would raise serum calcium with an inappropriately normal or high PTH. Urine oxalate is below 45 mg/day and citrate above 320 mg/day, so neither hyperoxaluria nor hypocitraturia is present.

   • A: Urine citrate of 560 mg/day is normal, above 320 mg/day.
   • C: Urine oxalate is normal at 34 mg/day.
   • D: Hyperparathyroidism would give a high serum calcium; his is normal.

5. Question 5 · Medium

   Pleural fluid pH is used to decide whether a parapneumonic effusion needs drainage. How should it be measured?

   1. AWith the pH pad of a urine reagent strip
   2. BAfter centrifugation, with the tube left uncapped
   3. CAnaerobically in a heparinised syringe, on a blood gas analyser
   4. DIn a plain tube with narrow-range pH paper

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   Answer: C · Anaerobically in a heparinised syringe, on a blood gas analyser

   A pleural fluid pH below about 7.20 in a parapneumonic effusion suggests a complicated effusion that needs drainage. The fluid must be collected without air into a heparinised syringe and run on a blood gas analyser, because loss of CO2 to air raises the pH. pH paper and reagent strips are too imprecise for a cut-off this narrow. Excess heparin or local anaesthetic in the syringe can lower the result.

   • A: Urine strip pH pads read only in whole units and are not accurate enough.
   • B: Leaving the tube open lets CO2 escape and falsely raises the pH.
   • D: pH paper is too imprecise near the 7.20 decision point.

6. Question 6 · Medium

   Bence Jones protein in urine is recognised by its unusual behaviour on heating. It:

   1. APrecipitates only when the urine is cooled to 4 °C
   2. BStays clear when heated but turns the strip protein pad dark
   3. CPrecipitates at 40-60 °C and redissolves near boiling
   4. DCoagulates at 100 °C and stays insoluble on cooling

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7. Question 7 · Hard

   A urinometer calibrated at 20 °C reads 1.034 in a urine at 20 °C. The urine contains glucose 2 g/dL and protein 1 g/dL. Using corrections of 0.004 per g/dL of glucose and 0.003 per g/dL of protein, what is the corrected specific gravity?

   1. A1.023
   2. B1.045
   3. C1.031
   4. D1.026

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8. Question 8 · Medium

   Infrared spectroscopy is preferred to wet chemical spot tests for urinary calculus analysis mainly because it:

   1. AMeasures how radio-opaque the stone will be
   2. BIdentifies the crystalline compounds and their mixtures
   3. CWorks only on stones that dissolve fully in acid
   4. DDetects ions such as calcium and oxalate separately

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9. Question 9 · Medium

   Xanthochromia in the CSF supernatant, 12 hours after a sudden severe headache, mainly helps to:

   1. AConfirm bacterial meningitis before culture
   2. BMeasure CSF protein without a chemical test
   3. CSeparate subarachnoid haemorrhage from a traumatic tap
   4. DShow that the sample was not refrigerated

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10. Question 10 · Medium

    Uric acid stones are best prevented by keeping the urine:

    1. AHigh in calcium and oxalate
    2. BAcid, near pH 5.0
    3. CAlkaline, near pH 6.5
    4. DConcentrated and low in volume

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11. Question 11 · Hard

    A 70 kg man brings a 24-hour urine for protein. Volume 900 mL, urine creatinine 66 mg/dL, protein 20 mg/dL. Expected creatinine excretion for an adult man is about 20-25 mg/kg/day. What should the laboratory conclude?

    1. AThe collection is complete and valid
    2. BThe collection is probably incomplete
    3. CThe man has moderate proteinuria
    4. DThe creatinine shows renal failure

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12. Question 12 · Easy

    CSF sent for glucose should be tested within an hour or collected in fluoride because, if left standing:

    1. AGlucose diffuses out through the tube wall
    2. BWater evaporates and glucose rises falsely
    3. CCells and bacteria in it consume the glucose
    4. DGlucose is converted to protein by enzymes

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13. Question 13 · Hard

    A 30-year-old man from Malappuram has had headache and fever for three weeks, now with drowsiness and a sixth nerve palsy. CSF: clear, a fine web-like clot forms on standing, cells 220/µL (85% lymphocytes), protein 260 mg/dL (reference 15-45), glucose 28 mg/dL with plasma glucose 118 mg/dL, Gram stain negative. What is the most likely diagnosis?

    1. AViral meningitis
    2. BAcute bacterial meningitis
    3. CSubarachnoid haemorrhage
    4. DTuberculous meningitis

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14. Question 14 · Medium

    A man with azoospermia has a low semen volume and absent seminal fructose. This points to:

    1. AAbsent or blocked seminal vesicles or ejaculatory ducts
    2. BBlockage of the epididymis on one side
    3. CLow prostatic secretion of acid phosphatase
    4. DFailure of sperm production in the testes

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15. Question 15 · Easy

    In an adult, oliguria means a urine output of less than about:

    1. A100 mL per day
    2. B400 mL per day
    3. C1,000 mL per day
    4. D2,500 mL per day

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16. Question 16 · Medium

    A milky pleural fluid with a triglyceride of 260 mg/dL that clears little on centrifugation most likely indicates:

    1. AChylothorax from thoracic duct leakage
    2. BEmpyema with many pus cells
    3. CPseudochylous effusion from cholesterol
    4. DHaemothorax after chest injury

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17. Question 17 · Easy

    Struvite (magnesium ammonium phosphate) stones are typically linked with urinary infection by:

    1. AEscherichia coli
    2. BProteus mirabilis
    3. CStaphylococcus saprophyticus
    4. DEnterococcus faecalis

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18. Question 18 · Easy

    A positive cyanide-nitroprusside test on urine from a stone former suggests a stone of:

    1. AUric acid
    2. BXanthine
    3. CCalcium oxalate
    4. DCystine

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19. Question 19 · Easy

    Moderately increased albuminuria (microalbuminuria), an early sign of diabetic kidney disease, is a urinary albumin excretion of:

    1. A30-300 mg per day
    2. B300-3,000 mg per day
    3. COver 3,500 mg per day
    4. D1-30 mg per day

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20. Question 20 · Medium

    When CSF is tested for oligoclonal bands in suspected multiple sclerosis, a serum sample is run alongside because:

    1. ABands must be present in CSF but absent in serum
    2. BSerum supplies the protein standard for the gel
    3. CCSF alone has too little protein to give bands
    4. DBands in serum confirm multiple sclerosis

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21. Question 21 · Hard

    A 50-year-old man with type 2 diabetes gives a spot morning urine: albumin 60 mg/L and creatinine 120 mg/dL. What is his albumin-creatinine ratio and its category?

    1. A50 mg/g, moderately increased albuminuria
    2. B5 mg/g, normal albumin excretion
    3. C0.5 mg/g, normal albumin excretion
    4. D500 mg/g, severely increased albuminuria

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22. Question 22 · Medium

    In an oliguric adult, paired spot urine and plasma samples give a fractional excretion of sodium (FENa) below 1%. This most strongly suggests:

    1. AAcute tubular necrosis
    2. BAdvanced chronic kidney disease
    3. CA recent loop diuretic dose
    4. DPrerenal azotaemia

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23. Question 23 · Hard

    A 26-year-old woman has her third calcium-containing stone. Plasma: bicarbonate 16 mmol/L (22-28), chloride 112 mmol/L (98-107), potassium 3.1 mmol/L, anion gap normal. Fasting urine pH is 6.8 and stays above 5.5 after an acid load. Urine citrate is low. Which stone is she most likely forming?

    1. ACalcium phosphate
    2. BUric acid
    3. CMagnesium ammonium phosphate
    4. DCystine

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24. Question 24 · Medium

    A urine with a negative protein dipstick but a positive sulphosalicylic acid test in an elderly patient with bone pain suggests:

    1. ANormal urine with a faulty acid reagent
    2. BGlucose interfering with the acid test
    3. CA falsely positive dipstick from alkaline urine
    4. DBence Jones protein, which the dipstick misses

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25. Question 25 · Medium

    In the heat and acetic acid test for urinary protein, a few drops of acetic acid are added after boiling to:

    1. AMake Bence Jones protein redissolve
    2. BPrecipitate the protein that heat missed
    3. CDestroy any reducing sugar in the urine
    4. DDissolve phosphate turbidity while protein stays

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