Physical examination of urine

10 DOH Abu Dhabi (HAAD) lab licensing practice questions on Physical examination of urine, part of Urinalysis and Body Fluids. The first 10 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 · Hard

   A 61-year-old man with melanoma that has spread to his liver is admitted for pain control. His urine is pale yellow and clear when passed, but a sample left in an open cup on the bench turns brown-black over 6 hours. Results on the fresh urine: SG 1.016, pH 6.0, blood negative, bilirubin negative, glucose negative, and no red cells are seen. A copper reduction tablet test (Clinitest) is negative. Ferric chloride added to the darkened urine gives a gray-black precipitate. His only medicines are morphine and paracetamol. The dark color is most likely due to:

   1. AMelanogen oxidizing to melanin
   2. BHomogentisic acid oxidizing in air
   3. CHemoglobin oxidizing to methemoglobin
   4. DPorphobilinogen forming porphobilin

   Show answerHide answer

   Answer: A · Melanogen oxidizing to melanin

   Melanoma cells can release melanogen, a colorless precursor that oxidizes to melanin when urine stands in air, so a urine that looks normal when passed darkens to brown-black. Ferric chloride gives a gray-black precipitate with melanin. Homogentisic acid in alkaptonuria also darkens on standing, but it reduces copper, so Clinitest would be positive, and ferric chloride gives only a fleeting blue color. Porphobilin gives a port-wine red color, and methemoglobin needs blood in the urine, which the negative blood pad and the absence of red cells rule out. Before reporting, ask about drugs that darken urine on standing, such as levodopa, methyldopa and metronidazole.

   • B: Homogentisic acid reduces copper, so Clinitest would be positive, and ferric chloride turns it a fleeting blue.
   • C: The blood pad is negative and no red cells are seen, so there is no hemoglobin to oxidize.
   • D: Porphobilin turns urine port-wine red, not brown-black.

2. Question 2 · Medium

   What can falsely raise a refractometer reading of urine specific gravity?

   1. ASmall differences in room temperature
   2. BAscorbic acid from vitamin supplements
   3. CConjugated bilirubin in liver disease or obstruction
   4. DGlucose, protein or radiographic contrast media

   Show answerHide answer

   Answer: D · Glucose, protein or radiographic contrast media

   Refractometry measures all dissolved substances, including large molecules. High glucose, protein or X-ray contrast media raise the reading without reflecting the kidney's concentrating ability. Corrections can be made for glucose and protein. Reagent strip specific gravity measures ions and is not affected by glucose or contrast.

   • A: Modern refractometers compensate for temperature.
   • B: Ascorbic acid does not meaningfully raise specific gravity.
   • C: Bilirubin does not meaningfully raise specific gravity.

3. Question 3 · Easy

   In a healthy adult, the specific gravity of random urines usually falls within:

   1. A1.003 to 1.035
   2. B1.020 to 1.060
   3. C1.010 to 1.050
   4. D1.000 to 1.010

   Show answerHide answer

   Answer: A · 1.003 to 1.035

   Depending on fluid intake, a healthy kidney can dilute urine to about 1.003 and concentrate it to about 1.035, a little more after fluid restriction; sources differ by a few thousandths. A specific gravity fixed near 1.010, that of the glomerular filtrate, means the tubules are neither diluting nor concentrating. A refractometer reading above about 1.040 is beyond what the kidney can produce and suggests radiographic contrast or another high-molecular-weight substance.

   • B: A healthy kidney regularly produces urine below 1.020 after drinking.
   • C: Values above about 1.040 are beyond normal renal concentrating ability.
   • D: 1.000 to 1.010 covers only dilute urine; most urines are more concentrated.

4. Question 4 · Hard

   A man who grew up where lymphatic filariasis is common passes milky white urine. It does not clear with dilute acetic acid or on warming to 60 °C, few cells are seen, and it clears after shaking with ether. The cloudiness is most likely due to:

   1. AAmorphous phosphates
   2. BLymph fat (chyluria)
   3. CAmorphous urates
   4. DPus cells (pyuria)

   Show answerHide answer

   Answer: B · Lymph fat (chyluria)

   Clearing tests narrow down the cause of milky urine: phosphates dissolve in acid, urates dissolve on warming, and cells and bacteria do not dissolve. Turbidity that clears only with a lipid solvent such as ether points to fat, and in someone from a filariasis area this suggests chyluria, where lymph leaks into the urinary tract after lymphatic obstruction by Wuchereria bancrofti. A fat stain such as Sudan III or Oil Red O on the sediment can confirm the lipid. Trauma and tumors that block lymph drainage are other causes.

   • A: Phosphates would have cleared with dilute acetic acid.
   • C: Urates would have cleared on warming to 60 °C.
   • D: Pus cells do not dissolve in ether and would be seen in large numbers.

5. Question 5 · Hard

   A urine reads above the refractometer scale. One part urine is mixed with three parts deionized water, and the diluted sample reads 1.012. What is the specific gravity of the undiluted urine?

   1. A1.012
   2. B1.036
   3. C1.003
   4. D1.048

   Show answerHide answer

   Answer: D · 1.048

   Mixing 1 part urine with 3 parts water is a 1 in 4 dilution, so the dilution factor is 4. Only the part after the decimal point is multiplied: 0.012 x 4 = 0.048, giving 1.048. A value this high is beyond the kidney's concentrating ability (about 1.040) and suggests radiographic contrast or another high-molecular-weight solute, so check the history or measure osmolality.

   • A: 1.012 is the diluted reading, not corrected for the dilution.
   • B: 1.036 uses a factor of 3; 1 part plus 3 parts is a 1 in 4 dilution.
   • C: 1.003 comes from dividing by the dilution factor instead of multiplying.

6. Question 6 · Easy

   When a urine refractometer is checked with distilled or deionized water, it should read:

   1. A1.003
   2. B1.022
   3. C1.000
   4. D1.010

   Answer and explanation in LearnFree account

7. Question 7 · Medium

   A 45-year-old man with thirst and frequent urination passes nearly colorless urine with a refractometer specific gravity of 1.035. Which finding would best explain this combination?

   1. AHeavy glycosuria
   2. BLack of ADH action
   3. CHigh water intake
   4. DConjugated bilirubin

   Answer and explanation in LearnFree account

8. Question 8 · Easy

   A man who started tuberculosis treatment last week notices that his urine has turned orange-red. Which drug is most likely responsible?

   1. AIsoniazid
   2. BPyrazinamide
   3. CEthambutol
   4. DRifampicin

   Answer and explanation in LearnFree account

9. Question 9 · Medium

   A clear red urine gives a negative blood pad, and no red cells are seen. Which cause fits best?

   1. AIntact red cells
   2. BBeetroot pigment
   3. CMyoglobin
   4. DFree hemoglobin

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    A white, cloudy urine with a pH of 7.5 clears when a few drops of dilute acetic acid are added. The cloudiness was most likely due to:

    1. AAmorphous phosphates
    2. BWhite blood cells
    3. CAmorphous urates
    4. DLipid droplets

    Answer and explanation in LearnFree account