A renal stone from a 38-year-old woman with recurrent urinary infections gives: effervescence with acid positive; calcium, magnesium, ammonium and phosphate positive; oxalate, uric acid and cystine negative. Which stone is it most likely to be?

Struvite with carbonate apatite

Brushite (calcium hydrogen phosphate)

Urinary and biliary calculi

18 Kerala PSC Lab Technician Gr II practice questions on Urinary and biliary calculi, part of Biochemistry. The first 18 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
Which urinary calculus is radiolucent on a plain abdominal X-ray?
1. ACalcium oxalate
2. BUric acid
3. CStruvite
4. DCalcium phosphate
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Answer: B · Uric acid
Pure uric acid stones contain no calcium and absorb X-rays poorly, so they do not show on a plain film. They are seen on ultrasound or CT. They form in persistently acid urine and can often be dissolved by making the urine alkaline. Calcium oxalate and calcium phosphate stones are dense and radio-opaque.
- A: Calcium oxalate stones are dense and radio-opaque.
- C: Struvite stones are radio-opaque and often staghorn-shaped.
- D: Calcium phosphate stones are strongly radio-opaque.
Question 2 · Easy
Black pigment gallstones, seen in chronic hemolysis such as sickle cell disease, consist mainly of:
1. ACalcium oxalate
2. BMagnesium ammonium phosphate
3. CCholesterol monohydrate
4. DCalcium bilirubinate
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Answer: D · Calcium bilirubinate
Chronic hemolysis raises the bilirubin in bile, and the unconjugated bilirubin precipitates with calcium as polymerized calcium bilirubinate. These black stones form in sterile gallbladder bile. Brown pigment stones form in infected bile ducts, where bacterial enzymes deconjugate bilirubin. Cholesterol and mixed stones are the other main types of gallstone.
- A: Calcium oxalate is a urinary stone, not a gallstone.
- B: Magnesium ammonium phosphate forms urinary infection stones.
- C: Cholesterol is the main component of yellow cholesterol stones.
Question 3 · Medium
In the chemical analysis of a urinary calculus, a yellow precipitate with ammonium molybdate in nitric acid indicates:
1. APhosphate
2. BOxalate
3. CCarbonate
4. DUric acid
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Answer: A · Phosphate
Phosphate forms yellow ammonium phosphomolybdate when warmed with ammonium molybdate in nitric acid. It is present in calcium phosphate and struvite stones. Other spot tests are effervescence with acid for carbonate, decolorization of permanganate for oxalate and the murexide test for uric acid. Infrared spectroscopy is now preferred, because spot tests miss minor components of mixed stones.
- B: Oxalate is shown by decolorizing acidified permanganate.
- C: Carbonate is shown by effervescence with dilute acid.
- D: Uric acid is shown by the murexide test.
Question 4 · Hard
A renal stone from a 38-year-old woman with recurrent urinary infections gives: effervescence with acid positive; calcium, magnesium, ammonium and phosphate positive; oxalate, uric acid and cystine negative. Which stone is it most likely to be?
1. AStruvite with carbonate apatite
2. BCalcium oxalate with uric acid
3. CBrushite (calcium hydrogen phosphate)
4. DCystine with calcium phosphate
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Answer: A · Struvite with carbonate apatite
Effervescence shows carbonate, and with calcium and phosphate this means carbonate apatite. Magnesium, ammonium and phosphate together mean struvite (magnesium ammonium phosphate). This mixture is the infection stone, formed when urease-producing bacteria such as Proteus split urea, making the urine alkaline and rich in ammonia. Brushite contains no magnesium or ammonium, and the negative oxalate, uric acid and cystine tests rule out the other stones.
- B: Oxalate and uric acid tests were both negative.
- C: Brushite contains no magnesium, ammonium or carbonate.
- D: The cystine test was negative.
Question 5 · Medium
Cholesterol gallstones form when bile is supersaturated with cholesterol relative to its content of:
1. ABile salts and lecithin
2. BBicarbonate and water
3. CMucin and protein
4. DBilirubin and calcium
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Answer: A · Bile salts and lecithin
Cholesterol is insoluble in water and is held in solution in bile by mixed micelles of bile salts and lecithin (phospholipid). When cholesterol is in excess, as in obesity, high estrogen or rapid weight loss, or bile salts are too few, cholesterol crystals separate out. Gallbladder stasis and mucin then help the crystals grow into stones. Cholesterol stones are pale yellow and usually radiolucent.
- B: Bicarbonate and water do not dissolve cholesterol.
- C: Mucin helps crystals grow but does not keep cholesterol dissolved.
- D: Bilirubin and calcium form pigment stones.
Question 6 · Medium
In calculus analysis, the powder is evaporated with nitric acid and ammonia is then added. A purple colour (murexide test) shows:
1. AUric acid
2. BPhosphate
3. COxalate
4. DCystine
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Question 7 · Hard
A 26-year-old woman has recurrent kidney stones. Serum bicarbonate is 15 mEq/L with a normal anion gap, yet her early-morning urine pH is repeatedly 6.8. Stone analysis: calcium and phosphate positive, slight effervescence with acid; oxalate, magnesium, ammonium and uric acid negative. Which stone and cause best fit?
1. ACalcium phosphate, distal renal tubular acidosis
2. BUric acid, gout with acid urine
3. CCalcium oxalate, primary hyperoxaluria
4. DStruvite, urease-producing infection
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Question 8 · Medium
A light, pale-yellow gallstone dissolves in hot chloroform, and the extract turns green with the Liebermann-Burchard reagent. The stone is mainly:
1. ACalcium carbonate
2. BCalcium bilirubinate
3. CCalcium phosphate
4. DCholesterol
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Question 9 · Easy
In stone analysis, which reagent gives a white precipitate with calcium?
1. AAmmonium molybdate
2. BNessler's reagent
3. CAmmonium oxalate
4. DTitan yellow
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Question 10 · Easy
The most common type of urinary calculus is:
1. ACalcium oxalate
2. BStruvite
3. CCystine
4. DUric acid
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Question 11 · Easy
Struvite stones form in alkaline urine infected with urea-splitting bacteria, most often:
1. AStreptococcus agalactiae
2. BEscherichia coli
3. CEnterococcus faecalis
4. DProteus mirabilis
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Question 12 · Hard
A 10-year-old boy has a second kidney stone; his brother has had stones too. His urine shows flat hexagonal crystals and a positive cyanide-nitroprusside test. Which other amino acids are expected in excess in his urine?
1. ALeucine, isoleucine and valine
2. BGlycine and proline
3. CPhenylalanine and tyrosine
4. DOrnithine, lysine and arginine
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Question 13 · Easy
Recurrent calcium stones with persistently high serum calcium and low phosphate suggest:
1. AUrinary infection
2. BPrimary hyperparathyroidism
3. CCystinuria
4. DGout
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Question 14 · Easy
In stone analysis, Nessler's reagent is used to detect:
1. AMagnesium
2. BCystine
3. CCalcium
4. DAmmonium
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Question 15 · Medium
Which urine condition most favours uric acid stones?
1. APersistently acid urine
2. BUrine with high citrate
3. CVery dilute urine
4. DPersistently alkaline urine
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Question 16 · Easy
In stone analysis, decolourisation of potassium permanganate in dilute sulphuric acid indicates:
1. APhosphate
2. BCarbonate
3. COxalate
4. DUric acid
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Question 17 · Hard
A 40-year-old man had part of his ileum removed for Crohn disease. He now passes a stone that is calcium positive, decolourises acidified permanganate, and is negative for carbonate, phosphate, urate and ammonium. Which stone and cause fit best?
1. ACalcium phosphate from renal tubular acidosis
2. BCalcium oxalate from enteric hyperoxaluria
3. CUric acid from low urine pH
4. DStruvite from urinary infection
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Question 18 · Medium
Brown pigment gallstones that form within the bile ducts are mainly linked to:
1. AChronic hemolysis
2. BBiliary infection
3. CObesity and estrogen
4. DHyperparathyroidism
Answer and explanation in LearnFree account

Urinary and biliary calculi

Which urinary calculus is radiolucent on a plain abdominal X-ray?

Black pigment gallstones, seen in chronic hemolysis such as sickle cell disease, consist mainly of:

In the chemical analysis of a urinary calculus, a yellow precipitate with ammonium molybdate in nitric acid indicates:

A renal stone from a 38-year-old woman with recurrent urinary infections gives: effervescence with acid positive; calcium, magnesium, ammonium and phosphate positive; oxalate, uric acid and cystine negative. Which stone is it most likely to be?

Cholesterol gallstones form when bile is supersaturated with cholesterol relative to its content of:

In calculus analysis, the powder is evaporated with nitric acid and ammonia is then added. A purple colour (murexide test) shows:

A light, pale-yellow gallstone dissolves in hot chloroform, and the extract turns green with the Liebermann-Burchard reagent. The stone is mainly:

In stone analysis, which reagent gives a white precipitate with calcium?

The most common type of urinary calculus is:

Struvite stones form in alkaline urine infected with urea-splitting bacteria, most often:

A 10-year-old boy has a second kidney stone; his brother has had stones too. His urine shows flat hexagonal crystals and a positive cyanide-nitroprusside test. Which other amino acids are expected in excess in his urine?

Recurrent calcium stones with persistently high serum calcium and low phosphate suggest:

In stone analysis, Nessler's reagent is used to detect:

Which urine condition most favours uric acid stones?

In stone analysis, decolourisation of potassium permanganate in dilute sulphuric acid indicates:

A 40-year-old man had part of his ileum removed for Crohn disease. He now passes a stone that is calcium positive, decolourises acidified permanganate, and is negative for carbonate, phosphate, urate and ammonium. Which stone and cause fit best?

Brown pigment gallstones that form within the bile ducts are mainly linked to: