Renal stones

Question 1

Hypercalciuria is a major risk factor
Hyperoxaluria may also increase risk
Hypocitraturia increases risk because citrate forms complexes with calcium making it more soluble
Stones are radio-opaque
Accounts for 85% of calculi

Answer 1

Calcium oxalate stones

Question 2

Inherited recessive disorder of transmembrane cystine transport leading to decreased absorption of cystine from intestine and renal tubule
Multiple stones may form
Relatively radiodense because they contain sulphur
Accounts for 1% of calculi

Answer 2

Cystine stones

Question 3

Product of purine metabolism
May precipitate when urinary pH low
May be caused by diseases with extensive tissue breakdown e.g. malignancy
More common in children with inborn errors of metabolism
Radiolucent
Accounts for 5-10% stones

Answer 3

Uric acid

Question 4

May occur in renal tubular acidosis, high urinary pH increases supersaturation of urine with calcium and phosphate
Renal tubular acidosis types 1 and 3 increase risk of stone formation
Radio-opaque stones
Accoutns for ~10% stones

Answer 4

calcium phosphate

Question 5

Stones formed from magnesium, ammonium and phosphate
Occur as a result of urease producing bacteria
=> associated with chronic infections
Under the alkaline conditions produced, the crystals can precipitate
Slightly radio-opaque

Answer 5

Struvite stones

Question 6

which renal stones cause acidic urine (pH ~5.5)?

Answer 6

uric acid

Question 7

Which renal stones cause alkaline urine (pH ~7.2)

Answer 7

Struvite