Which one of the following is radiolucent stone: September 2007

Ans. C: Uric acid Types of Kidney Stones Calcium Stones (as Ca-oxalate Stones): are usually combined with oxalate to form Calcium oxalate stone (black, grey, or white color). Calcium phosphate stones are next most common, affected by renal tubular acidosis. They are typically small less than 1 cm. They are opaque on x-ray. Causes: Hyperparathyroidism, high Calcium, Hyperoxaluria Uric Acid Stones are associated with hyperuricosuria in -25%. They are smooth, round, yellow-orange in color, and nearly x-ray transparent unless mixed with struvite or calcium stones. Types I & II primary hyperoxaluria are rare genetic defects that can casue urate stones. Uric acid stones are unique in that they can be managed medically. Causes: Hyperuricosuria, low urine pH Struvite (magnesium-ammoionium phosphate) and carbonate apatite stones are associated with Infection. Infection stones are made of struvite, tend to fill the entire collecting system (staghorn calculi), and are unlikely to pass into the ureter. Causes: Urease producing bacteria as: Proteus, Haemophilus, Ureaplasma urealyticum, and Klebsiella. Cystine stones: comprise about 1% of all kidney stones. Causes: cystinuria