Chronic laxative abuse can result in the formation of which of the following renal stones?
Correct Answer: Ammonium urate
Description: Ans. b. Ammonium urateTYPES OF NEPHROLITHIASISTypeFrequencyEtiology and characteristicsTreatmentCalciumoxalate/calciumphosphate83%The most common causes are idiopathichypercalciuria and1deg hyperparathyroidism. Canalso see in fat malabsorption(| oxalate absorption) Alkaline urine.RadiopaqueHydration, dietary sodium and protein restriction, thiazide diuretics. Do not | calcium intake (can leadto hyperoxaluria and an | risk of osteoporosis)Struvite(Mg-NH4 -PO4 )or "triple phosphate"9%Associated with urease producing organisms (e.g. Proteus). Form staghorn calculi. Alkaline urine. RadiopaqueHydration; treat UTI if present; surgical removal of staghorn stoneUric acid7%Associated with gout, xanthine oxidase deficiency, and high purine turnover states (e.g. chemotherapy). Acidic urine (pH < 5.5). Radiolucent on plain film, but detectable with CTHydration; alkalinize urine with citrate, which is converted to HC03- in the liver; dietary purine restriction and allopurinolCystine1%Due to a defect in renal transport of certain amino acids (COLA--cystine, ornithine, lysine, and arginine). Hexagonal crystals. Urinary cyanide nitroprusside test. RadiopaqueHydration, dietary sodium restriction, alkalinization of urine, penicillamineIndinavirRarePatients will be on protease inhibitors or HIV. Stones consist of precipitated indinavir. Radiolucent on KUB and CTHydration, surgical removal.AmmoniumUrateRareTypically occurs in the setting of chronic diarrheal state (Inflammatory bowel disease, laxative abuse). The gastrointestinal losses of fluids, sodium and potassium content, leaving ammonium (excreted in response to gastrointestinal alkali loss) as the major cation in urine to bind urate and precipitated as ammonium urateAntibiotics, in case of urinary tract infection, discontinuation of offending agent like laxative abuse, volume repletion and potassium supplementation as neededCRYSTALS FOUND IN NEPHROLITHIASISTypeShapeFigureCalcium oxalateEnvelope-shapedStruvite(Mg-NH4-P04)Coffin lid-shapedUric acidRhomboid shapedCystineHexagonal shaped
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