Laxative Abuse as a Cause for Ammonium Urate Renal Calculi

Abstract

Nine women with laxative abuse and predominantly ammonium urate renal calculi underwent metabolic studies to identify common chemical abnormalities and determine pathophysiology. The 24-hour urine studies demonstrated marked decreases in volume (902 cm.3), sodium (28 mEq.), citrate (116 mg.) and potassium (21 mEq.). A significant elevation in ammonium urate supersaturation was found compared to control subjects when studied by the computer model EQUIL 2. Of the patients 7 had 1 or more urine specimens positive for phenolphthalein. Gastrointestinal loss of fluid and electrolytes allowed for chronic extracellular volume depletion. Intracellular acidosis was present as judged by low urinary citrate and potassium. The fact that the ion product for ammonium urate is increased significantly compared to controls reflects the stated pathophysiological changes. Laxative abuse should be suspected whenever a woman has an ammonium urate renal calculus in sterile urine.

Pathophysiological and Physicochemical Basis of Ammonium Urate Stone Formation in Dolphins

“…For comparison, SI NH 4 U in one study of non-stone forming humans fed a standard metabolic diet was 1.5±0.9 (unpublished data). The preponderance of urinary ammonium over other urinary cations in the study dolphins is analogous to conditions reported in humans with NH 4 U stones 4-6, 24 .…”

Complication of short bowel syndrome: An infant with short bowel syndrome developing ammonium acid urate urolithiasis

“…Urinary ammonium and urate concentration should be high in order for AAU stones to develop. In addition, urine pH should be between 6.0 and 6.3 10 . Ammonia is produced in the proximal tubular cells in kidney.…”

Postrenal Failure due to Urinary Stones Associated with Acute Viral Gastroenteritis: Three Case Reports

“…The low urinary sodium owing to severe diarrhea allows for the coupling of urate with the abundant ammonium ion. This coupling, combined with at least a transient state of ammonium urate supersaturation, promotes the formation of AAU stones [9]. This mechanism is similar to that for the formation of stones induced by rotavirus in infants.…”