In vitro dissolution of cystine urinary calculi

Dissolution of cystine urinary calculi was studied in vitro. Sodium hydroxide, acetylcysteine and tris(hydroxymethyl)aminomethane (tromethamine) were tested for effectiveness in dissolving cystine calculi. Calculi were mounted in a dissolution apparatus. Dissolution rates were calculated from the amount of cystine released into solution per unit time and were compared with linear regression techniques. Calculated dissolution rates of all the irrigating agents tested were similar at a pH of 7.5 and were significantly different at pH 10.0. The most effective agent in the promotion of cystine dissolution was 2 per cent acetylcysteine. Sprague-Dawley rats were used to test the effect of 2 per cent acetylcysteine, 0.3 molar tromethamine and 2 per cent acetylcysteine mixed with 0.3 molar tromethamine on the urothelium. A nephrostomy tube was placed in the left kidney of each rat. The kidneys were irrigated for 3 days with either 2 per cent acetylcysteine, 0.3 molar tromethamine or 2 per cent acetylcysteine mixed with 0.3 molar tromethamine. The rats then were sacrificed at various intervals after infusion. Irrigation with 2 per cent acetylcysteine at a pH of 10 caused an acute inflammatory response at 3 days that was healed almost completely in 4 weeks. The addition of tromethamine to the acetylcysteine did not prevent the inflammatory response.