Objective: To evaluate the crystalline composition of encrustations on double-J ureteric stents in order to prevent their formation on the base of urolithiasis prophylaxis. Patients: 40 patients had a polyurethane double-J ureteric stent inserted between June 1994 and March 1995. Group 1 comprised 22 stone formers whose stents were placed in support of endourological treatment or extracorporeal shock wave lithotripsy of renal or ureteric calculi. Group 2 comprised 18 patients whose stents were inserted for advanced and obstructive malignancy (n = 8) or as an adjunct to reconstructive surgery or endourological techniques (n = 10). After removal, stents were examined for encrustation and obstruction. A biochemical semiquantitative analysis was performed for deposits > 5 mg, and smaller sediments were examined with a polarizing optical microscope. Results: The incidence of encrustation was significantly higher (p = 0.009) for stone formers. In addition, in this group indwelling times of encrusted and obstructed stents were significantly shorter (p = 0.03 and 0.02, respectively). No particular relationship was found between the incidence of encrustation and indwelling times for stone formers. Conversely, for patients without urolithiasis, indwelling times were significantly longer for encrusted or obstructed stents than for unaffected ones (p = 0.05 and 0.02, respectively). Biochemical and optical analyses of encrustations mainly revealed calcium oxalate, calcium phosphate and ammonium magnesium phosphate. Calcium oxalate was the main crystalline phase, especially in the absence of urinary infection. Conclusion: Calcium oxalate represents the principal component of double-J ureteric stent encrustations. Thus, prophylaxis of encrustation may consist of preventive measures usually applied in cases of recurrent idiopathic calcium oxalate urolithiasis.
SummaryThree patients with normal renal function developed acute renal failure between the ninth and twenty-seventh days of combined gentamicin and cephalothin therapy. The dose of gentamicin (4-6 mg/kg/day) was in the normal range, but that of cephalothin (180 mg/kg/day) was abnormally high. The nephropathy was of the tubularinterstitial type and the clinical picture similar to that seen in acute drug-induced nephropathies. Frusemide was given only after the onset of renal failure. In these three patients the high intravenous doses of cephalothin combined with gentamicin were probably nephrotoxic.
Stone depth has a significant influence on treatment outcome after piezoelectric SWL for both renal and ureteral calculi. We recommend particular attention be given to corpulent patients presenting with ureteral stones.
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