Concrement formation and urease‐induced crystallization in urine from patients with continent ileal reservoirs

Abstract

Objectives To study the relationship between urinary tract infection, urine composition and concrement formation in patients with continent ileal reservoirs for urinary diversion. Patients and methods The study comprised 27 patients (seven men and 20 women, mean age 47 years, range 23–76) with continent ileal reservoirs who were followed for a mean of 67 months (range 13–146) by annual reservoiroscopy, intravenous urography and urine culture; at the final follow‐up, a sample of their morning urine was analysed for a range of compounds and the number and size of any particles present or produced in response to incubation with urease. Results The presence of urease‐producing bacteria was associated with the formation of concrement. However, a few patients in whom an infection with urease‐producing organisms was not detected also formed concrement. Urine from those patients forming stones tended to have a high calcium and a low citrate concentration. After incubation with urease, significantly more and larger particles were formed in the urine from stone formers. There was a strong correlation (r=0.8) between urinary calcium content and urinary pH when the urease‐induced precipitation commenced, and between urinary calcium and the size and volume of the crystals developed (r=0.9) after 4 h of incubation. Conclusions There are many factors which might influence the formation of concrement, e.g. outflow conditions, the presence of staples or infection in the reservoir, and the composition of the urine is also important. It thus appears appropriate to determine if measures to reduce urinary calcium and increase urinary citrate can decrease the episodes of stone formation in those patients with continent ileal reservoirs for urinary diversion who frequently form stones.

Metabolic and functional consequences of urinary reconstruction with bowel

“…Risk factors include the presence of foreign material (e.g. staples), recurrent and chronic infection, abnormalities of the composition of the urine, mucus production, urinary stasis and noncompliance with irrigation and catheterization regimens [38–43]. Outflow conditions may be important, as stones formed more commonly after bladder outlet resistance procedures and in patients with catheterizable abdominal wall stomas in a study of 286 children after bladder augmentation [38].…”

“…After incubation with urease, significantly more and larger particles were observed in the urine from stone formers. There was a strong correlation between urinary calcium content and urinary pH when the urease‐induced precipitation commenced [41]. Osther et al [42] compared biochemical and physicochemical properties of urine from patients with ileal‐urethral Kock reservoirs, and normal men who served as controls.…”

“…Depending on stone size, trans‐stomal pouchoscopic ultrasonic lithotripsy, prone position ESWL, percutaneous approaches and open surgery have been used successfully, alone or combined, for fragmentation and clearance [38–42]. Daily irrigations to clear mucus and crystals, as well as complete emptying of the reservoir, may be important in preventing stone formation.…”

Continent urinary tract reconstruction – the Lund experience

“…We are not using staples for neobladder construction and for the Lundiana pouch they are placed on the outside of the bowel, but the incidence of stones was still 10% in both procedures. In addition to foreign material, residual urine, bacteria, hypercalciura and hypocitraturia seem to be important [10,13], and measures to prevent stone formation are avoiding staples and emptying the reservoir completely. Incomplete emptying and bacteriuria, with or without CISC, were possibly the main risk factors among the present patients.…”

Endoscopic management of lower ureteric stone after ureterosigmoidostomy

“…There was a strong correlation between urinary calcium content and urinary pH when the urease-induced precipitation commenced. 9 Thus oral citrate supplementation and acetohydroxamic acid, a urease inhibitor, have been suggested for prophylaxis.…”