Formation of calculi within orthotopic urinary reservoirs is a relatively uncommon late complication. While there is only a reported incidence of 0.3% in ileal neobladders, the rate of stone formation can range from 11 to 27% in some of the common catheterizable urinary diversion channels[7, 8].
The underlying etiopathogenetic factors are multiple and include the mucus production of bowel mucosa, the presence of urine infected by urease-producing germs that alkalinize the urine, metabolic acidosis from ammonia absorption by urinary diversion, leading to hypercalciuria,
hypocitraturia, hyperoxaluria, hyperuricosuria, and hyperphosphaturia, which can all contribute to increased risk of stone formation. Furthermore, the presence of chronic urinary retention and subsequent self-catheterisation promotes the stasis of lithogenic factors and introduction of microbes within the urinary diversion, respectively. Finally, even foreign bodies (as sutures in non-absorbable material, surgical staples) can act as a nidus for stone formation.
A stone in the neobladder may be asymptomatic and can be discovered as an incidental finding on a radiological investigation. However, when symptoms occur they may include severe lower abdominal pain, dysuria, haematuria or lower urinary tract symptoms. Without appropriate follow-up, these can grow to remarkable dimensions as illustrated in this case.
The main treatment for small stones in the neobladder is represented by endoscopic, percutaneous, or a combined approach. For the large stones in the neobladder, the main treatment is the cystolithotomy with open access for complete stone clearance as demonstrated by our case or endoscopic fragmentation which may require multiple treatments.
Even after clearing all the bladder stones, recurrence is still inevitable. Urolithiasis after urinary diversion poses a significant surgical challenge due to altered anatomy and carries a recurrence rate as high as 63% within 3–5 years after the initial intervention. Prevention is one of the most effective measures to deal with this complication. Maintaining adequate intake of fluids, daily irrigation of the pouch with normal saline, voiding by clock or double voiding, performance of regular clean intermittent catheterization in those who void ineffectively, and antibiotic prophylaxis in those who develop recurrent urinary tract infections are the recommended preventive measures.
The post-operative course has been characterized by a leak of neobladder cystotomy repair site and wound infection in this case, which was resolved after bilateral nephrostomy and secondary cystic suture repair with cystostomy. The reason for a leak of neobladder cystotomy repair site is still unknow,but we suspect that it was closely related to poor intraoperative wound protection and the retention of bacterial biofilm and debris on the stone surface in the incision. In addition, Unlike the blood supply to the normal bladder, the blood supply to the ONB is poor and very susceptible to ischemic necrosis, thus making healing at the bladder repair site very slow.
We learnt some lessons from this case. It is critical to be adequately prepared before conducting an open cystotomy on a patient with large stones in the neobladder. To begin, preoperative anti-infection using sensitive antibiotics, as well as bladder irrigation and drainage to treat pre-existing urinary tract infections is required. Second, blood glucose should be regulated as much as possible in diabetic patients to minimize high risk factors for postoperative infection. Finally, during surgery, precautions should be made to protect the neobladder incision and blood supply against infection by infectious stones. Tension-free suturing of the neobladder incision should also be a priority. Additionally, postoperatively post-pubic drainage tubes, cystostomy tubes, and urinary catheters should be left in place as much as possible to allow for proper urine drainage and to avoid tension in the neobladder.
When a patient has a leak at the cystotomy repair site following an open neocystotomy for lithotripsy and the leak is unlikely to cure on its own with conservative therapy, prompt and correct treatment is required. To begin, a double nephrostomy is performed as soon as feasible in order to drain daily urine output and promote an open effect on the neobladder. Second, with an indwelling cystostomy, adequate drainage is essential. Finally, mucus overproduction by the gut may have a role in the creation of calculi and infection in ONB, resulting in the adherence of tiny crystals and the formation of bacterial biofilms, which are not favourable to the repair of bladder leaks. As a result, flushing the urine bowel fluid and keeping the drainage open is critical.