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Urinary diversion: ileal conduit, neobladder and metabolic complications
After cystectomy urine is diverted to an ileal conduit (the commonest), an orthotopic neobladder or a reservoir with a catheterisable channel; the metabolic complication depends on the bowel segment — ileum and colon cause hyperchloraemic metabolic acidosis with hypokalaemia, jejunum causes hyponatraemia and hyperkalaemia, and stomach causes hypochloraemic alkalosis.
Why it matters in the exam
The exam asks about choosing the type of diversion, contraindications to a neobladder and the metabolic disorder of each segment. An ileal conduit (Bricker) is built from a 15 to 20 cm segment of ileum, about 15 cm from the ileocaecal valve, and the ureters are anastomosed to it. An orthotopic neobladder is joined to the urethra and allows voiding through the urethra, but needs reasonable renal and liver function, negative urethral margins, and a patient able to self-catheterise if needed. Contraindications: renal failure (eGFR below 35 to 40), liver disease, urethral tumour and inflammatory bowel disease involving the segment.
After resection of the terminal ileum, vitamin B12 deficiency (after years), bile salt diarrhoea and oxalate stones may follow. In a conduit or neobladder the bowel produces mucus that causes blockage and infection. Late complications: stricture at the ureter-bowel anastomosis (more common on the left), stomal stenosis or parastomal hernia, pyelonephritis, stones, and rupture of a neobladder or augmented bladder. In a patient with Crohn disease a colonic segment is preferred to ileum. Implanting the ureters into the colon (ureterosigmoidostomy) greatly raises the risk of bowel cancer at the anastomosis, so it requires yearly colonoscopy after 10 years.
The hyperchloraemic acidosis results from absorption of ammonium and chloride and secretion of bicarbonate by the bowel, and it is marked when renal function is poor and when urine dwells long in the reservoir. In a diverted patient who presents with confusion, hyperammonaemia must also be considered, especially with liver disease or infection with a urea-splitting organism. Treatment of the acidosis: bicarbonate or citrate, and good drainage of the reservoir.
Key points
- Ileal conduit — the commonest diversion.
- Ileum and colon — hyperchloraemic acidosis.
- Jejunum — hyponatraemia and hyperkalaemia.
- Stomach — hypochloraemic alkalosis.
- A neobladder needs renal function and negative urethral margins.
Summary table
| Bowel segment | Metabolic disorder | Note |
|---|---|---|
| Ileum | Hyperchloraemic acidosis, hypokalaemia | B12 deficiency and bile salt diarrhoea |
| Colon | Hyperchloraemic acidosis, hypokalaemia | Suits Crohn disease; ureterosigmoidostomy — cancer risk |
| Jejunum | Hyponatraemia, hypochloraemia, hyperkalaemia, acidosis | Almost never used |
| Stomach | Hypochloraemic alkalosis | Haematuria and dysuria |
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Sources
- EAU Guidelines on Muscle-invasive and Metastatic Bladder Cancer, 2025 edition — Urinary diversion after radical cystectomy
- Campbell-Walsh-Wein Urology, 12th edition (2020) — Use of Intestinal Segments in Urinary Diversion
- Campbell-Walsh-Wein Urology, 12th edition (2020) — Cutaneous Continent Urinary Diversion and Orthotopic Urinary Diversion
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.