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Ileal Conduit Acidosis — SCE Medical Oncology MCQ

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HardUrological CancersIleal Conduit AcidosisSCE Medical Oncology

A 62-year-old man with high-grade urothelial carcinoma of the bladder undergoes radical cystectomy with ileal conduit urinary diversion. Post-operatively, he develops metabolic hyperchloraemic acidosis (pH 7.28, HCO3 16, Cl- 118). What is the cause?

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Correct answer: C — Ileal ammonium and chloride absorption causing systemic bicarbonate loss

Urine contact with ileal mucosa promotes ammonium and chloride absorption with bicarbonate loss, producing a hyperchloraemic metabolic acidosis. Ileal sodium absorption and bicarbonate retention causing systemic chloride loss: that exchange would not produce the observed hyperchloraemic acidosis. Ileal potassium secretion and lactate absorption causing a raised anion gap: the measured biochemical pattern is a normal-anion-gap process. Ileal phosphate absorption and ammonium secretion causing respiratory acidosis: respiratory acidosis is not generated by urinary bowel electrolyte exchange. Ileal urate absorption and sulphate retention causing uraemic acidosis: uraemic acid retention would require substantial renal failure and a different mechanism.

Reference: EAUN guideline on incontinent urinary diversion (Published 2010; mechanism remains current): https://nurses.uroweb.org/wp-content/uploads/0628EAUN_Guideline_2010_HR.pdf; NICE NG2 bladder cancer: recommendations (Current NICE recommendations, accessed July 2026): https://www.nice.org.uk/guidance/ng2/chapter/1-Recommendations