Papers

Lithium toxicity after urinary diversion with ileal conduit

A Alhasso,  A A Bryden,  D Neilson. 

Blackburn Royal Infirmary, Blackburn, Lancashire BB2 3LR

A 71 year old woman underwent urinary diversion with ileal conduits for severe stress incontinence that had been refractory to previous treatments. She had longstanding bipolar affective disorder that was well controlled with lithium carbonate 600 mg daily. The lithium was discontinued preoperatively and recommenced at the original dose 48 hours postoperatively. Ten days later, after removal of the ureteric stents, she developed progressive confusion, dysarthria, nausea, and ataxia; her serum lithium concentration was increased at 2.1 mmol/l (treatment range 0.4-1.0 mmol/l). Lithium was discontinued and she made a full recovery with intravenous hydration alone. Subsequent dose titration required a reduction of lithium to 200 mg daily. This observation has been reported to the Committee on Safety of Medicines and the drug's manufacturer.

Metabolic complications (mainly hyperchloraemia and hypokalaemia) are well recognised after urinary diversion but infrequently require specific treatment.¹ Problems arising from drug reabsorption are rare but have been reported for phenytoin and methotrexate. ^{2 3} Lithium has a narrow treatment ratio, with toxicity occurring at only twice the upper limit of the treatment range. Steady serum concentrations occur as early as 2-5 days after starting treatment.⁴ About 95% of lithium is eliminated unchanged in urine, and it is readily absorbed by enteral mucosa.

The delayed toxicity in this patient was probably related to the ureteric stents: on their removal all urine drained through the ileal conduit, resulting in reabsorption of lithium. We advise that such patients are discharged only after stable serum lithium concentrations are re-established after stent removal. Additionally, owing to the long term changes associated with urinary diversion,⁵ continued vigilance is essential.

Any surgery resulting in exposure of bowel to urine should be taken into account when considering and monitoring pharmacotherapy, particularly of drugs excreted in a bioavailable form.

References

1.	Mills R, Studer U. Metabolic consequences of continent urinary diversion. J Urol 1999; 161: 1057-1066[CrossRef][Medline].
2.	Savarirayan F, Dixey G. Syncope following ureterosigmoidoscopy. J Urol 1969; 101: 844-845[Medline].
3.	Bowyer G, Davies T. Methotrexate toxicity associated with ileal urinary diversion. Br J Urol 1987; 60: 592[Medline].
4.	Hallworth M, Capps N, eds. Lithium. Therapeutic drug monitoring and clinical biochemistry. London: ACB Venture, 1993:65-69.
5.	De Kernion J, Trapasso JG. Urinary diversion and continent reservoir conduits. In: Gillenwater J, Grayhack J, Howard S, Duckett J, eds. Adult and paediatric urology, 3rd ed. Sacramento: Lippincott-Raven, 1997:1465-1500.