Benign tumours developing at the site of ureterosigmoidostomy.

Two cases of benign tumours complicating ureterosigmoidostomy are described. The latent period between diversion and the development of tumour is long and careful follow-up of patients with ureterosigmoidostomy is recommended. It would seem highly probable that adenomatous polyps developing at the site of anastomosis may, if undetected, undergo malignant change to adenocarcinoma. All of the tumours recorded following ureterosigmoid diversion have been associated with a nipple type ureterocolic anastomosis and mucosa-to-mucosa anastomosis may possibly prevent this complication.