Discussion
The association between urinary diversion with ureterosigmoidostomy and subsequent development of rectosigmoid adenocarcinoma has been described in the medical literature [4, 5]. Prevalence of ureterocolostomy in the population is thought to be approximately 2 in 100,000 people, with post diversion neoplasia occurring in 24% of these patients at a mean of 20 years follow up [3].
Since the first case report by Hammer in 1929, the mechanism of this increased risk of malignancy has remained elusive [6]. There are varying theories regarding the etiology, including exposure of colon mucosa to urine inciting hyperplasia, and alteration in bacterial flora resulting in elevated nitrite compounds or elevated free oxygen species [7, 8]. The tumor in our patient was near the site of original anastomosis with the ureter stump still in place, suggesting that the area was indeed exposed to urine during the 21 years that the ureterosigmoidostomy was functional.
There is usually a latent period between creation of ureterosigmoidostomy and cancer occurrence ranging from 6 to 55 years, with a median of 21-33 years reported in small series [9]. Our patient was 51 years removed from takedown of ureterosigmoidostomy and conversion to ileal conduit and 72 years from the original ureterosigmoidostomy as a neonate, which to our knowledge is the longest latent period reported to date. Due to her history of ureterosigmoidostomy, our patient should have been considered high-risk for rectosigmoid cancer. As recommended by other authors, a reasonable option for screening would be frequent flexible sigmoidoscopy and screening the remainder of the colon based on standard guidelines [2]. Although the number of patients with a history of prior ureterosigmoidostomy is dwindling, clinicians should be aware of the increased risk of rectosigmoid cancer in these patients and screen them appropriately.