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.