Enterolithiasis in posterior urethral diverticulum: BMJ case
A posterior urethral diverticulum (PUD) may be formed when a part of the terminal rectal stump is left attached to the posterior urethra during fistula ligation in surgery for anorectal malformation (ARM).

A 13-year-old boy presented with the complaints of burning micturition, postvoid dribbling and vague pain in the left lower abdomen for the last 4 months. The child had high ARM and underwent all three stages of surgery (colostomy, transabdominal pull-through procedure and colostomy closure) elsewhere.

On evaluation, the plain X-ray pelvis showed huge, multiple radio-opaque shadows in the region of the bladder (figure 1A). On an ultrasound, these acoustic shadows caused by the stones appeared to be posterior to the bladder and could not be appreciated well in full bladder state. A CT scan further confirmed these radio-opaque shadows to be posterior, but not within the urinary bladder and anterior to the rectum (figure 1B). This raised the suspicion of stones in a PUD.

On pelvic exploration, there were multiple huge stones found in a 5×6 cm rectal mucosal lined cavity. This was located posterior to the bladder but anterior to the rectum and was communicating with the bladder through a fistulous tract. The fistulous tract and the attached dilated rectal stump were excised, and all the stones were removed. There were no signs of urinary or bowel complaints until 6 months of follow-up.

Learning points
• In patients with high anorectal malformation with rectourethral fistula, the fistula should be ligated as close to the urinary tract as possible to prevent the formation of a posterior urethral diverticulum.

• Posterior urethral diverticulum may present with passage of mucus through urethra, repeated urinary tract infections, epididymo-orchitis and rarely with complications like enterolithiasis.

Read in detail here: http://casereports.bmj.com/content/2018/bcr-2018-226274.full