The urachus is an embryonic remnant of the communication between the bladder and the umbilicus.1
This communication is usually obliterated between the fourth and fifth month of gestation. It becomes a fibrous cord between the umbilicus and the bladder dome, also known as the median umbilical ligament.2
There is a 1 in 5000 incidence of a urachal anomaly on autopsy studies.4
Urachal disease is most commonly manifest in the pediatric population, with a variety of clinical presentations. Retrospective reviews at 2 pediatric urologic institutions2,3
have described 4 major categories of urachal disease: urachal sinus, urachal cyst, patent urachus and urachal diverticulum. Of these, the urachal cyst has the most potential to present later in life, after being complicated by rupture or infection.
Several options for diagnostic imaging are available to differentiate between different forms of urachal disease. These include abdominal ultrasound, computed tomography, sinography and cystography. The value of each method may vary based on the clinical findings and suspected diagnosis. In patients presenting with umbilical discharge in whom a urachal sinus, patent urachus or ruptured urachal cyst is suspected, the sinogram may be most useful.3
Although rare, the majority of adult urachal diseases reported in the literature comprise entero-urachal fistulae. Those involving small bowel in patients with Crohn's disease are most commonly reported, while only 2 other cases of urachal-sigmoid fistulae have been reported.5,6
One was related to diverticular disease,5
while the other was not associated with any bowel pathology.6
Both patients were treated surgically with resection of the involved colon segment and excision of the urachal remnant.
Our patient represents the second reported case of urachal-sigmoid fistula associated with diverticular disease. The CT sinogram was valuable in establishing the diagnosis in this patient. After eradicating the infection with a 6-week course of antibiotics, we preformed an elective resection of the involved sigmoid colon and urachal remnant, with good results.