Abstract
Acute peritonitis due to a perforation of infected urachal cyst is rare and 9 cases including this case have been reported in Japan. A 41-year-old male was seen at the hospital because of lower abdominal pain with a low grade fever. A 3 cm paintful tumor was palpated approximately on the median of the lower abdomen but no peritoneal irritating sign was noted. Ultrasonography (US) revealed a possible tumor arising in the urachal cyst localized in the extraabdomen beneath the rectus abdominis muscle. CT, however, pointed out a low density area under the rectus muscle but it was unclear whether the mass was localized in the intraabdomen or extraabdomen. In the course of conservative treatment, peritoneal irritating sign and fever appeared. US was performed again, and acute peritonitis due to perforation of the infected urachal cyst was suspected. Total urachectomy was carried out. Postoperative course was uneventful and the patient was discharged from the hospital.
Generally infected urachal cyst is treated by antibiotics followed by radical operation of an one-step approach. During this preoperative period US would be very useful to observe the infected urachal cyst with a rare possibility of perforation into the abdomen.
