Sung Hwan Lee, et al. 13,000/uL, hemoglobin level of 12.5 g/dL; others were within the normal limit. An abdominal ultrasonograph study revealed a huge mass showing mixed echogenecity and arising from the umbilicus. He was referred for ab- dominal computed tomography scan revealing a 14 × 11.3 × 8.6 cm abscess cavity arising from the umbilicus and ex- tending to the superior surface of the bladder along the ur- achus tract (Fig. 1). There was no evidence of communica- tion between the abscess cavity and the bladder. Incision and drainage were performed promptly under local anesthesia and then, intravenous antibiotics and wound dressing were maintained for a week. After the umbilical lesion and general conditions improved, a lapa- rotomy under general anesthesia was performed in order to remove the abscess cavity. The operative finding re- vealed that the abscess was derived from a urachal duct cyst (Fig. 2). The patient was discharged at postoperative day #7 without any complications. The pathologic report was consistent with urachal duct cyst (Fig. 3). DISCUSSION The urachus is an embryonic remnant of the cloaca and the allantois which is present after birth as a midline fi- brous cord extending from the anterior dome of the uri- nary bladder to the umbilicus [1]. If the obliteration of the urachal patency does not proceed normally after birth, the persistent urachal remnant may result in various clinical problems. The congenital urachal anomalies are more common in males and have 4 types including patent ur- achus (about 50% of cases), urachal cyst (about 30%), ura- chal sinus (about 15%), and urachal diverticulum (about 5%) [2]. The incidence of urachal anomalies in infancy and childhood has been reported at about 1 in 5,000 with 3:1 male to female ratio [3]. Because urachal disease is usually detected in infancy and childhood, it is rare in adults. Yiee et al. [4] reported that there were approximately two cases of urachal abnormality per 100,000 hospital admissions in adults. Clinical presentation is usually associated with super- added infection of the urachal cyst. Infected urachal cysts present with various symptoms; low abdominal mass, 256 umbilical discharge, tenderness with erythema, fever, uri- nary tract infection, hematuria, and peritonitis. Infected urachal cyst can occasionally lead to urachal abscess and can develop to systemic septic condition. With a severe urachal cyst infection, pyourachus can form a fistula with bladder, bowel or umbilicus. Abscess rupture due to ex- pansion of infected urachal cyst can cause acute abdomen requiring emergency operation [5]. Diagnosis of urachal cyst is usually made with either ul- trasonography or computed tomography. Cystography or cystoscopy can be useful to define the full extent of the cyst wall and delineate the urachal sinus [6]. Initial administer- ing of IV antibiotics and definitive surgical excision is rec- ommended in the treatment of urachal abscess. Simple drainage of the cyst is not recommended due to high re- currence rates (approximately 30%) [7]. If the patient has a huge size of abscess with poor general condition, it is bet- ter to perform percutaneous drainage of the urachal ab- scess before surgical excision [8]. Because of the high re- currence rate and possibility of developing carcinoma in the urachal remnant, it is a key point to complete resection of the cyst wall throughout its length during operation [9]. Operation may include removal of cuff of the bladder if there is communication between the urachal cyst and the bladder. Open excision has been performed as the treat- ment of choice, traditionally. However, recently, the lapa- roscopic method has been accepted as an alternative op- tion because of faster recovery, less postoperative pain and better cosmetic results [10]. In summary, urachal abscess is rare in adulthood but should be considered as differential diagnosis of abdomi- nal pain, because it may require emergency surgical management. This case demonstrates that urachal ab- scesses are a rare but critical disease presenting with ab- dominal pain in adults. CONFLICTS OF INTEREST No potential conflict of interest relevant to this article was reported. thesurgery.or.kr