Picture of the Month—Diagnosis

The lesion was surgically excised, and histopathologic analysis revealed an infected urachal cyst with an umbilical artery remnant.

The urachus is a fibrous structure derived from the embryonic communication that extends from the bladder to the umbilicus.¹ In the newborn period, it becomes a fibrous structure known as the medial umbilical ligament. It is normally obliterated, but urachal abnormalities result from a failure of this structure to regress. Four types of urachal abnormalities are recognized, including patent urachus, urachal sinus, urachal diverticulum, and urachal cyst. The patent urachus is the most severe and is usually diagnosed early in the newborn period because of its more obvious presentation of urinary drainage from the umbilicus. It is a direct connection between the bladder and the umbilicus due to complete persistence of the urachus. The urachal sinus and diverticulum, by contrast, represent partial urachal remnants. The urachal sinus communicates with the umbilicus but is closed to the bladder. The urachal (or vesicourachal) diverticulum is open to the bladder but closed to the umbilicus. The final and most common type is the urachal cyst—a partial remnant, but with no direct connection to either the umbilicus or the bladder.² Data derived from autopsies indicate an incidence of urachal cysts of 1 in 5000 births and a 3:1 male-female ratio.³

Urachal anomalies can have diverse presentations because the size of the defect and extent of the communication can vary significantly. Clinical presentations include palpable masses, umbilical drainage, and vesicular obstruction due to bladder compression. They are occasionally diagnosed at autopsy. Urachal cysts can rupture and cause symptoms of an acute intraperitoneal process. If a cyst becomes infected, umbilical erythema or drainage, dysuria, abdominal pain, or peritonitis may occur.^4,5 The route of infection may occur via direct extension from the skin, umbilicus, or bladder, or via hematogenous or lymphatic means.⁶

The differential diagnosis of umbilical abnormalities is broad, and it can include cellulitis, omphalitis, urinary tract infection, pelvic inflammatory disease, appendicitis with or without rupture, inflammatory bowel disease, Meckel diverticulum, strangulated umbilical hernia, bowel perforation, and intra-abdominal abscesses.^4,6

The urachal cyst represents a diagnostic challenge. Retrospective studies have documented the sensitivity of ultrasound to be between 75% and 100% for urachal cysts.^7,8 Alternative imaging studies include the use of contrast fistulography if drainage is present or computed tomography if a malignant process is suspected.⁷ In addition, the high rate of associated urinary tract abnormalities warrants routine intravenous pyelography and/or retrograde cystourethrography.⁷

Simple incision and drainage of an infected urachal cyst may address the acute infection, but it is not curative, as the rate of reinfection is approximately 30%.⁹ Additionally, any remaining urachal tissue is at risk for adenocarcinomatous transformation.⁹ Therefore, optimal treatment of urachal cysts requires surgical excision. If no infection or limited infection is present, primary excision is possible.^3,9 Primary excision of an acutely infected cyst creates the risk of perioperative complications, including wound infection and bladder injury. Secondary excision after antibiotic therapy reduces the risk of complications and allows for faster healing and resolution of inflammation.^3,9,10

In adult patients, laparoscopy has been successfully used for the removal of urachal remnants. However, its use in younger patients requires further investigation.^2,11-13

Patients with infected urachal cysts have varied clinical presentations. Clinicians should maintain an index of suspicion for this process in young patients with acute intra-abdominal processes marked by abdominal distention or rigidity or by apparent cellulitis of the abdominal wall.⁹ Antibiotic therapy and primary or secondary excision will be required for complete treatment.

Correspondence: Melanie Pitone, MD, Division of Pediatric Emergency, Alfred I. duPont Hospital for Children, 1600 Rockland Rd, Wilmington, DE 19899 (mpitone@nemours.org).

Accepted for Publication: September 14, 2005.