Fig. 22.1
Infected urachal remnant (sinus)—4-week-old baby boy. Sagittal scan on the midline. Thickening of the urachus (arrows) extending from the umbilicus (U) till the dome of the bladder (B)
Fig. 22.2
Infected urachal remnant—2-year-old girl. (a) US Sagittal scan a loculated mass extends from the umbilicus (U) towards the bladder representing a urachal remnant (Ur) abscess. (b) Color Doppler US—transverse scan below the umbilicus—massive peri-abscess hypervasularization corresponding to inflammatory response
The treatment will be mostly medical with antibiotics and the infection will resolve within a few weeks. The urachal remnant will return to a normal appearance. If necessary, the normalization can be followed up on US. As such no further treatment will be necessary [1, 7–10].
22.3 Complicated Urachal Cysts
A urachal cyst develops if the urachus remains patent in a localized segment somewhere between the umbilicus and the bladder. This occurs most commonly in the lower third of the urachus. Urachal cysts may be detected incidentally in asymptomatic patients. They will become symptomatic due to their rapid enlargement generally secondary to infection. Clinically the patient will complain of abdominal fullness or pain; he/she may present with lower urinary symptoms in relation with a secondary cystitis.
A thin walled cyst with echo-free fluid content will be the usual appearance in incidental asymptomatic urachal cysts. The cyst being typically located on the midline, above the bladder. This particular type of congenital urachal remnant is a different entity from the urachal remnant that can appear as a nodular nubbin on the top of the bladder, within its wall. Especially, since this latter type of remnant may sometimes present a confusing protruding cystic appearance within the bladder [7, 8, 10].
Superinfected urachal cysts will manifest on US as a thick wall cystic mass with echogenic or heterogeneous content (Fig. 22.3a,b). The wall may appear hypervascularized on color Doppler as the surrounding tissues and the wall may become inflamed. Similar findings will be demonstrated on CE-CT or MR imaging (Fig. 22.3c–e). A thick wall cyst enhancing after contrast injection will be demonstrated. Inflamed surrounding tissues may show enhancement as well and determine irregular boundaries. Rarely the cyst may rupture rendering the diagnosis more difficult.
Fig. 22.3
Infected urachal cyst in a 5-year-old girl. (a) US—Sagittal scan showing a distended urachal remnant (Ur) cyst filled with echogenic material and extending from the bladder (B) towards the umbilicus. (b) US—Transverse scan below the umbilicus. The infected cyst appears round and located anteriorly just behind the abdominal wall (Ur urachal remnant cyst). (c) MR imaging—T2-weighted sequence—It demonstrates the infected cysts, lying on the dome of the bladder. (d) MR imaging—T1-weighted after Gd injection. Enhancement of the wall of the cyst and surrounding inflammatory tissues. (e) MR imaging DWI—Striking hypersignal of the abscess
The differential diagnosis of an infected urachal sinus includes all potentially infected cysts of the abdomen especially those developing around the midline such as Meckel’s diverticulum, mesenteric cyst, lymphangioma, or duplication cyst. A connecting tract from the cyst to the umbilicus (or to the bladder) is a clue for a urachal remnant [1].
The treatment is controversial. In young infants, it will be mainly medical; surgery being reserved for unfavorable evolution or recurrence. The treatment would more often be surgical in older children, as excision of the infected cyst is performed to prevent reinfection (30% of reinfection rate). Furthermore, some authors have reported the increased risk of tumoral development in unresected or incompletely resected urachal remnant (see below). As mentioned, this remains controversial [1, 3, 11, 12].
22.4 Other Umbilical Anomalies
Various other umbilical anomalies need to be considered whenever a urachal remnant is suspected. The pathologies may be self-limited to the umbilicus or the “tip of an iceberg,” as part of the anomaly extends within the abdomen.
22.4.1 Localized Anomaly
Omphalitis is defined as erythema and edema of the umbilical region with or without discharge from the abdomen. An umbilical granuloma may develop after the cord separation when the epithelialization has been incomplete. The granulation tissue may overgrow and form a granuloma. Both entities do not require imaging and will be treated medically.
Rarely, an abscess may develop and masquerade as urachal remnant; imaging will demonstrate the limited localized lesion (Fig. 22.4).
Fig. 22.4
Infected umbilical abscess—15-year-old adolescent. (a) US—Transverse scan at the umbilical level; a small collection (between the crosses) measuring 7×6 mm is visible with the umbilicus. (b) CE-CT confirms that the abscess is limited to the umbilicus without deep extension
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