A patent urachus is one of the spectrum of congenital urachal anomalies. It has occasionally been termed "urachal fistula".

Clinical presentation

A patent urachus is often diagnosed in neonates when urine is noted leaking from the umbilicus. The umbilicus may also have an abnormal appearance on physical exam.

If the patent urachus is very narrow, it may present later in life if high pressures in the bladder develop (e.g. bladder outlet obstruction), forcing urine through the patent urachus.

A patent urachus predisposes to infection.

Pathology

A patent urachus represents the failure of the entire course of the fetal allantois to involute into the median umbilical ligament. This results in an open channel between the bladder and the umbilicus.

Radiographic features

Contrast studies (VCUG)

A patent urachus can be demonstrated by:

retrograde injection of contrast material into the orifice of the channel at the umbilical end

reflux up the urachus during VCUG (better seen in the lateral projection)

Ultrasound

A patent urachus can be seen on longitudinal ultrasound images of the midline ventral abdomen as a tubular connection between the anterosuperior aspect of the bladder and the umbilicus.