Pediatric Urachal Remnant

Etiology:
— Urachus is canal connecting bladder of fetus with allantois which is a structure that contributes to formation of umbilical cord
— Lumen of urachus normally obliterated during embryonic development which transforms urachus into solid cord and functionless remnant
Imaging US:
— Patent urachus: Bladder communicates with umbilicus
— Urachal sinus: Starts at umbilicus and terminates blindly along tract
— Urachal cyst: Urachus closed at each end with cyst in middle
— Urachal diverticulum: Starts at bladder and terminates blindly along tract
DDX:
Complications:
Treatment: Surgical
Clinical:
— May have umbilical discharge of pus or urine
— Inflammed anterior abdominal wall

Radiology Cases of Urachal Remnant

Radiology Cases of Urachal Sinus

US of urachal sinus — Sagittal US of the lower abdomen just inferior to the umbilicus (above) shows a hypoechoic, blind-ending tubular structure that originates from the bladder and which extends inferiorly. Lateral image from a voiding cystourethrogram (below) shows no communication between the bladder and the umbilicus.

Radiology Cases of Urachal Cyst

CT of infected urachal cyst — Axial (left) and sagittal (right) images from a CT with contrast of the abdomen shows a midline cystic lesion with a thick enhancing wall and surrounding inflammatory change just inferior to the umbilicus that appears to course to the dome of the bladder on the sagittal image.

US of urachal cyst — Sagittal (above) and transverse (below) US of the infraumbilical region in the midline shows a round structure superior and anterior to the bladder that is primarily hypoechoic in appearance with an echogenic center.

Radiology Cases of Patent Urachus

VCUG of patent urachus and urachal diverticulum — Lateral image from a voiding cystourethrogram performed by catheterizing the site of urine drainage at the patient’s umbilicus shows contrast filling the bladder and urethra as well as a large diverticulum at the dome of the bladder that nearly extends to the patient’s anterior abdominal wall.

Radiology Cases of Urachal Diverticulum

VCUG of patent urachus and urachal diverticulum — Lateral image from a voiding cystourethrogram performed by catheterizing the site of urine drainage at the patient’s umbilicus shows contrast filling the bladder and urethra as well as a large diverticulum at the dome of the bladder that nearly extends to the patient’s anterior abdominal wall.

US of cystic renal dysplasia — Sagittal US of the kidneys (above) show small echogenic kidneys bilaterally with some cysts but no hydronephrosis. AP image from a VCUG (below left) shows bilateral grade 4 vesicoureteral reflux with intrarenal reflux and the bladder is trabeculated. Lateral image from the VCUG (below right) shows a urachal diverticulum arising from the dome of the bladder anteriorly. The urethra was normal.

VCUG of ectopic ureterocele and urachal diverticulum — Lateral image from a voiding cystourethrogram exam shows a round lucency / filling defect near the trigone of the bladder. There is also contrast filling a blind ending tubular tract at the dome of the bladder.

Radiology Cases of Obliterated Urachal Remnant

CT of obliterated urachal remnant — Axial CT with contrast of the abdomen shows a small, round, solid structure in the midline anterior to the bladder, which arises from the dome of the bladder and courses superiorly towards the umbilicus.

CT of obliterated urachal remnant — Axial (above) and sagittal (below) CT with contrast of the pelvis shows a small oval solid soft tissue mass in the midline of the anterior wall / dome of the bladder.