A rare case of patent urachus in association with a giant cystic of the umbilical cord

Background. Patent urachus (PU) results from a failure in the closing of the remnant of the allantois constituting a connection between the bladder and umbilicus, which occurs in 1-2 babies in 100,000 births.
Case presentation. A 26-year-old female patient was referred at 21 weeks of gestation. Ultrasound (US) detected the presence of an extra-abdominal cystic formation of 22.7 × 23.8 mm, communicating with the fetal bladder and surrounded by the umbilical vessels. No genitourinary tract anomalies, nor abdominal wall defects were found at US controls. Fetal MR (Figure 1) was performed at 32 weeks and a diagnosis of allantois cyst and patent urachus was made. A full- term male weighing 2940 g was born by vaginal delivery. Neonatal findings confirmed a patent urachus with urine leak and circumferential erythema but normal genitalia with no alterations in the infra-abdominal wall or pubic bone diastasis. Urinary infection occurred in II postnatal day and cystography was performed once the infection was resolved confirming communication with the bladder. A plastic reconstruction of the dome of the bladder and resection of the urachus was completed at 20 days-of-life.
Patient was discharged after 6 days with transurethral catheter left in place, lately removed in outpatient clinic after 4 days. US performed at six months showed a normal bladder with no pelvic dilation.
Conclusions. Prenatal diagnosis of PU is rare, sometimes difficult due to its rarity, but usually with good outcomes. PU must be differentiated from other more complex causes of cord cysts.