RESUMEN
The urachal cyst is a rare congenital anomaly due to a lack of apposition of sheets remains allantoid. Diagnosis is based on prenatal ultrasound. We report the case of an urachal cyst diagnosed in a female fetus in the third trimester of pregnancy which regressed spontaneously in the postnatal period. Mrs. CD, a 27 year-old consulted us as part of the regular monitoring of a normal course of pregnancy. At 32 weeks, ultrasounds showed an anechoic oval-shaped and well-limited image located above the upper pole of the bladder, below the insertion of the cord. Diameter was 12 mm and the image was connected to the baldder through a thin orifice. The umbilical ring appeared wide and connected to the abdominal collection by a 5 mm-channel. However, the skin surface was normal with no solution of continuity. On ultrasound at 37 weeks gestation [WG], the pelvic anechoic image kept the same features but the thin connection was no more visible. Vaginal delivery occurred at 40 GW and 5 days. Examination of the newborn found normal abdominal skin covering. By 12 months, ultrasounds found that the cyst completely disappeared. The permeable urachus is a progressive disease. Its development depends on the clinical form of its manifestation. Surgical treatment is often necessary, but spontaneous regression is possible for simple cysts until postnatal period