Urachal remnant

Urachal remnant anomalies are a range of anomalies that occur when the fetal urachus does not disappear after birth. The urachus is a hollow structure that connects the top of the bladder to the umbilicus (belly button) during fetal development. By the time birth occurs it changes from the urachus to the median umbilical ligament and should close off, sometimes leaving a remnant or it just completeley disappears.If the urachal remnant doesn’t completely close then the urachus can be left open giving a urachal anomaly.There are four types of anomalies: patent urachus (fistula), urachal cyst, umbilical-urachal sinus, and vesicourachal diverticulum. The most common (approx. 50%), patent urachus, is when the path between the bladder and umbilicus has not completely closed. The second most common (approx 30%), urachal cyst, is a dilatation of the mid urachus filled with fluid. Third most common (approx. 15%), umbilical-urachal sinus, is a dilatation/outpouching at the umbilical end of the urachus. Finally, the least common (approx. 5%), vesicourachal diverticulum, is a dilatation/pouch at the bladder end of the urachus.There is an increased risk of developing an adenocarcinoma from a urachal remnant.