Urachal insufficiency

The urachal tube allows communication between the developing bladder and the placenta and is usually atrophied at birth. If this is not done, the urachal tube may remain, making closure of the entire urachal tube impossible. A urachal cyst may occur anywhere along the length of the urachal tube, and failure of bladder urachal closure may result in the formation of a bladder diverticulum at the apex of the bladder. Urachal disease includes umbilical leakage, urine dripping from the navel, and urinary tract infections. Urachal cysts are often discovered incidentally but may become more apparent when underlying lower urinary tract disease is present.

The urachus is a thin tubular cord that connects the umbilicus to the bladder during the early embryonic period. It gradually closes into a fibrous cord during the subsequent embryonic and infant periods, loses its function as an excretory duct, and gradually disappears.

The clinical manifestations of unclosed urachus are redness and swelling of the umbilicus, water leakage (urinary incontinence), repeated local infections, cyst formation in the umbilicus and palpable abdominal masses.

The urachal tube is located in the loose connective tissue between the transverse abdominal fascia and the peritoneum. It is about 3-10 cm long and 0.8-1.0 cm in diameter. It is the residual structure connecting the bladder and the allantois in the early embryo. It is closed after birth to form the median umbilical ligament.

Anatomy of the urachal tube

During embryonic development, the bladder descends from the umbilicus along the anterior abdominal wall.

During the descent, a thin tube, the urachus, connects to the bladder from the navel and later degenerates into a fibrous cord.

Under normal circumstances, the urachal tube degenerates into a fibrous cord from the top of the bladder to the navel after birth, namely the median umbilical ligament, with a length ranging from 2 to 15 cm, located in the loose connective tissue between the transverse abdominal fascia and the peritoneum. When the urachal tube is incompletely closed or completely patent during development, different types of clinical malformations may occur. It is a rare congenital developmental abnormality.

The main urachal diseases are

1. Urachal fistula, that is, the urachal tube is completely patent.

2. Urachal cyst, that is, the two ends of the urachal cyst are blocked.

3. Urachal diverticulum, that is, only the part connected to the top of the bladder is not closed.

4. The urachal sinus tract is that only the umbilical end is not closed.

Urachal fistula After birth, the urachus are not completely closed, forming an open urachus fistula, also called an open urachus. Bladder urine can flow out of the abdomen through the umbilicus.

Clinical manifestations :

1. Intermittent urine leakage from the umbilicus.

2. When secondary infection occurs, the navel becomes red and swollen, and purulent urine flows out.

For patients suspected of having urachal cyst, B-ultrasound examination is the first choice. Its characteristics are described as follows:

1. A fusiform anechoic mass can be seen deep in the mid-abdominal wall below the navel, located between the navel and the bladder.

2. The mass moves in the same direction as deep breathing.

3. When the cyst cavity is infected, dense dot-like echoes appear, which are caused by the accumulation of pus, necrotic and dissolved tissue debris, and exudate from the cyst wall.

4. The inner wall of the cyst cavity is rough and the outer wall is unclear.

5. The cyst changes shape as the bladder fills or empties.

6. Intracystic stones may appear strongly echogenic. In addition, IVU, cystoscopy and abdominal CT scan can not only help to confirm the diagnosis, but also help to differentiate it from other abdominal lesions.