Patent urachus

Pathophysiology

Congenital urachus syndrome

• Urachus never closes at birth .
• Unknown etiology possibly due to distention from cord torsion in utero or during delivery leading to tension of the umbilicus, dilation of the urachus and preventing occlusion/ incomplete urachal involution.
• Often accompanied by other congenital abnormalities.

Acquired urachus syndrome

• Re-opens post-partum as the dried umbilical stump falls off.
• Associated with umbilical infection/inflammation.
• Any cause of increased intra-abdominal pressure, eg meconium retention (tenesmus, dysuria etc).
• Excessive wetness or trauma to the umbilical stump, eg iatrogenic, over-zealous dam, etc.
• Prolonged recumbency in debilitated calves.
• Urine leakage   →   persistent irritation and potential source of infection.
• Urachal wall thinner than bladder wall and hence more prone to rupture.
• Spread of infection to intra abdominal umbilical remnants common in calves. Ascending infection can affect the bladder and if infection tracks up the umbilical blood vessels, the liver.

Timecourse

• Acquired forms develop in the first 2 weeks of life.
• Congenital forms are present at birth.