NAVLE Reproductive

Equine Patent Urachus Study Guide

Patent urachus is one of the most common umbilical abnormalities in neonatal foals, occurring at a frequency of approximately 7.8% of all foals up to 14 days of life.

Overview and Clinical Importance

Patent urachus is one of the most common umbilical abnormalities in neonatal foals, occurring at a frequency of approximately 7.8% of all foals up to 14 days of life. This condition represents the failure of the urachus (the fetal conduit connecting the bladder apex to the umbilicus for urine drainage into the allantois) to close properly at birth.

The urachus normally fibroses and regresses after parturition, becoming the median (middle) ligament of the bladder. When this closure fails, urine continues to leak from the umbilicus, creating a moist environment that predisposes to bacterial infection and potentially life-threatening complications including septicemia, septic arthritis, and pneumonia.

Structure Fetal Function Adult Remnant
Urachus Drains fetal urine from bladder to allantoic cavity Median (middle) ligament of bladder
Umbilical Vein (1) Carries oxygenated blood from placenta to fetus Round ligament of liver (falciform ligament)
Umbilical Arteries (2) Carry deoxygenated blood from fetus to placenta Round ligaments of bladder

Anatomy of the Fetal Umbilical Structures

The equine umbilical cord contains four clinically important structures that undergo involution after birth:

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