Vitelline duct

The vitelline duct, also known as the omphalomesenteric duct, is an embryological structure that connects the yolk sac to the midgut lumen. In normal development, the vitelline duct undergoes obliteration by the 7th week of gestation. Failure of this process leads to various anomalies, each with distinct clinical features.

Vitelline Duct Anomalies

1. Vitelline Duct (Normal Development)

Timeline: By the 7th week of development, the vitelline duct typically closes completely.
Result: No remnant connection between the yolk sac and the midgut lumen.

2. Vitelline Fistula

Definition: Complete failure of the vitelline duct to close.
Clinical Presentation:
- Meconium discharge from the umbilicus due to direct communication between the intestines and the umbilicus.

3. Meckel’s Diverticulum

Definition: Partial closure of the vitelline duct, leaving a patent section attached to the ileum, forming a true diverticulum.
Features:
- Often asymptomatic but may present with symptoms.
- May contain heterotopic gastric or pancreatic tissue.
Symptoms:
- Melena (dark stools indicating gastrointestinal bleeding)
- Hematochezia (bright red blood in stools)
- Abdominal pain

Table of Vitelline Duct Anomalies

Anomaly	Description	Key Features	Possible Symptoms
Normal Development	Complete obliteration by 7^th week	No remaining connection to the yolk sac	None
Vitelline Fistula	Complete failure to close	Meconium discharge from the umbilicus	Umbilical discharge
Meckel’s Diverticulum	Partial closure with patent portion attached to ileum	True diverticulum, may contain gastric/pancreatic tissue	Melena, hematochezia, abdominal pain

Points to Remember for USMLE Step 1

Normal Closure: By the 7th week, the vitelline duct should normally obliterate.
Vitelline Fistula: Failure of complete closure results in meconium discharge from the umbilicus.
Meckel’s Diverticulum: Often asymptomatic but may present with melena, hematochezia, or abdominal pain due to ectopic tissue.

Clinical Correlation

Understanding vitelline duct anomalies is critical as they can present in clinical practice with abdominal or gastrointestinal symptoms in pediatric and adult patients. Early diagnosis and management of symptomatic Meckel’s diverticulum, for instance, can prevent complications like bleeding and inflammation.

USMLE Step 1 Review Series

Curriculum