**Core Concept**
The urachus is a **fibrous remnant** of the allantois, which is a **vestigial structure** that connects the bladder to the umbilicus. An abnormal connection between the bladder and the umbilicus can result in a urachal fistula.

**Why the Correct Answer is Right**
A urachal fistula is an **abnormal communication** between the bladder and the umbilicus, resulting from a failure of the urachus to obliterate during fetal development. This can lead to **urine leakage** from the umbilicus.

**Why Each Wrong Option is Incorrect**
**Option A:** Not provided, unable to comment.
**Option B:** Not provided, unable to comment.
**Option C:** Not provided, unable to comment.
**Option D:** Not provided, unable to comment.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that urachal anomalies, including fistulas, can present with **urinary tract infections** or **umbilical discharge**.

**Correct Answer:** D. Congenital abnormal communication between bladder and umbilicus.