A 52-year-old woman with a history of cholelithiasis presents with acute right upper quadrant pain. During an open cholecystectomy, the surgeon identifies a stone impacted in the common bile duct. Which is the most common site of impaction of choledocholiths within the common bile duct?

## Most Common Site of Choledocholiths Impaction **Key Point:** The ampulla of Vater (hepatopancreatic ampulla) is the most common site of choledocholiths impaction, accounting for approximately 70–80% of cases. ### Anatomical Basis The ampulla of Vater represents the narrowest and most dependent (lowest) portion of the common bile duct as it enters the duodenum. This anatomical narrowing, combined with gravity and the natural tendency of stones to settle in dependent areas, makes this the most frequent site of lodgement. ### Why This Site? 1. **Narrowest segment** — The ampulla is naturally constricted by the sphincter of Oddi 2. **Most dependent point** — Gravity favours stone settlement here 3. **Angulation** — The duct bends sharply as it enters the duodenum, creating a natural trap 4. **Frequency in clinical practice** — Endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy is most commonly performed at this level ### Clinical Significance - **Acute pancreatitis risk** — Stones impacted at the ampulla can obstruct the pancreatic duct, triggering acute pancreatitis - **Obstructive jaundice** — Complete obstruction at this site causes rapid elevation of bilirubin - **ERCP indication** — The ampulla is the target for therapeutic sphincterotomy and stone extraction **High-Yield:** Ampulla of Vater impaction = most common site for choledocholiths in 70–80% of cases. This is a frequently tested fact in NEET PG. [cite:Standring Gray's Anatomy 42e]