What is the most common complication of an esophageal stent?

The most common complications associated with esophageal stents include:

- Migration - Stent migration refers to when the stent moves from its original placement location. This occurs more often with fully covered stents since they do not have tissue ingrowth to anchor them. Migration rates range from 5-40% in studies.

- Tissue ingrowth/overgrowth - With partially covered and uncovered stents, tissue can grow through or over the stent mesh. This can obstruct the esophageal lumen, causing symptoms like difficulty swallowing. It occurs in 5-20% of cases.

- Food bolus obstruction - Food or pills can get stuck in the stent, blocking the esophageal opening. This occurs in up to 25% of patients with esophageal stents.

- Gastroesophageal reflux - The stent can disrupt the lower esophageal sphincter, increasing the reflux of stomach contents back up into the esophagus. This happens in around 10-15% of patients.

- Pain - Some patients experience chest pain after stent placement, occurring in around 10% of cases. This is more common with rigid plastic stents.

- Stent fracture - Metal stents can sometimes fracture or break, especially if they are in a bending location like the lower esophagus. The fracture rate is up to 7%.

- Perforation - Rarely, the sharp ends of a stent can perforate or tear the esophageal wall during placement. The perforation rate is less than 1%. 

So in summary, migration, tissue ingrowth, and food obstruction are among the most prevalent esophageal stent complications to monitor for after placement.