A Zenker’s diverticulum (ZD) is a pouch in the upper part of the esophagus (swallowing tube) that develops slowly over time. It seen most commonly in older patients. The diverticulum occurs between two muscles at the top of the esophagus when swallowing pressures cause a bulge in the muscular wall. This bulge can grow slowly over time eventually resulting a pouch that can retain food, liquids, and pills.