<prompt> Bird beak appearance on barium swallow study is seen in:Achalasia cardiaCarcinoma esophagusHiatus herniaDiffuse esophageal spasm  <response>: Barium study feature of few esophageal diseases Diffuse esophageal spasm: Yo-Yo motion of barium Corkscrew appearance scalloped configuration of barium column Rosary-beadShish kebab configuration compamentalization of barium column Feline esophagus: Gastroesophageal reflux disease Double-barrel esophagus: Mallory-Weiss tear Intramural abscess Intraluminal diveiculum Achalasia cardia: Bird beak deformity Absence of primary peristalsis below level of cricopharyngeus Candidal esophagitis: Cobble stone mucosa Cytomegalovirus esophagitis: Giant ovoid flat ulcers vasculitis of submucosal vessels Herpes esophagitis: Discrete superficial punctatelinear serpentinestellatediamond shaped ulcers Hiatus hernia: Epiphrenic bulge 4 longitudinal coarse thick gastric folds above gastroesophageal junction or in the suprahiatal pouch Distance between B ring and hiatal margin 2 cm Scleroderma: Esophageal shoening Sliding hiatus hernia Carcinoma oesophagus: Rat-tail esophagus Shouldering sign 