Afferent loop obstruction is a relatively rare but significant complication of Billroth II gastrojejunostomy. We report the imaging findings in a patient in whom obstruction presented acutely and was due to the presence of an enterolith. CT showed dilatation of both the main pancreatic duct and the biliary ducts, and a markedly dilated afferent loop within which a 5-cm mass was present. The lesion had a heterogeneous, laminated appearance and did not show any contrast enhancement. Edema of fatty tissues surrounding the pancreatic tail, which extended to the left pararenal spaces, a small amount of free peritoneal fluid surrounding the spleen, and an aneurysm of the splenic artery of about 3 cm were also present. The diagnosis of afferent loop obstruction has to be considered in patients with previous Billroth II gastrojejunostomy who present with acute abdominal pain and laboratory findings indicating pancreatitis. Although rarely, an enterolith can be the cause of obstruction. CT allows to establish the diagnosis.