Abstract Background Lemmel syndrome, first described in 1934, is the presence of biliary obstruction as a consequence of duodenal diverticula. The precise aetiology remains uncertain. Multiple causative theories have been proposed. These include mechanical biliopancreatic duct occlusion, functional disruption of the sphincter of Oddi and alteration of the course of the distal biliary and pancreatic ducts. We present a case of biliary obstruction caused by diverticulitis of a solitary duodenal diverticulum. Methods A 71-year-old woman with no co-morbidities presented with early satiety, cachexia and upper abdominal pain. An epigastric mass was palpable, alkaline phosphatase was 247 iu/L, alanine transaminase 124iu/L, bilirubin 4umol/L and C-reactive protein 68mg/L. Computed tomography (CT) of the abdomen and pelvis revealed obstructed biliary tree with D2 duodenal diverticulitis. Magnetic resonance cholangiopancreatography (MRCP) displayed a causative enterolith. Treatment with antibiotics was initiated and the patient commenced on liquid diet. Liver function tests and inflammatory markers normalised. After a seven day admission patient was discharged and oral intake normalised. Interval MRCP revealed resolution of obstruction and inflammation. Results Duodenal diverticula occur in 1-20% of individuals. Complications are symptoms are uncommon. Diverticulitis is a rare complication. Malignancy and cholelithiasis should be excluded in diagnostic workup. The mainstay of therapy for duodenal diverticulitis is conservative. CT and MRCP are effective diagnostic tools. Diverticulectomy carries substantial risk of morbidity and mortality. Endoscopic sphincterotomy or lavage have a role in relief of biliary obstruction when present. Comparative prospective studies of management do not exist and retrospective enquiry is sparse. Management is thereby best determined clinically on a case by case basis. Surgery is reserved for failed conservative and medical therapy. Conclusions Duodenal diverticulitis should be considered in patients with unexplained upper abdominal pain and elevated inflammatory markers. In combination with obstructive jaundice, suspicions should be raised for acute inflammation causing obstruction to the biliary tree. Cross sectional imaging is useful in determining the diagnosis. Antibiotics and conservative therapy are prudent first line management in the absence of perforation. Where these measures are inadequate endoscopic and operative strategies may be employed but have no robust evidence basis.