Background: Simple renal cysts are usually asymptomatic and benign. Rarely, symptoms and complications can develop from local mass effect which is illustrated by this case. Case Presentation: 77 year old Caucasian male presents with abdominal pain for five days. Abdominal exam was diffusely tender, markedly distended, tympanic with absent bowel sounds. His work-up included an abdominal x-ray showing a colonic obstruction and abdominal CT showing a large 27 cm renal cyst. Drainage of the renal cyst resolved obstructive symptoms. Conclusion: A simple renal cyst should not be overlooked as the reason for acute abdominal pain. Simple renal cysts, though benign are not without complications. © Harrington et al.; Licensee Bentham Open. This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.