A 53-yr-old woman presented with a 2-yr history of recurrent episodes of severe abdominal pain and nausea. Multiple investigations by a general surgeon, a urologist, and a gastroenterologist failed to identify the cause. She was referred to our Biliary Service for ERCP and sphincter of Oddi manometry. However, a detailed history was inconsistent with biliary pain, and the patient, having discussed the risks and benefits, elected not to proceed with ERCP. The patient was asked to come to the hospital during an acute attack of her pain for assessment. When this was done, transabdominal ultrasound revealed right hydronephrosis; intravenous urography showed obstruction at the level of the ureteropelvic junction, consistent with the presence of an aberrant artery. The syndrome of episodic abdominal pain and hydronephrosis caused by extrinsic pressure from such an artery is known as Dietl's crisis. In our patient, the diagnosis was confirmed at surgery, when the ureteric obstruction was dealt with by pyeloplasty. She made an uneventful recovery and remains asymptomatic 12 months later. The keys to diagnosing Dietl's crisis are awareness of the entity, taking a detailed pain history, and timely cross-sectional abdominal imaging during an attack.