A 22-year-old girl who had a background of reflux nephropathy and urinary tact infection presented during the night with renal angle pain and vomiting. She was treated on the emergency department (ED) pyelonephritis protocol and admitted to the short stay ward. When reviewed the next morning she was aymptomatic and feeling better. It seemed likely that she would be discharged but an ED ultrasound showed right-sided hydronephrosis and some fluid between the liver and the right kidney. CT examination confirmed the suspicion of renal tract obstruction and ruptured calyx. An 8 mm calculus was found to be the cause of the pathology. Urgent urological review was organised and the system formally decompressed with a J-J stent inserted cystoscopically later that day.