Spontaneous perforation of the ureter proximal to an obstruction has not been well described in the literature. We present a rare case of spontaneous perforation of the ureter, proximal to a radiolucent upper ureteric stone, in a 58-year-old diabetic female, causing a large infected urinoma and septicaemia in a solitary functioning kidney. The diagnosis was confirmed by computer tomography scan. We managed the case successfully by endourology only. The case emphasizes the importance of the differential diagnosis in a diabetic patient with obstructive uropathy.