Spontaneous perforation of the collecting system constitutes a rare entity masked by the presentation of a typical renal colic. However, it should not be forgotten when managing patients with colic, since missed diagnoses may carry significant morbidity. We herein present a series of spontaneous perforation of the collecting system without an apparent obstruction site evident in helical CT urography. Four consecutive patients who presented with typical renal colic were initially subjected to KUB and renal ultrasound imaging and were ultimately diagnosed with perforation of the collecting system via contrast enhanced- helical CT urography. Despite thorough evaluation, the cause responsible obstructive was not discovered and an exclusion diagnosis of idiopathic collecting system perforation was assigned to all patients. Due to the rarity of a spontaneous perforation traditional retrograde urography was performed in an effort to identify the possible cause but was also unrevealing. All patients were successfully treated with endourological means. Perforation of the collecting system without an evident obstructive cause is a rare entity with obscure etiology. A reasonable but yet unconfirmed speculation is that of a transient obstruction capable of a significant increase of intraluminal pressures.