When a bubble bursts

: A 47-year-old man with a medical history of nephrolithiasis of the right kidney presented with abdominal pain at the level of the right hip. Ultrasonography showed an anechoic area with irregular contours in the lower pole of the right kidney, where a previous ultrasound scan had signalled the presence of a large cyst. Abdominal computed tomography revealed the presence of a fluid area within the lower pole of the right kidney. Subsequent ultrasonography showed progressive reduction of the anechoic area, which was associated with gradual reduction of the pain. The case was diagnosed as spontaneous rupture of a renal cyst. Renal cyst rupture is an infrequent, usually self-limiting event that may engender diagnostic dilemmas.