2018 Volume 43 Issue 2 Pages 269-272
Although simple renal cysts are often found during routine health checkups, spontaneous disappearance of the cysts is rare. A 57-year-old male patient was referred to our department because of right renal cyst found by ultrasound during his annual health checkup. CT showed a simple renal cyst, 2.5cm×2.3cm in size, at the middle pole of the right kidney, and patient had been followed yearly by ultrasound. On the follow-up ultrasound performed 8 years after the diagnosis, the cyst was not detected. The following CT revealed the disappearance of the cyst, leaving only minute residual tissue of the cyst wall. As the patient has been asymptomatic over the past year after the last examination when the cyst was noted by ultrasound, the cyst was considered to have disappeared spontaneously. We reported the present case because including this case, there has only been a total of 3 reported cases of spontaneous disappearance of simple renal cyst in Japan, and because we thought it is worthwhile to let not only urologist but surgeon know this phenomenon.
