Clinical and radiological course of simple renal cysts in children

To evaluate the clinical and, particularly, radiological course of simple renal cysts in children.

Children with simple renal cysts were retrospectively evaluated, especially for change in the cyst diameter during follow-up and complications. In addition, the rate of increase in cyst size per year was calculated, and those characteristics of the cyst were analyzed to predict aggressiveness.

Simple renal cysts were detected in 45 (21 male) patients. Mean ages at diagnosis and follow-up period were 7.4 ± 4.9 and 2.9 ± 1.8 years, respectively. Forty-one of the 45 patients were followed up for longer than 1 year. Diameter of the cyst increased in 20 (49%), decreased in 4 (10%), unchanged in 13 (31%), and disappeared in 4 (10%) of patients. The average size increase and average rate of enlargement in simple cysts were 0.3 mm and 1.0% per year, respectively. Furthermore, in 19 (95%) patients, the cyst size increased in the first 2 years. Among baseline parameters, only initial cyst size was an independent predictor of annual growth rates (beta = 0.628; P <.001). The relationship between the initial cyst size and annual growth rates was determined as positive (r = 0.459, P = .003). Two patients with large cysts developed severe complication in the first 6 months. One of these underwent nephrectomy because of rapid increase in cyst diameter (170 mm), renal artery/vein compression, and massive hematuria. In the other patient with severe loin pain regarding simple cyst (73 mm), percutaneous aspiration was performed.

Simple renal cysts in childhood tend to slowly increase in size. However, regular radiological follow-up might be important, especially in children with large size of cyst at diagnosis, because of more rapid increase in cyst size.