Significance of thickening of the wall of the renal collecting system in children: an ultrasound study.

Objective: To evaluate the significance of thickening of the wall of the renal collecting system by US.
Materials and Methods: Wall thickening of the renal collecting system was seen during US in 62 collecting systems of 51 patients over a period of 2 years. The medical and radiological records of these patients were reviewed with special attention to the definitive diagnosis and other clinical and radiological parameters. Moreover, a control group consisting of 48 renal collecting systems was examined to establish normal values for the thickness of the wall of the collecting system.
Results: Of the 62 collecting systems (mean wall thickness 1.6 mm, range 0.8-3.1 mm), vesicoureteric reflux (VUR) was present in 18 cases, urinary tract infection (UTI) in 11, and both VUR and UTI in 9 cases. In 10 cases, intermittent dilatation was present caused by primary obstructive megaureter (n = 2), pelvi-ureteric junction stenosis (n = 4), high-pressure bladder (n = 3), or of unknown cause (n = 1). In 11 cases, transient dilatation had been present in the recent past (usually prenatally detected hydronephrosis), but had disappeared at the time of the US examination. In 3 patients, no definite cause for the wall thickening could be established. In the control group, wall thickness ranged from 0.1 to 0.8 mm.
Conclusions: The upper limit for wall thickness of the normal collecting system in children is 0.8 mm. Thickening of the wall of more than 0.8 mm should be considered as pathological and is caused by urinary tract infection, intermittent dilatation (e. g., VUR), and dilatation in the recent past.