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 re nal collecting system by US. Materials and methods. Wall thickening of the renal collecting system was s een during US in 62 collecting systems of 51 patients over a period of 2 ye ars. The medical and radiological records of these patients were reviewed w ith special attention to the definitive diagnosis and other clinical and ra diological parameters. Moreover, a control group consisting of 48 renal col lecting systems was examined to establish normal values for the thickness o f 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 tra ct infection (UTI) in 11, and both VUR and UTI in 9 cases. In 10 cases, int ermittent 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 be en 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 sy stem in children is 0.8 mm. Thickening of the wall of more than 0.8 mm shou ld be considered as pathological and is caused by urinary tract infection, intermittent dilatation (e.g., VUR), and dilatation in the recent past.