New grading system for upper urinary tract dilation using magnetic resonance urography in patients with Neurogenic Bladder

BACKGROUND In patients with neurogenic bladder (NB), elevated intravesical pressures can be transmitted to the upper urinary tract, causing hydronephrosis (HN) and ureteral dilation (UD), which are referred to as upper urinary tract dilation (UUTD). Ureteral obstruction at the bladder wall is another cause for UUTD, but is less of a concern. UUTD can lead to chronic renal failure. Therefore, evaluation and protection of UUT function is extremely important in the management for NB. Currently, the most common method by which to detect HN and UD is ultrasonography (US). The Society for Fetal Urology (SFU) established an US HN grading system in 1993, but this system was found to have some defects. The purpose of this study is to describe a new grading system for UUTD, including both HN and UD, based on magnetic resonance urography (MRU) and to correlate the new grading system with the SFU grading system for HN. METHODS A retrospective review of 70 patients with unilateral or bilateral UUTD was completed. Ninety-five sides in patients with UUTD were graded by the MRU-UUTD and SFU-HN grading systems. The results from the two grading systems were compared for each UUTD. RESULTS The MRU-UUTD grading system revealed the following percentages for each grade: grade 0, 0; 1, 10.5%; 2, 19%; 3, 42.1%; and 4, 28.4%. The SFU-HN grading system revealed the following percentages for each grade: 0, 0; 1, 10.5%; 2, 19%; 3, 36.8%; and 4, 33.7%. There was no significant systematic difference between the two grading systems (p > 0.05), but a significant difference between grades 3 and 4 (p < 0.05). CONCLUSIONS The MRU-UUTD grading system correlates well with SFU-HN grade, provides an objective and comprehensive evaluation for UUTD, and can be used for longitudinal monitoring of UUTD. This new grading system allows for better informed clinical decision-making, identifying changes in UUTD.