Relationship of renal apparent diffusion coefficient and functional MR urography in children with pelvicalyceal dilation

The aim is to evaluate the age-related changes and relationship of renal apparent diffusion coefficient (ADC) against the morphological and functional changes detected by functional magnetic resonance urography (fMRU) in children with pelvicalyceal dilation, with suspected or known ureteropelvic junction obstruction. We retrospectively analyzed fMRUs with diffusion-weighted imaging (DWI) of the kidney in 35 subjects (25 males; median age: 7.1 years, range: 0.3–22.7 years) with 70 kidneys (40 with pelvicalyceal dilation and 30 with no pelvicalyceal dilation). Inclusion criteria were pelvicalyceal dilation, the absence of duplex kidneys and no ureteric dilation. DWI was performed with 3 diffusion gradient directions (b values = 0, 200, 500, 800 and 1,000 s/mm${}^2$). Metrics for fMRU included calyceal and renal transit times (CTT, RTT), time-to-peak (TTP), differential renal function based on volume (vDRF), Patlak number (pDRF) and combined volume and Patlak number (vpDRF). The grades of pelvicalyceal dilation, cortical thinning and corticomedullary differentiation were evaluated. The relationship between ADC values and the fMRU parameters was analyzed. ADC increases with age in kidneys without pelvicalyceal dilation (R${}^2$=0.37, P<0.001). Renal ADC does not correlate with any of the morphological or fMRU parameters (P>0.07). The median ADC of kidneys without pelvicalyceal dilation was 3.73×10${}^{\text{â}\text{ˆ}\text{’}3}$ mm${}^2$/s (range: 2.78–5.37×0${}^{\text{â}\text{ˆ}\text{’}3}$ mm${}^2$/s) and the median ADC of kidneys with pelvicalyceal dilation was 3.82×10${}^{\text{â}\text{ˆ}\text{’}3}$ mm${}^2$/s (range: 2.70–5.70×10${}^{\text{â}\text{ˆ}\text{’}3}$ mm${}^2$/s). There was no correlation between ADC and the absolute differences of vDRF or pDRF (P>0.33). Renal ADC does not correlate with morphological and functional results of fMRU changes in children with pelvicalyceal dilation due to suspected or known ureteropelvic junction obstruction.