Decoding kidney function: evaluating arterial resistive index and cystatin C serum values in individuals with spinal...

Individuals with neurogenic lower urinary tract dysfunction after spinal cord injury should undergo regular scintigraphy to assess renal function. However, renal scintigraphy entails radiation exposure and is not widely available. Consequently, reliable alternative diagnostic parameters are needed. We have, thus, investigated whether renal sonography and cystatin-C measurements are consistent with renal scintigraphy results in this population.

Adult individuals with chronic spinal cord injury (duration ≥ 5 years) underwent renal sonography and cystatin-C measurement during routine consultation, followed by renal scintigraphy within six weeks. The correlation between renal sonographic parameters (arterial resistive index, renal parenchymal thickness, and kidney dimensions), serum cystatin-C, and scintigraphy clearance values was assessed using Pearson and Spearman's rank correlation coefficients. Furthermore, the classification accuracy (for scintigraphy clearance ≤ 150 ml/min) of variables with statistically significant correlation coefficients was investigated.

Data of 8 women and 42 men (54 ± 14 years old; duration spinal cord injury 24.4 ± 14.6 years) were analyzed. There was a fair correlation between scintigraphy clearance and cystatin-C levels (r = -0.37, p = 0.013) as well as left renal resistive index (r = -0.44, p = 0.002). However, there were no correlations between scintigraphy clearance and renal parenchymal thickness (p > 0.45) as well as kidney dimensions (p > 0.13). Cystatin-C and left renal resistive index showed good classification performance (area under curve = 0.74/0.84, p < 0.00001).

Individuals with reduced renal function can be identified reliably using cystatin-C serum concentration and renal arterial resistance. These parameters may serve as additional diagnostic parameters to assess renal function and to determine whether scintigraphy examination is required.

NCT04241666.