Value of Doppler ultrasonography in predicting deteriorating renal function after spinal cord injury

The authors sought to study the relationship between Doppler ultrasonography and deterioration of renal function in patients with spinal cord injury.

Nineteen patients who underwent follow-up with radioisotopic renography were evaluated. Median patient age was 50 [interquartile ratio (IQR) 35-57] years, and time since injury was 4.7 (IQR 1.3-9.2) years. Following Doppler ultrasound, patients were divided into groups based on baseline renal resistive index (RRI): normal RRI (≤ 0.7), group 1 (n=14); and abnormal RRI (> 0.7), group 2 (n=5), and were followed up with radioisotopic renography 1 or more years later. Annual change in effective renal plasma flow (ERPF) was analysed.

The 38 kidneys (two for each patient) were stratified by initial RRI, with 28 in group 1 and ten in group 2. Result of univariate generalised estimation equation (GEE) analysis for the factors affecting the change in effective renal plasma flow (ERPF) indicated that the high RRI value (RRI > 0.7) correlated with the change in ERPF. ERPF value in group 2 was significantly decreased (p=0.01) by an average of 60.33 ml/min (standard error = 23.26).

An RRI > 0.7 is a risk factor for future renal function deterioration in patients with spinal cord injury. Thus, annual Doppler ultrasonography to assess the RRI and the degree of hydronephrosis is recommended.