Purpose: We studied changes in the renal resistive index (RI) of the remaining kidney after live donor nephrectomy.
Materials and methods: The study included 24 healthy live kidney donors (14 males and 10 females) with a mean age of 42 years. After donor evaluation Doppler ultrasound was done of the 2 kidneys the day before nephrectomy with RI measurement of each kidney. After nephrectomy the RI of the remaining kidney was measured on days 2, 4, 6, 8 and 10, and then at weeks 2, 3, 6 and 12. Mean RI of the remaining kidney before nephrectomy was compared to values at different time points after nephrectomy. Changes in the RI of the remaining kidney were screened at the followup time points.
Results: There was no difference between the mean RIs of the right and left kidneys before nephrectomy (0.67 +/- 0.04 and 0.67 +/- 0.04, respectively). The RI of the remaining kidney increased from 0.67 +/- 0.04 before nephrectomy to 0.71 +/- 0.06 on day 2 after nephrectomy, which was significantly different (p <0.0001). The mean RI increase of the remaining kidney on day 2 was 0.05 +/- 0.03. The RI of the remaining kidney remained almost stable on days 4, 6, 8, and 10, and also at week 2. Comparison between the mean RI at weeks 2 (0.72 +/- 0.05) and 3 (0.73 +/- 0.05) showed a further increase of significant value (p <0.0001). The mean RI remained stable at weeks 6 (0.73 +/- 0.05) and at 12 (0.73 +/- 0.05).
Conclusions: The RI of the remaining kidney significantly increases after nephrectomy of the contralateral kidney. Therefore, an RI value of 0.7 is not suitable to diagnose a pathological condition in a solitary kidney in adults.