DOPPLER SPECTRUM ANALYSIS TO DIAGNOSE REJECTION DURING POSTTRANSPLANTACUTE-RENAL-FAILURE

During posttransplant acute renal failure (ARF), the diagnosis of allo graft rejection constitutes a major problem. We evaluated the value of Doppler ultrasonography in identifying grafts at risk of rejection du ring ARF. In 184 recipients of a renal allograft, Doppler examinations were performed on the first and fifth postoperative day. Doppler spec tra were quantitatively analyzed with a user-written computer program. Doppler findings were not used in clinical decision making. ARF was d efined as a diuresis < 400 ml/24 hr and/or the necessity for dialysis. Doppler spectra obtained on the first day after transplantation showe d a resistance index (RI) of 0.59+/-0.09 in recipients with immediatel y functioning cadaveric grafts (n=123), while living related donor gra fts (n=20) showed a lower RI (0.55+/-0.07; P<0.05). Grafts with ARF (n =41) showed a considerably higher RI (0.67+/-0.13; P<0.05). When graft s with a duration of ARF less than or equal to 4 days (n=17) were comp ared with ARF > 4 days (n=24), RI was not significantly different (0.6 3+/-0.07 vs. 0.68+/-0.15; NS). However, the acceleration time of the s ystolic deflection of the spectrum waveform (Tmax) was shorter in graf ts with ARF > 4 days (86+/-47 msec vs. 128+/-39 msec; P<0.05). On the fifth day after transplantation, Doppler spectra in grafts with ARF > 4 days (n=24) showed a Tmax < 90 msec in 9 patients, 8 of whom experie nced rejection during ARF (positive predictive value, 8/9=89%). In the 15 patients with Tmax greater than or equal to 90 msec, only 2 reject ions occurred (negative predictive value, 13/15=87%). For the RI (> 0. 85), positive predictive value was 4/5=80% and negative predictive val ue (RI less than or equal to 0.85) was 13/19=68%. In conclusion, a sho rt acceleration time of the Doppler waveform on the first day after tr ansplantation is associated with a longer duration of ARF. Quantitativ e analysis of Doppler spectra can be helpful in the identification of patients at risk for rejection and in the timing of allograft biopsy d uring ARF. Persistently short Tmax values on the fifth day after trans plantation perform better in identifying grafts at risk of rejection t han high RI values.