DOPPLER SPECTRUM ANALYSIS IN THE DIFFERENTIAL-DIAGNOSIS OF RENAL-TRANSPLANT DYSFUNCTION

Cyclosporin A (CyA) nephrotoxicity and rejection of a renal allograft each demands a specific therapy. This study was designed to establish the capability of Doppler spectrum analysis to diagnose either one of these causes during renal dysfunction. Between October 1989 and Octobe r 1991 we performed echo-Doppler examinations in 209 renal transplant recipients on a routine basis during the first three months after tran splantation. Echo-Doppler examinations during periods of renal dysfunc tion were analyzed. A total of 93 periods of renal dysfunction, retros pectively due to rejection (n=40) or CyA toxicity (n=53), occurred in 70 patients during the study period. A control group consisted of 82 p atients with normal functioning grafts, When compared to the control g roup, the Doppler features (in segmental arteries) of the rejection gr oup showed significant lower frequency shifts [Fmax (Hz) 1637+/-423 vs . 1436+/-465; p<0.05; Fdia (Hz) 582+/-180 vs. 458+/-225; p<0.05], a sh orter deceleration time of the Doppler spectrum [Tdown (ms) 340+/-100 vs. 276+/-102; p<0.05], and a higher Resistance Index (RI 0.64+/-0.08 vs. 0.68+/-0.13; p<0.05). Doppler spectra during CYA toxicity showed o nly a significantly longer acceleration time [Tmax (ms) 123+/-36 vs. 1 39+/-40; p<0.05]. The capability of differentiation between the two ca uses was assessed with ROC analysis of single Doppler features, stepwi se regression and canonic discriminant analysis on a set of Doppler fe atures and with manual selection of several features with extreme valu es. ROC analysis yielded maximum sensitivity and specificity for the d iagnosis of rejection using Tdown (sensitivity 65%; specificity 68%), Stepwise regression and canonic discriminant analysis of a set of feat ures rendered a sensitivity and specificity of 73% and 64%, respective ly. Explorative selection of extreme Doppler feature values showed tha t 18 of the 40 grafts with rejection had values that were only seen in 2 cases with CYA toxicity (positive predictive value 90%; sensitivity 45%; specificity 96%). In half of these cases Doppler features preced ed the clinical diagnosis of rejection by a median of 4 d. In conclusi on, Doppler spectra are influenced by rejection and CyA toxicity in sp ecific ways. The Doppler features, however, do not enable definite dif ferentiation between rejection and CyA toxicity in all cases. Some cha nges in Doppler spectra are only seen in cases of rejection and thus e nable positive identification of grafts with rejection, often earlier than clinical signs indicate rejection. A normal Doppler spectrum does not exclude rejection as the cause of renal dysfunction.