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The use of renal transplant duplex ultrasound as a predictor for return to dialysis in renal transplant patients
Alison O. Flentje, BS, Stephen Gayle, Sadaf S. Ahanchi, MD, Reynold Lopez-Soler, MD PhD, Dave J. Dexter, MD, John Colonna, MD, Jean M. Panneton, MD.
Eastern Virginia Medical School, Norfolk, VA, USA.
Objectives: Renal transplants are frequently monitored using duplex ultrasound (DUS) to assess for vascular complications, which includes transplant renal artery stenosis. While the DUS criteria of peak systolic velocity (PSV) and resistive index (RI) have been proven to have a predictive value for renal stenosis and renal failure in native renal arteries, the clinical implications of these DUS values have not been investigated in transplanted renal arteries.
Methods: A retrospective chart review was conducted on patients who underwent renal transplant at a single institution from 2008 to 2012. The primary endpoint was return to dialysis. Secondary endpoint was survival. Area under the receiver operating characteristic curve (AUROC) was used to determine the predictive value of PSV, RI, renal iliac ratio (RIR), and systolic rise time (SRT) on the endpoints. A student t-test was also performed on the DUS values.
Results: Of the 327 patients reviewed, 63 were removed from the study (4 for lack of data, 1 for bilateral renal transplantation, 1 for immediate postoperative thrombosis of the graft, and 57 for immunologic rejection). The remaining 264 patients had a mean age of 51 with 58% males and an average BMI of 30. Comorbidities included hypertension (98%), hyperlipidemia (60%), diabetes (50%), and coronary artery disease (34%). At a mean follow up of 17 months the overall rate of return to dialysis was 9% and the overall survival was 91%. The best predictors for return to dialysis were RI (AUROC=0.634) and PSV (AUROC =0.531). ). A RI value of ≥0.75 gave a sensitivity (SN) of 61% and a specificity (SP) of 59% with a positive predictive value (PPV) of 10% and a negative predictive value (NPV) of 95%. A PSV of ≥250 gave a SN of 39% and SP of 75% with a PPV of 10% and NPV of 94%. The average RI of patients who returned to dialysis was 0.8, which was significantly higher than the patients who did not return to dialysis (RI=0.73, p=0.008).
Conclusions: In conclusion, the resistive index (RI) and peak systolic velocity (PSV) values of a renal transplant DUS are the strongest predicators of return to dialysis.
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