THE INFLUENCE OF PRIMARY NON-FUNCTION ON THE ACCURACY OF ULTRASOUND MEASUREMENTS IN THE DIAGNOSIS OF RENAL-ALLOGRAFT REJECTION

Daily ultrasonographic measurements of transplant cross-sectional area were used to quantify allograft swelling as a diagnostic test for acu te rejection in a series of 120 renal transplants. Initial graft funct ion (IF) occurred in 86 patients (72%) and primary non-function (PNF) occurred in the remaining 34 (28%). An increase in allograft cross-sec tional area greater than or equal to 10% was defined as a positive ult rasound scan suggesting an acute rejection episode and was investigate d by needle core biopsy. During periods of PNF, allografts with consis tently negative ultrasound scans were submitted to needle core biopsy on a weekly basis. The diagnosis of rejection was based exclusively on the histological findings. In the IF group, agreement between ultraso und and histological diagnosis was good (k = 0.63, sensitivity 81%, sp ecificity 83%, positive predictive value 76%, negative predictive valu e 86% and overall accuracy 82%). In the PNF group, agreement between u ltrasound and histology was only fair (k = 0.46, sensitivity 77%, spec ificity 70%, positive predictive value 69%, negative predictive value 78% and overall accuracy 73%). It it concluded that a degree of allogr aft swelling is sometimes associated with acute tubular necrosis, and this makes ultrasound measurements of transplant size a less useful te chnique of monitoring kidneys with PNF.