No abstract

We describe a safe method of percutaneous renal transplant biopsy using real time ultrasound guidance. The method provides a good histological sample, is straightforward and has a low complication rate.

Serial ultrasonographic measurements of renal transplant cross-sectional area were used to quantify allograft swelling as a diagnostic test of acute rejection. Eighty consecutive episodes of acute allograft dysfunction (rise in creatinine level > or = 10 per cent or > or = 30 mumol l-1) were investigated. Needle core biopsy was performed in all cases to diagnose acute rejection. Rejecting transplants demonstrated a median (interquartile range) swelling of 16.2 (12.1-25.5) per cent compared with 2.2 (-2.0 to 8.4) per cent for non-rejecting organs (P < 0.001). A > or = 10 per cent increase as the diagnostic threshold for rejection yielded a sensitivity of 80 per cent, specificity of 77 per cent, positive predictive value of 85 per cent, negative predictive value of 71 per cent and overall accuracy of 79 per cent. Using a logistic regression model, predictive probabilities of rejection for individual changes in cross-sectional area were calculated. A 20 per cent increase was associated with a predicted probability of rejection of 87 per cent (95 per cent confidence interval 75-94 per cent). There was a significant correlation between the functional severity of rejection and the degree of transplant swelling (rs = 0.63, P < 0.001). Ultrasonographic measurement of renal transplant cross-sectional area is a simple non-invasive test for the diagnosis of acute rejection.

In this prospective study we have used ultrasonographic measurements of the cross-sectional area of transplanted kidneys, as an objective assessment of graft size, for diagnosis of acute rejection episodes. Sixty episodes of acute graft dysfunction (serum creatinine rise of greater than or equal to 30 mumol/l) were studied in 40 patients. Tru-Cut biopsy under ultrasound control was performed in all cases and 36 episodes of acute cellular rejection were identified. An increase in graft cross-sectional area of greater than or equal to 10 per cent was defined as a positive scan, indicative of an acute rejection episode. Using these criteria, ultrasound correctly diagnosed rejection in 29 out of 36 cases (sensitivity 81 per cent) and there were four false positive results (specificity 83 per cent). The investigation had a predictive value of 88 per cent when positive and 74 per cent when negative.

Daily ultrasonographic measurements of transplant cross-sectional area were used to quantify allograft swelling as a diagnostic test for acute rejection in a series of 120 renal transplants. Initial graft function (IF) occurred in 86 patients (72%) and primary non-function (PNF) occurred in the remaining 34 (28%). An increase in allograft cross-sectional area greater than or equal to 10% was defined as a positive ultrasound scan suggesting an acute rejection episode and was investigated by needle core biopsy. During periods of PNF, allografts with consistently 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 ultrasound and histological diagnosis was good (k = 0.63, sensitivity 81%, specificity 83%, positive predictive value 76%, negative predictive value 86% and overall accuracy 82%). In the PNF group, agreement between ultrasound and histology was only fair (k = 0.46, sensitivity 77%, specificity 70%, positive predictive value 69%, negative predictive value 78% and overall accuracy 73%). It is concluded that a degree of allograft swelling is sometimes associated with acute tubular necrosis, and this makes ultrasound measurements of transplant size a less useful technique of monitoring kidneys with PNF.