Christopher Beirne MBBCh, MRCS, Presenter: Nothing to Disclose

Aisling Courtney MRCP, MBBCh, Abstract Co-Author: Nothing to Disclose

John Trevor Lawson MD, Abstract Co-Author: Nothing to Disclose

Ultrasonography is routinely performed following renal transplantation to assess for early complications including acute tubular necrosis, accelerated rejection, obstruction or collections and renal vein/renal artery thrombosis. The schedule of scans has been based on historical practice and many patients have multiple scans. The resistive index, which is a measure of pulsatile flow affected by vascular resistance, heart rate and pulse pressure, is measured in all patients however its predictive relationship to post-operative complications has been debated and we have also assessed the value of routine RI measurement.

Data from a prospectively maintained transplant surgery database was analysed and correlated with the ultrasound scan findings over a 4-year period January 2010 to December 2013. Initially a retrospective audit of all data was performed between January 2010 and December 2012. This was used to identify potential areas for service improvement. This included a review of the referral pattern and development of an optimal schedule for imaging as well as issues such as patient transportation and service provision in the out-of-hours setting. These factors were subsequently addressed by a prospective audit performed immediately over the following 4 month period. As a consequence of this second audit, a protocol was then introduced to optimise service provision for all renal transplant patients. All subsequent transplant patients up until December 2013 were prospectively audited to ensure protocol safety. The timing of renal transplant ultrasonography (by post-operative day), CFUS, R.I. and significant renal and extra-renal findings were recorded. The R.I. of patients requiring post-operative biopsy, post-operative haemodiaysis or prolonged sonographic investigation (>5 days) were also analysed for significance.

Total number of patients (n=324). Mean age = 44 years (range 3-73 years). Living related/unrelated donor (n=204) versus cadaveric donor (n= 120). Within the initial audit period January 2010 –December 2013: Transplant cases, n = 223. Mean number of ultrasound exams performed per patient, n=6.1 (4 – 14). Number of acute transplant rejections (n=3, 1.6%), RI >1 (n=2). There was no significant difference in RI within surviving grafts (live or cadaveric donor) assessed at days 1, 3, 4 or 5 (p=0.69, 0.5, 0.71 or 0.83 respectively). RI was not significantly different in patients requiring biopsy or post-operative haemodialysis (p=0.71, 0.82). During the first prospective audit January 2013 – April 2013: Transplant cases, n= 36. Mean number of ultrasound exams performed per patient, n=4.19 (2 – 9). Number of acute transplant rejections (n=0), RI >1 (n=1). With the protocol implemented during May 2013 – December 2013: Transplant cases, n = 65. Mean number of ultrasound exams performed per patient, n = 3.4 (2 – 12). Number of acute transplant rejections (n = 1, 1.5%), R.I. >1 (n=0). During both the re-audit and protocol implemented period the R.I was not found to be significantly different between patients who had a satisfactory post-transplant course and those patients who were not progressing satisfactorily and required biopsy or post-operative haemodialysis (p=0.64, 0.5). There was also a marked reduction in examinations performed within both the re-audit and protocol period, when the patients were imaged according to an agreed schedule and directed referral pattern.

Renal transplant patients in the immediate post-operative period do not routinely require multiple CFUS with RI calculation. RI does not reliably predict patients requiring biopsy or prolonged post-operative dialysis. Patients with elevated RI’s (>1) have an increased association with acute rejection, and a low threshold for performing ultrasound is indicated when graft rejection is suspected. In those patients who have undergone uncomplicated surgical and who have a smooth post-operative course we have successfully introduced a protocol within our institution to perform CFUS on Day 1 and 5 (living donor) and Day 1, 3 and 5 (cadaveric donor). This enables a more efficient use of the ultrasound department and our out of hours service with no detriment to patient care. Those patients who are at increased risk are also better identified as the request forms have been re-designed to ensure that all relevant clinical details are available to the radiologist. An additional benefit is a significant cost saving (annual reduction in CFUS examinations of approximately 2.7 scans per patient with approximately 100 transplants per year), with much of the reduction being in out of hours scanning.

Beirne, C, Courtney, A, Lawson, J, Analysis of 4-years Experience of Renal Transplant Colour Flow Ultrasonography (CFUS) and Renal Arterial Resistive Index (RI) Measurement to Determine the Optimum Post-operative Renal Transplant Imaging Protocol.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012877.html