Reversible stenosis of the renal artery following renal transplantation

Comparing the diagnostic accuracy of contrast-enhanced computed tomographic angiography and gadolinium-enhanced magnetic resonance angiography for the assessment of hemodynamically significant transplant renal artery stenosis

To compare diagnostic accuracy of contrast-enhanced computed tomographic angiography (CTA) and gadolinium-enhanced magnetic resonance angiography (MRA) for the assessment of hemodynamically significant transplant renal artery stenosis (TRAS). After institutional review board approval, records of 27 patients with TRAS confirmed on digital subtraction angiography (DSA) were retrospectively reviewed. A total of 13 patients had MRA and 14 had CTA before DSA. Two board-certified fellowship-trained radiologists, one each from interventional radiology and body imaging blindly reviewed the DSA and CTA or MRA data, respectively. Sensitivity (SN), specificity (SP), positive predictive value, and negative predictive value of MRA and CTA were estimated using 50% stenosis as the detection threshold for significant TRAS. These parameters were compared between modalities using the Fisher exact test. Bias between MRA or CTA imaging and DSA was tested using the Wilcoxon signed-rank test. Two patients were excluded from the MRA group owing to susceptibility artifacts obscuring the TRAS. The correlation between MRA and DSA measurements of stenosis was r = 0.57 (95% CI:-0.02, 0.87; P = 0.052) and between CTA and DSA measurements was r = 0.63 (95% CI: 0.14, 0.87; P = 0.015); the difference between the 2 techniques was not significant (P = 0.7). Both imaging modalities tended to underestimate the degree of stenosis when compared with DSA. MRA group (SN and SP: 56% and 100%, respectively) and CTA group (SN and SP: 81% and 67%, respectively). There were no significant differences in detection performance between modalities (P>0.3 for all measures). We did not find that either modality had any advantage over the other in terms of measuring or detecting significant stenosis. Accordingly, MRA may be preferred over CTA after positive color Doppler ultrasound screening when not contraindicated owing to lack of ionizing radiation or nephrotoxic iodinated contrast. However, susceptibility of artifacts owing to surgical clips at the anastomosis may limit diagnostic utility of MRA as found in 2 of 13 patients. Trend towards no significant difference between the CTA and enhanced MRA in the detection of hemodynamically significant TRAS.

Duplex-Doppler Long-term Follow-up of Renal Transplant Artery Stenosis: Case Controlled Study

The aim of this retrospective clinical study was to assess a long-term course of renal transplant artery stenosis with duplex-Doppler ultrasound, and its influence upon serum creatinine, hemoglobin concentration and hypertension, as well as to investigate a possible association between stenosis and the number of acute rejections. Thirty-four renal transplant recipients, aged 43 +/- 13 years, with significant (>50%) renal transplant artery stenosis as seen on Doppler ultrasound were compared with 34 renal transplant recipients without stenosis (excluded by Doppler). Patients of both groups were matched by age, sex, time of transplantation, type of renal transplant, and number of previous transplantations. We analyzed peak systolic velocity (PSV) in the renal transplant artery, resistance index (RI) at the level of intra-renal arteries, serum creatinine, hemoglobin concentration, blood pressure, the number of antihypertensive medications, and the number of acute rejections on a yearly basis. In the stenosis group, PSV was 2.1 +/- 0.5 m/s at 1 year after transplantation (controls 1.1 +/- 0.4), 1.9 +/- 0.5 at 2 years (0.9 +/- 0.4), 1.9 +/- 0.5 at 3 years (0.9 +/- 0.4); RI was 62 +/- 10% at 1 year (controls 68 +/- 7), 65 +/- 9 at 2 years (67 +/- 7), 63 +/- 9 at 3 years (67 +/- 7); serum creatinine was 128 +/- 58 micromol/L at 1 year (controls 129 +/- 43), 119 +/- 47 at 2 years (121 +/- 33), 125 +/- 54 at 3 years (127 +/- 32). Long-term course of renal transplant artery stenosis (>50%), treated medically or interventionally, seems to be stable and non-progressive (during a 3-year follow up). Spontaneous regression of stenosis to non-significant level is possible. No difference in graft function, blood pressure or the number of acute rejections was observed comparing the stenotic and non-stenotic groups.

High-grade renal transplant artery stenosis after suboptimal angioplasty: favourable long-term outcome

The purpose of our report is to present the long-term outcomes of three renal transplant recipients with high-grade stenosis and suboptimal percutaneous angioplasty (PTA) because of technical difficulties. Two men and one woman of age 67, 53, and 54 years, who maintained functional cadaveric graft for 17, 9, and 13 years, and had diagnosed significant renal transplant artery stenosis at 2, 1, and 2 years after renal transplantation, respectively, were studied. Stenoses were diagnosed angiographically in the first patient and by Doppler in other two patients, then confirmed by angiography. All three patients had difficult-to-treat hypertension with deterioration of graft function in the presence of or after introducing ACE-inhibitor therapy. PTA was performed in all patients with suboptimal or unsuccessful results as assessed by angiography or control Doppler examination--the residual stenosis was significant and practically unchanged. Surgery was not performed because of high risk, so patients were further treated conservatively. Hypertension was treated avoiding ACE inhibitors. Twelve, 7, and 7 years after angioplasty the serum creatinine is stable in all patients, even decreased compared to pre-PTA and early post-PTA levels, namely, 134, 102, and 75 micromol/L, respectively. Control Doppler examinations revealed a residual stenotic jet in all patients, with slightly decreased peak systolic velocity over time, indicating a slightly decreased grade of stenosis. These observations suggest that renal transplant artery stenosis, even of high grade, can be stable, or even regress with time with excellent long-term graft survival. Randomized studies comparing conservative treatment versus revascularization are warranted.

The use of expandable metal stents in transplant renal artery stenosis

The management of resistant transplant renal artery stenosis (TRAS) poses difficult problems. There is no consensus on the most appropriate course of action if severe stenosis recurs despite repeated percutaneous transluminal balloon angioplasty (PTA). Expandable metallic vascular stents have been increasingly successful as an adjunct to PTA in the coronary and peripheral circulation and more recently in the management of resistant native renal artery stenosis. We report four cases in which such stents were successfully used to treat resistant stenosis in transplant renal arteries. The cases illustrate the range of problems that may be caused by TRAS, from resistant hypertension to impending graft failure. The stents were successfully deployed in all four patients. One patient had an acute stent thrombosis successfully treated with immediate thrombolysis and two patients required repeat stenting. In all the cases there was arrest or slowing of previously aggressive recurrent TRAS and at the close of follow-up (4-24 months) all patients had adequate stable allograft function, and satisfactory blood pressure control including the one patient with a significant residual stenosis.