Heart, renal, hepatic, and pancreatic transplantations are being performed with increasing frequency, leading to a greater demand for knowledgeable evaluation of vascular complications involving these grafts. Arterial anomalies associated with implantation of these grafts and arterial complications following transplantation, both present unique anatomic and physiologic problems. Arterial and venous stenoses and occlusions, pseudoaneurysms, and arteriovenous fistulas may occur in this patient population. Here, we summarize the most common arterial complications that take place in transplant recipients with a discussion of how to approach these complications.
ARTERIAL COMPLICATIONS IN RENAL TRANSPLANTATION
There is a wide spectrum of vascular complications that can occur with renal transplantation. Fortunately renal artery complications are not very common. The most frequent arterial problems seen are renal artery stenosis, renal artery thrombosis, dissection of the external, internal iliac or common iliac arteries, renal artery pseudoaneurysm, and renal transplant arteriovenous fistula.
While postrenal transplant hypertension is a common problem, renal artery stenosis should be considered in patients presenting with severe or intractable hypertension after renal transplantation. Transplant renal artery stenosis (TRAS) is important to identify because it is a correctable form of hypertension. Although it can present at any time, renal artery stenosis usually becomes evident between 3 months and 2 years posttransplant.1
Diagnosis of hemodynamically significant renal artery stenosis rests on a radiologic demonstration of ≥50% reduction in renal artery diameter.2 The rationale for this assumption is derived from experimental evidence that the stenosis needs to occlude at least 50% of the lumen before renal blood flow and perfusion pressure start to decrease and systemic blood pressure increase.2 The risk factors for renal transplant artery stenosis include atherosclerotic disease of donor or recipient vessels, cytomegalovirus (CMV) infection, delayed allograft function, and rejection.3,4,5,6 In a recent retrospective study of 29 recipients with stenosis and a case-control group of 58 patients, an increased risk of stenosis was significantly associated with CMV infection (41% versus 12%) and delayed graft function (48% versus 16%).3
Renal artery stenosis can present with short segment, long segment, unifocal, and multifocal involvement. The prevalence of anastomotic renal transplant artery stenosis can be difficult to assess because of discrepancy in the definition of hemodynamically significant lesions and the use of different diagnostic modalities. Renal artery stenosis occurs in 1% to 12% of the patients after transplantation.7
Persistent, uncontrolled hypertension, flash pulmonary edema, and an acute elevation in blood pressure are other common features of this disorder and should alert the clinician.8,9
Multiple techniques have been used to diagnose renal artery stenosis. Arteriography remains the procedure of choice for establishing the definitive diagnosis of renal artery stenosis after transplantation, but other noninvasive techniques such as duplex ultrasound (US), magnetic resonance (MR) angiography, and computed tomography (CT) angiography are increasingly utilized ...