Interventional uroradiologic procedures can be divided into two major groups: vascular and percutaneous nonvascular. Percutaneous nonvascular interventional procedures are discussed elsewhere. Regarding vascular interventions, transcatheter embolotherapy is frequently performed to treat urinary tract and pelvic hemorrhage. Embolization is also used for tumor devascularization, for the cessation of renal function, and for the treatment of testicular vein and ovarian vein varices. Balloon angioplasty and stenting of stenotic renal arteries may be performed for secondary hypertension refractory to medical therapy. Renal artery aneurysms may also be treated using catheter-directed techniques such as stent grafting and selective embolization. This chapter will review these and other intravascular interventions.
Renal AV Fistulas, AV Malformations, and Pseudoaneurysms
Transcatheter embolization is the treatment of choice for renal arteriovenous fistulae (AVFs), which may be congenital, spontaneous, or acquired. Iatrogenic AVFs are the type most commonly treated by transcatheter embolization. These occur as a complication of such procedures as percutaneous renal biopsy (Libicher et al, 2006), nephrostomy placement, and pyelolithotomy. Trauma or surgery can also result in AVFs. AVF occurring in the transplant kidney is successfully managed by embolization. The classical angiographic finding of spontaneous or acquired AVF is a feeding artery with an early draining vein. Renal pseudoaneurysms may be seen with or without an associated AVF. Psuedoaneurysms, unlike true aneurysms, are not contained by the three normal layers of the arterial wall. In some cases, pseudoaneurysms are contained only by the periadventitial tissues adjacent to a blood vessel. These lesions can be seen not only after biopsy but also after partial nephrectomy. A congenital arteriovenous malformation (AVM) consists of a group of multiple coiled communicating vessels that may be associated with enlarged feeding arteries and draining veins.
The most common clinical presentations are hematuria and retroperitoneal hemorrhage. Congestive heart failure may be seen in patients with large, high-flow AVMs. Hypertension can also occur in the setting of high-volume shunting, as normal renal parenchyma becomes relatively ischemic. Computed tomographic angiography (CTA) or magnetic resonance angiography (MRA) will diagnose and characterize these vascular lesions before angiographic intervention.
Successful intervention requires the angiographic identification, selective catheterization, and embolization of the feeding branches. Using a transfemoral approach, a selective renal angiogram with a 5 French (5Fr) diagnostic catheter is performed to characterize the arteries of the bleeding kidney. In the case of a renal transplant, an initial pelvic angiogram in a steep oblique projection may be useful to characterize the renal artery anastomosis prior to selective injection. A 3Fr or smaller coaxial microcatheter is then used for subselective catheterization and embolization of the feeding artery. Microcoils are used for the occlusion of iatrogenic AVFs and pseudoaneurysms because they can be deployed very precisely in small branches, thereby minimizing the loss of renal parenchyma due to resultant ischemia (Figure 7–1A, B). Inadvertent nontarget embolization and renal artery dissection are uncommon complications of the procedure.