Renal Artery Aneurysm Treatment & Management

Emergency Surgical Repair of Ruptured Renal Artery Aneurysm

Emergency surgery is required to control hemorrhage and prevent death from a ruptured aneurysm. A midline approach with supraceliac aortic control is required because exposure of the renal vessels may be difficult in the presence of a large perinephric hematoma. The aortic cross clamp can be removed once the renal artery is controlled. In most cases of rupture, renal salvage may not be possible because of hemodynamic instability; therefore, nephrectomy may be necessary. In a hemodynamically stable patient, renal salvage with renal artery reconstruction may be considered.^[25]

Management of the gravid uterus in a pregnant patient with acute renal artery aneurysm (RAA) rupture should follow the same principles observed when treating hemorrhage caused by intra-abdominal trauma in a pregnant patient. Cesarean delivery should be avoided if possible because it increases operative time and results in additional blood loss. Specific indications for cesarean delivery at the time of emergency laparotomy include interference of the gravid uterus with adequate exposure, fetal distress that outweighs the risk of fetal prematurity, and impending or recent maternal death.^{[34, 18]}

Elective Open Surgical Repair of Renal Artery Aneurysm

Elective repair of an RAA is generally undertaken to obviate the risk of rupture or treat the symptoms from RAA. Various operations are available for patients; aneurysm morphology and anatomical location determine which approach to use. At times, partial nephrectomy may be needed, but with improved surgical technique, renal preservation is now the standard of care.

• Tangential excision with primary repair or patch angioplasty

  • This is the procedure of choice for solitary saccular aneurysm at a proximal bifurcation and should be performed whenever feasible. This procedure is associated with good anatomical and clinical results. Approximately one third of RAAs are amenable to such treatment. Aneurysms with small necks may be repaired primarily; otherwise, a patch angioplasty using autogenous saphenous vein or prosthetic material may be needed, as depicted in the image below.^{[29, 6]} (A) Extraparenchymal saccular aneurysm. (B) Tangential excision with patch angioplasty.
• Aneurysm excision with reconstruction using bypass

  • This is indicated if excision of the aneurysm and patch angioplasty is not possible. Fusiform aneurysm, large aneurysms, or aneurysms associated with proximal renal artery stenosis or FMD are usually repaired in this manner. After segmental excision of the aneurysm and renal artery, the preferred arterial reconstruction is with an autogenous saphenous vein aortorenal bypass graft. This is typically constructed with an end-to-side configuration for the proximal anastomosis and an end-to-end configuration for the distal anastomosis, as depicted in the image below.^{[29, 13]} Saphenous vein graft or prosthetic material are both acceptable options, although saphenous vein graft is preferred given it superior patency rates.^[6] (A) Fibromuscular dysplasia with string-of-beads appearance and wide-necked extraparenchymal saccular aneurysm. (B) Aneurysm excision with reconstruction using a bypass graft.
  • If the aorta is heavily diseased by atherosclerosis, alternative bypass donor arteries may be used. These include splenorenal bypass, hepatorenal bypass, and iliac-to-renal bypass.
• Extracorporeal vascular reconstruction with autotransplantation

  • With complex hilar or intrarenal aneurysms involving multiple arterial segments, in situ exposure of the renal hilum is difficult. Extracorporeal or ex vivo surgery allows for adequate exposure. The renal artery and vein are divided to facilitate elevation of the kidney from the renal fossa onto the abdominal wall. Simple continuous perfusion of the kidney via the renal artery with a cold (4° C) preservative solution such as that used in kidney transplantation allows the kidney to be maintained ex vivo for an extended time. Surface hypothermia is also maintained with a constant drip of chilled solution onto the kidney wrapped in an iced laparotomy pad.^{[5, 6, 13]}
  • Once ex vivo reconstruction with saphenous vein is complete, the kidney may be autotransplanted into the iliac fossa, as in renal transplant recipients, or placed into the original renal fossa and revascularized by attaching the arterial graft to the aorta and the renal vein to the vena cava or renal vein remnant. Autotransplantation into the renal fossa is favored over the iliac fossa because many ex vivo procedures are performed in relatively young patients. The iliac arterial system is susceptible to significant atherosclerotic disease, and attachment of the kidney there may adversely affect the long-term success of renovascular reconstruction.^[5]
  • Given the complex nature of repairs at the hilum, there can be up to 45 minutes of warm ischemia time. Making the determination that ex vivo repair will be needed before surgery is important. If not, considerable warm ischemia time may accumulate while in situ repair is being attempted, thus dooming the eventual ex vivo repair to failure.
  • The advantages of extracorporeal reconstruction include a superficial blood-free operating field and the possibility of needing an operating microscope.
• Nephrectomy

  • Nephrectomy is often needed to treat intrarenal aneurysms because these are not amendable to other repair techniques, except possible coil embolization.
  • Partial nephrectomy may be combined with RAA repair in certain scenarios, as follows:
    • Multiple RAAs in both intraparenchymal and extraparenchymal location
    • RAA with associated renal lesions (malignancy or tumors)
    • Total nephrectomy is indicated in patients with the following conditions:
      • Multiple, large intrarenal aneurysms, not amendable to partial nephrectomy
      • RAA with associated renal lesions, not amendable to partial nephrectomy
      • Aneurysmal rupture in a patient with shock who cannot tolerate the operative time needed for renal artery reconstruction
      • RAA in a nonfunctional kidney (as in severe ischemic renal atrophy or end-stage renal disease)
      • Prior failed revascularizations.^{[3, 18]}

Endovascular Treatment of RAAs

Advances in endovascular techniques have led investigators to attempt endovascular therapy for visceral aneurysms, including RAAs.^[19] Although the clinical and angiographic success rates using these techniques are very high, the long-term results remain unclear. Periodic surveillance for patients treated with endovascular techniques is essential.

• Coil embolization

  • Coils are thin platinum or steel wires with retained memory that allows them to coil once deployed from a catheter. They cause a disturbance of blood flow with subsequent thrombosis, as depicted in the 1st image below. With the advent of microcoils and more flexible delivery catheters, coil embolization is being used more often,^[10] but potential disadvantages still exist. If the entire aneurysm sac is not filled with coils, the aneurysm will continue to expand, as depicted in the 2nd image below.
  • Originally, only saccular aneurysms with small necks were filled with coils because of the fear of coil migration. More recently, investigators have begun treating wide-necked saccular aneurysm by placing a bare metal stent across the neck, then filling the aneurysms with coils through the interstices of the stent.^[35] One last advantage of coil embolization is that it can be used in extraparenchymal or intrarenal aneurysms.^[36] Arteriogram of saccular renal artery aneurysm after coil embolization. Subsequent expansion of aneurysm 6 months after coil embolization.
• Stent graft

  • Stent grafts are bare metal stents lined with PTFE or Gore-Tex. Originally hand made, stent grafts that are more flexible with lower profiles are now commercially available.^[37] Stent grafts require a length of nondilated artery proximal and distal to the aneurysm in order to form a seal and exclude the aneurysm from circulation. They have limited use at renal artery bifurcations but can be used in fusiform or saccular aneurysm. An additional benefit of stent grafts is the ability to treat both renal artery stenosis and RAA, as depicted in the image below.^[38] (A) Renal artery stenosis with poststenotic fusiform aneurysm. (B) Exclusion of aneurysm and dilatation of stenosis with endovascular stent graft.

Once the patient has been deemed a candidate for surgery, appropriate preparations are needed. At a minimum, all patients should have a complete blood cell count, chemistry panel, coagulation profile, urinalysis, and blood cross-match for 2 units. Patients older than 35 years should have an electrocardiogram and be appropriately screened and evaluated for cardiac disease prior to elective surgery. Patients older than 50 years or those with a history of pulmonary disease should have a preoperative chest radiograph.

Depending on the planned procedure, the patient should be positioned for either a transperitoneal or retroperitoneal approach. In most cases, a retroperitoneal incision provides adequate exposure for the renal artery and ex vivo repairs. A transperitoneal incision is indicated mainly for ruptured renal artery aneurysms, but this incision requires bowel manipulation, causing postoperative ileus. This is minimized with a retroperitoneal incision.^[18]

As with all aneurysm surgery, the principles of carefully obtaining proximal and distal control prior to dissecting around the aneurysm are essential. If a complex repair is anticipated, early consideration should be given to performing an ex vivo reconstruction.

Attention should be paid to a patient’s renal function (with urine output) and chemistries. Otherwise, standard principles of postoperative care should be applied.

Ideally, patients should have yearly postoperative renal artery duplex scan to monitor the patency of arterial reconstruction and identify new aneurysms. Abnormal findings on duplex images can be confirmed by performing CT scan, MRA, or arteriography. Those who have undergone endovascular repair merit close follow-up because long-term data on the success of this approach are lacking.^[39]

Aside from the usual complications that may accompany major abdominal surgery, the complications inherent to this type of surgery include the following:

• Native renal artery or graft occlusion in the early postoperative period, most often due to technical error
• Diminished renal function due to prolonged warm ischemia time
• Greater risk of postoperative cardiac events due to the high prevalence of atherosclerotic disease in this group of patients
• Postoperative graft occlusion due to technical error, prothrombotic nature of some graft material, or hypercoagulability from a variety of sources
• Segmental ischemia of the kidney from occlusion of a branch vessel from emboli during open repair, coil migration, or incorrect stent graft placement

The morbidity and mortality rates associated with elective repair are very low. Many authors have reported no mortality and minimal morbidity after surgery.^{[6, 14, 15]}

The prognosis after rupture of renal artery aneurysm (RAA) has improved in the last few decades. One review documented that the mortality rate dropped from 62% before 1949 to 6% after 1970.

Rupture of RAA during pregnancy still carries a high mortality rate. According to one report, renal artery rupture and its treatment resulted in death of the mother in 56% of the cases and death of the fetus in 78% of the cases.^[4]

The cure rate of hypertension may be as high as 50-100% in selected patients with aneurysms associated with renal artery stenosis.^{[3, 6, 12, 14]}

Surgical repair of RAA appears to have long-term durability, although most reported series are small and from single centers.

Further refinements in endovascular techniques may allow more renal artery aneurysms (RAAs) to be treated in this manner. Gadolinium-enhanced MRA and CT angiography with 3-dimensional reconstruction have essentially replaced conventional arteriography as a diagnostic tool and for preinterventional planning.

Controversy still exists regarding the diameter at which an asymptomatic aneurysm should be repaired. Suggested diameters range from 1.5-3 cm.^[6] Some reports even suggest that larger asymptomatic saccular aneurysms may be managed expectantly. Finally, the protective effect of aneurysm sac wall calcification against rupture is still debated.^[16]