Abdominal Vascular Exposures

Exposure of Major Abdominal Arteries

Anatomic Considerations

The aorta enters the abdomen through the aortic hiatus in the diaphragm at the level of T12 vertebra. It is surrounded at this level by the right and left crura of the diaphragm and runs anterior to the spine. The first two branches off the aorta are the two phrenic arteries, which arise anterolaterally. The celiac axis refers to a short arterial trunk originating from the anterior surface of the proximal abdominal aorta as it passes between the diaphragmatic crura. The celiac trunk and its proximal branches are surrounded by tough, splanchnic ganglionic tissue, making dissection challenging. Most often (in 75% of patients) the celiac trunk splits 1 cm beyond its origin, into three branches: the splenic, the common hepatic, and the left gastric artery. ^, The common hepatic arises from the celiac and runs on the posterior wall of the lesser sac, forming the lower boundary of the foramen of Winslow. It follows the upper border of the pancreas before it divides into the gastroduodenal and proper hepatic arteries. The proper hepatic lies anterior to the portal vein and gives rise to the right gastric before it divides into the left and right hepatic arteries. In approximately 18% of cases the right hepatic artery is “replaced” and originates from the superior mesenteric artery (SMA). A “replaced” left hepatic artery originates from the left gastric artery in approximately 12% of cases. The SMA arises from the anterior aorta at the level of mid-L1, then courses inferiorly behind the pancreas and anterior to the third and fourth portions of the duodenum, to enter the root of the mesentery. Its origin is associated with large lymphatics which can make exposure tedious. The main branches of the SMA are: the inferior pancreaticoduodenal artery (which forms an arcade with the superior pancreaticoduodenal artery originating from the proper hepatic), several jejunal branches (the first of which is usually spared in embolic occlusions of the SMA ), the middle colic, the right colic, and the ileocolic arteries. There are extensive collateral networks between the celiac trunk, SMA, inferior mesenteric artery (IMA), and internal iliac arteries. The celiac axis and SMA collateralize through the superior and inferior pancreaticoduodenal arteries. The SMA and IMA collateralize through the meandering mesenteric artery (arc of Riolan) and the marginal artery of Drummond. ^, The meandering mesenteric artery is a collateral vessel that enlarges in the presence of SMA occlusive disease. It lies at the base of the mesentery and is at risk of being ligated along with the inferior mesenteric vein during exposure of the infrarenal aorta. The collateral circulation should be verified when there is SMA and/or celiac occlusive disease, and following colectomy as unnecessary ligation of the IMA may cause intestinal necrosis.

The juxtarenal aorta is the segment of aorta between 1 cm above and 1 cm below the renal arteries and frequently overlaps the visceral segment. The renal arteries usually arise at the level of first lumbar vertebra, but there is considerable variability. Multiple renal arteries occur in up to 30% of patients. The left renal artery runs posterior to the left renal vein (LRV), whereas the right renal artery courses posterior to the vena cava.

The aortic bifurcation is usually at the level of L4–L5, with the IMA arising 2 to 3 cm above this split. The IMA gives rise to the left colic artery, 2–3 sigmoid arteries, and the superior rectal artery. The right common iliac artery runs anterior to the inferior vena cava (IVC) and the origin of the left common iliac vein, hence caution should be exercised when dissecting the whole circumference of the right common iliac artery at its origin. Splanchnic nerve branches providing sympathetic innervation to the pelvis run over the origin of the left common iliac and should be carefully preserved to avoid retrograde ejaculation after open aortic surgery. At the level of the iliac bifurcation each artery is crossed by the ureter. Placing a ureteral stent preoperatively in redo operations helps identify the ureters. During surgery, it is vital that the ureter is not skeletonized and that a prosthetic graft is not placed in direct contact with a ureter. The cisterna chyli lies posterior and to the right of the aorta and passes beneath the right crus of the diaphragm to enter the chest as the thoracic duct.

Abdominal Incisions

Vascular surgeons need to be familiar with a variety of approaches for exposing the abdominal vasculature ( Figs. 56.1 and 56.2 ). Transperitoneal exposure through a midline celiotomy incision is the most versatile and therefore remains the standard approach. Virtually every major artery and vein can be exposed through this incision. Disadvantages compared with transverse or oblique incisions are a greater degree of postoperative pain and a higher incidence of incisional hernia. The risk of incisional hernias after aortic surgery is not insignificant and may be as high as 10% per year for midline incisions. There is increasing evidence that prophylactic mesh placement can decrease the incidence of postoperative hernias after open aortic replacement for aneurysmal pathology. Transverse and oblique retroperitoneal incisions are less painful (helpful in patients with pulmonary compromise) and less prone to hernias (3%–5% per year) but lack the versatility of a midline incision. ^, ^, The following is a more detailed description of the various abdominal incisions used by vascular surgeons.

Figure 56.2, Patient Positioning for Left Flank Approach to Abdominal Aorta.

Midline Incision

As mentioned previously, this is considered the most versatile approach, allowing unrestricted exposure of the infrarenal aorta and its branches (see Fig. 56.1 ). It can also provide exposure to the suprarenal aorta when combined with medial visceral rotation. The patient is positioned supine, with one arm abducted to 90 degrees and accessible to the anesthesia team. Skin preparation should extend from the nipples to include both groins down to mid thighs for access to the femoral arteries, and saphenous veins if needed. The incision starts at the level of the xiphoid in the upper abdomen and is carried down around the umbilicus. It can be extended to just above the pubic bone if the iliac vessels need to be exposed. The peritoneal cavity is entered through the linea alba, and the viscera are packed into the lower abdomen if one is working on the upper abdominal vessels, or in the right side of the abdomen if one is working on the infrarenal aorta. If the small bowel is eviscerated, it is placed in a bowel bag to keep the heat in and collect the transudate; a moist towel may also be used. A large mechanical retraction system (i.e., Omni Tract or Thompson) is useful to retract the bowel and help with exposure.

Transverse and Subcostal Incisions

The transverse and subcostal incisions are transperitoneal incisions (see Fig. 56.1 ). The transverse incision is carried across both rectus muscles from the contralateral anterior/mid-axillary line to the ipsilateral anterior/mid-axillary line (depending on the amount of exposure needed), midway between the costal margins and the iliac crests. When unilateral flank exposure is contemplated, the incision can be limited to one side and end at the contralateral midclavicular line. Transverse incisions can be supraumbilical (“frown”) or infraumbilical (“smile”). The apex of the supraumbilical incision is centered halfway between the umbilicus and the xiphoid, and the center of the infraumbilical incision is 3 to 4 cm below the umbilicus. A supraumbilical transverse incision is good for infrarenal aortic exposure, particularly when concomitant distal renal artery exposure is necessary. An infraumbilical incision provides excellent pelvic exposure (e.g., for large iliac/hypogastric aneurysms) but offers poor access to the pararenal aorta. When compared with a midline incision, some studies show a significant decrease in postoperative pain, pneumonia, and hernias, whereas others show no difference in outcomes or complications. ^,

Subcostal incisions are transverse incisions, infrequently used by vascular surgeons, which run parallel to the costal margins and two fingerbreadths below them. The most common variety is an extended right or left incision which begins at the lateral edge of the contralateral rectus sheath and is carried across the midline as far laterally on the ipsilateral side as necessary (usually the anterior axillary line). The subcostal incision is helpful in exposing the hepatic, splenic, and renal arteries, as well as upper abdominal venous structures.

Oblique Flank Incision

These incisions are usually combined with extraperitoneal dissection and are helpful for exposing the aorta and its branches through the left flank, and the IVC through the right flank. A left retroperitoneal flank incision (see Figs. 56.2–56.4 ) is excellent for patients with complex aortic anatomy. Different segments of the aorta from hiatus to bifurcation can be exposed based on which intercostal space is used. The restrictions of this incision are limited exposure of the right iliac system and poor visualization of the right renal artery beyond its origin. This approach is extremely helpful in redo-aortic operations, suprarenal aortic pathology, horseshoe kidney with multiple renal arteries, morbid obesity, inflammatory aneurysms, diastasis of the abdominal wall, and in patients with respiratory compromise (because the incision generates less pain). The patient is placed in a modified right lateral decubitus position, with the left shoulder at 50 to 70 degrees to the operating table, and the pelvis rotated posteriorly as far as possible (corkscrew position). A vacuum “bean bag” helps to maintain this position. The left arm is supported on an over-arm board. The table may be broken at the level of the umbilicus to open-up the space between the left costal margin and iliac crest. An oblique incision is made from the lateral edge of the left rectus sheath, a centimeter or so above the midpoint between the umbilicus and pubis and extended a few centimeters into the 11th intercostal space. This incision is particularly good for infrarenal aortic exposure. Extension across the rectus to the midline aids in more distal right iliac exposure. For more proximal aortic exposure, the incision can be extended posteriorly or taken into a more proximal intercostal space (10th or 9th), which requires entry into the chest (a thoracoretroperitoneal approach; see Figs. 56.2 and 56.4 ). The external and internal oblique and transversus muscles are divided to the margin of the left rectus sheath medially, which is partially split. Posteriorly the intercostal muscles are divided on the superior aspect of the 12th (or 11th or 10th) rib, making no attempt to stay out of the chest. The extraperitoneal space is entered at the tip of the chosen rib, and the peritoneum stripped away from the musculature anteriorly (with or without the transversalis fascia). Dorsally, the peritoneum is stripped off the lumbodorsal fascia to the level of the psoas, and using blunt dissection, a retroperitoneal plane is developed by retracting the spleen, tail of pancreas, and left colon to the patient’s right. This plane is developed either anterior or posterior to the left kidney depending on the nature of the procedure, posterior to the kidney being much easier. A right flank incision can be performed in a similar fashion to expose the IVC. Shorter oblique incisions (extending from the lateral edge of the rectus just to the tip of the 12th rib) can also be used, but these provide very limited exposure.

Figure 56.3, Left Flank Incision Retroperitoneal Dissection.

Figure 56.4, Left flank thoracoretroperitoneal approach with exposure of aorta from distal descending thoracic segment to aortic bifurcation.

Thoracoabdominal Incision

This incision is used to expose the upper abdominal and lower thoracic aorta (see Figs. 56.1 and 56.4 ). It can be considered as an extended version of the retroperitoneal approach for exposure of the thoracic aorta. A double-lumen endobronchial tube is helpful when collapse of the left lung is needed during extensive work on the thoracic aorta; when only limited exposure is required a single lumen endotracheal tube is used and the lung retracted out of the way. After intubation, the patient is rolled into a right lateral decubitus position and the scapula set between 60 and 90 degrees to the table, depending on the exposure needed. The hips are rotated as far posteriorly as 30 degrees to the table if access to the femoral arteries is necessary. A vacuum “bean bag” aids in maintaining the patient’s torso in the ideal position. Other safety measures to minimize nerve injury include an axillary roll, and positioning of the lower extremities, with the bottom leg (the right) bent at the knee, the top leg (left) straight, and pillows placed between the legs.

The incision starts above the desired rib, depending on the aortic segment that needs to be exposed and is extended towards the midline ending at the lateral border of the left rectus sheath. The incision is then deepened, preserving the latissimus dorsi if possible, and incising the serratus anterior muscle. Depending on the extent of the aneurysm, the thorax may be entered through any appropriate intercostal space (from the fifth interspace for an extent II thoracoabdominal aneurysm (TAAA), to the ninth interspace for an extent IV aneurysm) (see Ch. 79 , Thoracic and Thoracoabdominal Aortic Aneurysms: Open Surgical Treatment). After entering the chest, the inferior pulmonary ligament is divided, and the lung is mobilized and retracted. Distally, the incision may extend to the upper abdomen if the aneurysm involves only the upper visceral aorta (extent I and V TAAA), or it may extend to the midline and then be carried distally if exposure of the infrarenal aorta or iliac arteries is required. The abdomen can be entered through a retroperitoneal plane or transperitoneally, with left medial visceral rotation. The diaphragm is partially divided peripherally (50% of the circumference), 2 to 3 cm away from its attachments to the chest wall. ^, This avoids injury to the phrenic nerve. Leaving the diaphragm intact may result in earlier ventilator weaning. A portion of the costochondral cartilage is excised to help with postoperative healing. Excising a 1.5- to 2-cm posterior segment of rib under the paraspinous muscles can assist with the exposure and reduces pain postoperatively.

Lower Quadrant Incisions

Lower quadrant incisions are useful for exposure of the iliac arteries (see Fig. 56.1 ). The patient is placed supine, with a roll under his flank on the side of the incision. The classic transplant incision is a curvilinear (“hockey stick”) incision, beginning one or two fingerbreadths above the symphysis pubis and lateral to the midline. This incision curves up laterally to the edge of the rectus sheath and is then extended superiorly along the lateral edge of the rectus for a distance determined by how much of the iliac system needs to be exposed. The fascia at the edge of the rectus is divided along with the transversalis fascia to expose the peritoneum. The crossing inferior epigastric vessels caudally are ligated and divided. The spermatic cord should be preserved in male patients (freed up laterally and retracted medially), but the round ligament in females can be sacrificed if deemed necessary. A retroperitoneal plane is gently created laterally, and the peritoneal sac and contents retracted medially to expose the iliac vessels from the aortic bifurcation to the inguinal ligament. Shorter suprainguinal incisions, running parallel to, and one or two fingerbreadths above, the inguinal ligament, provide excellent exposure for control of the distal external iliac artery, when femoral artery exposure is deemed hazardous (e.g., in the presence of a large femoral artery pseudoaneurysm).

Exposure of Infrarenal Abdominal Aorta and Iliac Arteries

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