Low Anterior Resection—Open

Michael A. Valente

INDICATIONS/CONTRAINDICATIONS

Low anterior resection (LAR) is primarily performed for mid and low rectal adenocarcinoma. The definition of low anterior differs from an anterior resection in that the dissection in an LAR proceeds beyond the peritoneal reflection. Most often, LAR is for rectal tumors located within 10 cm from the anal verge. Sphincter-preservation surgery has become the standard of care for low rectal tumors; and in our experience, approximately 85% of all patients with rectal cancers can undergo sphincter preservation.

Contraindications to performing a LAR with colorectal or coloanal anastomosis include patients with extensive comorbid conditions and inability to achieve an oncologically sound surgery with adequate distal and circumferential resection margins, due to extensive adjacent organ/pelvic bony invasion and/or poor anal sphincter function. These patients are best suited for abdominal perineal resection or possibly just fecal diversion.

PREOPERATIVE PLANNING

LAR is primarily performed for mid and low rectal adenocarcinoma, and thus there is an extensive decision-making process that must take place for successful oncologic cure and for maximum functional quality of life after surgery.

The key components of evaluation begin with the fundamental principles of a detailed personal and family history, physical examination, histologic confirmation of the tumor, and a full colonoscopy. Essential elements in the multidisciplinary workup of rectal cancer include the following:

Patients’ age and medical comorbidities (physiological age; ability to undergo abdominopelvic surgery, and/or receive chemoradiotherapy)
Tumor location
Tumor stage (tumor, node, metastasis [TNM] classification)
Anal sphincter status (physiological function)
Obstetric history in women
Previous anal or pelvic surgery
History of radiation treatment
Patient’s wishes/expectations
Surgeon experience and skill

Accurate diagnosis and staging of rectal cancer is of the utmost importance to make a sound multidisciplinary decision for surgical treatment. Tumor location with respect to the anorectal ring (anorectal junction), anal verge and peritoneal reflection, TNM staging, and circumferential resection margins all need to be evaluated before treatment can begin.

A combination of both a digital rectal examination (DRE) and rigid proctoscopy is the most accurate method for localizing rectal tumors, especially in the low and mid level of the rectum; flexible endoscopy may potentially be less accurate. In both DRE and endoscopy, the anal verge is the anatomical landmark that is used as a reference point for accurate measurement. All rectal tumors should be noted according to their most distal edge measured from the anal verge and categorized as anterior, posterior, and right or left. Localization is absolutely mandatory for surgical decision making and to help determine whether sphincter preservation is feasible. When determining whether sphincter preservation can be accomplished, the examiner must assess the tumor’s lower edge in relationship to the anorectal ring. In addition, anal sphincter status must be evaluated with physical examination and potentially manometry to ensure adequate sphincter strength and function. Even patients with marginal sphincters and decreased mobility may have poor quality of life because of the inability to quickly reach the toilet and may be counseled to have a permanent stoma.

Depth of invasion and nodal status must be evaluated for the potential utilization of neoadjuvant chemoradiotherapy. The author suggests that endorectal ultrasound (EUS) and/or dedicated high-resolution rectal magnetic resonance imaging (MRI) should be performed on all mid and distal tumors and select upper tumors. There are advantages and disadvantages to both modalities and therefore can be considered complementary to each other. EUS, however, is not well suited for high tumors and/or bulky tumors (T4). In addition, stenotic tumors pose a technical problem, because the ultrasound probe may not be able to traverse the lesion for accurate staging. However, T3 lesions are well distinguishable from T4 lesions with the aid of MRI. The accurate diagnosis of T3 from T2 lesions is important, because T3 lesions of the mid and low rectum should receive neoadjuvant chemoradiation in most instances. In the authors’ experience, ultrasound may be better when looking anteriorly (invasion into prostate/bladder or vagina) and MRI is better for evaluating the circumferential margin. In terms of lymph node status, MRI is the recommended modality for diagnosis of nodal disease, despite an overall low sensitivity and specificity (66% and 76%, respectively). In general, at our institution, all patients with T3-T4 and/or N+ mid-to-low rectal adenocarcinomas will receive neoadjuvant longcourse chemoradiotherapy followed by radical excision 8-12 weeks after completion.

Metastatic evaluation should include preoperative carcinoembryonic antigen levels and computed tomography (CT) scans of the chest, abdomen, and pelvis. Dedicated MRI of the liver may be useful for equivocal lesions seen on CT scan. Brain CT and bone scans should be obtained for those with specific symptoms. Positron emission tomography (PET/CT or PET/MRI) should be used on a case-by-case basis and is not recommended as an initial staging modality, unless suspicious lesions are found on CT or MRI and positivity will alter the surgical plan.

A multidisciplinary team approach is compulsory at our institution. Every rectal cancer case, regardless of clinical stage, is discussed with the multidisciplinary team, which consists of medical oncology, radiation oncology, gastrointestinal (GI) pathology, GI radiology, colorectal surgeons, liver/thoracic surgeons, genetic counselors, and the other members of the nursing support staff. Treatment is built upon accurate staging, but tailored to each individual patient, based on age, physiological status, functional status, and a thorough understanding by the patient of the various treatment options that exist. This approach is also a standard with the American College of Surgeons Commission on Cancer National Accreditation Program for Rectal Cancer.

SURGERY

Preparation and Positioning

For all patients undergoing elective surgery, formal preoperative assessment is conducted, including cardiopulmonary evaluation, basic blood work, and appropriate imaging tests to prepare the patient for the operating room. Nutritional parameters are checked, including albumin and pre-albumen. All patients receive preoperative oral antibiotics (metronidazole and neomycin), a full mechanical bowel preparation, and are also provided a chlorhexidine body wash for the night before surgery. In addition, all patients see a member of the enterostomal nursing team to appropriately preoperatively mark the planned ileostomy/colostomy site (temporary or permanent). Appropriate education on ostomy care is given before the surgery and during and after the patient’s hospitalization.

Patients are placed in the modified lithotomy position with Yellowfin or padded Allen stirrups (Allen, Acton, MA) and careful attention is paid to protect bony prominences to try to prevent nerve damage, especially to the peroneal nerve. We prefer to tuck both arms at the patient’s sides for all abdominopelvic cases for easy access and ergonomic comfort for the surgeons performing the operation.

Guidelines for appropriate antibiotic use are strictly followed in all patients, which consist of 2 g of intravenous ceftriaxone and 500 mg intravenous metronidazole within 60 minutes of incision; penicillin-allergic patients will receive 400 mg intravenous ciprofloxacin and 500 mg metronidazole; routine postoperative antibiotics are not given. Bladder catheter and orogastric tube are routinely placed. Ureteral stents are very selectively placed to aid in identification of the ureters. Ureteral stents are generally reserved for complex reoperative cases with anticipated extensive fibrosis or inflammatory changes.

Deep pelvic surgery can be quite difficult because of inadequacies in lighting and improper exposure. We routinely use a self-retaining Balfour retractor with an associated C-arm attachment, which allows for packing of the small bowel contents out of the pelvis. The use of lighted St Mark’s or Lloyd Davis retractors (Electrosurgical Instrument Company, Rochester, NY) proves quite useful for exposure within the narrow confines of the pelvis. For very narrow anatomic variations of the pelvis, the lighted Britetrac retractor (Vitalcor, Inc., Westmont, IL) proves quite beneficial as well.

Basic operative steps in open low anterior resection

Abdominal exploration
High ligation of inferior mesenteric artery (IMA) and inferior mesenteric vein (IMV)
Sigmoid and left colon mobilization
Mobilization of splenic flexure
Proximal colon transection
Total mesorectal excision (TME)
Distal rectal transection
Colorectal or coloanal anastomosis
Creation of diverting loop ileostomy

Abdominal Exploration

A midline incision is made from the umbilicus down to the level of the pubic symphysis. Upon entering the abdomen, a thorough exploration is performed to exclude metastatic disease. The peritoneum is inspected for tumor implantation and the liver is examined and palpated. Adnexal structures are examined in the pelvis for any signs of metastatic spread. Next, the pelvis is examined and feasibility of a sound oncologic resection is undertaken. Assessment of any lateral extension of the tumor or potential invasion into any adjacent structures is also addressed at this time.

High Ligation of the Inferior Mesenteric Artery and Vein

A medial-to-lateral approach is undertaken by the author for all cancer operations (open and laparoscopic). The peritoneum on both sides of the rectum is incised at the level of the sacrum promontory, with care to avoid the ureters and the sympathetic nerves. The dissection is undertaken under the superior rectal artery and the dissection is continued to the origin of the IMA off of the aorta. Branches of the hypogastric nerve plexus are identified and cautiously swept caudally toward the aorta. The left ureter should be identified at this time before any vessel is ligated. The IMA should be isolated and skeletonized and doubly clamped (Fig. 13-1). A suture ligature is applied to the artery.

Preservation of the left colic artery is surgeon and case specific (high tie vs. low tie). The vast majority of cases at our institution and the preference of this author and the editors are to divide the IMA in a high-ligation manner at the takeoff from the aorta, thereby sacrificing the left colic artery (Fig. 13-2). Preservation of the left colic artery may result in a more predictable blood flow to the anastomosis, but may not give sufficient bowel length. After the IMA and IMV have been ligated at this level, dissection proceeds toward the fourth portion of the duodenum and ligament of Treitz. The IMV can be found just lateral to the duodenum and proximal to the inferior edge of the pancreas before it joins the splenic vein to become the portal vein. It is routine in our practice to ligate the IMV at this level to allow excellent reach of the colonic conduit into the pelvis for a tension-free anastomosis (Fig. 13-3 A to C). In the scenario where the IMA is ligated at its origin and the IMV is ligated at the pancreatic level, the proximal blood supply to the anastomosis is supplied via the marginal artery of Drummond by way of the middle colic vessels. When these high-ligation maneuvers are employed, it is rare that the colon will not adequately reach into the pelvis.

Left Colon and Splenic Flexure Mobilization

Medial-to-lateral dissection proceeds after the IMA/IMV have been ligated. Although the lateral-to-medial approach may seem to be less difficult in open surgery, for oncologic purposes this author utilizes a
medial approach first for all cases. The retroperitoneal structures, including the ureter, gonadal vessels, and the psoas muscles are swept posteriorly and dissection is carried laterally to the abdominal wall, over Gerota’s fascia/perinephric fat and toward the spleen. Next, lateral dissection begins at the iliac fossa and continues superiorly toward the splenic flexure. The dissection is carried 1 mm medial to the white line of Toldt (because the white line should stay with the patient) until the spleen is reached. The splenic flexure is carefully mobilized to try not to cause either splenic capsular tear or colonic wall damage. Gentle medial traction on the colon will allow for the splenocolic and retroperitoneal
attachments to be safely and sharply dissected free (Fig. 13-4). If this approach becomes too difficult, we often will enter the lesser sac where the omentum attaches to the transverse colon and mobilize toward the spleen to meet up with the previous dissection plane. Routine separation in the avascular plane between the transverse mesocolon and the greater omentum is compulsory for proper reach into the pelvis.

Only gold members can continue reading. Log In or Register to continue