Abdominoperineal Resection

Anatomy and Physiology

An abdominoperineal resection involves the left colon, pelvic floor, rectum, and anal canal. Appreciation of the key anatomical features in this operation is crucial to understanding the procedural steps and potential complications that can occur.[8]

Descending and Sigmoid Colon 

The left colon is comprised of the descending colon and the sigmoid colon. The descending colon is a retroperitoneal structure descending on the left side of the abdomen towards the pelvis, becoming the sigmoid colon in the left lower quadrant. The sigmoid colon is attached to the posterior abdominal wall via the mesosigmoid, a piece of mesentery allowing the sigmoid to move freely within the abdomen.

The inferior mesenteric artery arises from the aorta and gives off the left colic artery and sigmoid artery, which travel to the descending and sigmoid colon. Lymphatic drainage and nerves follow the vasculature, all situated within the associated mesentery. 

Rectum 

The rectum begins at S3 and lacks features such as haustra and taenia coli, making it distinct from the colon. The upper third of the rectum is covered in peritoneum on the anterior and lateral surfaces. The middle rectum only has an anterior covering, with the lower third devoid of the peritoneum. Anterior to the rectum lies the seminal vesicles, prostate, and bladder in men and the vagina in women. 

There are three separate blood supplies to the rectum, the superior, middle, and inferior rectal arteries, arising from the inferior mesenteric, internal iliac, and internal pudendal artery, respectively. 

Pelvic Floor 

The pelvic floor is a cavity located beneath the pelvic brim, where structures including the bladder, rectum, and genital organs are found and supported by muscular walls attaching to the pelvis walls. A key component of the pelvic floor is the levator ani muscles, including puborectalis, pubococcygeus, and iliococcygeus. 

Anal Canal 

The anal canal is the final 4 cm of the gastrointestinal tract from the rectum to the anus. The internal anal sphincter surrounds the upper two-thirds and the external sphincter around the lower third. A fundamental structure for surgeons is the anorectal ring, where the anal sphincters and puborectalis muscle merge to mark the demarcation between the rectum and anal canal. It is formed by joining the puborectalis muscle, deep external sphincter, conjoined longitudinal muscle, and the highest part of the internal sphincter. Clinically, this point can be felt during a digital rectal examination and be used to assess low-lying rectal lesions. 

The anal canal is divided according to the embryological origin and is separated by the dentate (pectinate) line, an irregular circle formed by anal valves. This line divides the anal canal into upper and lower parts, which differ in structure and neurovascular supply. The tissue above the dentate line is derived from the hindgut and receives its blood supply from the superior rectal artery branching off the inferior mesenteric artery. Below the dentate line, the structures originate from the ectoderm and are supplied by the inferior rectal artery, a branch of the pudendal artery.

Indications

Abdominoperineal resection is indicated in patients with operable low rectal carcinomas who meet the following criteria:

• Within 5cm of the anal verge
• Otherwise not possible to get a negative distal margin (5 cm proximally and 2 cm distally) 
• And/or has an invasion of local structure such as the external sphincter

It is estimated that around 40% of patients with rectal cancer require surgical intervention as part of their management.[1]

Less common indications include Fournier gangrene, inflammatory bowel disease, and fecal incontinence not amenable to sphincter sparing surgery.[9][10]

Contraindications

Abdominoperineal resection is contraindicated in patients who are not considered fit for general anesthesia. Relative contraindications include those at high risk of poor postoperative outcomes such as poorly controlled diabetes, morbid obesity, frailty, and immunosuppression.

Equipment

The equipment required for an abdominoperineal resection depends on whether the procedure is being performed via open or minimal access (laparoscopic or robotic). Regardless of approach, an operating table capable of adjusting for lithotomy and prone jack-knife positions is essential. For an open procedure, the extent of instruments can vary but will typically include a scalpel (usually size 10 blade), monopolar and bipolar cautery, retractor, toothed forceps, Fraser-Kelly clips, McIndoe scissors, and suction. In laparoscopic surgery, other equipment required includes monitor screens, gas insufflator, camera scope (10 mm, 30-degree angled scope), laparoscopic instruments, endoscopic linear stapler, and advanced sealing devices (Harmonic, Ligasure).

Personnel

The essential theatre team for an abdominoperineal resection is composed of the surgeon, surgical assistant, anesthesiologist, and scrub nurse. Other members may also present to help position the patient, assist in the anesthetic process and retrieve equipment during the operation.

Preparation

Work Up 

Fitness for surgery is assessed in all patients during the pre-operative assessment clinic; this includes a clear, in-depth past medical history and basic investigations such as full blood count, urea and electrolytes, liver function tests, group and save, and electrocardiogram (ECG). Additional tests (spirometry, transthoracic echocardiogram (TTE), and cardiopulmonary exercise testing (CPET)) may also be performed where indicated to investigate cardiovascular and respiratory fitness in high-risk patients.

Patients should be warned about the possible risks in the surgical clinic, most notably sexual dysfunction, parastomal herniation, and chronic pelvic pain. Normally, a stoma nurse will also meet the patient pre-operatively to discuss the practicalities of stoma care and mark them for a suitable stoma site, considering the patient's body morphology, lifestyle and preferences.[2][11]

In patients undergoing elective surgery, many studies have been conducted around the use of mechanical bowel preparation and antibiotic prophylaxis to prevent surgical site infection. Current guidance recommends using mechanical bowel preparation before surgery and a single administration of intravenous prophylactic antibiotics.[12]

Preparing the Patient in Theatre 

1. The colostomy site is marked by the surgeon if not already done so pre-operatively. The ideal position is in the left iliac fossa, avoiding scar tissue, abdominal folds, and bony prominences.
2. Parenteral prophylactic antibiotics are given just before the operation.[13][14]
3. Once under general anesthesia, the patient is typically placed in the modified lithotomy position using stirrups. The sacrum is cushioned to avoid a pressure point while the coccyx is positioned at the end of the operating table. A urethral catheter is inserted to decompress the bladder and monitor urine output during the procedure. 
4. A digital rectal examination is performed to determine the position of the tumor relative to the anal verge.[3]

Technique or Treatment

The procedure can be divided into two phases which can be carried out synchronously or sequentially. The principles of abdominoperineal resection described below apply to all techniques regardless of whether the procedure is performed via an open, laparoscopic, or robotic approach.[2]

Part One - Abdominal Operation[3]

Access to the abdomen is achieved through a lower midline incision in open surgery or the use of up to 6 laparoscopic ports for laparoscopic or robotic techniques. 

1. An initial survey of the abdomen is performed to look for any signs of metastasis and identify the location of the tumor.
2. The distal sigmoid colon is mobilized in either a medial to lateral or lateral to medial approach. Mobilization of the colon in a medial to lateral fashion allows early ligation of the vascular pedicle. The main advantages are reduced bleeding and maximal time for demarcation between ischaemic and perfused health colon. Gentle traction is applied to the sigmoid colon, and the mesentery is incised behind the superior rectal artery overlying the sacral promontory. The avascular areolar plane is developed behind the superior rectal artery by repetitive sweeping actions.
3. As the avascular areolar tissue is swept down, a window is created, and the critical retroperitoneal structures (ureter and gonadal vessels) are identified and preserved. 
4. The superior rectal artery is dissected to its origin from the inferior mesenteric artery. At this point, either a low (ligation of the superior rectal artery) or high tie (ligation of the inferior mesenteric artery) can be performed. 
5. Once the vascular pedicle has been controlled, the left colon can be brought medially and released from its lateral attachments by dividing along the 'white line of Toldts,' representing the junction between the posterior and visceral peritoneum. The marginal vessels are ligated, and the mesocolon is divided. 
6. Total mesorectal excision (TME) is performed by entering the avascular alveolar plane between the presacral and mesorectal fascia at the level of the sacral promontory, paying careful attention to avoid the iliohypogastric nerves and medial sacral artery. 
7. Dissection is continued posteriorly, laterally, and anteriorly. Judicious use of electrocautery is needed when dissecting in the posterior plane to avoid injury to the parasympathetic fibers. Extra care is also taken to prevent coning of the specimen during circumferential dissection. 
8. Mobilization of the rectum anteriorly is terminated just below the level of the seminal vesicles (in males) or cervix (in women) and at the upper border of the coccyx posteriorly. The mesorectum is not dissected off the levator muscles at this point. 
9. The colon is transected using a linear cutting stapler at least 5cm proximal to the rectal tumor but with enough mobility and length to prevent tension at the stoma site.  
10. A trephine is made at the stoma site by removing a 2 cm disc of skin and dissecting it down to the peritoneum. The proximal colon is extruded through the trephine incision, and a colostomy is formed by suturing the edge of the colon to the trephine incision.
11. The abdominal fascia and the skin incision are closed, often before the colostomy is formed.

Part Two - Perineal Operation (extralevator abdominoperineal excision)[3]

This part of the procedure can be carried out in a prone jack-knife or lithotomy position. The perineal area is exposed by taping apart the buttocks. 

1. The anus is sutured with a purse-string suture to prevent any fecal leakage. 
2. A teardrop skin incision is made around the anus extending down to the lower edge of the sacrum and exposing the fat of the ischiorectal fossae. Dissection is typically extended outside the external anal sphincter, using a lone star retractor to provide optimal exposure and access.
3. Dissection is continued posteriorly, dividing the anococcygeal raphe and reaching the coccyx. In some instances, the coccyx is resected to allow better visualization or obtain the necessary resection margin. 
4. Laterally the levator muscles are identified and dissected up to their point of insertion on the pelvic sidewalls to enter the abdominal cavity.
5. The inferior haemorrhoidal and pudendal vessels are ligated. 
6. The mesorectum is separated from the anterior presacral fascia to enter the same plane as the abdominal part of the operation. 
7. Anterior dissection is performed by retracting the rectum posteriorly and making a transverse incision to expose the transverse perineal muscles.
8. The pubococcygeus and puborecto-urethralis muscles and underlying fascia are divided to expose the rectal wall. 
9. The disconnected sigmoid colon and rectum are brought through the perineal incision and sent for histological analysis. 
10. The pelvic floor is closed in two layers with interrupted absorbable 2-0 sutures. A drain is often left in situ to avoid pelvic collection. 
11. The skin is closed with an absorbable subcuticular suture. 
12. Some defects are too large to close primarily. They may require reconstruction with biological mesh or a myocutaneous flap, typically a pedicled gluteus maximus, gracilis, or rectus abdominis flap.

Complications

Common complications associated with abdominoperineal resection include the following:

Abdominal Complications 

• An intraabdominal abscess (32% of patients)   
• Post-op ileus (2%) 
• Small bowel obstruction
• Stoma complications e.g. ischemia, prolapse, parastomal hernia[15]

Perineal Complications[16]

• Delayed wound healing (86%)
• Dehiscence (22%) 
• Infection (27%) 
• Pelvic collections (7%) 

Other Complications 

• Venous thromboembolism 
• Bleeding (3%) 
• Sexual or urinary dysfunction (10 to 60%) 
• Complications of anesthesia

Clinical Significance

Abdominoperineal resection is a major operation that requires significant work-up, operative planning, and post-operative care. This procedure involves multiple team members ranging from surgeons and anesthesiologists to specialists, nurses, nutritionists, physical therapists, and social services. Recovery from this procedure takes resilience, time, and effort. Understanding operative steps and potential complications allows clinicians to prepare for the operation and recognize issues earlier on, leading to better patient outcomes. Similarly, an appreciation of the general process involved in the care of these patients will help Nurses, and other healthcare members troubleshoot problems and support patients in the pre- and post-operative setting.

Enhancing Healthcare Team Outcomes

Good interprofessional teamwork is crucial for successful abdominoperineal resection. Operative planning and successful treatment of rectal cancer require a multidisciplinary approach involving surgeons, radiologists, oncologists, and histopathologists. Cancer nurse specialists and stoma care nurses play a pivotal role in the overall care of the patient and provide psychological support, expert advice, and specialist symptom control. In addition, enhanced recovery protocols have greatly improved patient outcomes by standardizing post-operative care and integrating surgeons, anesthesiologists, pain specialists, nursing staff, physical and occupational therapists, social services, and hospital administration.[17]