Ileal Pouch-Anal Anastomosis

The ileal pouch–anal anastomosis (IPAA) is a surgical procedure that is used to restore gastrointestinal continuity after surgical removal of the colon and rectum.[1] Various conditions, including inflammatory states, cancer, or infection, may necessitate the complete surgical removal of the colon and rectum.

Also called a J pouch or an internal pouch, the procedure involves the creation of a pouch of small intestine to recreate the removed rectum. Two or more loops of intestine are sutured or stapled together to form a reservoir for stool. This reservoir is then attached to the anus for reestablishment of anal fecal flow. The IPAA is often protected by temporarily diverting the path of stool through the abdominal wall in the form of an upstream ileostomy. After a period of recovery, this ileostomy is reversed during a separate procedure.

The IPAA procedure is performed after the colon and rectum have been completely removed. Removal of the colon and rectum is termed proctocolectomy. When an IPAA follows, the procedure is called a restorative proctocolectomy.[2] Indications for restorative proctocolectomy include the following[3] :

• Inflammatory bowel disease ( ulcerative colitis or, rarely, Crohn disease)
• Certain cancers, such as those associated with hereditary nonpolyposis colorectal cancer
• Disorders of excessive colonic polyps, including familial adenomatous polyposis
• Toxic megacolon from infectious causes

Creation of a J pouch is contraindicated when the small bowel is involved in the disease process. Such involvement is most common when proctocolectomy is performed for Crohn disease, because the distal ileum is often affected. IPAA is also contraindicated when the distal rectum or anal canal is diseased, as with Crohn disease or rectal cancer.

Concerns have been expressed about the safety of IPAA in older patients. A systematic review by Ramage et al found that the procedure was safe in this population, provided that the increased risk of dehydration and electrolyte loss was kept in mind.[4]  Older IPAA patients appeared to have worse postoperative function, but this impaired function seemed to level out over time, and there appeared to be no significant impact on overall quality of life and patient satisfaction.

Complication prevention

Several standardized practices are followed to decrease the incidence of perioperative complications. Antibiotics are given within 1 hour of surgery to lower the rate of wound infection. Compression devices are placed on the legs to decrease the likelihood of blood clot formation. Patients are typically asked to stop taking any antiplatelet agents (eg, aspirin or clopidogrel) 1 week prior to surgery. This reduces bleeding complications.

Finally, before starting the surgical procedure, the surgeons, operating room staff, and anesthesia team should verify the correct patient and procedure in order to prevent errors.

In a systematic review with meta-analysis and metaregression (11 studies; N = 6770), Pellino et al evaluated the outcome of IPAA for Crohn disease (n = 352) against that for ulcerative colitis (n = 6418).[5]  They found that patients with Crohn disease had a fivefold higher risk of failure and a twofold higher risk of strictures after IPAA than patients with ulcerative colitis. Function in Crohn patients who retained the pouch was similar to that in ulcerative colitis patients. Crohn disease did not increase the risk of pouchitis. The authors concluded that IPAA could be offered to selected Crohn patients after appropriate preoperative counseling.

In a systematic review and meta-analysis (six retrospective studies; N = 3460), Emile et al compared IPAA outcome of IPAA in patients with obesity and patients with ideal weight.[6]  They found that obese patients who underwent IPAA were more likely to have open (rather than laparoscopic) procedures; a longer operating time; greater blood loss; higher rates of complications, anastomotic leakage, and incisional hernia; and longer hospital stays.

Written patient education materials are available at most colorectal surgery offices and inflammatory bowel disease (IBD) centers. Additionally, nutritionists provide valuable education regarding dietary modifications recommended following ileal pouch–anal anastomosis (IPAA). Nurses with specialized training in ostomy care play a key role in helping patients become comfortable with and care for their stomas. Finally, online material is available, such as that provided by the American Society of Colon & Rectal Surgeons and the Crohn’s & Colitis Foundation of America.

Various devices and surgical equipment are used in the creation of an IPAA. The proctocolectomy can often be performed wholly or partially by using a laparoscopic technique. In these cases, laparoscopy equipment such as the laparoscope, insufflator, and laparoscopic instruments are used. If a hand-assisted approach is used, a hand port device is employed. Energy devices are frequently used to mobilize the colon and rectum for removal and to divide the blood supply to these organs.

The ileum is typically divided with a gastrointestinal anastomosis (GIA) stapler, and the rectum is divided with a thoracoabdominal (TA) stapler or a curved TA stapler. For the IPAA portion of the procedure, the pouch is most frequently created with several firings of the GIA stapler. The ileal pouch is then connected to the anal canal by using the end-to-end anastomosis (EEA) stapler; alternatively, the two structures may be sewn together by hand.

Before the IPAA procedure, patients are typically asked to perform a bowel preparation with the aims of potentially reducing infectious complications and allowing easier handling of the colon and rectum. A bowel preparation clears the colon of fecal material, thereby decreasing the bacterial load. This is usually accomplished the day before surgery with 4 L of a polyethylene glycol electrolyte solution or 300 mL of a magnesium citrate solution. The patient is asked to maintain a clear liquid diet the day before surgery and to fast after midnight the day of surgery.

Anesthesia

The IPAA procedure is usually done with the patient under general endotracheal anesthesia. This means that the patient is completely asleep, with the airway protected by means of a breathing tube.

Positioning

The patient is positioned in the low lithotomy position on his or her back with the legs in stirrups (the “frog-leg" position).

Postoperatively, patients are monitored on a regular basis to ensure that their surgical wounds heal appropriately and that they are able to maintain adequate hydration despite sometimes copious fluid losses. Once bowel movements have slowed, follow-up visits occur less frequently. In patients who have undergone IPAA, it is important to survey the rectal cuff endoscopically at regular intervals to assess for precancerous or cancerous changes.[7]

After restorative proctocolectomy, bowel habits and stool character are significantly different. Initially, patients pass liquid stool as often as 15 times daily and frequently experience urgency. Over time, this frequency decreases, and stool becomes more formed as the body adapts to the new anatomy. Because the ileal pouch does not accommodate to the same degree as a healthy rectum and the colon normally absorbs 90% of the 1-2 L of water it is presented with daily, bowel movements will never be as infrequent or formed as what is considered normal.

Patients should expect between three and eight bowel movements daily that resemble toothpaste in consistency. If necessary, antimotility agents and bulking agents can be used to help slow the passage of stool.

In response to the changes in the body’s physiology, patients must adhere to several dietary modifications to stay healthy.[8, 9] High fluid losses in liquid stool can lead to dehydration and electrolyte disturbances. For this reason, patients are encouraged to drink copious amounts of fluids. Salt losses are replaced with supplemental dietary salt or electrolyte drinks.

Meals high in carbohydrates can help thicken stool output. Patients often eat frequent small meals throughout the day to avoid large small-bowel loads and subsequent urgency. Avoiding late meals may decrease nighttime awakenings for bowel movements. Finally, metabolic complications, such as B12 deficiency and iron deficiency, can occur after IPAA. These can be prevented by means of regular vitamin and mineral supplementation.[10]

The ileal pouch–anal anastomosis (IPAA) procedure (see the image below) is usually performed over two or three separate operations (ie, is usually a staged procedure).[11] In select circumstances and in select centers, restorative proctocolectomy is performed in a single operation.[12] The operative stages of the IPAA are usually separated by a period of 6-12 weeks (sometimes as long as 6 months.

In a two-stage procedure, the first stage includes proctocolectomy, IPAA, and creation of a diverting ileostomy; the ileostomy diverts the fecal stream, allowing for healing and maturation of the pouch. The ileostomy is then reversed during the second stage. In a three-stage procedure, the colon is removed during the first stage. The second stage involves removal of the rectum (proctectomy), IPAA, and diverting ileostomy. The third stage is reversal of the ileostomy.

The three-stage procedure is typically performed in ill patients with severe colon or rectal inflammation, usually as a result of inflammatory bowel disease (IBD) or infectious states. Removal of the diseased colon with diversion of the fecal stream from the remaining rectum avoids a lengthy operation and anastomosis in already compromised patients who are at higher risk for complications. After a period of time during which the patient recovers, proctectomy and IPAA are undertaken.

Proctocolectomy

The IPAA procedure is performed in cases where the disease process involves the entire colon and rectum, necessitating complete surgical removal of these organs (ie, proctocolectomy). This can be accomplished either laparoscopically[13, 14, 15]  or by means of laparotomy; robotic-assisted and hybrid approaches have also been described.[16] The small bowel and anus are preserved.

The first step in a proctocolectomy is to mobilize the colon by dividing its congenital peritoneal attachments. The omentum is dissected from the transverse colon, typically with an energy device. The terminal ileum is divided with a gastrointestinal anastomosis (GIA) stapler. The colon mesentery, where the blood vessels and lymph nodes reside, is next divided in a stepwise fashion by using either an energy device or a clamp-and-tie technique.

The rectum is mobilized from the pelvis down to the level of the anus, with care taken to identify and preserve the pelvic nerves. Finally, the rectum is divided, ideally in such a way as to leave a cuff of rectal tissue no longer than 1-2 cm. This is done with a straight or curved thoracoabdominal (TA) stapler.

Total abdominal colectomy with end ileostomy

The colon is mobilized as described above. The junction between the colon and rectum (ie, the rectosigmoid junction) is identified and divided with a stapler. Pelvic dissection is avoided during this stage of surgery in order to minimize pelvic scar tissue formation, which significantly increases the difficulty of subsequent rectal surgery. The colon mesentery is then divided and ligated.

An appropriate ileostomy site is determined, which is typically several centimeters to the right of and below the umbilicus and within the rectus abdominis. The ileostomy site should be chosen preoperatively, so that an area clear of any major skin folds and bony prominences with the patient in sitting, standing, and supine positions can be identified. A circular hole in the skin is made, and the underlying fascia is divided. The rectus abdominis is preserved in order to buttress the ostomy site, thereby decreasing the risk of hernia formation.

The ileum is brought through the fascial opening, either with the colon specimen or after first dividing the terminal ileum and removing the colon. The ileum is opened and sutured to the dermal layer of the ostomy site with a Brooke technique to create protrusion of the ileostomy. This allows improved fitting of an ostomy appliance.

Completion proctectomy

In the three-stage procedure, the colon is removed and an end ileostomy created during the first stage of surgery. During the second stage, the rectum is mobilized and divided as described above. This procedure is termed completion proctectomy. IPAA construction follows.

Creation of ileal pouch and anastomosis to anus

This portion of the procedure involves the creation of a pouch of ileum as a reservoir for stool and the connection, or anastomosis, of this pouch to the remaining anus. In the case of a three-stage procedure, the ileostomy is first taken down from the skin. The ileum is bent upon itself in the shape of a J, and the two bowel segments are connected in order to create a larger lumen and thereby a pouch. To do this, an opening is made at the bend of the small bowel, and a GIA stapler is inserted with one side of the stapler in each limb of the J.

The two bowel loops are connected with one or more firings of the GIA stapler in such a way as to create a reservoir that ideally is 15-20 cm long. The GIA insertion site is then anastomosed to the anus with an end-to-end anastomosis (EEA) stapler or with handsewn sutures between the pouch and the rectal cuff. Some studies have demonstrated improved outcomes when the stapled technique is used.[17] Occasionally, S- and W-shaped pouches are created rather than the more standard J-shaped pouch.

Diverting loop ileostomy

In both the two- and three-stage restorative proctocolectomy, a protective loop ileostomy is created in order to divert the fecal stream from the healing pouch. This is done by bringing a loop of small bowel proximal to the J pouch out through the skin in the right lower portion of the abdomen as described above. To mature the ileostomy, both the proximal and distal limbs of the eviscerated small bowel loop are sutured to the dermis.

Ileostomy reversal

The final stage of the two- and three-stage restorative proctocolectomy involves reversal of the diverting loop ileostomy. An incision is made around the ileostomy, and the ileostomy is dissected from the abdominal wall. Once it is free, the two limbs of the ileostomy are reconnected, often with bowel staplers. The bowel is returned to the abdominal cavity, and the ostomy site fascial incision is closed. The skin is either closed loosely or left open to heal by secondary intention.

General complications of IPAA include those seen with any surgical procedure, such as the following:

• Bleeding
• Infections, such as wound infections, urinary tract infections (UTIs), and pneumonia
• Heart complications
• Blood clots

Complications specific to restorative proctocolectomy can be divided into those that occur in the short term and those that occur in the long term.

Short term

Short-term complications include pelvic sepsis and anastomotic leakage.[18] These serious problems may necessitate percutaneous drainage procedures or even emergency reoperation.

Long term

Fecal soilage or incontinence, intestinal obstruction, anastomotic narrowing, and sexual dysfunction are infrequent long-term complications of IPAA. More common long-term complications include female infertility and pouchitis.

Pouchitis occurs in as many as 50% of patients[19] ; typical symptoms include the following:

• Diarrhea
• Abdominal cramping
• Fecal urgency
• Tenesmus
• Anorexia
• Rectal bleeding (occasionally)

Pouchitis usually is readily treated with antibiotics. For chronic antibiotic-refractory pouchitis, some authors have found monoclonal antibody therapy to be effective.[20, 21, 22]  Steroids have been used as second-line treatment, and other agents and interventions (eg, fecal microbiota transplant) have been tried in small studies.[23] A 2019 Cochrane review stated that the effects of antibiotics, probiotics and other interventions for treating and preventing pouchitis remain uncertain and that well-designed and adequately powered studies are needed to determine optimal therapeutic and prophylactic approaches.[24]

A study by Machiels et al suggested that the presence of specific microorganisms in the gut may be associated with a higher risk of post-IPAA pouchitis.[25] ​ 

A study by Klos et al suggested that obesity increases the risk of post-IPAA pouch-related complications.[9]  However, a review by McKenna et al found no difference in pouchitis rates between obese and nonobese IPAA patients in long-term follow-up, though obesity did increase the complexity of the operation and was related to worse 30-day outcomes.[26]

Sacral nerve stimulation (SNS) has been suggested as a possible means of reducing high stool frequency or fecal incontinence after proctocolectomy with IPAA.[27]