Pouch Configuration

Paris P. Tekkis

Constantinos Simillis

INDICATIONS/CONTRAINDICATIONS

The only reason for restorative proctocolectomy, through the formation of an ileal pouch-anal anastomosis (IPAA), is to avoid a permanent ileostomy. A conventional proctocolectomy gives otherwise excellent results. The main causes for creating an IPAA would be after proctocolectomy for ulcerative colitis (UC) or for familial adenomatous polyposis (FAP). An IPAA should be avoided when the small bowel is involved in the disease process (as in Crohn’s disease), or when the anal canal is diseased (as with Crohn’s disease or anal cancer), and in patients with poor anal sphincter function.

In the absence of medical contraindications to the formation of an IPAA, the choice between a restorative and a conventional proctocolectomy lies largely with the patient. To make an informed decision, the patient should be aware of the risks of an IPAA, including failure and complication rates, total treatment time, the possibility of pouchitis, and the likely functional outcome. A pouch support nurse, stoma therapist, and patient-support group can offer valuable advice to the patient during this decision-making process.

The creation of a pouch allows the formation of a reservoir for stool. Evidence from comparative and physiological studies of patients who have had either a straight ileoanal anastomosis (IAA) or an IPAA demonstrated decreased frequency of defecation, increased capacity and compliance, decreased propulsive drive, and overall, improved functional results with an IPAA. Furthermore, studies demonstrated an inverse relationship between reservoir volumes and frequency of defecation.

When the operation was first reported by Parks and Nicholls, a three-loop form of reservoir was used. This “S” pouch was connected to the anal canal after a mucosectomy by an anastomosis between a point just above the dentate line and a segment of the terminal ileum projecting from the reservoir for a few centimeters. Parks stated that his main aim was to avoid incontinence, and to do so he favored this form of reconstruction. Although this goal was achieved, as reported in the first few publications, the price paid was failure of spontaneous evacuation in at least half of the patients having the procedure, because the “S” pouch was associated with the need to catheterize the pouch for emptying. This problem was radiologically shown to be due to presence of the 5-cm efferent limb, which acted as an impedance to outflow.

The two-loop reservoir described by Utsunomiya did not have this feature, being directly joined to the anal canal without an efferent limb. Evacuation was spontaneous in almost all patients. For this reason, and for its ease of construction by linear stapling, the two-loop, or “J” pouch, quickly became the most widely used reconstruction. Subsequently, Nicholls developed a four-loop “W” pouch with the intention of achieving increased reservoir volume, and, therefore, decreased frequency of defecation compared to the “J” pouch, and did not require intubation unlike the “S” pouch (Fig. 32-1). Other pouch configurations have included the “H” reservoir described by Fonkalsrud, and the Kock “K” design used with IAA.

PREOPERATIVE PLANNING

Preoperative patient education is invaluable using written materials, pouch support nurses, stoma therapists, and patient-support groups. As long as an IAA is possible, there is no particular preoperative planning required for the reservoir. There are no particular indications other than the surgeon’s preference in choosing which pouch should be used other than the “S” reservoir, which has been virtually relegated to use in patients where the pouch does not reach. If the outlet becomes a problem, a transanal advancement works well to straighten the outlet. The choice of configuration is unaffected
by general factors such as the patient’s disease activity level or comorbidities. There are no local anatomic or pathologic factors, which would influence the choice of pouch design. Thus, the width of the pelvis, mobility of the mesentery, state of the anal sphincter, and the extensiveness of any adhesions do not influence the choice of reservoir. In current practice, the “J” and, to a much lesser extent, the “W” reservoirs are the most common types of pouches used. The subsequent technical descriptions are confined to these pouch types. The length of small intestine used for each version is similar and the mobility of the mesentery that determines whether there will be some tension on the anastomosis is also similar for both “J” and “W” reservoirs.

FIGURE 32-1 Various pouch designs.

SURGERY

General Precautions

Perioperative prophylactic antibiotics, especially in immunosuppressed patients
Anti-thromboembolism prophylaxis using subcutaneous heparin, and pneumatic compression stockings
Stopping antiplatelet agents (e.g., aspirin or clopidogrel) 1 week before surgery
Preoperative bowel preparation to clear the colon and rectum of fecal material
Cross-matched blood
Consider a central venous line insertion for total parenteral nutrition (TPN) in the malnourished patient
Intraoperative orogastric or nasogastric tube insertion
Epidural anesthetic or patient-controlled analgesia for pain control
Bladder catheterization
Insertion of a proctoscope or irrigation through a catheter before starting the operation to drain the bowel of as much liquid feces and flatus as possible

Positioning

The reverse Trendelenburg position with the legs raised in Lloyd-Davies-type stirrups should be used to allow access to the anus. The tip of the coccyx should lie over the end of the operating table to gain adequate exposure of the perineum. Whether an open or laparoscopic technique is used, this position gives excellent access to the abdomen and suitable deployment of surgeon and the assistants around the patient.

General Considerations of Pouch Construction

There are three principles that should be observed in constructing a reservoir:

Minimal tension of the small bowel mesentery: To minimize tension, adhesiolysis, and mobilization of the mesentery as extensively as possible, combined with division of selected mesenteric vessels if necessary, should be performed and combined with a trial descent.
Adequate volume of the pouch: To achieve adequate capacity, a minimum length of small bowel of 30-40 cm is generally preferred.
Absence of distal ileal segment: Using the apex of a folded pair of loops as the point for the enterostomy to form the IAA will avoid any distal ileal segment.

Mobilization of the Mesentery

An assessment of the mobility of the small bowel to descend to the pelvis is made by holding the apex of a loop of terminal ileum intended to form part of the IAA down into the pelvis. This most mobile point is around 15 cm from the ileocecal junction. If there is no evidence of tension, no further mobilization of the mesentery is carried out. If, however, there is some tension, then further mobilization of the mesentery is required. This goal is achieved in three ways (Fig. 32-2):

Duodenal mobilization: It may be necessary to mobilize the duodenum using Kocher’s maneuver. The uncinate process of the pancreas can be freed from the origin of the superior mesenteric artery and vein if necessary. Care should be taken to avoid damage to the superior mesenteric vein or its major tributaries.
Transverse incisions of the peritoneum: Four or five small transverse cuts made in the peritoneum on each side of the mesentery result in lengthening by 1-2 cm.
Division of selected vessels: If, despite these maneuvers, there is still tension restricting descent of the apex of the terminal ileal loop into the pelvis, then division of a selected restraining vessel in one of the vascular arcades will be necessary. This maneuver must be done with great care to avoid small bowel ischemia. The vessel restraining the mobility of the mesentery is identified by putting
gentle stretch on the mesentery and using transillumination. The vessel is then dissected from its connective tissue bed. A bulldog clamp is applied to the vessel and the end of the terminal ileum is inspected to see whether there is adequate perfusion. If vascularity is satisfactory, the vessel is then divided. Fluorescence imaging may be used to verify adequate perfusion before vascular division. This maneuver is rarely necessary if a stapled IAA is used.

FIGURE 32-2 Mobilization of the mesentery.

Trial Descent

A trial descent of the small bowel, testing its ability to descend to the level of the anal canal, is recommended, where the bowel has been divided to leave an open anal stump as would have been done in patients in whom a manual IAA with mucosectomy is intended. It is not possible to perform trial descent if the anorectal stump has been closed by a transverse stapler in preparation for a stapled IAA; but in this circumstance, there is less tension on the mesentery because the IAA will be at a slightly higher level. The trial descent is undertaken jointly by abdominal and perineal operators. A stay suture is placed on the apex of the loop selected for the IAA and this is passed through the pelvis and anal canal to be taken by the perineal operator. Gentle traction is applied and the small bowel is drawn down to the anal canal. If it reaches the dentate line, it will do so after the pouch is formed. If it does not, then further mobilization is necessary as described earlier (Fig. 32-3). Alternatively, a trial descent can be undertaken with transanal digital palpation while the apex of the intended pouch is delivered to the distal pelvis. Regardless of the method employed, it is desirable to confirm sufficient reach before pouch construction.

“S” Pouch

The original three-limb “S” pouch used 25 cm of terminal ileum with a 5-cm distal conduit for the IAA. This pouch design was associated with a significantly greater need for pouch intubation to facilitate emptying, and soon fell out of favor. If an “S” pouch is used, however, the distal ileal segment should be kept to a minimum of 2 cm to reduce the need for intubation. The “S” pouch may be preferred by some surgeons because the efferent limb fits well into the anal canal and the body of the pouch lies on the levators; whereas the blunt end of a “J” pouch may be distorted by being forced into the tight muscular tube of the stripped anus.

“K” Pouch

To create a “K” pouch, two 15-cm ileal segments are sutured side to side and split open. A finger-wide opening is left distally to the suture line. The “K” pouch is formed by folding the opened bowel upward along a transverse axis. The corners of the created pouch are pushed inward between the mesenteric leaves, bringing the posterior aspect of the pouch anteriorly and the opening for the IAA distally.

FIGURE 32-3 Trial descent before making the pouch.

“H” Pouch

The full thickness of the ileum is anastomosed to the free edge of the anal mucosa at the dentate line and the ileum is divided 25 cm proximal to the peritoneal reflection. After the two ends of the ileum are closed, a side-to-side ileo-ileal anastomosis is constructed over a distance of 20 cm using the GIA stapling instrument. The anastomosis is extended to the peritoneal reflection, thus leaving only about 8-12 cm of ileum between the reservoir and the IAA.

Stapled “J” Pouch

The “J” pouch has become the design of choice because of its ease of construction by stapling in preference to the “S” and “W” pouches, which require a more time-consuming hand-sewn construction. Larger “J” pouch are being favored since the description of the “W” design. A “J” pouch should have a volume of at least 300 ml at the time of construction. A 20×20 cm loop achieves an intraoperative volume of more than 300 ml with a postoperative capacity of 380 ml. Once adequate mesenteric length is assured, the pouch is constructed by stapling or manual suturing (Fig. 32-4). Most surgeons now use the former technique, but stapling may result in a short distal stump (the “dog ear”) that can perforate and fistulize.

To form a stapled “J” pouch, three stay sutures can be placed on the antimesenteric border of the ileum to ensure that the staple line is truly antimesenteric. The limbs of the pouch should each measure 20 cm in length. A transverse enterotomy not more than 3 cm long is made at the apex of the folded loops. The procedure is performed entirely through this enterotomy, accordioning the limbs of the ileum over the stapler. A 10-cm linear cutting stapler is introduced into the two loops of the ileum and the limbs are advanced as far as possible. The stapler is closed and an inspection is made to ascertain that no mesenteric vessels are included in the shafts of the stapler. If not, the instrument is fired. A second stapler is introduced and advanced beyond the now open loops of ileum and closed and fired. The number of cartridges required to form a stapled “J” pouch will usually be two of a 90-mm or 100-mm stapler; three of the 75-mm stapler; and four of the 50-mm stapler. The aim should be to achieve a pouch of 17-20 cm limb length.

The pouch may be everted through its mesentery to expose the posterior staple line to exclude for any defect and to assess hemostasis. The integrity and capacity of the pouch are tested by placing a non-crushing clamp over the afferent limb while injecting saline into the pouch through a catheter introduced through the apical enterotomy. The terminal ileum will have been closed by a transverse stapler applied before constructing the pouch. This results in a “dog ear” at its most distal part, which is oversewn. Care should be taken to ensure that it is no more than 2 cm in length and is intact because fistula formation can occur from leakage at that point.

FIGURE 32-4 Construction of the “J” pouch; stapled and manual techniques.

Sutured “J” Pouch

The two loops are approximated using a seromuscular continuous suture of absorbable material. The bowel is then opened and a full-thickness continuous suture is undertaken from the posterior layer coming round to the anterior layer of the two loops. In this manner, the “dog ear” deformity is completely avoided because the anatomic end of the terminal ileum is incorporated end to side into the pouch. The suture is continued to the apex of the pouch and terminated at a point that leaves the enterotomy for the IAA just able to take two fingers comfortably. If a stapled IAA is intended, however, the last few sutures up to this point should be interrupted to avoid unravelling of the continuous suture line, which may occur if it is cut by the knife of the circular stapler. It takes about 30 minutes to construct a sutured “J” pouch, but its advantages include maximizing the pouch volume by using all the bowel length for constructing the reservoir, avoiding the “dog ear” with its risk of fistulation, and lowering the cost. It may, however, result in more contamination.

“W” Pouch

It is not practical to construct a four-loop pouch by stapling. The terminal 40 cm of the ileum is folded into four 10-cm loops. The proximal two limbs are offset from the distal two limbs by about 2 cm. The loops are united using a continuous absorbable suture. The bowel is then opened along the suture lines and a full-thickness suture is applied along the posterior layer of the pouch. As with the “J” construction, this is continued onto the anterior surface of the pouch finally to leave an aperture for the IAA, which comfortably takes two fingers.

Harms et al. suggested that it is better to construct the W-pouch with a slightly longer distal loop so that it fits more comfortably into the pelvis for IAA, rather than using four equal lengths of ileum. These authors suggest a configuration measuring 11, 13, 10, and 10 cm. Thus, the distal enterotomy forms an apex, which is used for the IAAs. This detail is a modification of the abovementioned description. The integrity and capacity of the pouch should then be checked by distending it with saline as for the “J” pouch.

Ileoanal Anastomosis

In the description of pouch construction, the technique of the IAA requires some mention. This issue is relevant to the degree of mobilization of the mesentery required and to the completeness of removal of the disease, whether UC or FAP. A manual anastomosis with mucosectomy is more distal and may result in increased tension in some cases. Conversely, it results in minimal remaining disease and it can be accurately placed under direct vision. Although it is believed that function after a manual IAA with mucosectomy is less satisfactory than after a stapled anastomosis, comparative studies of the two techniques showed no significant difference.

In the case of a stapled IAA, although there is the advantage of less liability to tension owing to a more proximal IAA, there is the danger of making it too proximal such that a length of inflamed rectal mucosa is left in the patient. This consideration may not matter in most cases; but in some patients with severe inflammation and ulceration, function after closure of the ileostomy may be poor with anal burning, urgency, and bleeding because of the presence of the inflamed mucosa itself and the frequent passage of small-volume stool secondary to incomplete emptying of the pouch owing to the presence of the distal anorectal stump. A stapled IAA must therefore be sufficiently distal to avoid this complication.

A meta-analysis published in 2006, based on 21 studies and 4,183 patients, compared hand-sewn versus stapled IAA and found no significant difference in the incidence of postoperative complications between the two groups, including anastomotic leak, pelvic sepsis, pouch-related fistula, pouchitis, anastomotic stricture, and pouch failure. There was no significant difference between the two techniques with regard to stool frequency per 24 hours, defecation at night, use of antidiarrheal medication, seepage during the daytime, and daytime pad usage. However, the meta-analysis demonstrated significantly more frequent nocturnal seepage, incontinence of liquid stool, and use of pads overnight with hand-sewn IAA compared to stapled IAA, and this correlated with significantly reduced resting and squeeze pressures of the hand-sewn IAA. Others have found significantly higher rates of sepsis, fecal incontinence, and ultimate failure with a hand-sewn IPAA.

Stapled Ileoanal Anastomosis

For the stapled anastomosis of a stapled “J” pouch to the anorectal stump, a purse string suture is placed in the distal opening of the pouch and the anvil of the circular stapler (CEEA 28 or 29 mm) is inserted into the pouch and the suture is tied. The stapler is inserted into the anus and the anastomosis performed by firing it in the normal way.

For the stapled anastomosis of a hand-sutured “J” pouch, the technique differs in one important aspect (which was described earlier): the last few sutures of the anterior wall of the pouch should be placed in an interrupted manner to prevent cutting and unravelling of the continuous suture. Otherwise, the insertion of the purse string suture and firing of the instrument are identical.

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