Pouchoscopy

Pouchoscopy is an important procedure for patients with a pelvic pouch or a continent ileostomy. It is a complicated procedure however, because intestinal pouches are complicated distortions of the gastrointestinal tract with their own physiology and pathophysiology. The understanding of pelvic pouches is key to performing an informed pouchoscopy, especially in patients with dysfunction, and is reviewed more completely in its own section. Please read this now.

The Pelvic Pouch

There are several aspects of the pelvic pouch that are important for pouchoscopy.

1. Preparation

One fleet enema just before the examination is usually enough preparation. Some patients have an excoriated anus or a stenotic anus and cannot take an enema. In these patients the stool must be irrigated out during the examination

2. The Scope

Examination of the anus reveals any condition that may make pouchoscopy difficult or painful. An anal stenosis may require dilation before any scope can be inserted, or at least the use of the “ileoscope” (see above). An excoriated anus is common with a handsewn ileal pouch anal anastomosis (IPAA) and needs to be numbed with xylocaine jelly before the scope is inserted. An ileoscope is also better in this circumstance. For a “normal” IPAA, with no stenosis and no excoriation, a pediatric colonoscope can be used.

3. Surveying the ATZ

The anal transition zone is an area of epithelium that extends for an average of 5mm proximal to the dentate line. Most IPAA are 2 to 4 cm above the dentate line and so include rectal epithelium in the residual “cuff”. This area is prone to polyp formation in patients with FAP and inflammation in patients with ulcerative colitis. It is best examined during insertion of the scope. After a gentle digital examination to determine the status of the anus, the anastomosis, and the angulation of the IPAA, the endoscope is inserted. Air and water is insufflated during insertion through the anus and IPAA. The anus usually contracts in response to the stimulation of the scope but then will relax and open up, giving a decent view of the epithelium. Biopsies can be done by opening the forceps against the end of the scope, waiting for the anus to open, and then taking the biopsy. Polyps can be removed in this way too, although use of electrocautery will be painful and should be done when the patient is at least sedated, and often anesthetized. The longer the retained “cuff” the easier it is to survey.

Patients with a handsewn anastomosis often have painful excoriation of the anal canal due to seepage of stool and may also have a stenosis. These are the most difficult patients to survey and may need anesthesia to do it accurately.

4. Surveillance pouchoscopy.

An S pouch will have an efferent “spout” of straight ileum between the pouch and the IPAA. Ideally this is only 2 to 4 cm but sometimes it is longer. The pouch itself is obvious by the suture lines and wide diameter. A J pouch has no efferent spout and the scope passes through the IPAA straight into the pouch itself. The upper part of the S pouch is similar to the lower part with the afferent ileum exiting from one side of the pouch. The upper end of a J pouch is recognized by the “owl’s eye’ appearance of the afferent ileum and “tip of the J” as side by side lumens separated by a staple line. The scope is advanced for 20 cm into the terminal ileum.

Surveillance pouchoscopy looks for polyps in patients with familial adenomatous polyposis. These can be quite subtle and can occur in the tip of the J as well as the pouch. The tip of the J can be quite long so try and get to the occluding staple line. The anal transition zone and residual rectum just below the IPAA is most difficult to examine but the most important area to survey. In FAP patients count the polyps and estimate the range of sizes. Polyps over 5mm in diameter should be removed. This can usually be dome with a snare. Large pouch polyps can also be snared although the risk of hemorrhage seems higher than for colorectal polyps. It is better to snare the larger lesions (>2cm) piecemeal.

Ulcers are common findings in an ileal pouch. They are often seen near or on staple lines, especially the staple line between the afferent limb and the tip of the J. These do not mean pouchitis. Apthous ulcers are also common due to ulceration of the lymphoid follicles that are so common in the wall of the terminal ileum. These do not mean pouchitis. The mucosa is normally uniform and normal. Normal pouch mucosa need not be biopsied as invisible dysplasia is extremely uncommon. Biopsies will always show chronic inflammation, which is normal in the wall of the pouch and does not mean pouchitis.

5. Diagnostic pouchoscopy

When investigating symptoms related to a pouch, there should be a differential diagnosis that can be clarified by the examination. Stool frequency is a common symptom that can be due to an acute inflammation of the pouch mucosa, but is more often due to inefficient emptying of the pouch. Causes of inefficient emptying include poor diet (too much roughage), use of bowel stoppers, or a bad bowel habit. All these factors come from a misunderstanding of pouch physiology and are easily correctible. Causes of inefficient emptying that can be seen during pouchoscopy include anal stenosis (also a common cause of nocturnal incontinence), a twist or kink in the pouch body, or an afferent loop syndrome where the afferent ileum is partially obstructed by an adhesion or a kink. Acute inflammation, or true pouchitis, is usually seen as an erythematous, edematous mucosa with mucopus and scattered hemorrhages. Crohn’s proctitis is obvious as the usual longitudinal ulcers that are so characteristic of the disease, while ischemic pouchitis has an irregular border, variable depth, and a base color that could be red, yellow, green or grey.