What an ileoanal pouch is, and how it is built

Since the operation was first described in 1978, people with ulcerative colitis and other colonic diseases have been able to have surgery without the prospect of a permanent ileostomy. What follows is how Richard E Lovegrove and Neil J Mortensen, Professor of Colorectal Surgery, both of Oxford University Hospitals NHS Trust, describe it.

The aim, whether staged or not, is to remove all of the colon and rectum and create a reservoir — the pouch — from the remaining small bowel, connecting it to the top of the anus. The pouch acts as a substitute for the rectum, holding bowel content internally before defecation. It is normally 15–20cm long.

The stages

1. For people needing surgery during an acute flare: most of the colon is removed (subtotal colectomy), leaving a rectal stump, with an ileostomy in the lower right abdomen. Many centres now do this laparoscopically. Patients are normally given at least three months to recover before the next stage.
2. The remaining rectum is removed and the pouch created from the end of the small bowel. A new ileostomy is commonly made at the same time to let the joins heal safely.
3. Closure of the ileostomy — also called “takedown”. Before it, a special x-ray called a pouchogram may be done to check the pouch.

Shapes

The most common variant is a two-limbed J pouch, used because it has a simple structure that is quick to create. Three-limbed S and four-limbed W pouches have more complex designs and take longer. The pouch can be made and joined using sutures or a mechanical stapler; the choice rests with your surgeon.

Who it may not suit

The contraindications are set out candidly. Many surgeons regard Crohn’s disease as an absolute contraindication, as the likelihood of the pouch developing a fistula or failing is greatly increased. Success relies heavily on good anal sphincter tone, so previous anal surgery or traumatic vaginal deliveries may prompt tests called anorectal manometry. Increasing age raises the impact of complications, and pouch surgery is more difficult with higher complication rates in the presence of obesity.

What the pouch is replacing

It is worth understanding the normal anatomy before the operation that changes it. The small intestine is approximately 3–4 metres long, and its contents remain liquid: approximately one litre of fluid enters the colon each day, containing bile residue — which gives it a green colour — digestive enzymes and unabsorbed food. The colon is about one metre long, and its job is to resorb the water, turning liquid small bowel content into formed stool.

The rectum is a 15cm tube. The lower part of it has a rich nerve supply that lets you know whether there is gas, liquid or solid stool inside, and gives the sensation of wanting to open your bowels. The anus is a complex ring of muscles — the anal sphincter — which normally closes off the exit and is what gives us continence. It works subconsciously, but can be overridden when we clench it closed until it is socially convenient.

The alternatives

Proctocolectomy with a permanent end ileostomy is the main alternative — removing all of the colon and rectum without creating a pouch. The anus is often excised as well, to prevent troublesome discharge — with a consequence worth knowing before choosing: it is not possible to have an ileal pouch at a later stage if you change your mind.

A continent ileostomy, or Kock pouch, is performed at very few centres in the UK. It creates a pouch with an internal valve mechanism behind the abdominal wall, with a short length of bowel connecting to the skin as a stoma that sits flush rather than standing proud. It has to be catheterised to empty.