Continent ileostomy (Kock pouch)
The continent ileostomy was devised by the Norwegian surgeon Nils Kock in the 1960’s, and as such is often referred to as a Kock pouch or K-pouch. It is seen as a predecessor to the ileoanal pouch, and following the success of the ileoanal pouch, the Kock pouch fell out of favour. The continent ileostomy is made from small bowel created into a reservoir together with a valve mechanism to keep the reservoir continent. The valve is connected to the skin, as with a conventional ileostomy, however the stoma sits flush to the skin rather than sitting proud from it, and is often placed lower on the abdomen. In order to empty the pouch, the patient passes a Medena catheter through the stoma and valve mechanism into the pouch and then gently irrigates the pouch with some water.
Who is suitable?
Patients who have previously undergone surgical removal of all of their colon and rectum (proctocolectomy) may be suitable for a Kock pouch. This includes patients with Crohn’s disease, providing there has been no evidence of small bowel Crohn’s disease. It is recommended to wait at least 5 years after proctocolectomy before consideration of a continent ileostomy in someone with Crohn’s disease. Due to the way in which the Kock pouch is created, it is better suited to slimmer patients. Those with a body mass index (BMI) greater than 30 should try and lose weight before considering a Kock pouch.
Patients who have had a previous ileoanal pouch, in whom the pouch is failing, may be a candidate for a continent ileostomy. In these patients, it is sometimes possible to convert the existing ileoanal pouch to a continent ileostomy, although it may be necessary to create a new Kock pouch.
Patients need to be committed to the idea of having a continent ileostomy. The operation is associated with a significant risk of requiring further surgery (see below). Patients need to be prepared to insert a catheter into the stoma and irrigate (wash out) the pouch in order to empty it.
It is not possible to undertake Kock pouch surgery using laparoscopic (keyhole) surgical techniques, and the operation requires an incision along the midline of the abdomen. Once any scar tissue from previous surgery has been divided to free up the small bowel, the reservoir is planned and then sutured together. The reservoir is then checked for any potential leaks and to ensure that the valve mechanism is functioning to keep the reservoir continent. Once this has been done, the reservoir is attached to the back of the abdominal wall and the stoma secured.
Post operatively there will be a Medena catheter that is left in the reservoir on continuous drainage. This stays in place for 2 weeks, and patients will need to remain in hospital during this time. This is to allow the joins in the pouch to heal sufficiently without any tension being placed on them by the pouch filling up. If all is well at this time, patients can be discharged home with the Medena catheter still in place. During the day it is possible to cap off the catheter to allow the pouch to fill up. It should be emptied every 2 to 4 hours. Overnight, a drainage bag is attached to the catheter for continuous drainage.
Four weeks following the operation you will be seen back in clinic and the Medena catheter can be taken out. You will then be shown how to pass the catheter into the pouch (intubate) and to wash it out. You will now have a fully functioning Kock pouch.
Unfortunately, problems can arise following formation of a Kock pouch, and these can present many years after the original surgery. Reports in the literature show variable rates of needing further surgery of between 15% and 40%. Some of the more commonly encountered problems are outlined below.
Stoma stenosis (narrowing)
The stoma of a continent ileostomy can become traumatised by the repeated passing of the Medena catheter. This can lead to scar tissue developing and narrowing the stoma, making it difficult to pass the catheter. This can normally be fixed with an operation to revise the stoma, and is normally a relatively minor procedure. Sometimes complete revision of the Kock pouch is required.
The valve mechanism that keeps the Kock pouch continent can sometimes become unravelled or “slip”. This can lead to difficulties passing the Medena catheter, and patients may notice that the angle at which they need to pass the catheter changes. Valve slippage can also lead to the pouch becoming incontinent, which will lead to a constant passage of bowel content as with a conventional ileostomy.
Repair of a slipped valve requires a major abdominal operation, with similar post operative care as described above. It is often possible to reuse the bowel from the previous valve to make a new one, but sometimes it may become necessary to either make an entirely new valve mechanism or to construct a new pouch.
A fistula is an abnormal connection between two different parts of the body. In patients with a Kock pouch, the two most common types of fistulas are a fistula through the valve mechanism or a fistula from the body of the pouch to the skin.
A fistula through the valve mechanism can allow bowel content to bypass the valve which controls continence, leading to the Kock pouch becoming incontinent. There is normally no associated difficulty in passing the Medena catheter. The volume of bowel content leaking is often small as fistulas tend to be narrow. This can normally be diagnosed through a combination of special x-ray tests or a pouchoscopy (a camera test to look inside the pouch). Correction of this normally requires a major operation and revision of the valve mechanism.
A fistula from the pouch to the skin is known as an enterocutaneous fistula. This can lead to bowel content leaking through a small opening on the skin surface. Most commonly, this is in the midline wound on the abdomen. Through a combination of x-ray tests and a pouchoscopy it is usually possible to identify where the fistula is coming from on the pouch. If the amount of fluid leaking is small, then the fistula may close itself without the need for surgery. However, fistulas that prove persistent or are leaking a larger volume are likely to require surgery. This is a major operation to allow inspection of the pouch to identify where the fistula is coming from. It is often possible to repair the fistula site, but sometimes it becomes necessary to reconstruct a new pouch.