Don't Forget about the K-Pouch!

Abstract

The continent ileostomy (CI) was popularized by Nils Kock as a means to provide fecal continence to patients, most commonly in those with ulcerative colitis, after proctocolectomy. Although the ileal pouch-anal anastomosis (IPAA) now represents the most common method to restore continence after total proctocolectomy, CI remains a suitable option for highly selected patients who are not candidates for IPAA or have uncorrectable IPAA dysfunction but still desire fecal continence. The CI has exhibited a fascinating and marked evolution over the past several decades, from the advent of the nipple-valve to a distinct pouch design, giving the so-inclined and so-trained colorectal surgeon a technique that provides the unique patient with another option to restore continence. The CI continues to offer a means for appropriately selected patients to achieve the highest possible quality of life (QOL) and functional status after total proctocolectomy.

The Evolutionary History of the Continent Ileostomy

The continent ileostomy (CI) was most notably described in 1969 after Nils Kock published his results from a case study of five patients undergoing this operation as a means to improve quality of life (QOL), who either did not desire or would not tolerate a conventional end ileostomy. His design garnered the name the “Kock pouch” or the “K-pouch.” ^{1 2 3} The K-pouch is an ileal reservoir placed underneath the abdominal wall that stores stool until the patient voluntarily intubates the reservoir with a catheter through a flush stoma, thus evacuating retained stool from the reservoir. This eliminates the need to wear a stoma appliance and allows for controlled and predictable evacuation of stool at a socially convenient time. Early results in the early 1980s demonstrated improved patient satisfaction with carrying out leisure activities and quality of sexual life postoperatively. ⁴ The earliest iterations of the K-pouch did not include a nipple-valve as it was postulated that the abdominal wall musculature at the distal end of the reservoir outlet would contract and sufficiently prevent uncontrolled release of gas or stool from the stoma. However, many patients did experience incontinence and thus the nipple-valve mechanism was added in later years to combat this undesirable result. ^{1 3} The CI offered an alternative to the conventional end ileostomy for patients with ulcerative colitis (UC), familial adenomatous polyposis (FAP), and other diseases requiring total proctocolectomy, and heralded a new era in the realm of reconstructive colorectal surgery.

By the 1970s, Dr. Kock had described the technique for a nipple-valve using animal models and incorporation of a nipple-valve soon became standard of care in human patients as well. ^{5 6} The nipple-valve is formed by the intussusception of the efferent limb of ileum into the pouch and has been demonstrated to prevent unintended leakage of stool from the stomal aperture. Despite these advancements, the early K-pouch did suffer from untoward complications of valve slippage and prolapse, resulting in incontinence and making pouch intubation more difficult for patients. In subsequent years, Dr. Victor Fazio and others developed methods for stabilizing a nipple-valve using surgical staplers to prevent valve slippage. ^{7 8} Other surgeons proposed the use of synthetic mesh to further stabilize the nipple-valve, but this approach was associated with fistula formation and fell out of favor. ^{9 10 11} Another method to prevent valve slippage used ultrasonic mucosectomy on the mesenteric side of the nipple-valve with suture fixation to the posterior wall of the pouch. ¹² The application and integration of the nipple-valve continued to spur new developments and modifications for the CI to improve continence and success.

In 1984, Dr. Barnett proposed his self-named modifications in his report of 16 patients undergoing his novel isoperistaltic nipple-valve creation compared to 5 patients who underwent standard antiperistaltic valve creation. ¹³ He coined this the Barnett continent intestinal reservoir (BCIR), one of the more common variations of the K-pouch that we see today. In his series, 40% of patients with traditional antiperistaltic valves suffered valve dysfunction requiring reoperation while those with isoperistaltic valves had no cases of valve slippage during the study period. ¹³ Barnett asserted that the optimal technique for nipple-valve formation, which minimizes valve slippage and fistula development, includes an intestinal “living collar” of isoperistaltic ileum wrapping around the neck of the pouch, a hallmark of his BCIR. ¹⁴

Another less-popularized attempt at CI improvement was the “T-pouch,” which utilized a structural arrangement more commonly seen in successful continent urostomies. The T-pouch is formed by creating a valve mechanism in which the distal ileum is placed in a tunnel of apposed loops of serosa-lined bowel. ¹⁵ Although the T-pouch concept was applied in response to the high reoperation rate for nipple-valve slippage in CI surgery, the reoperation rate of the T-pouch is actually largely equivalent to other modified CI. ^{15 16} While the Koch pouch and BCIR have shown a reoperation rate between 40 and 58%, the reoperation rate of the T-pouch has been cited at 55% by Kaiser and colleagues after following a cohort of patients with T-pouches for 10 years. ^{16 17 18 19 20}

Since the introduction of ileal pouch-anal anastomosis (IPAA) by Parks and Nicholls in 1978 and its modification to a double-limbed “J” configuration in early 1980s, surgeons and patients alike favor IPAA over CI as an alternative to conventional ileostomy. ^{21 22} However, CI remains an appealing option for very highly and appropriately selected patients who are not candidates for IPAA but still wish to avoid a conventional ileostomy.

The Design and Function of the K-Pouch

The K-pouch is an intermittently catheterized abdominal ileal reservoir that is created using 3 to 15 cm ileal limbs fashioned in an S-configuration, with an intussuscepted nipple-valve within the pouch to confer continence ( Fig. 1 ). Immediately after creation, patients maintain the catheter in the stoma to evacuate stool continuously and decompress the pouch for several weeks, but in the long term, patients can expect to intermittently intubate the pouch four to six times throughout the day and in many cases, are able to sleep at night without the need to self-catheterize. ^{23 24} Patients require extensive education about pouch care in the perioperative period, and are taught maintenance maneuvers such as pouch irrigation if the reservoir becomes mechanically obstructed with food particulates. ²⁴ The stoma opening is covered by a small bandage after completing the pouch intubation to capture the small volume of mucoid discharge from the exposed mucosa of the flush stoma. ² The care of a CI is quite manageable in patients who are highly motivated and educated in pouch care and who are willing and able to comply with pouch intubations, irrigations, and other general care routines. This is one of the most critical components to pouch success. Maintaining a CI is a full-time, daily responsibility and the patient cannot neglect these duties, not even for one day.

Fig. 1.

Intussusception of small bowel to create a nipple-valve.

The physics of the CI involve a high-volume, low-pressure reservoir for storage of enteric contents that is contained by a continent outlet or valve that remains closed when not in use, but whose pressure can be easily overcome when the patient introduces a soft catheter in the valve to empty stool from the pouch. Kock and colleagues outlined the necessary features of each of these components, specifically, that the small intestinal reservoir should have a low intraluminal pressure, be capable of storing between 400 and 500 mL of stool, and that the outlet should have a mechanism to prevent unintended leakage of stool, the so-called “nipple valve.” ^{23 25} The nipple-valve is formed from an intussuscepted ileal segment fixed it in its intussuscepted state using a non-cutting stapler, taking care to avoid the mesenteric edge. Contemporary operative techniques involve stapling or suturing the nipple-valve, cauterizing the seromuscular layers of the nipple-valve, creation of a fascial mesenteric sling, and stripping of the mesentery to promote adhesion and scar formation between the intussuscepted bowel, thus preventing valve slippage. ^{8 25 26}

Patient Selection and Considerations

There are several “nonnegotiable” requirements for CI. The first requirement is a surgeon who has the training and experience to appropriately select patients, to create a proper pouch, and to have the wherewithal and institutional support to maintain these pouches over the lifetime of the patient. This in and of itself is a gargantuan task that should not be taken lightly. Second, the patient must be very motivated to undergo surgery and maintain a pouch for a lifetime, and have the education, judgment, and physical ability to do so. Finally, the patient must have anatomic requirements for success, such as a thin abdominal wall, adequate small bowel length, and no inherent small bowel pathology (such as Crohn's disease [CD], although the nuances will be discussed later). Only with ALL of these factors in place is there any hope of success with CI. Despite these obstacles, one should not underestimate the potential that creating a CI has for reaching a level of QOL in our patients that is unparalleled. The authors would put forth that achieving a high QOL for our patients is the quintessential raison d'etre for a reconstructive colorectal surgeon.

With this said, CI is an attractive option in appropriately selected patients who understand and accept the necessary lifestyle modifications and risks of surgery including surgical site infections, need for reoperation, inflammatory pouch syndrome, fistulae, strictures, intra-abdominal abscesses, nipple-valve dysfunction, and hernias. ^{27 28 29} After undergoing total proctocolectomy, if a patient desires an alternative to ileostomy, does not desire or is not a candidate for a pelvic pouch, or if a patient has not had success with a pelvic pouch, CI may be thoughtfully considered. ³⁰ CI is also advantageous over a pelvic pouch in patients who desire fewer number of stool evacuations per day (5 to 6 intubations per day with K-pouch vs. 6 to 8 or greater per day with IPAA), patients with pelvic floor or sphincter dysfunction/anal disease, or patients who have insufficient bowel length to reach the anus with an acceptable amount of tension. ²⁷ Conversely, contraindications to CI include obesity (abdominal obesity in particular), physical, mental, or learning disabilities that would prevent proper care and management of a CI, and unwillingness to accept the risks of surgery (including future revisions when indicated). ³⁰

Disease-State Considerations

Proctocolectomy with conventional ileostomy is a surgical offering for several disease states including inflammatory bowel diseases and familial polyposis syndromes, most notably, FAP. Special consideration for each disease state should be considered when evaluating the candidacy for CI.

CD is a particularly challenging situation when considering a patient for CI, as many CD patients have an ileostomy at a young age and may desire an alternative. In fact, there are selected patients with isolated colorectal CD who do well with CI after careful selection and multidisciplinary approach to care. However, the increased risk of inflammatory pouch conditions, concerns regarding preservation of bowel length, and future need for reoperation make surgeons pause when considering CI in CD ^{31 32} ( Fig. 2 ). While some surgeons may consider offering a CI to patients with CD, it remains a debated topic as data have highlighted less than ideal outcomes in CD pouches. ³²

Fig. 2.

Crohn's disease of the continent ileostomy.

Patients undergoing proctocolectomy for UC may ultimately be acceptable candidates for CI but often present initially with acute on chronic illness, toxic megacolon, or evidence of perforation and benefit from a staged approach to CI similar to that of a staged IPAA creation. ³³ One study suggested that K-pouch outcomes are better when it is performed at the time of completion proctocolectomy to avoid multiple operations. ²⁸ However, the authors recommend against this for a few reasons. First, the patient often presents for initial surgery in a malnourished, thin state and will gain weight and subsequently, abdominal fat after their health improves. In our practice, we create a CI that is tailored to the individual's abdominal wall thickness, and gaining (or losing) this thickness may negatively affect valve function. Additionally, preoperative screening and education for potential CI patients is rigorous, time-consuming, and requires large consumption of information and an ill patient is not likely to have the mental fortitude necessary for this. Staging the operations and making a proper assessment when the patient is well and at a healthy weight that can be maintained over a lifetime is ideal.

FAP patients with a K-pouch require ongoing pouch surveillance just as those who have an IPAA, in order to detect adenomatous polyps and carcinoma in the pouch (with adenoma rates in IPAA/K-pouch theoretically lower than in patients with ileorectal anastomoses). ³³ The BCIR form of the CI has been reported in patients with FAP with good results. ³⁴

Converting a J-Pouch to a K-Pouch

The IPAA more closely mirrors physiologic defecation and is the preferred reconstruction choice after proctocolectomy in contemporary times. However, if an IPAA becomes dysfunctional and fails revisional attempts, it may be subject to excision with conversion to a conventional ileostomy, leading to reduced QOL and poor control of continence. In selected cases, conversion of an IPAA to a CI in lieu of conventional ileostomy may be an option to preserve continence and prevent loss of bowel length. This technique was first described in the 1990s and overall results have been quite promising, again, in the thoughtfully chosen candidate. ^{35 36}

After the J-pouch is excised from the pelvis and detached from the anus, the afferent limb is transected at a site that allows enough length for it to be intussuscepted to form the nipple-valve of the K-pouch and is eventually brought through the abdominal wall to form a flush stoma. The neoterminal ileum is then joined to the apex of the pouch to become the neo-afferent limb. ³⁰ This technique is the most simplistic and widely described; however, several modified forms exist to address multiple anatomic or patient-specific variants. For example, if the afferent limb of the J-pouch is of inappropriate diameter to form an adequate nipple-valve, then a more proximal segment of jejunum is transected, transposed, and used instead. ³⁷ The existing J-pouch is commonly preserved, unless augmentation is needed due to insufficient pouch volume, in which case a side-to-side anastomosis of small intestine is made to form an S-pouch. ³⁶ Similarly, if the J-pouch is damaged during pelvic dissection, then partial reconstruction with augmentation may be indicated, with creation of the nipple-valve performed in a similar manner. ³⁷

Outcomes after IPAA to K-pouch conversions are similar to those of primary K-pouch operations, as described by Ecker et al. ³⁷ Preliminary results from a cohort of patients in 1996 showed durable pouch function in 80% of patients, and in following years these findings were corroborated by other studies. ³⁵ Wasmuth et al found that the combined revision or removal rate of K-pouch after IPAA failure at their institution was 27%, but that 72% of the patients who kept their pouch were completely continent after a median follow-up of 7 years. ³⁸ Börjesson et al also quote a 76% rate of complete continence in patients undergoing CI creation after failed IPAA. ³⁹ Another retrospective study found that major and minor revision rates as well number of daily and nightly pouch intubations were similar between patients with conversion to CI after failed IPAA versus primary CI creation without history of IPAA. ⁴⁰ They also found no relationship between history of failed IPAA and failure of CI. ⁴⁰ Lian et al prospectively studied outcomes in patients undergoing K-pouch creation after IPAA and found that 25% of patients were able to have a K-pouch created out of an existing J-pouch, 43% of patients required pouch revision (consistent with primary K-pouch reoperation rates), and that patients had high QOL scores. ⁴¹ This “robust for this topic” body of data supports consideration of a CI in selected patients who failed IPAA but desire fecal continence as a means to preserve bowel length and QOL.

Functional Outcomes

CI remains a good option in the thoughtfully selected patient, but a major consideration is the likely need for reoperation during the lifetime of the pouch for a multitude of reasons, most notably dysfunction of the nipple-valve mechanism. ⁴² The largest cohort of patients studied for this topic were followed for an average of 11 years and found to have pouch survival rates of 87% at 10 years and 77% at 20 years, but required average of 2.9 revisional operations per patient. ⁴³ Similarly, another study from Fazio and Church found a pouch excision rate of only 6% (with 80% of these patients having CD) and a pouch continence rate of 91%, but reported a reoperation rate of up to 42.5%. ²⁷ In summary, many patients with CI are able to maintain their pouch and achieve continence, but at the expense of multiple revisions or other surgical interventions.

Careful consideration should be given to patients with CD prior to surgical planning for a CI. Some early studies resolutely recommended against a CI in patients with CD, while others advocated for selective consideration of CI in this patient population with a specific disease-free interval (i.e., 5 years). ^{31 44} More recent data demonstrate that a diagnosis of CD in patients undergoing CI creation portends worse clinical outcomes and puts the patient at risk for further loss of intestinal length and potential malabsorption-related complications. ³² Conversely, a systematic review of UC patients undergoing CI creation reported high rates of pouch survival, low rates of anastomotic leaks, and excellent QOL (notably with similar QOL outcomes as IPAA). ⁴⁵ The authors strongly recommend caution when approaching the CD patient requesting a CI, even if the individual has been well for years after proctocolectomy. They commonly suffer complications and stand to lose a long segment of precious small intestine and risk sequelae of the dreaded short bowel syndrome.

Despite the high reoperation rate required to successfully maintain a CI, patients report good QOL afforded to them by having a functional CI. Studies have documented patient self-reported satisfaction scores of 84% as well as positive results describing physical, social, and mental health when compared to age-matched controls. ⁴⁶ Furthermore, patients with CI report improvements in social, athletic, and sexual activities, and report spending less time and money caring for their stomas compared to patients with conventional ileostomies. ⁴⁷ These data support the notion that patients have generally good QOL with CI despite its high maintenance requirements and the potential need for revisional surgery.

Revisional K-Pouch Surgery and Outcomes

Up to 60% of CI patients require reoperation in their lifetime for management of complications, thus revisional techniques play a critical role in maintenance of these challenging pouches. ^{18 42 48} Again, studies report an average of 2.9 revisional surgeries per patient and a median revision-free time period of 14 months. ⁴³ Ecker et al examined factors associated with CI revisions as well as functional outcomes in patients requiring revisional surgeries. ⁴⁹ They found that nipple-valve dysfunction accounted for 33.1% of all revisions and that the nipple-valve could be salvaged with stabilization rather than reconstruction 44.9% of the time, while pouch complications (i.e., fistulae or stricture) accounted for a similar percentage of revisions (33.8%) ⁴⁹ ( Fig. 3 ). They found that 35.1% of patients required a second pouch revision, 14.3% required a third, 8.0% required a fourth, and 2.6% required a fifth. ⁴⁹ Despite the possibility of multiple revisional surgeries after CI, the pouch can be salvaged in most cases, allowing patients to continue to enjoy the social and psychological benefits of preserving continence.

Fig. 3.

Nipple-valve stricture and fistula.

To date, there are limited data regarding QOL and other patient-centered outcomes specifically in patients undergoing revision of a CI, but QOL data in the CI patient population as a whole is reported to be favorable. Litle et al report a 60% pouch survival rate over a mean of 15.1 years with participants reporting improved state of health after they underwent CI creation. ⁵⁰ Nessar et al describe 10- and 20-year pouch survival at 87 and 77%, respectively, with patients with CI reporting better QOL than those who suffered from failed CI converted to conventional end ileostomy. ⁴³

Despite its eccentricities, CI remains a valuable tool in the reconstructive surgeon's toolbox to afford patients with no option other than a conventional ileostomy some degree of control of continence. IT IS NOT FOR EVERYONE. But for some, it makes a world of difference. So don't forget the K pouch!