Postoperative ileus, mechanical small-bowel obstruction
Often spontaneous resolution
Often requires complex interventions and reconstructive surgery
Crohn’s disease with abdominal sepsis
Massive small-bowel resection
Small-bowel transplantation, small bowel lengthening, or glucagon-like peptide 2 agonist therapy can be considered in selected cases
37.3 Epidemiology of Intestinal Failure
Postoperative paralytic ileus and small bowel obstruction are by far the most common causes of type 1 IF. The incidence of type 1 IF greatly depends on how ileus is defined, since the duration of postoperative gastrointestinal dysmotility varies greatly. For example, patients typically cannot eat for about 3 days after elective open colorectal surgery performed with traditional perioperative care, whereas patients undergoing laparoscopic surgery within an enhanced-recovery protocol usually tolerate solid food after 1 day . Many definitions of ileus have been put forward, but regardless of which is used, it is clear that a substantial proportion of patients require parenteral fluids, and often parenteral nutrition, for periods lasting from days to weeks in both acute and elective surgical care. The incidence of type 1 IF is therefore substantial.
The incidence of type 2 IF is probably far less common than type 1 IF, although there are relatively few good epidemiological data. In the United Kingdom, the prevalence of type 2 IF, estimated from the number of patients receiving in-hospital parenteral nutrition lasting 28 days or more, indicates a point prevalence of 9 in 1 million population . This is an indirect estimate based on actual total parenteral nutrition prescriptions and may underestimate the number of cases. Thus the true prevalence of type 2 IF remains unknown, but it is probably somewhat higher than usually reported.
The prevalence of type 3 IF can similarly be estimated from the number of patients who receive HPN. This is known to vary greatly between and within countries, indicating important regional variations in both the availability of and indications for HPN. In the United Kingdom, where HPN is not frequently prescribed as part of palliative care, the number of patients receiving HPN in 2011 was 624, yielding an estimated prevalence of type 3 IF of ten per million population .
37.4 Etiology and Prevention of IF
37.4.1 Type 1 IF
The most common preventable cause of type 1 IF is postoperative ileus. Several perioperative interventions and techniques have been shown to attenuate this common condition, including avoidance of fluid overloading, minimising opioid administration, using mid-thoracic epidural analgesia, and administration of peripheral opioid antagonists. The combination of such interventions in enhanced-recovery protocols has been shown to preserve normal gastrointestinal function after major colorectal surgery  (see Chap. 36).
37.4.2 Type 2 IF
In at least one-third of patients with IF, the underlying cause is a major complication of abdominal surgery  (Table 37.2). The second most common underlying cause is Crohn’s disease, followed by mesenteric ischaemia.
Underlying causes of intestinal failure in patients admitted to Salford Royal Hospital Intestinal Failure Unit (institutional audit data from 2002–2005; n = 134)
Type 2 IF can result from any abdominal surgical procedure. Laparoscopic division of adhesions, laparoscopic hernioplasty, and bariatric surgery are increasingly important causes of type 2 IF. The characteristic sequence of events that leads to type 2 IF is an unrecognized or inadequately treated enteric injury or an anastomotic or suture line dehiscence resulting in abdominal sepsis, for which further surgery may have been performed, leading to a high output stoma or intestinal fistula.
Emergency surgery for sepsis or trauma may occasionally necessitate leaving the abdomen open in an attempt to control sepsis and prevent intra-abdominal compartment syndrome. Leaving the abdomen open in the setting of trauma seems to be associated with relatively low (<5 %) rates of intestinal fistulation and type 2 IF, whereas in patients with sepsis the rates of intestinal fistulation and type 2 IF may exceed 10 %; some studies have suggested rates in excess of 20 %. Use of negative-pressure devices to manage the open abdomen in this setting is highly controversial, with some studies reporting a significant increase in fistulation and mortality [10, 11]. However, the largest prospective study reported to date failed to identify an increase in the rate of fistulation or type 2 IF in patients with an open abdomen (caused by sepsis in 70 %), treated with negative-pressure wound therapy .
Avoiding type 2 IF depends not only on the careful selection of patients and meticulous surgical technique avoid complications but also prompt recognition and expert senior management of complications when they arise. Anticipating and avoiding bowel injury in reoperative surgery  and avoiding construction of an anastomosis in unfavorable circumstances  may enable type 2 IF to be avoided completely in many such cases.
In patients with mesenteric ischemia, revascularization is occasionally possible in cases of early arterial embolic ischemia. It may be appropriate to retain bowel that is not clearly necrotic, which can be reexamined at a planned second-look laparotomy 24–72 h later. Anastomosis should only be considered if the bowel is clearly viable and the patient hemodynamically stable. In the event that the bowel is viable but the patient unstable, a double-barreled stoma is preferable, and bowel continuity can be restored later, without the need for a full laparotomy.
Crohn’s disease is the second most common underlying cause of type 2 IF, as indicated earlier. Patients with complications of surgery for Crohn’s disease represent one of the largest groups with type 2 IF. This association between Crohn’s disease and IF must be recognized so that unnecessary surgical risks and bowel resection can be avoided. Bowel-sparing techniques such as balloon dilatation of strictures and stricturoplasty, in association with biologic therapy, may be important to conserve the bowel.
The vast majority of type 3 IF in Crohn’s disease results from poor management of type 2 IF. In other words, progression from severe acute to chronic IF in Crohn’s disease is mainly the result of complications of surgery rather than bowel loss resulting from multiple, uncomplicated bowel resections . The risks of complications from surgery for Crohn’s disease can be reduced by meticulous technique and careful selection of cases for primary anastomosis  (see Chap. 15).
37.4.3 Type 3 Intestinal Failure
Patients with type 3 IF represent the end stage of processes that lead to irreversible functional or anatomic loss of small intestine, beyond the amount required to maintain life without parenteral nutrition. The majority of patients with type 3 IF have short bowel syndrome, most commonly as a consequence of the conditions that lead to type 2 IF. A smaller proportion of patients develop type 3 IF as a result of conditions that neither arise from, nor usually require, surgical treatment, including scleroderma and motility disorders. Their etiology is beyond the scope of this chapter.
37.5.1 Management of Type 1 IF
The management of type 1 IF is usually relatively simple, and the expertise and facilities required should be available in every center in which patients with abdominal surgery are treated. The vast majority of patients with type 1 IF require little more than safe and effective parenteral fluid therapy – and often parenteral nutrition – until the underlying condition resolves. Whether resolution requires active intervention (e.g., the management of some cases of mechanical intestinal obstruction) or conservative treatment (e.g., the management of an ileus resulting from severe acute appendicitis) is irrelevant. In all cases, the focus must be on providing complication-free and effective nutritional and fluid therapy. The role of dedicated nutrition support teams and avoidance of catheter-related sepsis are important to ensure the best outcomes .
37.5.2 Management of Type 2 IF
The presentation of type 2 IF is complex and often life-threatening. Patients are usually systemically unwell from multiple disease processes, including sepsis, malnutrition, electrolyte disturbances, underlying disease activity, and concurrent complications. In addition, there is often an open abdominal wound and/or enterocutaneous fistulation (Fig. 37.1). A structured approach is therefore essential for a successful outcome. The goals in managing type 2 IF are multiple: to prevent mortality; to restore as much intestinal function as possible, thus avoiding progression to chronic (type 3) IF; to establish HPN when indicated; and to close fistulas, stomas, and open abdominal wounds when possible.
Severe abdominal sepsis associated with fistulation in the open abdomen
A multidisciplinary team comprising nurses (with specialized nutrition and stoma care experience), dieticians, pharmacists, intensivists, physicians, clinical psychologists, and surgeons is needed to manage such patients effectively. Recognizing this, many centers in the United Kingdom and elsewhere have begun to centralize the care of such patients in dedicated intestinal failure units.
To address the multiple clinical challenges that type 2 IF presents in the order in which they cause mortality and morbidity, the so-called SNAP (sepsis, nutrition, anatomy, procedure) approach was proposed and has evolved over time . This mnemonic outlines a rational approach to management in an appropriate order of clinical priorities for the majority of patients with type 2 IF.
37.6 Sepsis and Skin Care
A majority of patients with type 2 IF have active intra-abdominal infection at presentation. Sepsis, as conventionally defined (i.e., by the presence of signs such as fever, tachycardia, tachypnea, and leukocytosis), is frequently absent in patients with type 2 IF, possibly because infection is long-standing and walled off. More than half of patients with active abdominal infection in type 2 IF have no overt clinical signs of sepsis. Infection in this group more often presents with subtle signs such as persistent hypoalbuminemia, hyponatremia, high levels of inflammatory markers, deranged liver function (notably unexplained jaundice), and failure to gain weight (or even cachexia) despite appropriate nutritional support.
Whether overt or subtle, diagnosis and treatment of infection are nevertheless the first priority, for two main reasons. First, sepsis locks intermediary metabolism in a state of catabolism. Thus, until sepsis has resolved, there is resistance to the normally anabolic effects of insulin on carbohydrate and protein metabolism, and little progress is possible, even though nutritional needs can be met or even exceeded .
Second, severe sepsis can develop quickly in this population, often following surgical intervention. Sepsis remains the most common direct cause of death in IF; some 70 % of deaths in an intestinal failure unit are a direct result of sepsis . Therefore, as soon as possible after presentation, blood and line cultures, wound swabs, urine cultures, chest films, and computed tomography (CT) of the abdomen and pelvis with oral and intravenous contrast should be obtained. These tests may need to be repeated in patients who fail to thrive and complemented as required by echocardiography, magnetic resonance cholangiopancreatography, labelled leucocyte scintigraphy, and occasionally positron emission tomography/CT to identify occult septic foci.
Radiologically guided percutaneous drainage of abdominal and pelvic abscesses is the treatment of choice, unless the anatomic position of collection renders this impossible or anastomotic continuity is completely lost (in which case drainage without a defunctioning stoma is unlikely to provide adequate source control). Drainage should be supported (but not replaced) by antibiotic therapy, guided by expert microbiological advice, and adjusted following microbiological analysis of samples sent at the time of drainage.
Emergency laparotomy in type 2 IF should be undertaken only in systemically unwell patients in whom abdominal infection cannot be treated adequately by other means. At laparotomy, collections should be thoroughly washed out and cavities controlled with large-bore drains. Importantly, any suspicion of a visceral leak “feeding” the septic cavity warrants diversion of intestinal contents by resection and exteriorization of the bowel ends or the formation of a proximal diverting loop stoma. Severe, poorly controlled abdominal or pelvic sepsis, especially when there are multiple small-bowel loops fixed within the inflammatory process, may necessitate leaving the abdomen open. This improves control of abdominal sepsis, but at the cost of more complex wound management, more demanding abdominal wall reconstruction during later definitive surgery, and an increased risk of enteroatmospheric fistulation .