Intestinal failure (IF), including surgical short bowel syndrome (SBS), is a life-threatening condition that is associated with several major medical complications as well as limitations in quality of life. The evolution of treatment strategies for IF/SBS has seen significant changes in the past 30 years. Like several major advances in surgery, the discovery of anastomotic techniques by Alexis Carrel in the early 1900s paved the way for intestinal transplantation (ITx). As a parallel to surgical discoveries, the development and implementation of parenteral nutrition (PN) and hormonal analogs has allowed clinicians to support IF patients and bridge them toward the ultimate therapy of ITx. The purpose of this chapter is to provide an overview of the causes and medical management of IF/SBS, indications for and various surgical techniques within ITx. The chapter reviews the landmark developments in surgical therapy techniques and provides an outline for the different technical variations within ITx.

The evolution in the medical management of IF/SBS has relied heavily on the advent of PN. Prior to 1968, patients who suffered a massive infarction of their small intestine were often left unresected at the time of laparotomy due to the lack of intravenous nutritional support in the perioperative setting.¹ This often led to consecutive operations for resections of necrotic bowel and patients would ultimately succumb to sepsis and multiorgan failure. The first major breakthrough for PN was ushered in as an alternative therapy for the IF patient in 1968. Wilmore and colleagues were able to demonstrate that the infusion of a hypertonic nutrient solution through a dedicated central venous catheter (CVC) could deliver all of the necessary nutrients to sustain growth and development in an infant with intestinal atresia and IF/SBS.² This development was a major stepping stone that paved the way for the surgical developments that followed.

Richard Lillehei and Thomas Starzl established the early techniques of ITx in canine models in the 1950-1960s.^3,4 However, the first reports of ITx came in the mid-1980s when Williams, Starzl, and others documented the first successful isolated intestine, multivisceral, and liver-intestine transplants in humans.^5–8 Together, these landmark medical and surgical establishments set the groundwork for the modern era of ITx.

The complex mechanisms and relationships of the neurohormonal, enteric nervous, and immune systems of the intestine are beyond the scope of this chapter. However, it must be noted that IF/SGS results from an inadequate delivery of micronutrients, fluid, and electrolytes via the gastrointestinal tract. In the IF/SBS patient, compensatory mechanisms of adaptation can be achieved in the remnant bowel in an attempt to restore the threshold for nutrient delivery.^9–11 Clinically, the cornerstone of successful adaptation relies upon enterocyte mass. Likewise, patients with a greater length of functional bowel and the presence of an ileocecal valve (ICV) are likely to succeed at achieving an adapted state. The functional response of the remnant gut in the IF/SBS patient is primarily to modify sodium, water, and glucose absorption. Enterocyte hyperplasia contributes to increasing enterocyte mass; however, modifications in enterocyte-specific gene expression that leads to improved nutrient trafficking also adds a functional increase to the enterocyte mass, thus rendering an adapted state.^9–11 These molecular mechanisms have been the foundation that have led to the surgical concepts which focus on bowel lengthening procedures. The techniques such as the Bianchi and the serial transverse enteroplasty (STEP) procedures strive to increase overall enterocyte mass, and these are discussed in further detail later in this chapter.

Historically, “short bowel syndrome” was a blanket term that had been used for patients who suffered a catastrophic loss of bowel length that rendered them incapable of maintaining enteral nutrition. These patients were all managed with total parenteral nutrition (TPN), and thus there was no need to further stratify the definition or causes of IF. Advances in prenatal and neonatal intensive care along with more recent developments in medical therapies such as recombinant growth hormone, somatostatin, and glucagon-like peptide-2 (GLP-2) analogs have forced us to further classify the definition of IF. In 2006, a group of experts developed a consensus definition whereby “Intestinal failure results from obstruction, dysmotility, surgical resection, congenital defect, or disease-associated loss of absorption and is characterized by the inability to maintain protein-energy, fluid, electrolyte or micronutrient balance.”¹² With a well classified definition, we are now better able to evaluate the relative efficacy of these therapies and thus offer some patients the opportunity to regain nutritional autonomy free of PN or intravenous fluids.¹² Thus, it is important to recognize that while IF can occur as a result of surgical resection of the gut (“short bowel syndrome”) it can also result from conditions that disrupt gastrointestinal motility or enterocyte function. In these latter cases, the length of remnant intestine is irrelevant and usually normal.

The pathogenesis of IF in the pediatric population can be classified into (1) anatomic/surgical reductions of bowel (necrotizing enterocolitis, intestinal atresia, gastroschisis, and midgut volvulus), (2) neuromuscular diseases of the gut (intestinal aganglionosis or Hirschsprung disease), chronic intestinal pseudoobstruction, and (3) congenital diseases of the intestinal epithelium (microvillous atrophy, tufting enteropathy, intestinal epithelial dysplasia). In some cases, overlap can occur as in a pseudo-obstruction patient with multiple small bowel resections. The details of the complex medical management and maintenance of nutrition in this patient population is beyond the scope of this chapter. However, it must be noted that growth can be achieved on long-term PN, and the aim of appropriate medical management should be to prevent complications of PN such as catheter-related sepsis and vascular thrombosis. Moreover, a combined use of early enteral feeding with supplemental PN can help prevent intestinal failure−associated liver disease (IFALD) as the ultimate complication of PN use.

IF within the adult population is largely attributable to massive resection of bowel following a catastrophic event suffered by the patient. Generally, it is the result of a surgical complication from a previous procedure.¹³ However, adult causes of IF can be categorized into iatrogenic complications, ischemic complications, infiltrative disease processes, obstruction related, and functional problems (see Table 42-1).

When referring to iatrogenic complications, we will focus on how IF/SBS can occur as a result of bariatric surgery for example. These patients are at risk of developing postoperative adhesions, incisional hernias, mesenteric ischemia, and internal hernias that can occur after a mesenteric defect is created during Roux-en-Y gastric bypass (RYGB) surgery. Internal hernias can develop through this defect that result in an obstruction and ultimately infarction of significant segments of bowel. The incidence of internal hernias is approximately 5% in patients who have undergone RYGB.¹⁴ The three main locations where internal hernias can develop are posterior to the roux limb mesentery known as the Petersen hernia, through the mesenteric defect created for the jejunojejunostomy, or through the transverse mesocolic defect created for a retrocolic roux limb (Fig. 42-1).¹⁵ Although the incidence of internal hernias is low, the treatment of this complication is highly time-sensitive and if left unexplored, catastrophic loss of bowel can occur that renders the patient with SBS if they are even able to survive the initial insult.

Ischemic events can be classified based on the distribution of blood supply to the bowel; namely, the celiac axis, the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). The celiac trunk supplies blood to the liver, stomach, duodenum, and the foregut up to the proximal jejunum. The SMA takes over and perfuses the remainder of the small bowel and the colon up to the splenic flexure. Finally, the IMA supplies blood to the remainder of the colon and rectum. Ischemia to these segments of bowel can occur as a result of direct trauma from penetrating missile/stab injuries or blunt trauma, as described by Asensio in his multi-institutional, retrospective series.¹⁶ In this review, the authors highlighted that although the incidence of these injuries is minimal, at approximately 1%, they are often lethal and the patients who survive are often left with a short segment of bowel. More commonly, embolic events from atrial fibrillation and severe atherosclerotic vascular disease results in perfusion defects, with the most devastating being to the SMA.¹⁷ These patients can often present with the sine qua non of “pain out of proportion to physical exam”; however, the onset of symptoms can be insidious, and late intervention is often fatal. After diagnosis with helical CT scan, angiographic or open embolectomy is often undertaken with the hopes of instituting thrombolytic therapy and reconstituting blood flow. The advantage of open procedures in this scenario is the ability to inspect the bowel and thus facilitate a second-look laparotomy if needed.

Mesenteric venous thrombosis is another type of vascular insult that can occur, although less commonly. The most common clinical scenario is that of a chronically ill or institutionalized patient who becomes progressively dehydrated, resulting in venous thrombosis. Without sufficient outflow, the bowel becomes progressively engorged, ultimately restricting arterial inflow resulting in ischemia. In previously healthy individuals, mesenteric venous thrombosis can often occur after routine laparoscopic surgery as a result of pressure effects from pneumoperitoneum. These clinical scenarios often coincide with an underlying hypercoagulable disorder such as Protein S or C deficiency that contributes to the mesenteric venous thrombosis.¹⁸

The infiltrative processes that lead to IF/SBS are from small bowel amyloidosis or desmoid, carcinoid, and other metastatic tumors that not only invade the bowel wall but can often infiltrate the vasculature at the mesenteric root, compromising long segments of bowel. Desmoid tumors are often associated with Gardner syndrome, and these tumors create a desmoplastic reaction with a subsequent area of dense fibrosis that cause local obstructions and enterocutaneous fistulae formation.¹⁹ Carcinoid tumors (see Chapter 40) are similar to desmoids; however, they are also notorious for mesenteric involvement, with a dense desmoplastic reaction that results in much wider areas of bowel resection.¹⁹ Finally, metastatic cancers that infiltrate the small bowel or retroperitoneum such as gynecologic tumors, colon cancers, and retroperitoneal sarcomas can all cause the same degree of local destruction as primary bowel tumors.

Functional causes of IF/ SBS are largely due to pseudo-obstruction, Hirschsprung disease, or scleroderma, which were briefly mentioned in the “Pediatric Causes of Intestinal Failure” section. These are pure motility disorders that affect the transit and ultimate absorption of nutrients. The functional causes of IF/SBS are generally diagnosed at a young age, although they can progress into adolescence and even early adult years if patients can be maintained on effective PN.

Crohn’s disease is mainly classified as a mucosal etiology of IF/SBS (see Chapter 46). Although SBS is classically defined by having less than 200 cm of bowel, Crohn’s results in SBS due to the malabsorption that occurs at the mucosal surface, rendering patients with normal bowel length functionally with SBS. The severe forms of Crohn’s disease result in IF/SBS through the development of fistulae, bowel perforations, and abscesses which frequently necessitate surgical resection and subsequent gradual shortening of bowel.²⁰ The cornerstone of treatment for Crohn’s disease are the aminosalicylates, antibiotics, corticosteroids, and immunosuppressants such as Azathioprine and 6-mercaptopurine. However, newer therapies such as anti-TNF drugs (infliximab, adalimumab) are being used with the intention to reduce morbidity and the amount of bowel resections that are associated with moderate to severe Crohn’s disease.²¹ In an effort to ward off the need for ITx, bowel lengthening procedures such as the STEP procedure and stricturoplasty are often being employed in order to preserve bowel length in Crohn’s patients.^22,23

Intractable diarrhea of infancy comprises a spectrum of disorders that includes microvillous atrophy or microvillous inclusion disease, tufting enteropathy, and autoimmune enteropathy. The general features of these congenital enteropathies are that they affect the development of the intestinal mucosa that leads to intractable diarrhea during infancy and is not related to a bacterial or viral pathogen. The clinical features of these disorders are large volume diarrhea associated with electrolyte abnormalities and the ultimate need for PN. Although the clinical features are distinct, diagnosis is most commonly achieved with histopathological analysis.

Patients with SBS and IF/SBS often have very complex past medical histories and the approach to their care can be overwhelming. When evaluating these patients, it is of paramount importance to approach the evaluation in a consistent, systems-based manner. Langnas et al. best described the components of the history and physical evaluation as follows:

1. 
   

   A thorough review and summary of the past medical record. This is extremely important and painstaking. Every effort should be made to review appropriate surgical and pathological documentation to confirm the preexisting diagnoses.

   
   
2. 
   

   The cause of SBS, the anatomy and length of the intestine, including a detailed review of prior surgical procedures and any related complications. Upper GI small bowel series, barium enema, and endoscopic studies should be reviewed to determine the anatomy of the remnant bowel and anastomotic locations.

   
   
3. 
   

   The number of central lines and the reasons they were changed.

   
   
4. 
   

   Causal microorganisms for central line infections.

   
   
5. 
   

   Nutritional assessment including parenteral and enteral intake, daily caloric requirements, and macro- and micronutrient components of PN.

   
   
6. 
   

   Laboratory evaluation including serum electrolytes, liver function tests, glomerular filtration rate (GFR), albumin/prealbumin, prothrombin time, vitamin B₁₂, fat-soluble vitamins, serum citrulline, and stool calprotectin levels.

   
   
7. 
   

   Detailed vaccination status.

   
   
8. 
   

   Complete physical exam with focus on hydration status, nutritional status (height, weight, basal metabolic index), type of central line, and inspection for signs of nutritional deficiencies and complications from PN such as dermatitis or signs of chronic liver disease.²⁴

Prognostic factors for adaptation include length of remnant bowel, location (ileum>jejunum), presence of ICV, absence of stoma, presence of colon in continuity, absence of liver disease, age of patient, time since onset, and the absence of an underlying GI disease/disorder. Of the aforementioned factors, the length and function of a patient’s remnant bowel are the main parameters that determine the need for PN dependence. In all cases of IF/SBS, it is critical to first assess the ability to maintain at least partial enteral nutrition, as it has been shown that partial feeding via the enteral route is associated with a better prognosis than a nonfunctioning gut.²⁵ Thus, exclusive use of PN should be avoided because this population of patients has the highest incidence of vascular, infectious, and metabolic complications including IFALD.^26–30 To that end, a thorough assessment to determine the ability to establish intestinal/colonic continuity and to surgically correct any forms of obstruction in order to restore intestinal continuity should be carried out prior to initiating PN.

The typical PN formula contains macronutrients (in the form of hypertonic dextrose up to 70%), lipids, amino acids, vitamins, minerals, electrolytes, and fluid. Conceptually, the dextrose is included as a source of carbohydrate delivery, protein as crystalline amino acids, lipids provide essential fatty acids, and sterile water helps meet the patient’s fluid requirements.¹ It should also be noted that all of the components of PN including electrolytes, vitamins, and trace elements play a collaborative role in nutritional efficiency, and along with energy, in maintaining a positive nitrogen balance. Thus, when instituting a home PN plan, it is important to ensure that the patient and caregivers are properly trained and capable of executing the plan at home.

Problems related to PN can be broken down into three categories: catheter-related, metabolic, and organ dysfunction.³¹ Catheter-related problems are the most demanding components of caring for IF/SBS patients; however, it must be recognized that these catheters and maintenance of vascular access are literally the lifelines for these patients. Ideally, CVCs should be tunneled and placed in the superior vena cava (SVC) with the tip outside of the heart borderline on the post-procedure chest x-ray. These catheters should ideally be reserved for PN only and should be single lumen, although patients who are chronically requiring other intravenous solutions such as IV antibiotics or frequent replacement fluids may benefit from a dual-lumen catheter.