Medical Management of Short Bowel Syndrome

Introduction

Short bowel syndrome (SBS) is a form of intestinal failure that most often results from surgical resection related to Crohn disease, mesenteric infarction, radiation enteritis, or surgery for recurrent bowel obstructions. It is characterized by the inability to absorb protein/energy requirements or to maintain fluid, electrolyte, or micronutrient balance when consuming a normal diet. After surgical resection, the remaining small intestine undergoes structural and functional adaptation over 1 to 2 years that gradually improves absorption. Successful medical management of SBS is dependent on a combination of diet, medications, oral or tube enteral supplements, parenteral nutrition (PN), and intestinotrophic hormones ( Fig. 72-1 ).

FIGURE 72-1, Algorithm for medical management of short bowel syndrome. IVF, Intravenous fluid; ORS, oral rehydration solution; PN, parenteral nutrition; SB, short bowel; SBS, short bowel syndrome.

Anatomy of Short Bowel Syndrome

A thorough evaluation of the patient’s remaining gastrointestinal tract is the basis for making therapeutic recommendations. Operative reports should have antimesenteric measurements of residual bowel, its location, and any gross pathologic changes. In addition, the extent and location of bypassed segments should be noted as an aid to potential reconstruction in the future. An upper gastrointestinal barium radiograph with small bowel follow-through or computed tomography (CT) scan enterography provide an estimate of the length of the remaining small bowel. Three anatomic configurations of SBS that have management and outcomes implications have been described. Type 1 is an end jejunostomy with most of the small intestine and all of the colon either resected or out of continuity. A minimum of 100 cm of intestine is needed to avoid permanent PN. Type 2 is a remnant small bowel anastomosed to part of the colon. In this configuration, at least 60 cm of residual small intestine is required to avoid permanent PN. Type 3 anatomy is a jejunoileal colonic anastomosis with the entire colon intact, in which case at least 30 cm of small intestinal length is required to avoid permanent PN. Table 72-1 summarizes the anatomic factors favoring enteral autonomy and anatomic configurations that make permanent PN dependence likely. Plasma citrulline levels lower than 20 μmol/L in adults and 15 μmol/L in pediatric patients also have been associated with permanent dependence on PN. Citrulline is produced mainly by small intestinal enterocytes, and its level correlates with residual small intestine length and functional enterocyte mass.

TABLE 72-1

Anatomic Factors Affecting Enteral Autonomy

Factors Favoring Enteral Autonomy	Factors Associated with Parenteral Nutrition Dependence
Length of remaining bowel >30 cm of small bowel with colon >100 cm of small bowel alone Jejunum resection Preserved ileocecal valve Presence of colon Absence of mucosal disease Normal hepatic and pancreatic function	Jejunoileal anastomosis and remaining small bowel length <35 cm Jejunocolic anastomosis and remaining small bowel length <60 cm Large ileal resection Patients with end jejunostomy and remaining small bowel length <115 cm

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