Intestinal rehabilitation: a management program for short-bowel syndrome

Progress in Transplantation, Dec 2004 by Brown, Cindy R, DiBaise, John K

Over the last 3 decades, there has been significant improvement in the survival and quality of life of patients who require home parenteral nutrition; however, parenteral nutrition remains costly, is associated with multiple complications, and does not promote the function of the remaining bowel. Intestinal rehabilitation refers to the process of restoring enteral autonomy and decreasing dependence on parenteral nutrition by utilizing dietary, pharmacological, and, occasionally, surgical interventions. A major focus of research has been to identify a trophic factor that will enhance adaptation of the remaining gastrointestinal tract following massive gut resection and allow enteral autonomy. Whether intestinal rehabilitation occurs as the result of increased intestinal adaptation or as the result of a comprehensive approach to care has yet to be determined. This article reviews intestinal failure as the result of short-bowel syndrome and the management strategy of an intestinal rehabilitation program in the care of these patients. (Progress in Transplantation. 2004;14:290-298)

Notice to CE enrollees:

A closed-book, multiple-choice examination following this article tests your ability to accomplish the following objectives:

1. Discuss the physiological abnormalities associated with short-bowel syndrome

2. Identify important parameters in assessing the patient with short-bowel syndrome

3. Describe considerations for the diet and fluid plan for the patient with short-bowel syndrome

4. Review pharmacological and surgical strategies for management of short-bowel syndrome

Before the development of total parenteral nutrition in 1968, the medical community had little to offer a patient with intestinal failure due to short bowel syndrome.1,2

Intestinal failure (IF) is commonly defined as any intestinal condition that requires the use of parenteral support to maintain nutritional and hydrational balance. A child who cannot grow without intravenous support would also be characterized as having IF.3 IF may be acute or chronic, and occurs in general because of inadequate intestinal length or function (Table 1). The most common cause of IF is short-bowel syndrome (SBS), which results from massive intestinal resection and usually occurs in the setting of Crohn disease, mesenteric vascular events, necrotizing enterocolitis, congenital intestinal anomalies, or trauma.4 The incidence and prevalence of SBS remain poorly understood, with previous estimates being extrapolated from the number of patients on home parenteral nutrition (PN) because SBS is the most common reason for requiring home PN.4 However, these numbers do not account for patients with SBS who never received home PN or were successfully weaned from PN.

Short-Bowel Syndrome

In adults, SBS can be defined as the presence of less than 200 cm of small intestine. The normal length of intestine in an adult is considered to be 300 to 800 cm.4 In infants, the diagnosis of SBS relies less on an anatomical definition and more on a functional one, as the amount of resection required to produce malabsorption varies with factors such as age, the presence or absence of an ileocecal valve, and length of residual colon.45 The full-term neonate has approximately 240 cm of small bowel and 40 cm of colon; however, the length of the jejunum, ileum, and colon doubles in the last trimester of pregnancy making the gestational age an important determinant of bowel length.6

Establishing an accurate estimation of bowel length and anatomy is important to optimize the care of the SBS patient, but is often difficult. Although information from operative reports is preferred, such notes frequently record the amount of bowel removed rather than the amount remaining. A barium contrast small bowel series may also provide an estimate of bowel length and is useful to delineate other structural features such as the bowel diameter. Frequently, a combination of these 2 methods is used. When considering small bowel length, the duodenum is generally not included and measurements begin at the ligament of Treitz.

Anatomical factors that affect the outcome of SBS patients include not only the length and region of the remaining small intestine but also the presence of the colon. In general, an SBS patient will have I of the following bowel anatomies: jejuno-colic anastomosis, end-jejunostomy, or jejuno-ileal anastomosis. Patients with a jejuno-colic anastomosis rarely have an ileocecal valve. Patients with a jejuno-ileal anastomosis have the best prognosis; however, this anatomy is the least common. Patients with an end-jejunostomy are the most difficult to manage and are most likely to require permanent parenteral support.7 In adults, at least 50 cm of small bowel in continuity with the colon or 120 cm of small bowel without colon is considered necessary to allow autonomy from PN.8,9

Intestinal Adaptation

Following massive intestinal resection, a process known as intestinal adaptation occurs in which the remaining bowel undergoes a variety of macroscopic and microscopic changes to increase its ability to absorb fluid and nutrients.10 Intestinal adaptation can be related to both structural and functional changes. In structural adaptation, the villi increase in size and absorptive surface, whereas functional adaptation refers primarily to a slowing in the rate of transit, allowing increased time for absorption to occur. The degree of bowel adaptation is dependent, in part, on the residual bowel anatomy. The ilcum is capable of both structural and functional adaptation whereas the jejunum mainly adapts functionally. The increased ability of the ileum to adapt is multifactorial and is related to its less permeable mucosa, making concentration of its contents possible; its slower transit time, which allows increased time for absorption; and its ability to absorb bile salts, which improves fat absorption and reduces the effects of these substances on colonie function. As a result of the differences in adaptive abilities between the ileum and the jejunum, a jejunal resection is generally better tolerated.10,11 Unfortunately, in most patients with SBS, the ileum has been resected, leaving only some portion of the jejunum-usually along with a portion of the colon.