Critical Care Medicine
Short bowel syndrome
- 1. Description of the problem
2. Emergency Management
- 3. Diagnosis
- 4. Specific Treatment
- 5. Disease monitoring, follow-up and disposition
What's the evidence?
Short bowel syndrome
Also known as: Short gut syndrome
Related conditions: Gastroschisis; Crohn's disease; Small bowel resection; Radiation enteritis; Malabsorption syndromes
1. Description of the problem
The main issue that characterizes short bowel syndrome is either anatomic (<200 cm of small intestinal length) or functional (luminal absorption failure regardless of length) that leads to insufficient luminal nutrient processing and absorption to sustain lean body mass.
Clinical features include unintentional weight loss, loose, malodorous stools, diarrhea, dehydration, multiple nutritional deficiencies leading to severe protein-calorie malnutrition, skin/hair/nail abnormalities, weakness, lethargy, and possibly death.
Key management points
Key management points are as follows:
1. Establish a diagnosis in the non-critically ill patient
2. Ensure adequate fluid resuscitation in the critically ill patient prior to making a diagnosis
3. Initial intestinal rest
4. Intravenous nutritional support
5. Correction of essential and conditionally essential nutrient deficiencies and assessment of end-organ function
6. Intestinal rehabilitation including hormonal manipulation, immunonutritional support, and antimicrobial control of intestinal flora
7. Consider intestinal lengthening procedures (serial transverse enteroplasty [STEP])
8. Evaluate for the appropriateness of intestinal transplantation for failure of medical or lesser surgical management
2. Emergency Management
Emergency management of the patient with short bowel syndrome is little different from any patient with inadequate effective circulating volume with one exception. This patient population has both an intravascular deficit as well as an extravascular interstitial and extravascular intracellular set of deficits.
Therefore, a combined resuscitation approach with both crystalloid and colloid plasma volume expanders is appropriate.
Since there is an association of short bowel syndrome and hepatic failure, specific inquiry into hepatic function should be undertaken along with the standard assessment for end-organ failures that accompany any patient with hypoperfusion.
Nasogastric decompression to correct aerophagia-related luminal distension is appropriate. Bladder catheterization is essential in determining fluid balance. Severely dehydrated and hypoperfused patients should be admitted to an ICU or High Dependency Unit as they are at risk for severe electrolyte disorders during resuscitation and re-feeding syndrome when nutritional support is undertaken.
The first key to an accurate diagnosis is prior history. A specific history of prior operative undertakings, radiation therapy, bowel habits (stool character, frequency, relationship to food intake and type), allergies (dietary, environmental, medication), travel history, pets, and ill contact is essential in identifying patients who are likely to have an anatomic or functional short bowel syndrome as opposed to those with infectious, ischemic, allergic, inflammatory, iatrogenic, or factitious syndromes.
Normal lab values
There are no pathognomonic laboratory values that will firmly establish the diagnosis of short bowel syndrome. However, citrullinemia at >20 micromol/L is associated with functional and anatomic loss of GI luminal cells and is suggestive of the diagnosis.
The mainstay of diagnosis is history of intestinal resection coupled with evidence of short transit time and involuntary weight loss. Support is also derived by excluding concomitant intestinal infection as well as excluding dietary intolerance and malabsorption syndromes. Generally, the latter occur in those without intestinal resection. While intolerances (i.e. lactose) and malabsorption syndromes (e.g. gluten enteropathy, etc.) can result in the functional equivalent of short gut syndrome, there is sufficient intestinal length to maintain health once the patient's diet is correctly managed.
Since many medical conditions present with decreased intestinal transit time, malabsorption, diarrhea, dehydration and hypoperfusion, there are a host of conditions in the differential diagnosis. These include:
1. viral gastroenteritis
2. bacterial enteritis or colitis
4. bacterial overgrowth
5. dumping syndrome
6. radiation enteritis
7. allergic enteropathies
9. gluten enteropathy
10. lactose intolerance
11. Crohn's disease
12. iatrogenic catharsis (hyperosmolar, hypertonic)
13. WDHA syndrome
14. C. difficile colitis or enteritis
15. laxative abuse
Other conditions may present with significant unintentional weight loss but not the associated diarrhea and decreased transit time. These include:
1. chronic mesenteric arterial ischemia
2. body dysmorphic syndrome and deliberate starvation
4. untreated insulin-dependent diabetes mellitus
6. chronic pulmonary or cardiac disease with associated cachexia
8. AIDS enteropathy
1. Small bowel follow-through - this test will help to determine transit time (decreased), as well as measure the length of the small bowel that is present
2. Small bowel enteroscopy - this test will biopsy the small bowel for histologic, immunohistochemical, and microbiologic assessment
3. CT (computed tomography) enterography - this unique CT scan will provide information similar to that from a standard SBFT (small bowel follow through) but will also assess the other intra-abdominal viscera. Moreover, the data may be reformatted in a 3-dimensional fashion to assist in diagnostic accuracy.
4. Specific Treatment
Drugs and dosages
Medication management often proceeds in a tiered fashion.
anti-diarrheals, proton-pump inhibitors, histamine blockers
pancreatic enzymes, antimicrobial agents
bile acid binding agents, somatostatin analogues
probiotics, alpha2-adrenergic receptor antagonists
recombinant human growth hormone, glucagon-like peptide 2 hormone (GLP-2)
Dosages are individualized and titrated to effect with the exception of PPI and H2 blockers, as these have standard dosing. The exact medication used reflects formulary differences rather than an outcome advantage within a given class. It is not uncommon to have a multi-tier approach using one or more agents from tiers 1-3 to achieve initial control. Control failure generally leads to inclusion of and 5 agents. One should note that in particular is thought to represent agents that may promote intestinal adaptation (aka enteroplasticity).
Cases that are refractory to medical and dietary management should be considered for either intestinal lengthening (STEP) or intestinal transplantation. These procedures are both highly specialized and should be performed at unique centers of excellence that offer a team approach to the management of this difficult and challenging patient population. Often, intestinal lengthening precedes transplantation in a sequentially more invasive manner.
5. Disease monitoring, follow-up and disposition
Expected response to treatment
The ideal response to therapy is a decrease in transit time, enhanced nutrient absorption leading to weight maintenance or gain, and abrogation of the need for cycled tube feed supplementation of parenteral alimentation. Of course, the response rate varies with a host of factors, most notably is the length of remaining small intestine. The greater the amount, in particular when there is colon that is in-line as well, the more favorable is the response to therapy. Patient compliance may also factor into response rates as patients often need both medical and surgical therapy in concert - a regimen that is often difficult to manage, and certainly requires a different eating regimen than that which frequently occurs in social gatherings.
For those who have undergone intestinal transplantation, serial biopsy is required for monitoring. This also affords the clinician a regular follow-up and counseling opportunity using a team approach.
Incorrect diagnosis should be entertained when the patient is found to have a normal small bowel length and appearance or a small bowel length >200 cm, fails to respond to therapy, or symptoms and signs cannot be documented or are inconsistent. There is a small but non-zero incidence of factitious short gut syndrome that belies underlying psychopathology and overlaps with Munchausen.
During an acute illness, follow-up should be as often as needed for symptom re-evaluation and medication adjustment or to initiate appropriate consultation. Maintenance management can be on a 3- or 6-month basis and provides an opportunity for team-based counseling and re-evaluation. Transplant patients require more frequent monitoring as above and should receive team-based counseling and inquiry at those visits as well. Of course, immunosuppressive medication management will require more frequent testing and evaluation, the details of which are beyond the scope of this chapter.
The general pathophysiology is one of an absolute or functional lack of appropriate small intestine to manage nutrient processing and absorption as well as water absorption. This results in rapid transit of incompletely or unprocessed foodstuffs through the small bowel, representing a high volume of often hypertonic material to the colon. The volume and tonicity overwhelm the colon's capacity to appropriately absorb water and salt, and diarrhea results.
Dehydration, severe protein-calorie malnutrition and a host of micronutrient and essential vitamin deficiencies accrue. Importantly, immune function also suffers from severe malnutrition and may lead to infection as a presenting symptom for hospital admission.
Since the terminal ileum is often involved in inflammatory conditions, resection of the terminal ileum and more proximal ileum has been well studied. Significant deficiencies in bile salts should be predicted as the terminal ileum is essential for the enterohepatic circulation. Also, substantial vitamin B12 deficiency is common and should be addressed with monthly B12 supplementation via the IM route. Nonetheless, large-volume GI effluent loss from short gut syndrome is also associated with deficiencies of fat-soluble vitamins leading to coagulopathy, zinc leading to skin changes, and deficiencies of manganese, magnesium and potassium leading to electrical irritability of the myocardium and potentially dysrhythmia.
Epidemiology is highly variable as this condition often reflects injury sequelae and not the distribution of a genetic disease. Therefore, areas with a high prevalence of penetrating trauma as well as highway traffic accidents should expect a higher incidence of small bowel resections and a higher incidence of short gut syndrome. Similarly, areas with a high prevalence of inflammatory bowel disease will experience higher rates than regions with lesser prevalence rates.
Perhaps most importantly, since the management of these patients is complex and warrants a team approach, the incidence is highest at tertiary medical centers to which the patients are referred. Similarly, cancer hospitals that engage in aggressive malignancy therapy will have a higher incidence due to resection, intestinal bypasses, and highly cytotoxic chemotherapeutic regimens in the quest to eradicate malignant cells. Therefore, a population-based epidemiology is difficult to quantify with any degree of validity due to patient clustering and referral.
It is clear that patients may be entirely managed using parenteral nutrition and may live a normal lifespan. However, that lifespan may be punctuated by multiple admissions for catheter-related infection and sepsis despite optimal catheter care. Perhaps more importantly, such patients may have significant psychosocial issues that stem from their unmanageable GI tracts, the lack of participation in social eating, as well as food fear (oral intake leads to rapid, unpredictable and uncontrollable diarrhea and pain). However, for those who may be successfully medically and/or surgically managed, life expectancy should be normal, although the attention that must be paid to dietary intake and medical therapy is indeed lifelong.
Transplantation patients may have a shorter life expectancy depending on the presence or absence of opportunistic and life-threatening infection. Recall that the transplanted intestine is not essential for life as one may be managed by parenteral means alone. Therefore, graft explantation may be life-preserving in those with rejection complicated by life-threatening infection or associated organ failure. The clinician should be cognizant that prognosis should also address quality of life and not just the absence of mortality in patients such as these who require intense medical management.
What's the evidence?
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Tzvetanov, IG, Oberholzer, J, Benedetti, E. "Current Opinion in Organ Transplantation". vol. 15. 2010 Jun. pp. 346-8.(Current status of living donor small bowel transplantation.)
Jones, BA, Hull, MA, McGuire, MM, Kim, HB. "Seminars in Pediatric Surgery". vol. 19. 2010 Feb. pp. 59-67.(Autologous intestinal reconstruction surgery.)
Sigalet, DL, Lam, V, Boctor, D. "Seminars in Pediatric Surgery". vol. 19. 2010 Feb. pp. 44-9.(The assessment, and glucagon-like peptide-2 modulation, of intestinal absorption and function.)
McMellen, ME, Wakeman, D, Longshore, SW, McDuffie, LA, Warner, BW. "Seminars in Pediatric Surgery". vol. 19. 2010 Feb. pp. 35-43.(Growth factors: possible roles for clinical management of the short bowel syndrome.)
Wales, PW, Christison-Lagay, ER. "Seminars in Pediatric Surgery". vol. 19. 2010 Feb. pp. 3-9.(Short bowel syndrome: epidemiology and etiology.)
Bines, JE. "Journal of Gastroenterology & Hepatology". vol. 24. 2009 Oct. pp. S86-92.(Intestinal failure: A new era in clinical management.)
Longshore, SW, Wakeman, D, McMellen, M, Warner, BW. "Minerva Pediatrica". vol. 61. 2009 Jun. pp. 239-51.(Bowel resection induced intestinal adaptation: progress from bench to bedside.)
Goulet, O, Colomb-Jung, V, Joly, F. "Journal of Pediatric Gastroenterology & Nutrition". vol. 48. 2009 Apr. pp. S66-71.(Role of the colon in short bowel syndrome and intestinal transplantation.)
Wallace, B. "Nutrition in Clinical Practice". vol. 24. 2009 Feb-Mar. pp. 50-9.(Clinical use of probiotics in the pediatric population.)
Florescu, D, Hill, L, Sudan, D, Iwen, PC. "Pediatric Infectious Disease Journal". vol. 27. 2008 Nov. pp. 1013-9.(Leuconostoc bacteremia in pediatric patients with short bowel syndrome: case series and review.)
Misiakos, EP, Macheras, A, Kapetanakis, T, Liakakos, T. "Journal of Clinical Gastroenterology". vol. 41. 2007 Jan. pp. 5-18.(Short bowel syndrome: current medical and surgical trends.)
Van Citters, GW, Lin, HC. "Current Gastroenterology Reports". vol. 8. 2006 Oct. pp. 367-73.(Ileal brake: neuropeptidergic control of intestinal transit.)
Martin, GR, Beck, PL, Sigalet, DL. "World Journal of Gastroenterology". vol. 12. 2006 Jul 14. pp. 4117-29.(Gut hormones, and short bowel syndrome: the enigmatic role of glucagon-like peptide-2 in the regulation of intestinal adaptation.)
DiBaise, JK, Matarese, LE, Messing, B, Steiger, E. "Journal of Clinical Gastroenterology". vol. 40. 2006 May-Jun. pp. S94-8.(Strategies for parenteral nutrition weaning in adult patients with short bowel syndrome.)
Sax, HC. "Gastroenterology". vol. 130. 2006 Feb. pp. S91-2.(Specific nutrients in intestinal failure: one size fits no one.)
Dibaise, JK, Young, RJ, Vanderhoof, JA. "Clinical Gastroenterology & Hepatology". vol. 4. 2006 Jan. pp. 11-20.(Enteric microbial flora, bacterial overgrowth, and short-bowel syndrome.)
Weseman, RA, Gilroy, R. "Nutrition in Clinical Practice". vol. 20. 2005 Oct. pp. 509-16.(Nutrition management of small bowel transplant patients.)
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