Short Bowel Syndrome


Article Author:
Barre Guillen


Article Editor:
Nichole Atherton


Editors In Chief:
Kranthi Sitammagari
Mayank Singhal


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Kyle Blair
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Abbey Smiley
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Daniyal Ameen
Altif Muneeb
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
4/2/2019 1:57:03 AM

Introduction

The normal length of small bowel in an adult, starting from the duodenojejunal flexure, measures between 275 to 850 centimeters. Around 9 liters of fluid passes through the small bowel daily in the form of oral fluids, saliva, gastric, biliary, and pancreatic secretions. On average, about 7 liters of those fluids are absorbed in the small bowel and 2 liters in the large bowel. The large, healthy bowel absorbs roughly 150 kilocalories per day but can absorb up to 1000 kilocalories per day in those patients with malabsorption.

The absorption of most nutrients occurs in the first 100 centimeters of the jejunum. B12 and bile salts are absorbed in the last 100 centimeters of the ileum; magnesium is absorbed in the terminal ileum and proximal colon; water and sodium absorption occur throughout the bowel.

Short bowel syndrome (SBS) in adults is defined as less than 180 to 200 centimeters of remaining small bowel leading to the need for nutritional and fluid supplements. Although there is no accepted definition for SBS in children, the need for intravenous supplementation when having less than 25% of remaining small bowel that is expected for gestational age has been suggested.

About 75% of cases of SBS develop after a single, massive resection of bowel; whereas, the remaining 25% occur after multiple resections. Around two-thirds of patients who develop SBS survive their initial hospitalization, and a similar number survive their first year after developing SBS. Age and underlying disease primarily determine a patient's long-term outcome.[1][2][3]

Etiology

SBS can result from extensive surgical resection or congenital intestinal diseases. The most common pathologies that lead to SBS in adults are Crohn disease, mesenteric ischemia, radiation enteritis, post-surgical adhesions, and post-operative complications. In children, the most common pathologies include volvulus, intestinal malformations, and necrotizing enterocolitis.[1]

Epidemiology

The epidemiology of SBS is not well-delineated as there are no data on the frequency of intestinal failure secondary to SBS.

Pathophysiology

SBS can be classified by anatomical, pathophysiological, and postoperative criteria. Anatomically, there are three types of SBS: end-jejunostomy, jejunocolonic anastomosis where the jejunum is in continuity, most commonly, with the left colon, and jejunoileal anastomosis. The pathophysiological criteria can also be subdivided into categories where the colon is in continuity and those where it is not.

The primary pathophysiological mechanism of chronic intestinal failure secondary to SBS is intestinal malabsorption due to the loss of intestinal absorptive surface and more rapid intestinal transit. The successful rehabilitation of a patient with SBS depends upon the management of the three phases of SBS: acute phase, adaptation phase, and maintenance phase.

The acute phase of SBS lasts 3 to 4 weeks and involves metabolic derangement and significant intestinal losses as well as gastric hypersecretion due to the lack of inhibitory hormones that are normally released from the terminal ileum. It requires close monitoring in the hospital setting to avoid sequelae such as dehydration with acute kidney failure, acid-base abnormalities, and electrolyte deficiencies.

The adaptation phase of SBS lasts 1 to 2 years and involves adaptive changes of remaining small bowel to increase the area of bowel available for nutrient absorption, slow down intestinal transit to maximize the time available for absorption, and adaptive hyperphagia. These processes are promoted by the presence of nutrients in the bowel, pancreatic and biliary secretions, and hormones released by the ileum and colon. Chronic intestinal failure – the condition that exists when the adaptation phase fails to occur – is more likely to be reversible in the following situations:

  • When there are more than 35 centimeters of small bowel along with a jejunoileal anastomosis and an intact ileocecal valve and colon
  • When there are more than 60 centimeters of small bowel with a jejunocolonic anastomosis
  • When there is more than 115 centimeters of small bowel with an end jejunostomy

The third and final phase of SBS is the maintenance phase. This phase is managed with special diets, oral or intramuscular supplementation of nutrients, and pharmacological treatments.[1]

Histopathology

Intestinal failure-associated liver disease is a complication of SBS. Histopathological findings include cholestasis, steatosis, steatohepatitis, ductopenia, and perivenular and portal fibrosis.

History and Physical

The primary adverse outcome of SBS is malabsorption secondary to decreased intestinal absorptive surface area and rapid intestinal transit. The most common signs, symptoms, and findings include malnutrition, weight loss, diarrhea, steatorrhea, dehydration, vitamin deficiencies, and electrolyte imbalance. The individual with SBS will likely have undergone extensive small bowel resection related to one of the underlying pathologies listed above.[1]

Treatment / Management

Initial management of SBS involves maintaining good nutritional status, maximizing the absorptive surface area of the remaining intestine, and preventing complications. This involves early postoperative parenteral nutrition as well as enteral nutrition once the patient's ileus has resolved. This promotes intestinal adaptation which improves absorption of nutrients over time.

Those patients in whom intestinal failure is irreversible will require either lifelong home parenteral nutrition or intestinal transplantation if a life-threatening complication of either SBS or home parenteral nutrition arises. Treatment of SBS, therefore, largely consists of managing and preventing complications that arise as a direct result of SBS or secondarily to home parenteral nutrition. The management of SBS and the prevention of its complications share many of the same treatments.

  • Intestinal failure-associated liver disease and liver cholestasis are treated with maintaining some oral feeding, promptly treating infection or inflammation, optimizing home parenteral nutrition, decreasing dependence on soy-based lipid emulsions or switching them to fish oil-based emulsions and non-transplant surgical procedures.
  • SBS patients with less than 180 centimeters of small bowel or an absent ileocecal valve are at increased risk of developing gallstones, frequently composed of calcium bilirubinate. These gallstones can be prevented or reversed by maintaining enteral feeding and limiting periods of oral fasting and by limiting the use of narcotic and anticholinergic medications.
  • Dehydration, hyponatremia, chronic renal failure, and nephrolithiasis secondary to SBS are managed with intravenous supplementation of fluids to maintain normal hydration and urinary flow. More specifically, the treatment of dehydration and hyponatremia in patients with SBS should maintain normal hydration with a urine output of 800 milliliters per day and urine sodium greater than 20 millimoles/liter.
  • Hypomagnesemia can be caused by malabsorption of magnesium due to loss of the distal ileum and right colon as well as chelation with fatty acids. Treatment consists of appropriate hydration as delineated above and magnesium supplementation to a level greater than 1.5 milligrams/deciliter.
  • D-lactic acidosis with an increased anion gap can occur in patients with SBS due to the fermentation of unabsorbed carbohydrates by colon microbiota. This can lead to a D-lactate encephalopathy that presents with slurred speech, ataxia, altered mental status, psychosis, and sometimes coma. D-lactic acidosis is primarily a clinical diagnosis. Treatment includes cessation of enteral feeds with carbohydrates, administration of an antibiotic active against D-lactate forming bacteria, appropriate hydration, and thiamine supplementation. Antibiotics include metronidazole, vancomycin, clindamycin, neomycin, and tetracyclines.
  • Almost all patients on long-term home parenteral nutrition have metabolic bone disease that manifests as osteopenia, osteomalacia, or osteoporosis. Diagnosis and evaluation are done with mineral bone density, serum and urine mineral levels, vitamin D, PTH, and markers of bone turnover. Management includes lifestyle and dietary changes, treatment of underlying disease, optimization of vitamin D status and parenteral nutrition, and sometimes bisphosphonates.

Surgical management is another important treatment strategy available to patients with SBS. Patients on parenteral nutrition who suffer from rapid transit may benefit from reversing intestinal segments or interposing segments of colon into the small bowel. Those with less than 60 centimeters of small bowel and parenteral nutrition-related complications may be candidates for intestinal transplantation. Patients with dilated bowel secondary to obstruction can sometimes be treated with intestinal tapering or strictureplasty if they have a bowel remnant greater than 120 centimeters or tapering with lengthening if the remnant is less 90 centimeters in adults or less than 30 centimeters in children.[1][3][4]

Prognosis

Those with greater than 180 cm of small bowel generally require no parenteral nutrition. Those with greater than 90 cm will usually require it for less than 1 year. And those with less than 60 cm will likely require lifetime parenteral nutrition.

Complications

The primary complications of malabsorption are malnutrition, weight loss, steatorrhea, diarrhea, electrolyte imbalance, and vitamin deficiencies. Other complications include nephrolithiasis due to hyperoxaluria, cholelithiasis, transient gastric hypersecretion, bacterial overgrowth, dehydration, hyponatremia, potassium deficiency, magnesium deficiency, renal failure, calcium oxalate kidney stones, cholestasis secondary to intestinal failure-associated liver disease, gallstones, and d-lactic acidosis.

In adults and older children, steatosis is more common, whereas in infants cholestasis and rapid progression to liver fibrosis is the more common progression. Intestinal failure-associated liver disease deaths are seen in between 16% and 60% of deaths in infants on home parenteral nutrition.[1]

Enhancing Healthcare Team Outcomes

Ultimately, management of SBS requires a multidisciplinary team led by a physician with gastrointestinal expertise. A gastrointestinal surgeon can provide the appropriate surgical recommendations and management, and a transplant surgeon can expand the patient's therapeutic options. Other essential team members include administrative support, a nurse coordinator to handle the patient's day-to-day management, and a nutritionist. A psychologist and social worker are important to address the psychosocial challenges of SBS.


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Short Bowel Syndrome - Questions

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A patient with short bowel syndrome is estimated to have 100 cm of remaining small bowel. What is the likely prognosis regarding the duration of parenteral nutrition in this patient?



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A 51-year-old female with a history significant for previous abdominal surgeries underwent extensive bowel resection after a closed loop small bowel obstruction nine months ago. She is successfully being managed with oral intake and reports a significantly increased appetite since her discharge from the hospital. In addition to the patient's increased appetite, this phase in her disease process is characterized by which of the following?



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A 34-year-old male presents to the trauma bay after suffering multiple gunshot wounds to the abdomen. He is taken to the operating room for exploratory laparotomy and found to have significant mesenteric vascular injuries. Bleeding is controlled during the damage control laparotomy; the patient is left open, and sent to the intensive care unit. During a second-look operation the following day he is found to have an extensive amount of necrotic bowel that is resected leaving 165 centimeters of the remaining proximal small bowel as well as distal sigmoid and rectum. Which of the following deficiencies is this patient most at risk?



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A 9-month-old boy is seen in the clinic for follow-up after undergoing a bowel resection one month ago. Before discharge from his hospitalization, he was started on parental nutrition after persistently poor appetite and fatty stools. Which of the following is the least likely etiology to have led to this patient's condition?



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A 66-year-old female with a known history of short bowel syndrome presents after developing right upper quadrant abdominal pain. She is on lifetime parenteral nutrition after undergoing multiple extensive bowel resections for Crohn's disease. Which of the following could have potentially prevented this patient's abdominal pain?



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Short Bowel Syndrome - References

References

Pironi L,Arends J,Baxter J,Bozzetti F,Peláez RB,Cuerda C,Forbes A,Gabe S,Gillanders L,Holst M,Jeppesen PB,Joly F,Kelly D,Klek S,Irtun Ø,Olde Damink SW,Panisic M,Rasmussen HH,Staun M,Szczepanek K,Van Gossum A,Wanten G,Schneider SM,Shaffer J, ESPEN endorsed recommendations. Definition and classification of intestinal failure in adults. Clinical nutrition (Edinburgh, Scotland). 2015 Apr     [PubMed]
Jeppesen PB,Fuglsang KA, Nutritional Therapy in Adult Short Bowel Syndrome Patients with Chronic Intestinal Failure. Gastroenterology clinics of North America. 2018 Mar     [PubMed]
Pironi L, Definitions of intestinal failure and the short bowel syndrome. Best practice & research. Clinical gastroenterology. 2016 Apr     [PubMed]
Nightingale J,Woodward JM, Guidelines for management of patients with a short bowel. Gut. 2006 Aug     [PubMed]

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