Short bowel syndrome occurs when patients have surgical removal of intestine due to a variety of illnesses, and the remaining small intestine is less than 200 centimeters in length. Short bowel syndrome may also be found even when a normal bowel length is present if there is reduced, poor function of the small intestine such as seen in intestinal motility disorders (disorders of intestinal movement). Multiple surgeries or radiation can injure the intestine and cause problems with motility. Autoimmune disorders such as scleroderma may result in poor movement of the intestine with functional short bowel syndrome.

It is estimated that in the United States, approximately 10,000–20,000 suffer from short bowel syndrome (SBS) [1]. The normal length of small bowel varies from 300–850 cm, and previous definitions of short bowel syndrome have included those patients with less than 200 cm of small bowel remaining after surgery. Most consensus articles define short bowel syndrome when 70–75% of the small intestine has been resected [2]. This does not always translate clinically, however, as patients can have symptoms of functional short bowel syndrome with greater than 200 cm of residual small intestine. Intestinal failure is therefore better defined by the degree of fecal energy loss due to decreased absorptive capacity, increased rapid transit through the gut, and decreased oral intake rather than residual bowel length [3]. More recently, efforts have focused on defining a subset of patients with intestinal failure, who have a worse prognosis and who require intensive intestinal rehabilitation [4]. Patients with SBS and intestinal failure and TPN dependence generally have either < 100 cm of small bowel ending in a jejunostomy, <35 cm of jejunum with a jejunoileal anastomosis, or <50 cm with a jejuno-colonic anastomosis [5].

Short bowel syndrome results from extensive removal of the intestine during surgery due to illnesses like Crohn’s disease, where the diseased intestine causes blockage, pain, or other complications that don’t respond to medication changes, and must be removed. There are many other diseases that can result in the need to remove large amounts of small intestine, including ischemic bowel , in which disease and sometimes death of the intestine is caused by lack of normal blood flow. Other causes include volvulus or internal herniation of the bowel, in which there is twisting or trapping of the intestine that causes bowel death due to strangulation. trauma , such as in car accidents, can result in severe damage to the intestine and its blood supply that portions of the bowel must be removed.

Short bowel syndrome can be subdivided into two categories: primary and secondary . Primary short bowel syndrome describes patients with a congenital process, generally confined to the pediatric population (i.e., jejunal or ileal atresia). Secondary short bowel syndrome typically is the result of surgical resection due to an acquired illness (i.e., obstruction due to volvulus or internal herniation, ischemia, multiple resections due to Crohn’s disease, malignancy). The etiology of the disorder which leads to SBS is therefore also relevant as the underlying disease status plays an important role in the patient’s prognosis and management [6–10].

Short bowel syndrome in adults is uncommon, and is estimated to affect between 10,000 and 20,000 people in the United States.Short bowel syndrome in adults is the result of surgical removal of the intestines for various reasons as mentioned above.

It is estimated that in the United States, approximately 10,000–20,000 suffer from short bowel syndrome (SBS) [1]. Due to the variety of etiologies that lead to SBS (i.e., Crohn disease, trauma, malignancy, radiation, mesenteric ischemia), the numbers above are derived from parenteral nutrition registries. A more accurate estimation is difficult to ascertain given the lack of ICD-10 codes and a comprehensive disease registry for short bowel syndrome. It has been reported that the United States has a similar prevalence of SBS compared to European cohorts.

The most common symptoms of SBS are weight loss and diarrhea . Many patients have abdominal pain and cramping, flatulence (gassiness), and symptoms of dehydration (fatigue and loss of energy). Because patients have reduced absorption of nutrients, vitamins, and minerals, patients may have symptoms related to these dietary deficiencies. These include tingling or numbness of the feet and hands, easy bruising, low blood counts with fatigue due to anemia or very low vitamin D levels. Many patients experience other less common symptoms of nutrient deficiency such as skin rashes or hair loss.

As previously mentioned the pathophysiologic changes that occur following small bowel resection include a loss of intestinal absorptive capacity and increased, more rapid transit time through the gut. This typically results in malnutrition, diarrhea, dehydration, vitamin deficiencies, and electrolyte imbalances. The portion of small bowel removed plays a large role in how much the absorptive capacity of the small intestine is affected. The duodenum typically measures 25–30 cm, extending from the duodenal bulb to the ligament of Treitz. The duodenum is responsible for absorption of micronutrients such as calcium, magnesium, iron, and folic acid. Also, the duodenum plays a key role in activating pancreatic enzyme secretion, thus resection may lead to impaired digestion. Resections of the duodenum may also contribute to causing dumping syndrome.

From the ligament of Treitz to the ileocecal valve, the proximal two-fifths are defined as the jejunum . The jejunum is responsible for absorbing complex proteins, carbohydrates, fats, vitamins, and minerals. Those with less than 100 cm of jejunum remaining following surgery typically have a net secretory response to food [11]. Though jejunal resections can lead to diarrhea, steatorrhea, and vitamin deficiencies, those with an intact ileocecal valve and colon left in continuity can typically better accommodate with regard to absorption of water and sodium. Calorie salvage via absorption of short-chain fatty acids to reduce energy loss also occurs in patients with even part of the residual colon in continuity.

The lack of inhibitory enterohormones produced by the jejunum such as gastric inhibitory peptide and vasoactive peptide results in gastric acid hypersecretion, which lowers intestinal pH and can inactivate pancreatic enzymes. This process typically leads to fat malabsorption, diarrhea, and steatorrhea [12].

The ileum comprises the latter three-fifths of the small intestine. Similar to the jejunum, it is responsible for the absorption of fats, fat-soluble vitamins, water, and electrolytes, but the ileum is specifically required for the absorption of nutrients such as vitamin B12 and for the salvaging/absorption of bile salts as part of the enterohepatic circulation. Loss of the ileum results in bile salt wasting into the colon which precipitates a secretory diarrhea . This process occurs when colonic bacteria deconjugate bile salts entering the colon into free bile acids, which stimulate colonic motility and secretion thus leading to diarrhea. The ileocecal valve serves as a transition point between the small bowel and the colon and allows for slowing of transit of gastric and small bowel contents into the colon. The ileocecal valve is also responsible for the prevention of reflux of colonic bacteria into the small intestine, thus resection can also predispose patients to developing small bowel bacterial overgrowth, which can also adversely affect nutrient digestion and absorption [13]. The presence of a colon in continuity with the remaining small bowel is also important as it can slow intestinal transit, increases absorptive capacity, and reduces the loss of water and nutrients which improves the chances of recovery to a point of nutritional autonomy where patients are no longer dependent upon parenteral support [14].

In addition to diarrhea , dehydration, and weight loss, patients with SBS who are not fed with parenteral nutrition and intravenous vitamin and micronutrient supplementation are at risk to develop symptoms associated with deficiencies. For example, patients may develop neurologic symptoms such as peripheral neuropathy or myopathy (due to B12, vitamin E, copper, or thiamine deficiencies), rashes (zinc, niacin, and vitamin A deficiency (rare)), and fatigue due to anemia from B12, folate, or iron deficiency. Fat soluble vitamin deficiency is common, so in addition to vitamin E deficiency, patients may develop fatigue due to vitamin D deficiency (associated with very low vitamin D levels), or easy bruising due to vitamin K deficiency. Vitamin A deficiency may result in reduced vision, bitot spots, and dermatitis (phrynoderma).

Short bowel syndrome in adults i s typically the result of surgical removal of the gut due to a variety of underlying illnesses as mentioned previously. When the remaining length of small intestine is less than 200 centimeters in length, patients are considered to have short bowel syndrome (SBS). This may occur however in those that have more than 200 centimeters of bowel remaining if there is reduced or poor function of the small intestine. The length of the remaining small bowel is typically measured by the surgeon during the resection. Another way to determine small bowel length following surgery is by radiologic imaging. There are no blood tests to diagnose short bowel syndrome; however, blood is typically tested to check vitamin, nutrient, and electrolyte levels which can be deficient in short bowel syndrome.

As previously mentioned, the normal length of small bowel varies from 300 to 850 cm, and previous definitions of short bowel syndrome have included those patients with less than 200 cm of small bowel remaining after surgery. This, however, does not always translate clinically as patient’s can have symptoms of functional short bowel syndrome with greater than 200 cm of residual small intestine. The residual length of the small intestine remaining following surgical resection is thus only one determinant of intestinal function and prognosis. Length of the remaining small bowel still remains a vital aspect in terms of need for long-term TPN or intravenous fluids. It is often difficult to ascertain an accurate estimate of residual small bowel length. The details of the operative report following surgical resection is typically the most useful source, however this sometimes may not be included in the final report. It is typical practice to report how much bowel was removed, however not all surgeons report how much small bowel remains following resection. It is also important to note whether or not the patient’s small bowel is in continuity with the colon as this plays an important role in the adaptation process and affects long-term prognosis. If intraoperative estimate of small bowel remnant length is unavailable, radiologic evaluation may provide valuable information. Magnetic resonance (MR), computed tomography (CT), and barium contrast radiography can all be used to estimate small bowel length. Radiologic studies are also useful as they may also help determine structural features that may be relevant to prognosis, such as the presence of inflammation, stricture, or small bowel dilatation.

The treatment of short bowel syndrome is focused on nutritional management, electrolyte replacement, and medications to reduce diarrhea and improve nutrient absorption . We absorb vitamins, nutrients, proteins, water, and electrolytes through our gut from our diet. Each portion of the gut plays a special role in absorption. When portions of the gut are removed, the ability of the gut to absorb adequate nutrition is impaired. Fluid and electrolytes can also be lost in diarrheal stools, which result from this reduced absorptive capacity. Part of the treatment for short bowel syndrome includes reducing diarrhea by using medications that slow down the time that food passes through the intestinal tract, to allow more time to absorb nutrients. There is a newer medication that can be injected under the skin that helps the intestinal absorptive surface grow and thus improve nutrient absorption. We prescribe vitamin, micronutrient, and electrolyte replacements (both by mouth and by injection) and special diets that help reduce diarrhea and improve nutrient absorption. We also prescribe “oral rehydration solutions ” that are specially formulated to improve fluid and electrolyte absorption from the shortened intestine.

As the gut adapts to its shortened length in short bowel syndrome, people often require additional nutritional support to help maintain a healthy weight. The most common form of nutritional support that can be used in addition to an oral diet is parenteral nutrition (PN). PN is a combination of vitamins, nutrients, and electrolytes that can be infused into the blood stream through an intravenous (IV) line to ensure that they get absorbed. The major complications associated with PN are infections of the IV line used to provide PN, blood clots in the IV line, liver test abnormalities, and even loss of bone strength, mineralization, and density, which we work hard to prevent by monitoring closely and by providing patients with extra vitamin D. The amount of gut remaining after surgery plays a large role in whether or not someone will require TPN , and how long they will require it.