Bile acid sequestrants are the main agents used to treat bile acid malabsorption. Cholestyramine and colestipol, both in powder form, have been used for many years. Unfortunately many patients find them difficult to tolerate; although the diarrhea may improve, other symptoms such as pain and bloating may worsen. Colesevelam is a tablet and some patients tolerate this more easily. A proof of concept study of the farnesoid X receptor agonist obeticholic acid has shown clinical and biochemical benefit.

As of March 15, 2016, Novartis Pharmaceuticals is conducting a phase II clinical study involving a farnesoid X receptor agonist named LJN452.

Treatment is directed largely towards management of underlying cause:

- Replacement of nutrients, electrolytes and fluid may be necessary. In severe deficiency, hospital admission may be required for nutritional support and detailed advice from dietitians. Use of enteral nutrition by naso-gastric or other feeding tubes may be able to provide sufficient nutritional supplementation. Tube placement may also be done by percutaneous endoscopic gastrostomy, or surgical jejunostomy. In patients whose intestinal absorptive surface is severely limited from disease or surgery, long term total parenteral nutrition may be needed.

- Pancreatic enzymes are supplemented orally in pancreatic insufficiency.

- Dietary modification is important in some conditions:

- Gluten-free diet in coeliac disease.

- Lactose avoidance in lactose intolerance.

- Antibiotic therapy to treat Small Bowel Bacterial overgrowth.

- Cholestyramine or other bile acid sequestrants will help reducing diarrhoea in bile acid malabsorption.

Treatment focuses on addressing the underlying cause of symptoms.

Treatment of gastritis that leads to pernicious anemia consists of parenteral vitamin B-12 injection. Associated immune-mediated conditions (e.g., insulin dependent diabetes mellitus, autoimmune thyroiditis) should also be treated. However, treatment of these disorders has no known effect in the treatment of achlorhydria.

Achlorhydria associated with "Helicobacter pylori" infection may respond to H pylori eradication therapy, although resumption of gastric acid secretion may only be partial and it may not always reverse the condition completely.

Antimicrobial agents, including metronidazole, amoxicillin/clavulanate potassium, ciprofloxacin, and rifaximin, can be used to treat bacterial overgrowth.

Achlorhydria resulting from long-term proton-pump inhibitor (PPI) use may be treated by dose reduction or withdrawal of the PPI.

Little is known on the prognosis of achlorhydria, although there have been reports of an increased risk of gastric cancer.

A 2007 review article noted that non-"Helicobacter" bacterial species can be cultured from achlorhydric (pH > 4.0) stomachs, whereas normal stomach pH only permits the growth of "Helicobacter" species. Bacterial overgrowth may cause false positive H. Pylori test results due to the change in pH from urease activity.

Small bowel bacterial overgrowth is a chronic condition. Retreatment may be necessary once every 1–6 months. Prudent use of antibacterials now calls for an antibacterial stewardship policy to manage antibiotic resistance.

Bile acid malabsorption was first recognized in patients with ileal disease. When other causes were recognized, and an idiopathic, primary form described, a classification into three types was proposed:

- Type 1: Bile acid malabsorption, secondary to ileal resection, or ileal inflammation (e.g. in Crohn's disease)

- Type 2: Idiopathic bile acid malabsorption, Primary bile acid diarrhea

- Type 3: Secondary to various gastrointestinal diseases including cholecystectomy, vagotomy, small intestinal bacterial overgrowth, radiation enteropathy, celiac disease, chronic pancreatitis, etc.

Symptoms of short bowel syndrome are usually addressed with medication. These include:

- Anti-diarrheal medicine (e.g. loperamide, codeine)

- Vitamin, mineral supplements and L-glutamine powder mixed with water

- H2 blocker and proton pump inhibitors to reduce stomach acid

- Lactase supplement (to improve the bloating and diarrhoea associated with lactose intolerance)

In 2004, the USFDA approved a therapy that reduces the frequency and volume of total parenteral nutrition (TPN), comprising: NutreStore (oral solution of glutamine) and Zorbtive (growth hormone, of recombinant DNA origin, for injection) together with a specialized oral diet. In 2012, an advisory panel to the USFDA voted unanimously to approve for treatment of SBS the agent teduglutide, a glucagon-like peptide-2 analog developed by NPS Pharmaceuticals, who intend to market the agent in the United States under the brandname Gattex. Teduglutide had been previously approved for use in Europe and is marketed under the brand Revestive by Nycomed.

Surgical procedures to lengthen dilated bowel include the Bianchi procedure, where the bowel is cut in half and one end is sewn to the other, and a newer procedure called serial transverse enteroplasty (STEP), where the bowel is cut and stapled in a zigzag pattern. Heung Bae Kim, MD, and Tom Jaksic, MD, both of Children's Hospital Boston, devised the STEP procedure in the early 2000s. The procedure lengthens the bowel of children with SBS and may allow children to avoid the need for intestinal transplantation. As of June 2009, Kim and Jaksic have performed 18 STEP procedures. The Bianchi and STEP procedures are usually performed by pediatric surgeons at quaternary hospitals who specialize in small bowel surgery.

The "treat empirically" route also has its difficulties, which have all come under wide debate and study. Recommendations are varied but seem to find some common ground around the notion that treatment should be individualized to the specific circumstances under which a patient has developed BLS since these circumstances affect the complex microbial make up of the affected bowel.

Tetracyclines have been the mainstay of treatment for BLS, but recent studies have concluded Rifaximin to be very effective in the treatment of BLS. One study by Di Stefano et al., however, concluded Metronidazole to be more effective than Rifaximin in the treatment of BLS.

Although it would seem to be the better way to go in terms of management, there has been recent criticism on the need for such testing because of reliability issues. However, it must be stated that there are options such as the glucose breath test and jejunal aspiration the explanations of which are beyond the scope of this current article.

There is no cure for short bowel syndrome except transplant. In newborn infants, the 4-year survival rate on parenteral nutrition is approximately 70%. In newborn infants with less than 10% of expected intestinal length, 5 year survival is approximately 20%. Some studies suggest that much of the mortality is due to a complication of the total parenteral nutrition (TPN), especially chronic liver disease. Much hope is vested in Omegaven, a type of lipid TPN feed, in which recent case reports suggest the risk of liver disease is much lower.

Although promising, small intestine transplant has a mixed success rate, with postoperative mortality rate of up to 30%. One-year and 4-year survival rate are 90% and 60%, respectively.

Fructose and fructans are FODMAPs (fermentable oligo-, di- and mono-saccharides and polyols) known to cause gastrointestinal discomfort in susceptible individuals. A low FODMAP diet has widespread application for managing functional gastrointestinal disorders such as IBS.

Bacterial overgrowth is usually treated with a course of antibiotics although whether antibiotics should be a first line treatment is a matter of debate. Some experts recommend probiotics as first line therapy with antibiotics being reserved as a second line treatment for more severe cases of SIBO. Prokinetic drugs are other options but research in humans is limited. A variety of antibiotics, including tetracycline, amoxicillin-clavulanate, fluoroquinolones, metronidazole, neomycin, cephalexin, trimethoprim-sulfamethoxazole, and nitazoxanide have been used; however, the best evidence is for the use of rifaximin.

A course of one week of antibiotics is usually sufficient to treat the condition. However, if the condition recurs, antibiotics can be given in a cyclical fashion in order to prevent tolerance. For example, antibiotics may be given for a week, followed by three weeks off antibiotics, followed by another week of treatment. Alternatively, the choice of antibiotic used can be cycled.

The condition that predisposed the patient to bacterial overgrowth should also be treated. For example, if the bacterial overgrowth is caused by chronic pancreatitis, the patient should be treated with coated pancreatic enzyme supplements.

Probiotics are bacterial preparations that alter the bacterial flora in the bowel to cause a beneficial effect. Animal research has demonstrated that probiotics have barrier enhancing, antibacterial, immune modulating and anti-inflammatory effects which may have a positive effect in the management of SIBO in humans. "Lactobacillus casei" has been found to be effective in improving breath hydrogen scores after 6 weeks of treatment presumably by suppressing levels of a small intestinal bacterial overgrowth of fermenting bacteria. The multi-strain preparation VSL#3 was found to be effective in suppressing SIBO. "Lactobacillus plantarum", "Lactobacillus acidophilus", and "Lactobacillus casei" have all demonstrated effectiveness in the treatment and management of SIBO. Conversely, "Lactobacillus fermentum" and "Saccharomyces boulardii" have been found to be ineffective. A combination of "Lactobacillus plantarum" and "Lactobacillus rhamnosus" has been found to be effective in suppressing bacterial overgrowth of abnormal gas producing organisms in the small intestine.

Probiotics are superior to antibiotics in the treatment of SIBO. A combination of probiotic strains has been found to produce better results than therapy with the antibiotic drug metronidazole and probiotics have been found to be effective in treating and preventing secondary lactase deficiency and small intestinal bacteria overgrowth in individuals suffering from post-infectious irritable bowel syndrome. Probiotics taken in uncomplicated cases of SIBO can usually result in the individual becoming symptom free. Probiotic therapy may need to be taken continuously to prevent the return of overgrowth of gas producing bacteria. A study by the probiotic yogurt producer Nestlé found that probiotic yogurt may also be effective in treating SIBO with evidence of reduced inflammation after 4 weeks of treatment.

An elemental diet taken for two weeks is an alternative to antibiotics for eliminating SIBO. An elemental diet works via providing nutrition for the individual while depriving the bacteria of a food source. Additional treatment options include the use of prokinetic drugs such as 5-HT4 receptor agonists or motilin agonists to extend the SIBO free period after treatment with an elemental diet or antibiotics. A diet void of certain foods that feed the bacteria can help alleviate the symptoms. For example, if the symptoms are caused by bacterial overgrowth feeding on indigestible carbohydrate rich foods, following a FODMAP restriction diet may help.

Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a variety of anaemias.

Normally the human gastrointestinal tract digests and absorbs dietary nutrients with remarkable efficiency. A typical Western diet ingested by an adult includes approximately 100 g of fat, 400 g of carbohydrate, 100 g of protein, 2 L of fluid, and the required sodium, potassium, chloride, calcium, vitamins, and other elements. Salivary, gastric, intestinal, hepatic, and pancreatic secretions add an additional 7–8 L of protein-, lipid-, and electrolyte-containing fluid to intestinal contents. This massive load is reduced by the small and large intestines to less than 200 g of stool that contains less than 8 g of fat, 1–2 g of nitrogen, and less than 20 mmol each of Na, K, Cl, HCO, Ca, or Mg.

If there is impairment of any of the many steps involved in the complex process of nutrient digestion and absorption, intestinal "malabsorption" may ensue. If the abnormality involves a single step in the absorptive process, as in primary lactase deficiency, or if the disease process is limited to the very proximal small intestine selective malabsorption of only a single nutrient may occur. However, generalized "malabsorption" of multiple dietary nutrients develops when the disease process is extensive, thus disturbing several digestive and absorptive processes, as occurs in coeliac disease with extensive involvement of the small intestine.

Researchers at Monash University in Australia developed dietary guidelines for managing fructose malabsorption, particularly for individuals with IBS.

Some individuals may benefit from diet modification, such as a reduced fat diet, following cholecystectomy. The liver produces bile and the gallbladder acts as reservoir. From the gallbladder, bile enters the intestine in individual portions. In the absence of gallbladder, bile enters the intestine constantly, but in small quantities. Thus, it may be insufficient for digestion of fatty foods. Postcholecystectomy syndrome treatment depends on the identified violations that led to it. Typically, the patient is recommended dietary restriction table with fatty foods, enzyme preparations, antispasmodics, sometimes cholagogue.

If the pain is caused by biliary microlithiasis, oral ursodeoxycholic acid can alleviate the condition.

A trial of bile acid sequestrant therapy is recommended for bile acid diarrhoea.

Some evidence suggests soluble fiber supplementation (e.g., psyllium/ispagula husk) is effective. It acts as a bulking agent, and for many IBS-D patients, allows for a more consistent stool. For IBS-C patients, it seems to allow for a softer, moister, more easily passable stool.

However, insoluble fiber (e.g., bran) has not been found to be effective for IBS. In some people, insoluble fiber supplementation may aggravate symptoms.

Fiber might be beneficial in those who have a predominance of constipation. In people who have IBS-C, soluble fiber can reduce overall symptoms, but will not reduce pain. The research supporting dietary fiber contains conflicting small studies complicated by the heterogeneity of types of fiber and doses used.

One meta-analysis found only soluble fiber improved global symptoms of irritable bowel, but neither type of fiber reduced pain.

An updated meta-analysis by the same authors also found soluble fiber reduced symptoms, while insoluble fiber worsened symptoms in some cases. Positive studies have used 10–30 grams per day of ispaghula (psyllium). One study specifically examined the effect of dose, and found 20 g of ispaghula (psyllium) were better than 10 g and equivalent to 30 g per day.

A diet restricted in fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) now has an evidence base sufficiently strong to recommend its widespread application in conditions such as IBS and IBD. They also state the restriction of FODMAPs globally, rather than individually, controls the symptoms of functional gut disorders (e.g., IBS), and the majority of IBD patients respond just as well. It is more successful than restricting only fructose and fructans, which are also FODMAPs, as is recommended for those with fructose malabsorption. Longer-term compliance with the diet was high.

The fat substitute Olestra, used to reduce digestible fat in some foods, was reported to cause leakage in some consumers during the test-marketing phase. As a result, the product was reformulated before general release to a hydrogenated form that is not liquid at physiologic temperature. The U.S. Food and Drug Administration warning indicated excessive consumption of Olestra could result in "loose stools"; however, this warning has not been required since 2003.

Some studies reported up to 80% of patients with irritable bowel syndrome (IBS) have SIBO (using the hydrogen breath test). Subsequent studies demonstrated statistically significant reduction in IBS symptoms following therapy for SIBO.

There is a lack of consensus however, regarding the suggested link between IBS and SIBO. Other authors concluded that the abnormal breath results so common in IBS patients do not suggest SIBO, and state that "abnormal fermentation timing and dynamics of the breath test findings support a role for abnormal intestinal bacterial distribution in IBS." There is general consensus that breath tests are abnormal in IBS; however, the disagreement lies in whether this is representative of SIBO. More research is needed to clarifiy this possible link.

Treatments are mainly correction of the underlying cause, as well as digestive enzyme supplements.

The treatment for bile reflux is the same as the treatment for acidic reflux. In general, everything that can

reduce acidic reflux can reduce bile reflux. Examples include lifestyle modification, weight reduction, and the avoidance of eating immediately before sleep or being in the supine position immediately after meals. In addition, smoking has been found to be a factor in the development of acidic reflux. Thus, all of these factors should be applied to bile reflux as well.

Likewise, drugs that reduce the secretion of gastric acid (e.g., proton pump inhibitors)

or that reduce gastric contents or volume can be used to treat acidic bile reflux. Because prokinetic drugs increase the motility of the stomach and accelerate gastric emptying, they can also reduce bile reflux. Other drugs that reduce the relaxations of the lower esophageal sphincter, such as baclofen, have also proven to reduce bile reflux, particularly in patients who are refractory to (medically unresponsive to) proton pump inhibitor therapy.

Medications used in managing biliary reflux include bile acid sequestrants, particularly cholestyramine, which disrupt the circulation of bile in the digestive tract and sequester bile that would otherwise cause symptoms when refluxed; and prokinetic agents, to move material from the stomach to the small bowel more rapidly and prevent reflux.

Biliary reflux may also be treated surgically, if medications are ineffective or if precancerous tissue is present in the esophagus.

Diseases of the hepatobiliary system affect the biliary tract (also known as the "biliary tree"), which secretes bile in order to aid digestion of fats. Diseases of the gallbladder and bile ducts are commonly diet-related, and may include the formation of gallstones that impact in the gallbladder (cholecystolithiasis) or in the common bile duct (choledocholithiasis).

Gallstones are a common cause of inflammation of the gallbladder, called cholecystitis. Inflammation of the biliary duct is called cholangitis, which may be associated with autoimmune disease, such as primary sclerosing cholangitis, or a result of bacterial infection, such as ascending cholangitis.

Disease of the biliary tree may cause pain in the upper right abdomen, particularly when pressed. Disease might be investigated using ultrasound or ERCP, and might be treated with drugs such as antibiotics or UDCA, or by the surgical removal of the gallbladder.

Gastrointestinal diseases refer to diseases involving the gastrointestinal tract, namely the esophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the liver, gallbladder, and pancreas.

A 2009 study which followed 189 patients found no excess mortality despite the increased risk of pancreatic cancer.

A gastrinoma is a tumor in the pancreas or duodenum that secretes excess of gastrin leading to ulceration in the duodenum, stomach and the small intestine. There is hypersecretion of HCl acid into the duodenum, which causes the ulcers. Excessive HCl acid production also causes hyperperistalsis, and inhibits the activity of lipase, causing severe diarrhea.

It is frequently the source of the gastrin in Zollinger-Ellison syndrome.

It is usually found in the duodenum, although it may arise in the stomach or pancreas. Those occurring in the pancreas have a greater potential for malignancy. Most gastrinomas are found in the gastrinoma triangle; this is bound by the junction of cystic and common bile ducts, junction of the second and third parts of the duodenum, and the junction of the neck and body of the pancreas.

The different treatment options for management of chronic pancreatitis are medical measures, therapeutic endoscopy and surgery. Treatment is directed, when possible, to the underlying cause, and to relieve pain and malabsorption. Insulin dependent diabetes mellitus may occur and need long term insulin therapy. The abdominal pain can be very severe and require high doses of analgesics, sometimes including opiates. Alcohol cessation and dietary modifications (low-fat diet) are important to manage pain and slow the calcific process. Antioxidants may help but it is unclear if the benefits are meaningful.