Proton pump inhibitors (such as omeprazole and lansoprazole) and histamine H2-receptor antagonists (such as famotidine and ranitidine) are used to slow acid secretion. Once gastric acid is suppressed, symptoms normally improve.

In general, treatment for PanNET encompasses the same array of options as other neuroendocrine tumors, as discussed in that main article. However, there are some specific differences, which are discussed here.

In functioning PanNETs, octreotide is usually recommended prior to biopsy or surgery but is generally avoided in insulinomas to avoid profound hypoglycemia.

PanNETs in MEN1 are often multiple, and thus require different treatment and surveillance strategies.

Some PanNETs are more responsive to chemotherapy than are gastroenteric carcinoid tumors. Several agents have shown activity. In well differentiated PanNETs, chemotherapy is generally reserved for when there are no other treatment options. Combinations of several medicines have been used, such as doxorubicin with streptozocin and fluorouracil (5-FU) and capecitabine with temozolomide. Although marginally effective in well-differentiated PETs, cisplatin with etoposide has some activity in poorly differentiated neuroendocrine cancers (PDNECs), particularly if the PDNEC has an extremely high Ki-67 score of over 50%.

Several targeted therapy agents have been approved in PanNETs by the FDA based on improved progression-free survival (PFS):

- everolimus (Afinitor) is labeled for treatment of progressive neuroendocrine tumors of pancreatic origin in patients with unresectable, locally advanced or metastatic disease. The safety and effectiveness of everolimus in carcinoid tumors have not been established.

- sunitinib (Sutent) is labeled for treatment of progressive, well-differentiated pancreatic neuroendocrine tumors in patients with unresectable locally advanced or metastatic disease. Sutent also has approval from the European Commission for the treatment of 'unresectable or metastatic, well-differentiated pancreatic neuroendocrine tumors with disease progression in adults'. A phase III study of sunitinib treatment in well differentiated pNET that had worsened within the past 12 months (either advanced or metastatic disease) showed that sunitinib treatment improved progression-free survival (11.4 months vs. 5.5 months), overall survival, and the objective response rate (9.3% vs. 0.0%) when compared with placebo.

Resection is sometimes a part of a treatment plan, but duodenal cancer is difficult to remove surgically because of the area that it resides in—there are many blood vessels supplying the lower body. Chemotherapy is sometimes used to try to shrink the cancerous mass. Other times intestinal bypass surgery is tried to reroute the stomach to intestine connection around the blockage.

A 'Whipple' procedure is a type of surgery that is sometimes possible with this cancer. In this procedure, the duodenum, a portion of the Pancreas (the head), and the gall bladder are usually removed, the small intestine is brought up to the Pylorus (the valve at the bottom of the stomach) and the Liver and Pancreas digestive enzymes and bile are connected to the small intestine below the Pylorus.

The removal of part of the Pancreas often requires taking Pancreatic Enzyme supplements to aid digestion. These are available in the form of capsules by prescription.

It is not unusual for a patient having received a Whipple procedure to feel perfectly well, and to lead his/her normal life without difficulty.

It is important for the procedure to be performed by a surgeon with extensive experience having done and observed the procedure, as specific competence makes a big difference.

Some patients need to be fitted with tubes to either add nutrients (feeding tubes) or drainage tubes to remove excess processed food that can not pass the blockage.

Treatment for FAP depends on the genotype. Most individuals with the APC mutation will develop colon cancer by the age of 40, although the less-common attenuated version typically manifests later in life (40–70). Accordingly, in many cases, prophylactic surgery may be recommended before the age of 25, or upon detection if actively monitored. There are several surgical options that involve the removal of either the colon or both the colon and rectum.

- Rectum involved: the rectum and part or all of the colon are removed. The patient may require an ileostomy (permanent stoma where stool goes into a bag on the abdomen) or have an ileo-anal pouch reconstruction. The decision to remove the rectum depends on the number of polyps in the rectum as well as the family history. If the rectum has few polyps, the colon is partly or fully removed and the small bowel (ileum) can be directly connected to the rectum instead (ileorectal anastomosis).

- Rectum not involved: the portion of the colon manifesting polyps can be removed and the ends 'rejoined' (partial colectomy), a surgery that has a substantial healing time, but leaves quality of life largely intact.

Prophylactic colectomy is indicated if more than a hundred polyps are present, if there are severely dysplastic polyps, or if multiple polyps larger than 1 cm are present.

Treatment for the two milder forms of FAP may be substantially different from the more usual variant, as the number of polyps are far fewer, allowing more options.

Various medications are being investigated for slowing malignant degeneration of polyps, most prominently the non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDS have been shown to significantly decrease the number of polyps but do not usually alter management since there are still too many polyps to be followed and treated endoscopically.

Surgery remains the front-line therapy for HNPCC. There is an ongoing controversy over the benefit of 5-fluorouracil-based adjuvant therapies for HNPCC-related colorectal tumours, particularly those in stages I and II.

Prior to reaching the advanced stages of colorectal cancer, the polyps are confined to the inner wall and thickness of the intestinal tract and do not metastasize or 'spread'. So provided FAP is detected and controlled either at the pre-cancerous stage or when any cancerous polyps are still internal to the intestinal tract, surgery has a very high success rate of preventing or removing cancer, without recurrence, since the locations giving rise to cancer are physically removed "in toto" by the surgery.

Following surgery, if a partial colectomy has been performed, colonoscopic surveillance of the remaining colon is necessary as the individual still has a risk of developing colon cancer. However, if this happened, it would be a fresh incident from polyps developing anew in the unremoved part of the colon subsequent to surgery, rather than a return or metastasis of any cancer removed by the original surgery.

Other medical treatments have been tried and include estrogen and progesterone therapy, Corticostreoids are effective, but are "limited by their side effects."

GAVE is treated commonly by means of an endoscope, including argon plasma coagulation and electrocautery. Since endoscopy with argon photocoagulation is "usually effective", surgery is "usually not required". Coagulation therapy is well-tolerated but "tends to induce oozing and bleeding." "Endoscopy with thermal ablation" is favored medical treatment because of its low side effects and low mortality, but is "rarely curative." Treatment of GAVE can be categorized into endoscopic, surgical and pharmacologic. Surgical treatment is definitive but it is rarely done nowadays with the variety of treatment options available. Some of the discussed modalities have been used in GAVE patients with another underlying disease rather than SSc; they are included as they may be tried in resistant SSc-GAVE patients. Symptomatic treatment includes iron supplementation and blood transfusion for cases with severe anemia, proton pump inhibitors may ameliorate the background chronic gastritis and minute erosions that commonly co-existed in biopsy reports.

Corticosteroids are the mainstay of therapy with a 90% response rate in some studies. Appropriate duration of steroid treatment is unknown and relapse often necessitates long term treatment. Various steroid sparing agents e.g. sodium cromoglycate (a stabilizer of mast cell membranes), ketotifen (an antihistamine), and montelukast (a selective, competitive leukotriene receptor antagonist) have been proposed, centering on an allergic hypothesis, with mixed results. An elimination diet may be successful if a limited number of food allergies are identified.

When "H. pylori" infection is present, the most effective treatments are combinations of 2 antibiotics (e.g. clarithromycin, amoxicillin, tetracycline, metronidazole) and a proton-pump inhibitor (PPI), sometimes together with a bismuth compound. In complicated, treatment-resistant cases, 3 antibiotics (e.g. amoxicillin + clarithromycin + metronidazole) may be used together with a PPI and sometimes with bismuth compound. An effective first-line therapy for uncomplicated cases would be amoxicillin + metronidazole + pantoprazole (a PPI).

H2 antagonists or proton-pump inhibitors decrease the amount of acid in the stomach, helping with healing of ulcers.

Antacids and sucralfate were found to be no better than placebo in a literature review. H2-RAs have been shown to have marked benefit in poor quality trials (30% relative risk reduction), but only a marginal benefit in good quality trials. Prokinetic agents would empirically seem to work well since delayed gastric emptying is considered a major pathophysiological mechanism in functional dyspepsia. They have been shown in a meta-analysis to produce a relative risk reduction of up to 50%, but the studies evaluated to come to this conclusion used the drug cisapride which has since been removed from the market (now only available as an investigational agent) due to serious adverse events such as torsades, and publication bias has been cited as a potential partial explanation for such a high benefit. Modern prokinetic agents such as metoclopramide, erythromycin and tegaserod have little or no established efficacy and often result in substantial side effects. Simethicone has been found to be of some value, as one trial suggests potential benefit over placebo and another shows equivalence with cisapride. So, with the somewhat recent advent of the proton pump inhibitor (PPI) class of medications, the question of whether these new agents are superior to traditional therapy has arisen.

Currently, PPIs are, depending on the specific drug, FDA indicated for erosive esophagitis, gastroesophageal reflux disease (GERD), Zollinger-Ellison syndrome, eradication of H. pylori, duodenal and gastric ulcers, and NSAID-induced ulcer healing and prevention, but not functional dyspepsia. There are, however, evidence-based guidelines and literature that evaluate the use of PPIs for this indication. A helpful chart summarizing the major trials is available from the functional dyspepsia guidelines published in the World Journal of Gastroenterology in 2006.

Functional and undifferentiated dyspepsia have similar treatments. Drug therapy decisions are difficult because trials included heartburn in the definition of dyspepsia. This led to the results favoring proton pump inhibitors (PPIs), which are effective for the treatment of heartburn.

Traditional therapies used for this diagnosis include lifestyle modification, antacids, H-receptor antagonists (H2-RAs), prokinetic agents, and antiflatulents. It has been noted that one of the most frustrating aspects of treating functional dyspepsia is that these traditional agents have been shown to have little or no efficacy.

The cancerous mass tends to block food from getting to the small intestine. If food cannot get to the intestines, it will cause pain, acid reflux, and weight loss because the food cannot get to where it is supposed to be processed and absorbed by the body.

Patients with duodenal cancer may experience abdominal pain, weight loss, nausea, vomiting, and chronic GI bleeding.

Certain foods and lifestyle are considered to promote gastroesophageal reflux, but most dietary interventions have little supporting evidence. Avoidance of specific foods and of eating before lying down should be recommended only to those in which they are associated with the symptoms. Foods that have been implicated include coffee, alcohol, chocolate, fatty foods, acidic foods, and spicy foods. Weight loss and elevating the head of the bed are generally useful. A wedge pillow that elevates the head may inhibit gastroesophageal reflux during sleep. Stopping smoking and not drinking alcohol do not appear to result in significant improvement in symptoms. Although moderate exercise may improve symptoms in people with GERD, vigorous exercise may worsen them.

The treatments for GERD include lifestyle modifications, medications, and possibly surgery. Initial treatment is frequently with a proton-pump inhibitor such as omeprazole.

Treatment is aimed at removing the irritant or infection. "Helicobacter pylori" infection is usually treated with antibiotics.

Acute treatment uses medications to treat any infection (normally antibiotics) and to reduce inflammation (normally aminosalicylate anti-inflammatory drugs and corticosteroids). When symptoms are in remission, treatment enters maintenance, with a goal of avoiding the recurrence of symptoms. Prolonged use of corticosteroids has significant side-effects; as a result, they are, in general, not used for long-term treatment. Alternatives include aminosalicylates alone, though only a minority are able to maintain the treatment, and many require immunosuppressive drugs. It has been also suggested that antibiotics change the enteric flora, and their continuous use may pose the risk of overgrowth with pathogens such as "Clostridium difficile".

Medications used to treat the symptoms of Crohn's disease include 5-aminosalicylic acid (5-ASA) formulations, prednisone, immunomodulators such as azathioprine (given as the prodrug for 6-mercaptopurine), methotrexate, infliximab, adalimumab, certolizumab and natalizumab. Hydrocortisone should be used in severe attacks of Crohn's disease. Biological therapies (biopharmaceuticals) are medications used to avoid long-term steroid use, decrease inflammation, and treat people who have fistulas with abscesses. The monoclonal antibody ustekinumab appears to be a safe treatment option, and may help people with moderate to severe active Crohn's disease. The long term safety and effectiveness of monoclonal antibody treatment is not known. The monoclonal antibody briakinumab is not effective for people with active Crohn's disease.

The gradual loss of blood from the gastrointestinal tract, as well as chronic inflammation, often leads to anemia, and professional guidelines suggest routinely monitoring for this. Adequate disease control usually improves anemia of chronic disease, but iron deficiency may require treatment with iron supplements. Guidelines vary as to how iron should be administered. Besides other, problems include a limitation in possible daily resorption and an increased growth of intestinal bacteria. Some advise parenteral iron as first line as it works faster, has fewer gastrointestinal side effects, and is unaffected by inflammation reducing enteral absorption.

Other guidelines advise oral iron as first line with parenteral iron reserved for those that fail to adequately respond as oral iron is considerably cheaper. All agree that severe anemia (hemoglobin under 10g/dL) should be treated with parenteral iron. Blood transfusion should be reserved for those who are cardiovascularly unstable, due to its relatively poor safety profile, lack of long term efficacy, and cost.

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.

Crohn's may result in anxiety or mood disorders, especially in young people who may have stunted growth or embarrassment from fecal incontinence. Counselling as well as antidepressant or anxiolytic medication may help some people manage.

As of 2017 there is a small amount of research looking at mindfulness-based therapies, hypnotherapy, and cognitive behavioural therapy.

Diagnostic measures can be used as interventions to help stop bleeding in some cases. Bleeding that occurs due to a neoplasm (cancer growth) can be treated using colonoscopy and clipping, surgical intervention, or other measures, depending on the form and stage of cancer. Similarly, gastric cancer is treated depending on the staging, although typically requires surgical and medical therapy.

The treatment for motility issues, namely constipation, is typically to improve the movement of waste though the GI tract. This is done by using stool softeners (which work by pulling water into the stool while in the colon), addition of fiber to the diet, and use of osmotic laxatives (which help fluid movement through the colon, improving overall motility). Improving a persons gut motility can reduce the straining during defection and decrease the risk of developing of anal fissures. Anal fissures are associated with pain and blood on the toilet paper, and require time for healing. Treatment includes topical nitrates or calcium channel blockers and surgical interventions for chronic or complex cases. Similar to anal fissures, internal hemorrhoids can cause blood on the tissue when wiping, and be felt at the opening of the anus. Treatment options for hemorrhoids can be dependent on whether an underlying cause exists. An anorectal varices related hemorrhoids caused by cirrhosis, however symptomatic treatment often involves removal.

Colitis can be divided into infectious and drug induced, as can the treatment for these conditions. With infectious colitis, treatment is pathogen dependent, and generally requires the use of antibiotics. With drug-induced colitis, treatment typically involves removal of the offending agent, as is the case in NSAID induced PUD, however, removing radiation from a cancer patient is not always practical within a treatment regimen, so medical treatment is the primary mode of treatment.

Structural compromise leading to blood in stool is caused by a variety of conditions, and therefore requires different treatment for each condition. Peptic ulcer disease alone can be divided into multiple causes, but is generally initially controlled primarily with a proton pump inhibitor, with the addition of an H blocker, or in serious cases, requiring surgical intervention. Diverticulitis and diverticulosis require antibiotic treatment, and may require surgical intervention.

Inflammatory bowel disease is also divided into separate conditions, namely ulcerative colitis and Crohn's disease, which have different medical treatment regimens, and may require surgical intervention in more serious conditions.

Gastrinoma causes the following symptoms:

- Hypergastrinemia

- Ulcers of the duodenum, stomach, and small intestine.

- Severe diarrhea.

- Generalized cancer symptoms.

Zollinger–Ellison syndrome (ZES) is a disease in which tumors cause the stomach to produce too much acid, resulting in peptic ulcers. Symptoms include abdominal pain and diarrhea.

The syndrome is caused by a gastrinoma, a neuroendocrine tumor that secretes a hormone called gastrin. The tumor causes excessive production of gastric acid, which leads to the growth of gastric mucosa and proliferation of parietal and ECL cells.

ZES may occur on its own or as part of an autosomal dominant syndrome called multiple endocrine neoplasia type 1 (MEN 1). The primary tumor is usually located in the pancreas, duodenum or abdominal lymph nodes, but ectopic locations (e.g., heart, ovary, gallbladder, liver, and kidney) have also been described.

Abdominal pain is often the predominant symptom in patients with acute pancreatitis and should be treated with analgesics.

Opioids are safe and effective at providing pain control in patients with acute pancreatitis. Adequate pain control requires the use of intravenous opiates, usually in the form of a patient-controlled analgesia pump. Hydromorphone or fentanyl (intravenous) may be used for pain relief in acute pancreatitis. Fentanyl is being increasingly used due to its better safety profile, especially in renal impairment. As with other opiates, fentanyl can depress respiratory function. It can be given both as a bolus as well as constant infusion.

Meperidine has been historically favored over morphine because of the belief that morphine caused an increase in sphincter of Oddi pressure. However, no clinical studies suggest that morphine can aggravate or cause pancreatitis or cholecystitis. In addition, meperidine has a short half-life and repeated doses can lead to accumulation of the metabolite normeperidine, which causes neuromuscular side effects and, rarely, seizures.

treatment of HP resemble that of chronic pancreatitis of other causes. Treatment focuses on enzyme and nutritional supplementation, pain management, pancreatic diabetes, and local organ complications, such as pseudocysts, bile duct or duodenal obstruction.(PMC1774562)