According to the Peripheral T-Cell Lymphoma Project, median overall survival is ten months, while median failure-free survival is only six months . The peripheral index for T-cell lymphoma is useful in defining prognosis for enteropathy-associated T-cell lymphoma. Among the most influential prognostic factors is bulky disease, defined by a tumor mass greater than 5 cm.

Autologous stem cell transplantation is feasible for selected patients with enteropathy-associated T-cell lymphoma and can yield durable disease control in a significant proportion of these patients. One study found a trend for better survival in patients transplanted in first complete or partial remission at four years (66% vs. 36%; P = .062).

In certain eligible patients, a conditioning regimen of high-dose chemotherapy followed by an autologous stem cell transplant may be used to extend a period of first complete remission. Likewise, a recent study suggests that high dose therapy and autologous stem cell transplantation results in favorable outcomes for elderly patients with Non-Hodgkin's Lymphoma.

There is a diagnostic test for AIE that looks for an antibody against the enterocyte. The diagnostic test contains the Western Blot which can identify the antibody IgG or IgA and with the immunohistochemistry can localize these antibodies. Endoscopy with biopsies of the colon, small colon, stomach, and other locations may be helpful in diagnosing. This test is done to look at the stomach and small intestines and to see what cells are infiltrating the digestive tract. There are also documented cases of autoimmune enteropathy where the auto-antibodies were undetectable and the diagnosis was made on the basis of clinical presentation and response to treatment.

Multiple disorders are found in patients with radiation enteropathy, so guidance including an algorithmic approach to their investigation has been developed. This includes a holistic assessment with investigations including endoscopies, breath tests and other nutritional and gastrointestinal tests. Full investigation is important as many cancer survivors of radiation therapy develop other causes for their symptoms such as colonic polyps, diverticular disease or hemorrhoids.

The appearance of microvillous inclusion disease on light microscopy is similar to celiac sprue; however, it usually lacks the intraepithelial lymphocytic infiltration characteristic of celiac sprue and stains positive for carcinoembryonic antigen (CEA).

The definitive diagnosis is dependent on electron microscopy.

The differential diagnosis of chronic and intractable diarrhea is:

- Intestinal epithelial dysplasia

- Syndromatic diarrhea

- Immunoinflammatory enteropathy

Some suggestions for surveillance for cancer include the following:

- Small intestine with small bowel radiography every 2 years,

- Esophagogastroduodenoscopy and colonoscopy every 2 years,

- CT scan or MRI of the pancreas yearly,

- Ultrasound of the pelvis (women) and testes (men) yearly,

- Mammography (women) from age 25 annually livelong, and

- Papanicolaou smear (Pap smear) every year

Follow-up care should be supervised by a physician familiar with Peutz–Jeghers syndrome. Genetic consultation and counseling as well as urological and gynecological consultations are often needed.

The first line of treatment are corticosteroids and other medicines used to suppress the immune system such as tacrolimus and sirolimus.

A intravenous nutrition such as total parenteral nutrition and/or a special diet may be necessary. Hematopoietic stem cell transplantation may be curative.

Prevention of radiation injury to the small bowel is a key aim of techniques such as brachytherapy, field size, multiple field arrangements, conformal radiotherapy techniques and intensity-modulated radiotherapy. Medications including ACE inhibitors, statins and probiotics have also been studied and reviewed.

Bile acid malabsorption is common in Crohn's disease but not always recognised. Most patients with previous ileal resection and chronic diarrhea will have abnormal SeHCAT tests and can benefit from bile acid sequestrants.

Patients with primary bile acid diarrhea are frequently misdiagnosed as having the irritable bowel syndrome as clinicians fail to recognize the condition. When SeHCAT testing is performed, the diagnosis of primary bile acid diarrhea is commonly made. In a review of 18 studies of the use of SeHCAT testing in diarrhea-predominant irritable bowel syndrome patients, 32% of 1223 patients had a SeHCAT 7-day retention of less than 10%, and 80% of these reported a response to cholestyramine, a bile acid sequestrant.

Estimates of the population prevalence taken from this review suggest that 1% of the adult population could have primary bile acid diarrhea (Type 2 bile acid malabsorption).

The current gold standard diagnostic test for EE is intestinal biopsy and histological analysis. Histological changes observed include:

- Villous blunting

- Crypt hypertrophy

- Villous fusion

- Mucosal inflammation

However, this procedure is considered too invasive, complex and expensive to be implemented as standard of care. As a result, there are various research efforts underway to identify biomarkers associated with EE, which could serve as less invasive, yet representative, tools to screen for and identify EE from stool samples.

In an effort to identify simple, accurate diagnostic tests for EE, the Bill and Melinda Gates Foundation (BMGF) has established an EE biomarkers consortium as part of their Global Grand Challenges initiative (specifically, the Discover Biomarkers of Gut Function challenge).

So far, various biomarkers have been selected and studied based on the current understanding of EE pathophysiology:

- Gut permeability/barrier function

- Dual sugar permeability (lactose-to-mannitol ratio)

- Intestinal inflammation

- Alpha-1 anti-trypsin

- Neopterin

- Myeloperoxidase

- Exocrine (hormonal) markers

- Bacterial translocation markers

- Endotoxin core antibody

- Markers of systemic inflammation

- Alpha-1 glycoprotein

- C-reactive protein (CRP)

It is postulated that the limited of understanding of EE is partially due to the paucity of reliable biomarkers, making it difficult for researchers to track the epidemiology of the condition and assess the efficacy of interventions.

Talley et al. suggested 3 diagnostic criteria which is still widely used:

1. the presence of gastrointestinal symptoms,

2. histological demonstration of eosinophilic infiltration in one or more areas of the gastrointestinal tract or presence of high eosinophil count in ascitic fluid (latter usually indicates subserosal variety),

3. no evidence of parasitic or extraintestinal disease.

Hypereosinophilia, the hallmark of allergic response, may be absent in up to 20% of patients, but hypoalbuminaemia and other abnormalities suggestive of malabsorption may be present.

CT scan may show nodular and irregular thickening of the folds in the distal stomach and proximal small bowel, but these findings can also be present in other conditions like Crohn's disease and lymphoma.

The endoscopic appearance in eosinophilic gastroenteritis is nonspecific; it includes erythematous, friable, nodular, and occasional ulcerative changes.

Sometimes diffuse inflammation results in complete loss of villi, involvement of multiple layers, submucosal oedema and fibrosis.

Definitive diagnosis involves histological evidence of eosinophilic infiltration in biopsy slides. Microscopy reveals >20 eosinophils per high power field. Infiltration is often patchy, can be missed and laparoscopic full thickness biopsy may be required.

Radio isotope scan using technetium (Tc) exametazime-labeled leukocyte SPECT may be useful in assessing the extent of disease and response to treatment but has little value in diagnosis, as the scan does not help differentiating EG from other causes of inflammation.

When eosinophilic gastroenteritis is observed in association with eosinophilic infiltration of other organ systems, the diagnosis of idiopathic hypereosinophilic syndrome should be considered.

A physical examination may reveal a mass or distention of the abdomen.

Tests which may be useful for diagnosis include:

- Abdominal x-ray

- Abdominal CT scan

- Contrast enema study

A small bowel follow-through may suggest the diagnosis of Crohn's disease and is useful when the disease involves only the small intestine. Because colonoscopy and gastroscopy allow direct visualization of only the terminal ileum and beginning of the duodenum, they cannot be used to evaluate the remainder of the small intestine. As a result, a barium follow-through X-ray, wherein barium sulfate suspension is ingested and fluoroscopic images of the bowel are taken over time, is useful for looking for inflammation and narrowing of the small bowel. Barium enemas, in which barium is inserted into the rectum and fluoroscopy is used to image the bowel, are rarely used in the work-up of Crohn's disease due to the advent of colonoscopy. They remain useful for identifying anatomical abnormalities when strictures of the colon are too small for a colonoscope to pass through, or in the detection of colonic fistulae (in this case contrast should be performed with iodate substances).

CT and MRI scans are useful for evaluating the small bowel with enteroclysis protocols. They are also useful for looking for intra-abdominal complications of Crohn's disease, such as abscesses, small bowel obstructions, or fistulae. Magnetic resonance imaging (MRI) is another option for imaging the small bowel as well as looking for complications, though it is more expensive and less readily available. MRI techniques such as diffusion-weighted imaging and high-resolution imaging are more sensitive in detecting ulceration and inflammation compared to CT.

A complete blood count may reveal anemia, which commonly is caused by blood loss leading to iron deficiency (a microcytic anemia) or by vitamin B deficiency (a macrocytic anemia), usually caused by ileal disease impairing vitamin B absorption. Rarely autoimmune hemolysis may occur. Ferritin levels help assess if iron deficiency is contributing to the anemia. Erythrocyte sedimentation rate (ESR) and C-reactive protein help assess the degree of inflammation, which is important as ferritin can also be raised in inflammation. Serum iron, total iron binding capacity and transferrin saturation may be more easily interpreted in inflammation. Anemia of chronic disease results in a normocytic anemia. Other causes of anemia include medication used in treatment of inflammatory bowel disease, like azathioprine, which can lead to cytopenia, and sulfasalazine, which can also result in folate deficiency. Testing for "Saccharomyces cerevisiae" antibodies (ASCA) and antineutrophil cytoplasmic antibodies (ANCA) has been evaluated to identify inflammatory diseases of the intestine and to differentiate Crohn's disease from ulcerative colitis. Furthermore, increasing amounts and levels of serological antibodies such as ASCA, antilaminaribioside [Glc(β1,3)Glb(β); ALCA], antichitobioside [GlcNAc(β1,4)GlcNAc(β); ACCA], antimannobioside [Man(α1,3)Man(α)AMCA], antiLaminarin [(Glc(β1,3))3n(Glc(β1,6))n; anti-L] and antichitin [GlcNAc(β1,4)n; anti-C] associate with disease behavior and surgery, and may aid in the prognosis of Crohn's disease.

Low serum levels of vitamin D are associated with Crohn's disease. Further studies are required to determine the significance of this association.

The diagnosis is usually confirmed by biopsies on colonoscopy. Fecal calprotectin is useful as an initial investigation, which may suggest the possibility of IBD, as this test is sensitive but not specific for IBD.

For practical purposes, gastric pH an endoscopy should be done in someone with suspected achlorhydria. Older testing methods using fluid aspiration through a nasogastric tube can be done, but these procedures can cause significant discomfort and are less efficient ways to obtain a diagnosis.

A complete 24-hour profile of gastric acid secretion is best obtained during an esophageal pH monitoring study.

Achlorhydria may also be documented by measurements of extremely low levels of pepsinogen A (PgA) () in blood serum. The diagnosis may be supported by high serum gastrin levels ().

The "Heidelberg test" is an alternative way to measure stomach acid and diagnose hypochlorhydria/achlorhydria.

A check can exclude deficiencies in iron, calcium, prothrombin time, vitamin B-12, vitamin D, and thiamine. Complete blood count with indices and peripheral smears can be examined to exclude anemia. Elevation of serum folate is suggestive of small bowel bacterial overgrowth. Bacterial folate can be absorbed into the circulation.

Once achlorhydria is confirmed, a hydrogen breath test can check for bacterial overgrowth.

Several methods have been developed to identify the disorder but there are difficulties with all of them. Fecal bile acid quantification is unpleasant for both the patient and laboratory. Diagnosis of bile acid malabsorption is easily and reliably made by the SeHCAT test. This nuclear medicine test involves two scans a week apart and so measures multiple cycles of bile acid excretion and reabsorption. There is limited radiation exposure (0.3 mSv). Retention of SeHCAT at 7 days is normally above 15%; values less than 15%, 10% and 5% predict respectively mild, moderate and severe abnormal retention and an increasing likelihood of response to bile acid sequestrants. This test is not licensed in the USA, and is underutilized even where it is available.

Older methods such as the C-glycocholic breath test are no longer in routine clinical use.

Measurement of 7α-Hydroxy-4-cholesten-3-one, a bile acid precursor, in serum, shows the increased bile acid synthesis found in bile acid malabsorption. This test is an alternative diagnostic means when available. Fasting blood FGF19 values may have value in the recognition of the disease and prediction of response.

Currently, there are two tests for evaluating BAM in the U.S. One test, currently available only for research purposes, measures serum levels of the marker 7α-hydroxy-4-cholesten-3-one (C4), a downstream product of CYP7A1. Plasma C4 levels increase when bile acid synthesis increases, and C4 levels are substantially elevated in BAM patients with a sensitivity and specificity of 90 percent and 79 percent, respectively. C4 levels have also been shown to correlate well with SeHCAT retention. This makes fasting serum C4 attractive as a screening test for BAM, although it can produce false-positives and false-negatives in patients who have liver disease or are taking statins.

The second test, which can now be clinically ordered, is the fecal bile acid excretion test. It quantifies individual and total bile acids in a 48-hour stool collection. Increased total fecal bile acids are seen in patients with chronic functional diarrhea and higher levels of CA and CDCA are associated with IBS-D.

A clinical validation involving 94 healthy volunteers, 60 patients with IBS-D and 28 patients with IBS with constipation (IBS-C) found that the sum of CA and CDCA concentrations above 3.7 percent were indicative of IBS-D with 72 percent sensitivity and 90 percent specificity. In addition, the upper limit of normal total fecal bile acid excretion over the 48 hours has been defined.

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.

There are multiple large-field, multi-country research initiatives focusing on strategies to prevent and treat EE.

- The MAL-ED project

- The Alive and Thrive nutrition project

- The Sanitation, Hygiene and Infant Nutrition Efficacy (SHINE) Trial (ClinicalTrials.gov identifier: NCT01824940)

- The WASH Benefits Study

A complete history and physical examination can be suggestive, especially if a palpable mass in the right lower quadrant of the abdomen is present (though this can be present in the absence of DIOS). Ultrasound and computed tomography (CT) imaging of the abdomen can confirm the diagnosis by demonstrating dilated loops of intestine with material in the intestinal lumen with bubbles. Air-fluid levels may be seen in those affected by DIOS.

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.

Little research is conducted on these cancers due to their relative rarity when compared to the more common colorectal cancers. APC-min mice which carry a gene deficiency corresponding to that of humans with FAP also go on to develop small intestinal tumors, though humans do not.

There is no single, specific test for malabsorption. As for most medical conditions, investigation is guided by symptoms and signs. A range of different conditions can produce malabsorption and it is necessary to look for each of these specifically. Many tests have been advocated, and some, such as tests for pancreatic function are complex, vary between centers and have not been widely adopted. However, better tests have become available with greater ease of use, better sensitivity and specificity for the causative conditions. Tests are also needed to detect the systemic effects of deficiency of the malabsorbed nutrients (such as anaemia with vitamin B12 malabsorption).

Risk factors for small intestine cancer include:

- Crohn's disease

- Celiac disease

- Radiation exposure

- Hereditary gastrointestinal cancer syndromes: familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome

- Males are 25% more likely to develop the disease

Benign tumours and conditions that may be mistaken for cancer of the small bowel:

- Hamartoma

- Tuberculosis