For medical purposes, the exact number of helminth eggs is less important and therefore most diagnoses are made simply by identifying the appearance of the worm or eggs in feces. Due to the large quantity of eggs laid, physicians can diagnose using only one or two fecal smears. The Kato technique (also called the Kato-Katz technique) is a laboratory method for preparing human stool samples prior to searching for parasite eggs. Eggs per gram is a laboratory test that determines the number of eggs per gram of feces in patients suspected of having a parasitological infection, such as schistosomiasis.

For the purpose of setting treatment standards and reuse legislation, it is important to be able to determine the amount of helminth eggs in an environmental sample with some accuracy. The detection of viable helminth eggs in samples of wastewater, sludge or fresh feces (as a diagnostic tool for the infection helminthiasis) is not straight forward. In fact, many laboratories in developing countries lack the right equipment or skilled staff required to do so. An important step in the analytical methods is usually the concentration of the eggs in the sample, especially in the case of wastewater samples. A concentration step may not be required in samples of dried feces, e.g. samples collected from urine-diverting dry toilets.

Specific helminths can be identified through microscopic examination of their eggs (ova) found in faecal samples. The number of eggs is measured in units of eggs per gram. However, it does not quantify mixed infections, and in practice, is inaccurate for quantifying the eggs of schistosomes and soil-transmitted helmiths. Sophisticated tests such as serological assays, antigen tests, and molecular diagnosis are also available; however, they are time-consuming, expensive and not always reliable.

Microscopic demonstration of the large typically shaped oocysts is the basis for diagnosis. Because the oocysts may be passed in small amounts and intermittently, repeated stool examinations and concentration procedures are recommended. If stool examinations are negative, examination of duodenal specimens by biopsy or string test (Enterotest) may be needed. The oocysts can be visualized on wet mounts by microscopy with bright-field, differential interference contrast (DIC), and epifluorescence. They can also be stained by modified acid-fast stain.

Typical laboratory analyses include:

- Microscopy

- Morphologic comparison with other intestinal parasites

- Bench aids for "Isospora"

Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including cryptosporidium, microsporidia, and isospora, are most common in HIV-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.

In regions where helminthiasis is common, mass deworming treatments may be performed, particularly among school-age children, who are a high-risk group. Most of these initiatives are undertaken by the World Health Organization (WHO) with positive outcomes in many regions. Deworming programs can improve school attendance by 25 percent. Although deworming improves the health of an individual, outcomes from mass deworming campaigns, such as reduced deaths or increases in cognitive ability, nutritional benefits, physical growth, and performance, are uncertain or not apparent.

Due to the wide variety of intestinal parasites, a description of the symptoms rarely is sufficient for diagnosis. Instead, medical personnel use one of two common tests: they search stool samples for the parasites, or apply an adhesive the anus to search for eggs.

Avoiding food or water that may be contaminated with stool can help prevent the infection of "Cystoisospora" (Isosporiasis). Good hand-washing, and personal-hygiene practices should be used as well. One should wash their hands with soap and warm water after using the toilet, changing diapers, and before handling food (CDC.gov). It is also important to teach children the importance of washing their hands, and how to properly wash their hands.

Anthelmintics such as mebendazole and albendazole have been reported to eliminate infestation of humans more effectively than thiabendazole.

Prevention is as simple as avoiding eating small, whole, uncooked fish. However, in "C. philippinensis" endemic areas, such dietary habits are common and have been practiced for many generations.

In cats, giardiasis responds to metronidazole, although this should not be administered to pregnant cats as it can cause developmental malformations. An alternative and effective drug is febendazole.

Diagnosis usually involves finding the eggs and/or adults of "C. philippinensis" in stool samples.

The CDC recommends hand-washing and avoiding potentially contaminated food and untreated water.

Boiling suspect water for one minute is the surest method to make water safe to drink and kill disease-causing microorganisms such as "Giardia lamblia" if in doubt about whether water is infected. Chemical disinfectants or filters may be used.

According to a review of the literature from 2000, there is little evidence linking the drinking of water in the North American wilderness and Giardia. CDC surveillance data (for 2005 and 2006) reports one outbreak (6 cases) of waterborne giardiasis contracted from drinking wilderness river water in Colorado. However, less than 1% of reported giardiasis cases are associated with outbreaks.

Person-to-person transmission accounts for the majority of "Giardia" infections and is usually associated with poor hygiene and sanitation. "Giardia" is found on the surface of the ground, in the soil, in undercooked foods, and in water, and on hands without proper cleaning after handling infected feces. Water-borne transmission is associated with the ingestion of contaminated water. In the U.S., outbreaks typically occur in small water systems using inadequately treated surface water. Venereal transmission happens through fecal-oral contamination. Additionally, diaper changing and inadequate hand washing are risk factors for transmission from infected children. Lastly, food-borne epidemics of "Giardia" have developed through the contamination of food by infected food-handlers.

Preventive measures for visitors to tropical areas where the condition exists include steps to reduce the likelihood of gastroenteritis. These may comprise using only bottled water for drinking, brushing teeth, and washing food, and avoiding fruits washed with tap water (or consuming only peeled fruits, such as bananas and oranges). Basic sanitation is necessary to reduce fecal-oral contamination and the impact of environmental enteropathy in the developing world.

The prognosis for tropical sprue may be excellent after treatment. It usually does not recur in people who get it during travel to affected regions. The recurrence rate for natives is about 20%, but another study showed changes can persist for several years.

Cultures of stool samples are examined to identify the organism causing dysentery. Usually, several samples must be obtained due to the number of amoebae, which changes daily. Blood tests can be used to measure abnormalities in the levels of essential minerals and salts.

The mouth, skin, and lips may appear dry due to dehydration. Lower abdominal tenderness may also be present.

Capillariasis is a disease caused by nematodes in the "Capillaria" genus. The two principal forms of the disease are:

- Intestinal capillariasis, caused by "Capillaria philippinensis"

- Hepatic capillariasis, caused by "Capillaria hepatica"

Diagnosis may be simple in cases where the patient's signs and symptoms are idiopathic to a specific cause. However this is generally not the case, considering that many pathogens which cause enteritis may exhibit the similar symptoms, especially early in the disease. In particular, "campylobacter, shigella, salmonella" and many other bacteria induce acute self-limited colitis, an inflammation of the lining of the colon which appears similar under the microscope.

A medical history, physical examination and tests such as blood counts, stool cultures, CT scans, MRIs, PCRs, colonoscopies and upper endoscopies may be used in order to perform a differential diagnosis. A biopsy may be required to obtain a sample for histopathology.

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

Until 1964, all available amoebicides were selective in their sites of action. The development of newer nitro-imidazole derivatives led to Niridazole. It was given in a daily dose of 25–30 mgm. per kg to 50 patients for seven days. The cure rate was found to be 84% with serious side effects in one patient. An Indian study of 30 patients on this drug revealed that it acted as a contact amoebicide and also against the invasive forms.23 The therapeutic action of Ambilhar was found to be significantly better than that produced by a combination of dehydroemetine and chloroquine.

Mild cases usually do not require treatment and will go away after a few days in healthy people. In cases where symptoms persist or when it is more severe, specific treatments based on the initial cause may be required.

In cases where diarrhoea is present, replenishing fluids lost is recommended, and in cases with prolonged or severe diarrhoea which persists, intravenous rehydration therapy or antibiotics may be required. A simple oral rehydration therapy (ORS) can be made by dissolving one teaspoon of salt, eight teaspoons of sugar and the juice of an orange into one litre of clean water. Studies have shown the efficacy of antibiotics in reducing the duration of the symptoms of infectious enteritis of bacterial origin, however antibiotic treatments are usually not required due to the self-limiting duration of infectious enteritis.

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).

This nitroimidazole compound, like metronidazole, has shown a marked therapeutic response in amoebic liver abscess. Occasional side effects include nausea and dizziness. Tinidazole is not widely available though it is more effective than metronidazole. Zuberi and Ibrahim found tinidazole to be effective in 86.7% cases of intestinal amoebiasis and in 100% cases of amoebic liver abscess.

Luminal amoebicides like halogenated oxyquinolines, e.g. diiodohydroxyquinoline in a dose of 0.6 G. thrice daily for 3 weeks, diloxanide furoate 0.5 G. three times a day for 10 days and sometimes tetracyclines 1–2 G./day for 5 days should be used concurrently with any of the above drugs as adjuncts to eliminate intestinal infection.

human intestinal spirochetosis, also intestinal spirochetes, colonic spirochetosis and colonic spirochetes, is an infection of the colonic-type mucosa with spirochete microorganisms.

Radiographs (x-rays) are sometimes used to look for sand and enteroliths. Due to the size of the adult horse's abdomen, it requires a powerful machine that is not available to all practitioners. Additionally, the quality of these images is sometimes poor.