Clinical features of intestinal pseudo-obstruction can include abdominal pain, nausea, severe distension, vomiting, dysphagia, diarrhea and constipation, depending upon the part of the gastrointestinal tract involved. In addition, in the moments in which abdominal colic occurs, an abdominal x-ray shows intestinal air fluid level. All of these features are also similar in true mechanical obstruction of the bowel.

Intestinal pseudo-obstruction is a clinical syndrome caused by severe impairment in the ability of the intestines to push food through. It is characterized by the signs and symptoms of intestinal obstruction without any lesion in the intestinal lumen. Clinical features can include abdominal pain, nausea, severe distension, vomiting, dysphagia, diarrhea and constipation, depending upon the part of the gastrointestinal tract involved. The condition can begin at any age and it can be a primary condition (idiopathic or inherited) or caused by another disease (secondary).

It can be chronic or acute.

The small intestine consists of the duodenum, jejunum and ileum. Inflammation of the small intestine is called enteritis, which if localised to just part is called duodenitis, jejunitis and ileitis, respectively. Peptic ulcers are also common in the duodenum.

Chronic diseases of malabsorption may affect the small intestine, including the autoimmune coeliac disease, infective Tropical sprue, and congenital or surgical short bowel syndrome. Other rarer diseases affecting the small intestine include Curling's ulcer, blind loop syndrome, Milroy disease and Whipple's disease. Tumours of the small intestine include gastrointestinal stromal tumours, lipomas, hamartomas and carcinoid syndromes.

Diseases of the small intestine may present with symptoms such as diarrhoea, malnutrition, fatigue and weight loss. Investigations pursued may include blood tests to monitor nutrition, such as iron levels, folate and calcium, endoscopy and biopsy of the duodenum, and barium swallow. Treatments may include renutrition, and antibiotics for infections.

The small and large intestines may be affected by infectious, autoimmune, and physiological states. Inflammation of the intestines is called enterocolitis, which may lead to diarrhoea.

Acute conditions affecting the bowels include infectious diarrhoea and mesenteric ischaemia. Causes of constipation may include faecal impaction and bowel obstruction, which may in turn be caused by ileus, intussusception, volvulus. Inflammatory bowel disease is a condition of unknown aetiology, classified as either Crohn's disease or ulcerative colitis, that can affect the intestines and other parts of the gastrointestinal tract. Other causes of illness include intestinal pseudoobstruction, and necrotizing enterocolitis.

Diseases of the intestine may cause vomiting, diarrhoea or constipation, and altered stool, such as with blood in stool. Colonoscopy may be used to examine the large intestine, and a person's stool may be sent for culture and microscopy. Infectious disease may be treated with targeted antibiotics, and inflammatory bowel disease with immunosuppression. Surgery may also be used to treat some causes of bowel obstruction.

The normal thickness of the small intestinal wall is 3–5 mm, and 1–5 mm in the large intestine. Focal, irregular and asymmetrical gastrointestinal wall thickening on CT scan suggests a malignancy. Segmental or diffuse gastrointestinal wall thickening is most often due to ischemic, inflammatory or infectious disease.

The signs and symptoms for esophagitis include:

- Heartburn feels like the inside of your chest is burning. It is a symptom of acid reflux or GERD.

- Nausea is the feeling of being sick, specifically with the urge to vomit.

- Swallowing is painful and difficult to pass food through your throat into your esophagus.

- Vomiting, also known as emesis, is the release of the contents of the stomach through the mouth or nose.

- Abdominal pain is when pain is felt in the abdomen.

- Food bolus impaction is an obstruction of the esophagus by swallowed food.

- Acid regurgitation is the backflow of acid from the stomach to the mouth.

- Chest pain is pain felt between the neck and upper abdomen. There are many causes and the pain can range.

- Cough is a reflex to clear the throat of irritants or mucus.

A doctor should be consulted if the signs and/or symptoms do not subside after a few days, are accompanied with flu-like symptoms, do not lessen after treating with over-the counter antacids, and/or make eating food difficult.

When vomiting is severe it may result in the following:

- Loss of 5% or more of pre-pregnancy body weight

- Dehydration, causing ketosis, and constipation

- Nutritional disorders such as vitamin B1 (thiamine) deficiency, vitamin B6 deficiency or vitamin B12 deficiency

- Metabolic imbalances such as metabolic ketoacidosis or thyrotoxicosis

- Physical and emotional stress of pregnancy on the body

- Difficulty with activities of daily living

Symptoms can be aggravated by hunger, fatigue, prenatal vitamins (especially those containing iron), and diet. Many people with HG are extremely sensitive to odors in their environment; certain smells may exacerbate symptoms. Excessive salivation, also known as sialorrhea gravidarum, is another symptom experienced by some women.

Hyperemesis gravidarum tends to occur in the first trimester of pregnancy and lasts significantly longer than morning sickness. While most women will experience near-complete relief of morning sickness symptoms near the beginning of their second trimester, some sufferers of HG will experience severe symptoms until they give birth to their baby, and sometimes even after giving birth.

A small percentage rarely vomit, but the nausea still causes most (if not all) of the same issues that hyperemesis with vomiting does.

Hyperemesis gravidarum is considered a diagnosis of exclusion. HG can be associated with serious problems in the mother or baby, such as Wernicke's encephalopathy, coagulopathy, peripheral neuropathy.

Women experiencing hyperemesis gravidarum often are dehydrated and lose weight despite efforts to eat. The onset of the nausea and vomiting in hyperemesis gravidarum is typically before the twenty-second week of pregnancy.

The esophagus is a muscular tube made of both voluntary and involuntary muscles. It is responsible for peristalsis of food. It is about 8 inches long and passes through the diaphragm before entering the stomach. The esophagus is made up of four different layers: serosa, muscularis externa, submucosa, and the mucosa. The mucosa, which is the inner most layer and lining of the esophagus, is composed of stratified squamous epithelium, lamina propria, and muscularis mucosae. At the end of the esophagus is the lower esophageal sphincter, which prevents stomach acid from moving to the esophagus. Sometimes the sphincter allows acid to backflow into the esophagus if it is not strong enough. Esophagitis occurs when there is an infection or irritation to the layers of the esophagus. Infection can be caused by bacteria, viruses, fungi, or diseases that weaken the immune system. Irritation can be caused by GERD, vomiting, surgery, medications, hernias, and radiation injury. Inflammation can cause the esophagus to narrow, which makes swallowing food difficult and may result in food bolus impaction. Irritation from the backflow of acid can cause the feeling of burning in the chest and can result in the flow of acid into the throat causing acid reflux or regurgitation . If irritation, infection, and/or inflammation to the esophagus continues, it is likely that the symptoms and signs will increase.

The signs/symptoms of protein losing enteropathy are consistent with diarrhea, fever, and general abdominal discomfort. Swelling of the legs due to peripheral edema can also occur, however if the PLE is related to a systemic disease such as congestive heart failure or constrictive pericarditis, then the symptoms could be of the primary disease development.

People may vomit or retch six to twelve times an hour, and an episode may last from a few hours to well over three weeks, and in some cases months, with a median episode duration of 41 hours. Acid, bile and (if the vomiting is severe) blood may be vomited. Some sufferers will ingest water to reduce the irritation of bile and acid on the esophagus during emesis. Between episodes the sufferer is usually normal and healthy otherwise but can be in a weak state of fatigue or suffer from muscle pain. In approximately half of cases the attacks, or episodes, occur in a time-related manner. Each attack is stereotypical; that is, in any given individual, the timing, frequency and severity of attacks is similar.

Episodes may happen every few days, every few weeks or every few months. For some there is not a pattern in time that can be recognized. Some sufferers have a warning of an attack. They may experience a prodrome, usually intense nausea and pallor, heightened sensitivity, especially to light, though sensitivity to smell, sound, pressure, and temperature, as well as oncoming muscle pain and fatigue, are also reported by some patients. The majority of sufferers can identify triggers that may precipitate an attack. The most common are various foods, infections (such as colds), menstruation, extreme physical exertion, lack of sleep, and psychological stresses both positive and negative.

A sufferer may also be light-sensitive (photophobic) during an attack, as well as sound-sensitive (phonophobic) and, less frequently, temperature- or pressure-sensitive. Some sufferers also have a strong urge to bathe in warm or cold water. Some sufferers report that they experience a restless sensation or stinging pain along the spine, hands, and feet followed by weakness in both legs. Some of these symptoms may be due to dehydration rather than the underlying cause of CVS.

The causes of protein-losing enteropathy can include GI conditions (among other causes), like the following:

In extreme cases of intestinal infestation, the mass and volume of the worms may cause the outer layers of the intestinal wall, such as the muscular layer, to tear. This may lead to peritonitis, volvulus, and gangrene of the intestine.

Microscopic identification of eggs, or more rarely of the adult flukes, in the stool or vomitus is the basis of specific diagnosis. The eggs are indistinguishable from those of the very closely related "Fasciola hepatica" liver fluke, but that is largely inconsequential since treatment is essentially identical for both.

Most infections are light and asymptomatic. In heavy infections, symptoms can include abdominal pain, chronic diarrhea, anemia, ascites, toxemia, allergic responses, sensitization caused by the absorption of the worms' allergenic metabolites (may eventually cause death of patient), and intestinal obstruction.

The signs and symptoms of helminthiasis depend on a number of factors including: the site of the infestation within the body; the type of worm involved; the number of worms and their volume; the type of damage the infesting worms cause; and, the immunological response of the body. Where the burden of parasites in the body is light, there may be no symptoms.

Certain worms may cause particular constellations of symptoms. For instance, taeniasis can lead to seizures due to neurocysticercosis.

There are several subtypes of CINV. The classifications of nausea and vomiting are:

- Acute: occurring within 24 hours of chemotherapy

- Delayed: occurring between 24 hours and 5 days after treatment

- Breakthrough: occurring despite prophylactic treatment

- Anticipatory: triggered by taste, odor, memories, visions, or anxiety related to chemotherapy

- Refractory: occurring during subsequent cycles when antiemetics have failed in earlier cycles

Chemotherapy-induced nausea and vomiting (CINV) is a common side-effect of many cancer treatments. Nausea and vomiting are two of the most feared cancer treatment-related side effects for cancer patients and their families. In 1983, Coates et al. found that patients receiving chemotherapy ranked nausea and vomiting as the first and second most severe side effects, respectively. Up to 20% of patients receiving highly emetogenic agents in this era postponed, or even refused, potentially curative treatments. Since the 1990s, several novel classes of antiemetics have been developed and commercialized, becoming a nearly universal standard in chemotherapy regimens, and helping to better manage these symptoms in a large portion of patients. Efficient mediation of these unpleasant and sometimes crippling symptoms results in increased quality of life for the patient, and better overall health of the patient, and, due to better patient tolerance, more effective treatment cycles.

Colorectal polyps are not usually associated with symptoms. When they occur, symptoms include rectal bleeding, bloody stools, abdominal pain and fatigue. A change in bowel habits may occur including constipation and diarrhoea. Occasionally, if a polyp is big enough to cause a bowel obstruction, there may be nausea, vomiting and severe constipation.

Most conditions of STH have a light worm burden and usually have no discernible symptoms. Heavy infections however cause a range of health problems, including abdominal pain, diarrhoea, blood and protein loss, rectal prolapse, and physical and mental retardation.

Severe ascariasis is typically a pneumonia, as the larvae invades lungs, producing fever, cough and dyspnoea during early stage of infection.

Hookworm infections insinuate a skin reaction (dermatitis), increased white blood cells (eosinophils), a pulmonary reaction (pneumonitis), and skin rash (urticarial).

Iron deficiency anaemia due to blood loss is a common symptom.

Whipworm ("Trichuris trichiura") is the third most common STH-causing nematode in humans. According to current estimate, nearly 800 million people are infected, and majority of the victims are children. Heavy infections could lead to acute symptoms such as diarrhoea and anaemia, and chronic symptoms such as growth retardation and impaired cognitive development. Medical conditions are more often serious since coinfection with protozoan parasites such as "Giardia" and "Entamoeba histolytica", and with other nematodes is common. Predominantly a tropical disease of developing countries, trichuriasis is quite common in the United States.

There are established criteria to aid in diagnosis of CVS; essential criteria are:

1. A history of three or more periods of intense, acute nausea and unremitting vomiting, as well as pain in some cases, lasting hours to days and even weeks or months

2. Intervening symptom-free or reduced-symptom intervals, lasting weeks to months

3. There are repeated cycles of periods (of varying duration) with intense/acute nausea, with or without vomiting, with or without severe pain, followed by periods of reduced symptoms, followed by gradual increase in CVS symptoms until it peaks (peak intensity is generally relative to cycle intensity).

4. There are differences between early-onset CVS (babies & children) and late onset CVS (adult).

5. Exclusion of metabolic, gastrointestinal, or central nervous system structural or biochemical disease, e.g., individuals with specific physical causes (such as intestinal malrotation)

"Taenia saginata" infection is asymptomatic, but heavy infection causes weight loss, dizziness, abdominal pain, diarrhea, headaches, nausea, constipation, chronic indigestion, and loss of appetite. It can cause antigen reaction that induce allergic reaction. It is also a rare cause of ileus, pancreatitis, cholecystitis, and cholangitis.

The most common general classification is:

- hyperplastic,

- neoplastic (adenomatous & malignant),

- hamartomatous and,

- inflammatory.

There are accidental consumptions of eggs of "T. solium" from contaminated vegetables or water. The eggs enter the intestine where they develop into larvae. The larvae enter the bloodstream and invade host tissues. This clinical condition, called cysticercosis, is the most frequent and severe disease caused by any tapeworm. It can lead to severe headaches, dizziness, occasional seizures, dementia, hypertension, lesions in the brain, blindness, tumor-like growths, and low eosinophil levels. It is the cause of major neurological problems, such as hydrocephalus, paraplegy, meningitis, convulsions, and even death.

Conditions that can cause saliva overproduction include:

- Rabies

- Pellagra (niacin or Vitamin B3 deficiency)

- Gastroesophageal reflux disease, in such cases specifically called a water brash, and is characterized by a sour fluid or almost tasteless saliva in the mouth

- Gastroparesis (main symptoms are nausea, vomiting, and reflux)

- Pregnancy

- Excessive starch intake

- Anxiety (common sign of separation anxiety in dogs)

- Pancreatitis

- Liver disease

- Serotonin syndrome

- Mouth ulcers

- Oral infections

Medications that can cause overproduction of saliva include:

- aripiprazole

- clozapine

- pilocarpine

- ketamine

- potassium chlorate

- risperidone

- rabeprazole sodium (Aciphex)

Toxins that can cause hypersalivation include:

- mercury

- copper

- organophosphates (insecticide)

- arsenic