CCD causes persistent secretory diarrhea. In a fetus, it leads to polyhydramnios and premature birth. Immediately after birth, it leads to dehydration, hypoelectrolytemia, hyperbilirubinemia, abdominal distention, and failure to thrive.

It is characterized by chronic, intractable diarrhea in new-born infants, starting in the first few days of life.

This results in metabolic acidosis and severe dehydration. Pregnancy and birth are usually normal.

Tricho-hepato-enteric syndrome is one particular form of intractable diarrhea of infancy, presenting typically in the first month of life. These babies were usually born small for their age and continue to experience failure to thrive, usually with a final short stature. Typical facial features include prominent forehead and cheeks, a broad nasal root and widely spaced eyes (hypertelorism). Their hairs are woolly, easily removed and poorly pigmented. Liver disease is mainly present as cirrhosis or fibrosis, and staining might reveal high iron content of the liver cells (consistent with hemochromatosis). Most evaluated patients had some degree of decrease in intelligence.

Congenital tufting enteropathy is an inherited disorder of the small intestine that presents with intractable diarrhea in young children.

The differential diagnosis of chronic and intractable diarrhea is:

- Intestinal epithelial dysplasia

- Syndromatic diarrhea

- Immunoinflammatory enteropathy

Diarrhea is defined by the World Health Organization as having three or more loose or liquid stools per day, or as having more stools than is normal for that person.

Acute diarrhea is defined as an abnormally frequent discharge of semisolid or fluid fecal matter from the bowel, lasting less than 14 days, by World Gastroenterology Organization.

Diarrhea, also spelled diarrhoea, is the condition of having at least three loose or liquid bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour. This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non-watery stools in babies who are breastfed, however, may be normal.

The most common cause is an infection of the intestines due to either a virus, bacteria, or parasite - a condition also known as gastroenteritis. These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected. The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks). The short duration watery diarrhea may be due to an infection by cholera, although this is rare in the developed world. If blood is present it is also known as dysentery. A number of non-infectious causes can result in diarrhea. These include lactose intolerance, irritable bowel syndrome, non-celiac gluten sensitivity, celiac disease, inflammatory bowel disease, hyperthyroidism, and a number of medications. In most cases, stool cultures to confirm the exact cause are not required.

Diarrhea can be prevented by improved sanitation, clean drinking water, and hand washing with soap. Breastfeeding for at least six months and vaccination against rotavirus is also recommended. Oral rehydration solution (ORS)--clean water with modest amounts of salts and sugar--is the treatment of choice. Zinc tablets are also recommended. These treatments have been estimated to have saved 50 million children in the past 25 years. When people have diarrhea it is recommended that they continue to eat healthy food and babies continue to be breastfed. If commercial ORS are not available, homemade solutions may be used. In those with severe dehydration, intravenous fluids may be required. Most cases; however, can be managed well with fluids by mouth. Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool. Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.

About 1.7 to 5 billion cases of diarrhea occur per year. It is most common in developing countries, where young children get diarrhea on average three times a year. Total deaths from diarrhea are estimated at 1.26 million in 2013 – down from 2.58 million in 1990. In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age. Other long term problems that can result include stunted growth and poor intellectual development.

Tricho-hepato-enteric syndrome (THE), also known as syndromic or phenotypic diarrhea, is an extremely rare congenital bowel disorder which manifests itself as intractable diarrhea in infants with intrauterine growth retardation, hair and facial abnormalities. Many also have liver disease and abnormalities of the immune system. The associated malabsorption leads to malnutrition and failure to thrive.

It is thought to be a genetic disorder with an autosomal recessive inheritance pattern, although responsible genes have not been found and the exact cause remains unknown. Prognosis is poor; many patients die before the age of 5 (mainly from infections or cirrhosis), although most patients nowadays survive with intravenous feeding (parenteral nutrition).

CCD may be detectable on prenatal ultrasound. After birth, signs in affected babies typically are abdominal distension, visible peristalsis, and watery stools persistent from birth that show chloride loss of more than 90 mmol/l.

An important feature in this diarrhea that helps in the diagnosis, is that it is the only type of diarrhea that causes metabolic alkalosis rather than metabolic acidosis.

The first cases appears to have been reported in 1978 by Davidson et al. These authors reported a five cases of intractable diarrhoea four of whom died. Post mortum showed a thin and dilated intestine with flat small bowel mucosa. A number of jejunal biopsies had been taken during life and these showed partial villous atrophy with by crypt hyperplasia and an increased number of mitotic figures in the crypts. Normal numbers and types of mononuclear cells were present in the lamina propria. Most notably focal epithelial tufts were found on the surface epithelium. These tufts were composed of closely packed enterocytes with apical rounding of the plasma membrane, resulting in a teardrop configuration of the cells. Inclusion bodies or secretory granules were not visualised on transmission electron microscopy within the cytoplasm of the villous enterocytes.

Reifen "et al" reported 2 additional cases in 1994 and coined the name congenital tufting enteropathy.

Substantial numbers of patients with intestinal malabsorption present initially with symptoms or laboratory abnormalities that point to other organ systems in the absence of or overshadowing symptoms referable to the gastrointestinal tract. For example, there is increasing epidemiologic evidence that more patients with coeliac disease present with anemia and osteopenia in the absence of significant classic gastrointestinal symptoms. Microcytic, macrocytic, or dimorphic anemia may reflect impaired iron, folate, or vitamin B12 absorption. Purpura, subconjunctival hemorrhage, or even frank bleeding may reflect hypoprothrombinemia secondary to vitamin K malabsorption. Osteopenia is common, especially in the presence of steatorrhea. Impaired calcium and vitamin D absorption and chelation of calcium by unabsorbed fatty acids resulting in fecal loss of calcium may all contribute. If calcium deficiency is prolonged, secondary hyperparathyroidism may develop. Prolonged malnutrition may induce amenorrhea, infertility, and impotence. Edema and even ascites may reflect hypoproteinemia associated with protein losing enteropathy caused by lymphatic obstruction or extensive mucosal inflammation. Dermatitis and peripheral neuropathy may be caused by malabsorption of specific vitamins or micronutrients and essential fatty acids.

Depending on the nature of the disease process causing malabsorption and its extent, gastrointestinal symptoms may range from severe to subtle or may even be totally absent. Diarrhea, weight loss, flatulence, abdominal bloating, abdominal cramps, and pain may be present. Although diarrhea is a common complaint, the character and frequency of stools may vary considerably ranging from over 10 watery stools per day to less than one voluminous putty-like stool, the latter causing some patients to complain of constipation. On the other hand, stool mass is invariably increased in patients with steatorrhea and generalized malabsorption above the normal with 150–200 g/day. Not only do unabsorbed nutrients contribute to stool mass but mucosal fluid and electrolyte secretion is also increased in diseases associated with mucosal inflammation such as coeliac disease. In addition, unabsorbed fatty acids, converted to hydroxy-fatty acids by colonic flora, as well as unabsorbed bile acids both impair absorption and induce secretion of water and electrolytes by the colon adding to stool mass. Weight loss is common among patients with significant intestinal malabsorption but must be evaluated in the context of caloric intake. Some patients compensate for fecal wastage of unabsorbed nutrients by significantly increasing their oral intake. Eliciting a careful dietary history from patients with suspected malabsorption is therefore crucial. Excessive flatus and abdominal bloating may reflect excessive gas production due to fermentation of unabsorbed carbohydrate, especially among patients with primary or secondary disaccharidase deficiency. Malabsorption of dietary nutrients and excessive fluid secretion by inflamed small intestine also contribute to abdominal distention and bloating. Prevalence, severity, and character of abdominal pain vary considerably among the various disease processes associated with intestinal malabsorption. For example, pain is common in patients with chronic pancreatitis or pancreatic cancer and Crohn disease, but it is absent in many patients with coeliac disease or postgastrectomy malabsorption.

MCAS is a condition that affects multiple systems, generally in an inflammatory manner. Symptoms typically wax and wane over time, varying in severity and duration. Many signs and symptoms are the same as those for mastocytosis, because both conditions result in too many mediators released by mast cells. It has many overlapping characteristics with recurrent idiopathic anaphylaxis, although there are distinguishing symptoms, specifically hives and angioedema.

Common symptoms include:

- "Dermatological"

- flushing

- easy bruising

- either a reddish or a pale complexion

- itchiness

- "Cardiovascular"

- lightheadedness, dizziness, presyncope, syncope

- "Gastrointestinal"

- diarrhea, cramping, intestinal discomfort

- nausea, vomiting

- swallowing, throat tightness

- "Psychological & Neurological"

- brain fog, short term memory dysfunction, difficulty with recalling words

- headaches, migraines

- "Respiratory"

- congestion, coughing, wheezing

- "Vision/Eyes"

- ocular discomfort, conjunctivitis

- "Constitutional"

- general fatigue and malaise

- food, drug, and chemical intolerances (especially fragrances)

- sense of being cold all the time

- "Musculoskeletal"

- osteoporosis and osteopenia (including young patients)

- Anaphylaxis "If too many mediators are spilt into a patient's system, they may also experience anaphylaxis, which primarily includes: difficulty breathing, itchy hives, flushing or pale skin, feeling of warmth, weak and rapid pulse, nausea, vomiting, diarrhea, dizziness and fainting."

Symptoms can be caused or worsened by triggers, which vary widely and are patient-specific.

Common triggers include:

- specific foods and drinks (especially alcohol, and high-histamine content foods)

- temperature extremes

- airborne smells including perfumes or smoke

- exercise or exertion

- emotional stress

- hormonal changes, particularly during adolescence, pregnancy and women's menstrual cycles

Bacterial overgrowth can cause a variety of symptoms, many of which are also found in other conditions, making the diagnosis challenging at times. Many of the symptoms are due to malabsorption of nutrients due to the effects of bacteria which either metabolize nutrients or cause inflammation of the small bowel, impairing absorption. The symptoms of bacterial overgrowth include nausea, flatus, constipation, bloating, abdominal distension, abdominal pain or discomfort, diarrhea, fatigue, and weakness. SIBO also causes an increased permeability of the small intestine. Some patients may lose weight. Children with bacterial overgrowth may develop malnutrition and have difficulty attaining proper growth. Steatorrhea, a sticky type of diarrhea where fats are not properly absorbed and spill into the stool, may also occur.

Patients with bacterial overgrowth that is longstanding can develop complications of their illness as a result of malabsorption of nutrients. Anemia may occur from a variety of mechanisms, as many of the nutrients involved in production of red blood cells are absorbed in the affected small bowel. Iron is absorbed in the more proximal parts of the small bowel, the duodenum and jejunum, and patients with malabsorption of iron can develop a microcytic anemia, with small red blood cells. Vitamin B is absorbed in the last part of the small bowel, the ileum, and patients who malabsorb vitamin B can develop a megaloblastic anemia with large red blood cells.

In older adults, small bowel bacterial overgrowth is associated with a higher frequency of diarrhea, a lower body mass index, and a significantly lower serum albumin concentration.

Bile acid malabsorption, known also as bile acid diarrhea, is a cause of several gut-related problems, the main one being chronic diarrhea. It has also been called bile acid-induced diarrhea, cholerheic or choleretic enteropathy and bile salt malabsorption. It can result from malabsorption secondary to gastrointestinal disease, or be a primary disorder, associated with excessive bile acid production. Treatment with bile acid sequestrants is often effective.

Individuals with acrodermatitis enteropathica may present with the following:

- Blistering of skin

- Dry skin

- Emotional lability

- Glossitis

- Pustule

Alopecia (loss of hair from the scalp, eyebrows, and eyelashes) may occur. Skin lesions may be secondarily infected by bacteria such as "Staphylococcus aureus" or fungi such as "Candida albicans". These skin lesions are accompanied by diarrhea.

The signs and symptoms of DOCK8 deficiency are similar to the autosomal dominant form, STAT3 deficiency. However, in DOCK8 deficiency, there is no skeletal or connective tissue involvement, and affected individuals do not have the characteristic facial features of those with autosomal dominant hyper-IgE syndrome. DOCK8 deficient children often have eczema, respiratory and skin staphylococcus infections.

Beyond these, many other recurrent infections have been observed, including recurrent fungal infections and recurrent viral infections (including molluscum contagiosum, herpes simplex, and herpes zoster), recurrent upper respiratory infection (including "Streptococcus pneumoniae", "Haemophilus influenzae", respiratory syncytial virus, and adenovirus), recurrent sinusitis, recurrent otitis media, mastoiditis, pneumonia, bronchitis with bronchiectasis, osteomyelitis, candidiasis, meningitis (caused by cryptococcus or H. influenzae), pericarditis, salmonella enteritis, and giardiasis. Other dermatologic problems include squamous-cell carcinoma/dysplasia (vulvar, anal, and facial). Immune problems are also common, including autoimmune hemolytic anemia, severe allergies (both food and environmental), asthma, and reactive airway disease. The nervous system may also be affected; observed conditions in DOCK8 deficient people include hemiplegia, ischemic stroke, subarachnoid hemorrhage, and facial paralysis. Vascular complications are common, including aortic aneurysm, cerebral aneurysm, vessel occlusion and underperfusion, and leukocytoclastic vasculitis.

The average incubation periods for giardiasis and cryptosporidiosis are each 7 days. Certain other bacterial and viral agents have shorter incubation periods, although hepatitis may take weeks to manifest itself. The onset usually occurs within the first week of return from the field, but may also occur at any time while hiking.

Most cases begin abruptly and usually result in increased frequency, volume, and weight of stool. Typically, a hiker experiences at least four to five loose or watery bowel movements each day. Other commonly associated symptoms are nausea, vomiting, abdominal cramping, bloating, low fever, urgency, and malaise, and usually the appetite is affected. The condition is much more serious if there is blood or mucus in stools, abdominal pain, or high fever. Dehydration is a possibility. Life-threatening illness resulting from WAD is extremely rare but can occur in people with weakened immune systems.

Some people may be carriers and not exhibit symptoms.

Symptoms may be absent or mild for the early onset of EAH and can include impaired exercise performance, nausea, vomiting, headache, bloating, and swelling of hands, legs, and feet. As water retention increases, weight gain may also occur. More severe symptoms include pulmonary edema and hyponatremic encephalopathy. Symptoms of hyponatremic encephalopathy are associated with an altered level of consciousness and can include sullenness, sleepiness, withdrawing from social interaction, photophobia, and seizures. In some reported cases, death has occurred.

MCAS is often difficult to identify due to the heterogeneity of symptoms and the "lack of flagrant acute presentation." The condition can also be difficult to diagnose, especially since many of the numerous symptoms may be considered "vague". Patients often see many different specialties due to the inherent multisystem nature of the condition, and do not get diagnosed until a holistic view is taken by a diagnostician. Lack of awareness of MCAS by many medical professionals is currently a hurdle to proper diagnosis.

1. Symptoms consistent with chronic/recurrent mast cell release: Recurrent abdominal pain, diarrhea, flushing, itching, nasal congestion, coughing, chest tightness, wheezing, lightheadedness (usually a combination of some of these symptoms is present)

2. Laboratory evidence of mast cell mediator (elevated serum tryptase, N-methyl histamine, prostaglandin D2 or 11-beta- prostaglandin F2 alpha, leukotriene E4 and others)

3. Improvement in symptoms with the use of medications that block or treat elevations in these mediators"

The World Health Organization has not published diagnostic criteria.

Small intestine bacterial overgrowth (SIBO), also termed bacterial overgrowths, or small bowel bacterial overgrowth syndrome (SBBOS), is a disorder of excessive bacterial growth in the small intestine. Unlike the colon (or large bowel), which is rich with bacteria, the small bowel usually has fewer than 10,000 organisms per millilitre. Patients with bacterial overgrowth typically develop symptoms including nausea, bloating, vomiting, diarrhea, malnutrition, weight loss and malabsorption, which is caused by a number of mechanisms.

The diagnosis of bacterial overgrowth is made by a number of techniques, with the gold standard being an aspirate from the jejunum that grows in excess of 10 bacteria per millilitre. Risk factors for the development of bacterial overgrowth include dysmotility; anatomical disturbances in the bowel, including fistulae, diverticula and blind loops created after surgery, and resection of the ileo-cecal valve; gastroenteritis-induced alterations to the small intestine; and the use of certain medications, including proton pump inhibitors.

Small bowel bacterial overgrowth syndrome is treated with an elemental diet or antibiotics, which may be given in a cyclic fashion to prevent tolerance to the antibiotics, sometimes followed by prokinetic drugs to prevent recurrence if dysmotility is a suspected cause.

Acrodermatitis enteropathica is an autosomal recessive metabolic disorder affecting the uptake of zinc through the inner lining of the bowel, the mucous membrane. It is characterized by inflammation of the skin (dermatitis) around bodily openings (periorificial) and the tips of fingers and toes (acral), hair loss (alopecia), and diarrhea. It can also be related to deficiency of zinc due to other, ie. congenital causes.

Other names for "acrodermatitis enteropathica" include Brandt syndrome and Danbolt–Closs syndrome.

Glucose-galactose malabsorption is a rare condition in which the cells lining the intestine cannot take in the sugars glucose and galactose, which prevents proper digestion of these molecules and larger molecules made from them.

Glucose and galactose are called simple sugars, or monosaccharides. Sucrose and lactose are called disaccharides because they are made from two simple sugars, and are broken down into these simple sugars during digestion. Sucrose is broken down into glucose and another simple sugar called fructose, and lactose is broken down into glucose and galactose. As a result, lactose, sucrose and other compounds made from carbohydrates cannot be digested by individuals with glucose-galactose malabsorption.

Glucose-galactose malabsorption generally becomes apparent in the first few weeks of a baby's life. Affected infants experience severe diarrhea resulting in life-threatening dehydration, increased acidity of the blood and tissues (acidosis), and weight loss when fed breast milk or regular infant formulas. However, they are able to digest fructose-based formulas that do not contain glucose or galactose. Some affected children are better able to tolerate glucose and galactose as they get older.

Small amounts of glucose in the urine (mild glucosuria) may occur intermittently in this disorder. Affected individuals may also develop kidney stones or more widespread deposits of calcium within the kidneys.

Glucose-galactose malabsorption is a rare disorder; only a few hundred cases have been identified worldwide. However, as many as 10 percent of the population may have a somewhat reduced capacity for glucose absorption without associated health problems. This condition may be a milder variation of glucose-galactose malabsorption.

Wilderness-acquired diarrhea – also known as wilderness diarrhea, or backcountry diarrhea – is a variety of traveler's diarrhea in which backpackers and other outdoor enthusiasts are affected. Potential sources are contaminated food or water, or "hand-to-mouth", directly from another person who is infected. Cases generally resolve spontaneously, with or without treatment, and the cause is typically unknown. The National Outdoor Leadership School has recorded about one incident per 5,000 person-field days by following strict protocols on hygiene and water treatment. More limited, separate studies have presented highly varied estimated rates of affliction that range from 3 percent to 74 percent of wilderness visitors. One survey found that long-distance Appalachian Trail hikers reported diarrhea as their most common illness. Based on reviews of epidemiologic data and literature, some researchers believe that the risks have been over-stated and are poorly understood by the public. U.S. adults annually experience 99 million episodes of acute diarrhea annually in a population of about 318 million. A very small fraction of these cases results from infections acquired in the wilderness, and all infectious agents occur in both wilderness and non-wilderness settings.