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Inflammation of the intestine causing diarrhea with blood

The cause of dysentery is usually the bacteria from genus Shigella, in which case it is known as shigellosis, or the amoeba Entamoeba histolytica; then it is called amoebiasis. Risk factors include contamination of food and water with feces due to poor sanitation. The underlying mechanism involves inflammation of the intestine, especially of the colon. While medications used to decrease diarrhea such as loperamide are not recommended on their own, they may be used together with antibiotics. In areas with poor sanitation nearly half of cases of diarrhea are due to Entamoeba histolytica. It commonly occurs in less developed areas of Central and South America, Africa, and Asia.

The most common form of dysentery is bacillary dysentery, which is typically a mild sickness, causing symptoms normally consisting of mild abdominal pains and frequent passage of loose stools or diarrhea. Symptoms normally present themselves after 1–3 days, and are usually no longer present after a week. The frequency of urges to defecate, the large volume of liquid feces ejected, and the presence of blood, mucus, or pus depends on the pathogen causing the disease. Temporary lactose intolerance can occur, as well. In some occasions, severe abdominal cramps, fever, shock, and delirium can all be symptoms. In extreme cases, people may pass more than one liter of fluid per hour. More often, individuals will complain of diarrhea with blood, accompanied by extreme abdominal pain, rectal pain and a low grade fever. Rapid weight loss and muscle aches sometimes also accompany dysentery, while nausea and vomiting are rare. In many cases there can be cascading cramps that affect the muscles surrounding the entire upper intestine; sometimes severe enough to cause the lining of the intestine to separate from the wall, leading to systemic infection. On rare occasions, the amoebic parasite will invade the body through the bloodstream and spread beyond the intestines. In such cases, it may more seriously infect other organs such as the brain, lungs, and most commonly the liver.

Dysentery results from bacterial, or parasitic infections. Viruses do not generally cause the disease. Some microorganisms – for example, bacteria of the genus Shigella – secrete substances known as cytotoxins, which kill and damage intestinal tissue on contact. Shigella is thought to cause bleeding due to invasion rather than toxin, because even non toxogenic strains can cause dysentery, but E. coli with shiga like toxins do not invade the intestinal mucosa, and are therefore toxin dependent. Definitions of dysentery can vary by region and by medical specialty. The U. S. Centers for Disease Control and Prevention (CDC) limits its definition to "diarrhea with visible blood". Others define the term more broadly. These differences in definition must be taken into account when defining mechanisms. For example, using the CDC definition requires that intestinal tissue be so severely damaged that blood vessels have ruptured, allowing visible quantities of blood to be lost with defecation. Other definitions require less specific damage.

Amoebiasis, also known as amoebic dysentery, is caused by an infection from the amoeba Entamoeba histolytica, which is found mainly in tropical areas. Proper treatment of the underlying infection of amoebic dysentery is important; insufficiently treated amoebiasis can lie dormant for years and subsequently lead to severe, potentially fatal, complications. When amoebae inside the bowel of an infected person are ready to leave the body, they group together and form a shell that surrounds and protects them. This group of amoebae is known as a cyst, which is then passed out of the person's body in the feces and can survive outside the body. If hygiene standards are poor – for example, if the person does not dispose of the feces hygienically – then it can contaminate the surroundings, such as nearby food and water. If another person then eats or drinks food or water that has been contaminated with feces containing the cyst, that person will also become infected with the amoebae. Amoebic dysentery is particularly common in parts of the world where human feces are used as fertilizer. After entering the person's body through the mouth, the cyst travels down into the stomach. The amoebae inside the cyst are protected from the stomach's digestive acid. From the stomach, the cyst travels to the intestines, where it breaks open and releases the amoebae, causing the infection. The amoebae can burrow into the walls of the intestines and cause small abscesses and ulcers to form. The cycle then begins again.

Dysentery may also be caused by shigellosis, an infection by bacteria of the genus Shigella, and is then known as bacillary dysentery (or Marlow syndrome). The term bacillary dysentery etymologically might seem to refer to any dysentery caused by any bacilliform bacteria, but its meaning is restricted by convention to Shigella dysentery.

Some strains of Escherichia coli cause bloody diarrhea. The typical culprits are enterohemorrhagic Escherichia coli, of which O157:H7 is the best known. These types of E. coli also make Shiga toxin.

A diagnosis may be made by taking a history and doing a brief examination. Dysentery should not be confused with hematochezia, which is the passage of fresh blood through the anus, usually in or with stools.

The mouth, skin, and lips may appear dry due to dehydration. Lower abdominal tenderness may also be present. Vaccination may eventually become a part of the strategy to reduce the incidence and severity of diarrhea, particularly among children in low resource settings. For example, Shigella is a longstanding World Health Organization (WHO) target for vaccine development, and sharp declines in age specific diarrhea/dysentery attack rates for this pathogen indicate that natural immunity does develop following exposure; thus, vaccination to prevent this disease should be feasible. The development of vaccines against these types of infection has been hampered by technical constraints, insufficient support for coordination, and a lack of market forces for research and development. Most vaccine development efforts are taking place in the public sector or as research programs within biotechnology companies.

Dysentery is managed by maintaining fluids using oral rehydration therapy.

With correct treatment, most cases of amoebic and bacterial dysentery subside within 10 days, and most individuals achieve a full recovery within two to four weeks after beginning proper treatment. If the disease is left untreated, the prognosis varies with the immune status of the individual patient and the severity of disease. Extreme dehydration can delay recovery and significantly raises the risk for serious complications including death.

Insufficient data exists, but Shigella is estimated to have caused the death of 34,000 children under the age of five in 2013, and 40,000 deaths in people over five years of age. Amoebiasis infects over 50 million people each year, of whom 50,000 die (one per thousand).

The seed, leaves, and bark of the kapok tree have been used in traditional medicines by indigenous peoples of the rainforest regions in the Americas, west central Africa, and Southeast Asia in the treatment of this disease. In 1915, Australian bacteriologist Fannie Eleanor Williams was serving as a medic in Greece with the Australian Imperial Force, receiving casualties directly from Gallipoli. In Gallipoli, dysentery was severely affecting soldiers and causing significant loss of manpower. Williams carried out serological investigations into dysentery, co authoring several groundbreaking papers with Sir Charles Martin, director of the Lister Institute. The result of their work into dysentery was increased demand for specific diagnostics and curative sera. Bacillus subtilis was marketed throughout America and Europe from 1946 as an immunostimulatory aid in the treatment of gut and urinary tract diseases such as rotavirus and Shigella, but declined in popularity after the introduction of consumer antibiotics.