Amebic dysentery is caused by Entamoeba histolytica and is common in the tropics or areas that use human excrement as fertilizer. Bacillary dysentery is caused by a bacterial organism, such as Shigella, Salmonella, or Campylobacter, and is usually seen in temperate zones. Bacterial dysentery is usually more severe than amebic dysentery.

Dysentery is transmitted through food and water contaminated with feces. It is spread by improper hand sanitation after defecation and occurs more frequently in overcrowded areas with poor sanitation.

Amebic dysentery may result in abscesses that affect the liver, lungs, or brain. It may also result in nonintestinal infections, such as amebic hepatitis. With either type of dysentery, GI ulceration with bleeding may occur, as well as appendicitis or inflammation of the colon. Bacillary dysentery may move to other organs and cause meningitis, encephalitis, or hemolytic-uremic syndrome and kidney failure. Seizures may also occur secondary to fever. Dysentery caused by Shigella may also cause Reiter syndrome, or reactive arthritis.

Both amebic and bacterial dysentery cause watery diarrhea, although the diarrhea is more severe with bacterial dysentery. Diarrhea may have a foul odor, appear bloody, and contain yellowish white mucus. Tenesmus, or the feeling of incomplete emptying of the bowel, may occur. The patient may also experience abdominal cramping and vomiting, which may be bloody. Fever may occur 1 to 3 days after exposure. Palpation of the abdomen may elicit tenderness, and bowel sounds may be hyperactive.