Crohns disease typically affects fairly well demarcated segments of bowel in the colon and often affects the end of the small bowel. Irritable bowel syndrome
Another possible cause of diarrhea is irritable bowel syndrome (IBS), which usually presents with abdominal discomfort relieved by defecation and unusual stool (diarrhea or constipation) for at least three days a week over the previous three months. Symptoms of diarrhea-predominant IBS can be managed through a combination of dietary changes, soluble fiber supplements and medications such as loperamide or codeine. About 30% of patients with diarrhea-predominant IBS have bile acid malabsorption diagnosed with an abnormal SeHCAT test. Other diseases
Diarrhea can be caused by other diseases and conditions, namely:

Chronic ethanol ingestion
Hyperthyroidism
Certain medications
Bile acid malabsorption
Ischemic bowel disease: This usually affects older people and can be due to blocked arteries. Microscopic colitis, a type of inflammatory bowel disease where changes are seen only on histological examination of colonic biopsies. Bile salt malabsorption (primary bile acid diarrhea) where excessive bile acids in the colon produce a secretory diarrhea. Hormone-secreting tumors: some hormones, e.g. serotonin, can cause diarrhea if secreted in excess (usually from a tumor). Chronic mild diarrhea in infants and toddlers may occur with no obvious cause and with no other ill effects; this condition is called toddlers diarrhea. Environmental enteropathy
Radiation enteropathy following treatment for pelvic and abdominal cancers. Medications
Some medications, such as the penicillin can cause diarrhea. Over 700 medications are known to cause diarrhea.
Breastfeeding
Breastfeeding practices have been shown to have a dramatic effect on the incidence of diarrheal disease in poor populations. Studies across a number of developing nations have shown that those who receive exclusive breastfeeding during their first 6 months of life are better protected against infection with diarrheal diseases. One study in Brazil found that non-breastfed infants were 14 times more likely to die from diarrhea than exclusively breastfed infants. Exclusive breastfeeding is currently recommended for the first six months of an infants life by the WHO, with continued breastfeeding until at least two years of age. Others
Probiotics decrease the risk of diarrhea in those taking antibiotics. Insecticide spraying may reduce fly numbers and the risk of diarrhea in children in a setting where there is seasonal variations in fly numbers throughout the year. Management
In many cases of diarrhea, replacing lost fluid and salts is the only treatment needed. This is usually by mouth – oral rehydration therapy – or, in severe cases, intravenously. Diet restrictions such as the BRAT diet are no longer recommended. Research does not support the limiting of milk to children as doing so has no effect on duration of diarrhea. To the contrary, WHO recommends that children with diarrhea continue to eat as sufficient nutrients are usually still absorbed to support continued growth and weight gain, and that continuing to eat also speeds up recovery of normal intestinal functioning. CDC recommends that children and adults with cholera also continue to eat.