Ileitis is an inflammation of the ileum, which is a section of the small intestine, according to MedicineNet. It is a type of Crohn's disease, though not all types of Crohn's disease involve the ileum or even the small intestine.
The disease causes ulcers in the inner walls of the ileum that worsen over time, according to MedicineNet. If left untreated, the ileum is scarred to the point that obstructions occur. Ulcers can perforate the wall of the small intestine, which lead to contamination of the abdominal cavity and the organs within it.
The symptoms of ileitis include cramping, vomiting, unexplained weight loss, fever and diarrhea, says MedicineNet. It can also cause joint inflammation and inflammation of the liver and eyes.