Symptoms of both ulcerative colitis and Crohn's disease usually include belly pain, diarrhea, rectal bleeding, extreme tiredness and weight loss. For some people, IBD is only a mild illness. But for others, it's a condition that causes disability and can lead to life-threatening complications., Crohn's disease is a type of inflammatory bowel disease (IBD) that causes swelling and irritation of the tissues, called inflammation, in the digestive tract. This can lead to belly pain, severe diarrhea, fatigue, weight loss and malnutrition., This includes ulcerative colitis, which causes inflammation and sores in the colon and rectum, and Crohn's disease, and inflammation of the lining of the digestive tract., Ulcerative colitis is an inflammatory bowel disease that causes chronic inflammation and ulcers in the superficial lining of the large intestine, also called the colon., An ulcerative colitis flare-up is the return of symptoms after not having any for a period of time. This may involve diarrhea, belly pain and cramping, rectal pain and bleeding, fatigue, and urgent bowel movements., Microscopic colitis is swelling and irritation, called inflammation, of the large intestine. This large intestine is also called the colon. Microscopic colitis causes symptoms of watery diarrhea. The condition gets its name from needing to look at colon tissue under a microscope to diagnose it..