Colitis is characterised by an inflammation of the lining of the colon. Symptoms Colitis starts in the lower part of colon and spreads upwards.One of the symptoms in the initial stage of the ailment is the increased urgency to move the bowel which may be followed by bloody mucous in the stool in the later stages. Root causes Persistent constipation leads to colitis.Colitis may also be caused by poorly digested roughage.It may also be caused due an overuse of purgatives.