Tenesmus most often occurs with inflammatory diseases of the bowels. These diseases may be caused by an infection or other conditions.
It can also occur with diseases that affect the normal movements of the intestines. These diseases are known as motility disorders.
The condition may be caused by:
Anorectal abscess
Colorectal cancer or tumors
Crohn's disease
Infection of the colon (infectious colitis)
Inflammation of the colon or rectum from radiation (radiation proctitis or colitis)
Inflammatory bowel disease (IBD)
Movement (motility) disorder of the intestines
Ulcerative colitis
Source:
www.nlm.nih.gov/medlineplus/ency/article/003131.htm