Rectal tenesmus (Latin, from Greek teinesmos, from teinein to stretch, strain) is a feeling of incomplete defecation. It is experienced as an inability or difficulty to empty the bowel at defecation, even if the bowel contents have already been excreted. It is frequently painful and may be accompanied by involuntary straining and other gastrointestinal symptoms. Tenesmus has both a nociceptive as well as a neuropathic component, and is usually accompanied by intense patient anxiety.
Tenesmus is a closely related topic to obstructed defecation.
Tenesmus is characterized by a sensation of needing to pass stool, accompanied by pain, cramping, and straining. Despite straining, little stool is passed. Tenesmus is generally associated with inflammatory diseases of the bowel, which may be caused by either infectious or noninfectious conditions. Conditions associated with tenesmus include:
- Irritable bowel syndrome
- Diverticular disease
- Cytomegalovirus (in immunocompromised patients)
- Inflammatory bowel disease
- Coeliac disease
- Pelvic floor dysfunction
- Prolapsed hemorrhoid
- Radiation proctitis
- Rectal gonorrhoea
- Rectal lymphogranuloma venereum
- Ulcerative colitis
- Colorectal cancer
- Anal Melanoma
- Rectal lower GI parasitic infection, particularly Trichuris trichiura (whipworm)
- Kidney stones, when a stone is lodged in the lower ureter 
Pain relief is administered concomitantly to the treatment of the primary disease causing tenesmus. Methadone has been shown to be an effective pain-reliever.
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