Rectal tenesmus (Latin, from Greek teinesmos, from teinein to stretch, strain) is a feeling of incomplete defecation. It is the sensation of inability or difficulty to empty the bowel at defecation, even if the bowel contents have already been excreted. Tenesmus indicates the feeling of a residue, and is not always correlated with the actual presence of residual fecal matter in the rectum. It is frequently painful and may be accompanied by involuntary straining and other gastrointestinal symptoms. Tenesmus has both a nociceptive and 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
- Chronic arsenic poisoning
- Colorectal cancer
- Anal melanoma
- Rectal lower gastrointestinal parasitic infection, particularly Trichuris trichiura (whipworm)
- Kidney stones, when a stone is lodged in the lower ureter 
- Ischemic colitis
Tenesmus (rectal) is also associated with the installation of either a reversible or non reversible stoma where rectal disease may or may not be present. Patients who experience tenesmus as a result of stoma installation can experience the symptoms of tenesmus for the duration of the stoma presence. Long term pain management may need to be considered as a result.
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