The persistent urge to pass stool despite having a bowel movement is known as tenesmus. At times this sensation may be due to incomplete emptying of the rectum. The stretched rectal walls coupled with mass movements in the colon is responsible for this sensation. It is influenced by other stimuli, apart from stretching of the colon and rectal wall, as outlined in defecation reflex.
In tenesmus, the sensation to defecate or feeling that the bowel movement was incomplete exists despite the bowel being empty. Attempting to defecate will result in little or no stool, however the urge persists for hours or even days. It is characterized by a nagging, persistent urge to defecate often accompanied by pain, intestinal cramps and straining during a bowel movement.
Causes of Tenesmus (Incomplete Bowel Movement Feeling)
The feeling of having an incomplete bowel movement associated with only partial emptying of the bowels may occur for various reasons, including constipation, anxiety, rectal masses and disturbances during defecation that prevents a person from having a complete bowel movement. Other factors like hemorrhoids may cause a person to quickly end a bowel movement in order to avoid exacerbating the problem.
With tenesmus, the bowel movement is usually complete and the rectum empty but the sensation to defecate persists. This may be related to a mass in the rectum (not stool) causing this sensation, abnormal stretching of the rectal walls, irritation or damage of the rectal wall and nerves, exaggerated defecation reflexes or overactivity of the colonic motility.
Some of the causes of tenesmus include :
- Anorectal abscess
- Colorectal cancer or tumors, including polyps
- Large / thrombosed hemorrhoids (swollen, distended veins)
Damage, Irritation or Scarring of the Bowel
- Inflammatory bowel disease – Crohn’s disease, ulcerative colitis
- Infectious colitis – infection of the colon with inflammation of the colonic wall
- Radiation proctitis/colitis – inflammation of the colon/rectum due to radiation exposure (often therapeutic radiation therapy to target neighboring tumors).
Colorectal Motility Disorders
These disorder primarily involve the large intestine but could extend as high up as the distal parts of the small intestine.
- Diarrhea, including infectious gastroenteritis
- Constipation, although the rectum is usually distended due to feces.
- Patients with diarrhea-predominant IBS (irritable bowel syndrome) may also report tenesmus and it is often related to large hemorrhoids as well.
- Various causes of fecal incontinence may also be responsible for tenesmus.