Causes and Risk Factors
What are hemorrhoids?
Hemorrhoids are veins near the anus that become inflamed and/or swollen, much like a varicose vein. Internal hemorrhoids are located inside the anus on the lower part of the rectum; they are not painful but can cause bleeding. Internal hemorrhoids can also restrict the passage of stool and can prolapse and protrude outside of the anus. Even though they are not painful, prolapsed hemorrhoids can cause discomfort during sitting or exercise and can make cleaning up after a bowel movement difficult. External hemorrhoids are located outside of the anus and can be very painful, especially during sitting or exercise. External hemorrhoids can also cause itching.
See some medical illustrations of hemorrhoids here.
What causes hemorrhoids?
Hemorrhoids are caused by straining the muscles and tissues near the anus (including the anal sphincter). Straining these muscles and tissues puts pressure on the veins that are close to the surface, causing the inflammation and swelling described above. This usually happens in one of two ways:
1. During pregnancy the weight of the baby may put stress on these muscles and tissues. During delivery, in particular, when a mother is trying to push the baby out, she inadvertently also uses the rectal muscles as well. (Women in labor will sometimes be told to push as if having a bowel movement, and some women will experience a bowel movement during delivery as a result.)
2. Any bowel movement that involves straining can result in hemorrhoids. Straining is usually the result of constipation or any firm bowel movement that requires using the rectal muscles to push out the stool. Ironically, hemorrhoids can also result from diarrhea, because if there isn't a solid stool for the muscles to push on, the muscles (and veins) can expand without limit until they reach the other side of the rectum (or until they meet another hemorrhoid).
What are some risk factors for hemorrhoids?
The biggest risk factor for hemorrhoids is being human! Ever heard of any animals with hemorrhoids? Walking on all fours makes the rectum point horizontally, reducing the pressure on the rectal muscles and anal sphincter. Our evolution into bipedal primates (walking on two legs), whatever its advantage for survival and reproduction, put us at risk for hemorrhoids (a condition which, for better or for worse, does not affect survival and usually does not affect reproduction). More specifically, here are some factors that put certain humans at higher risk for hemorrhoids:
- Pregnancy and childbirth
- Constipation
- Diarrhea
- Standing for long periods of time
- Sitting for long periods of time
How many people suffer from hemorrhoids?
At any given time, approximately 5% of Americans are experiencing hemorrhoid symptoms. It has been estimated that 50% of Americans have experienced hemorrhoids by the time they reach the age of 50. Hemorrhoids are rare in those under the age of 20. The prevalence of hemorrhoids peaks in the 45-65 age group and declines over age 65. This suggests that you can be "cured" from hemorrhoids. While this is certainly possible, there are other explanations as well.
Sources:
- Lorenzo-Rivero, S (August 2009). "Hemorrhoids: diagnosis and current management". Am Surg 75 (8): 635–42.
- Johanson JF, Sonnenberg A (February 1990). "The prevalence of hemorrhoids and chronic constipation. An epidemiologic study". Gastroenterology 98 (2): 380-6.