Causes and Risks Factors of Hemorrhoids

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Hemorrhoids, commonly referred to as piles, can be caused by straining during a bowel movement or by conditions such as pregnancy or obesity, which place undue pressure on the lower abdomen. By doing so, the veins in and around the anus can begin to stretch and swell abnormally, causing pain, burning, and itchiness.

As frustrating as hemorrhoids can be, even scientists are not entirely sure why some people develop them and others do not. What we do know is that there are certain factors that can increase a person's risk. Some of these (such as a tendency to be constipated) are modifiable, while others (such as genetics and age) are not.

causes of hemorrhoids

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Common Causes

Hemorrhoids will affect three of every four people at one time or another in their lives.

While adults between 45 and 65 are at greatest risk, hemorrhoids can affect people who are far younger, often without explanation.

Hemorrhoids are most commonly associated with bowel movement problems, including:

  • Chronic constipation or diarrhea
  • Straining during bowel movements
  • Sitting for a long time on the toilet

Any of these conditions can affect the blood vessels located in the so-called hemorrhoid cushion. This is an internal structure of the anal canal composed of connective tissues, smooth muscles, and blood vessels known as sinusoids.

Straining of any sort can cause a sudden rise in blood pressure in the hemorrhoid cushion. This, in turn, can cause a vessel to slip from the muscles and ligaments meant to hold it in place. 

Chronic diarrhea or constipation can make things worse by triggering persistent inflammation of the anal and rectal (anorectal) tissues. Sitting on the toilet only exacerbates the problem by stretching the walls of blood vessels so thinly that they begin to bulge and dilate. The same can occur if you have an enormous sneeze.

Lifestyle Risk Factors

While bowel movement problems are the most common causes of hemorrhoids, there are certain lifestyle factors that can increase a person's risk both directly and indirectly.

Poor Hydration

Dehydrated or drinking less than eight glasses of water per day (roughly half a gallon) can contribute to constipation and, therefore, the development of hemorrhoids.

Low-Fiber Diet

Dietary fiber is essential to digestive health, and many people simply don't get enough. Low-fiber diets (with less than 25 to 30 grams of fiber per day) can significantly increase your risk of constipation. 

According to guidance from the National Institute of Diabetes and Digestive and Kidney Disorders (NKNKD), diets rich in the following foods can significantly increase your risk of constipation:

  • Cheese
  • Chips
  • Fast food
  • Ice cream
  • Prepared foods, including frozen meals and snack foods
  • Processed foods
  • Red meat

By contrast, the increased intake of insoluble fiber may help restore normal bowel function.

Lack of Regular Activity

Physical inactivity and the absence of regular exercise can cause a general loss of muscle tone (including the anorectal muscles) while affecting gastrointestinal motility (often resulting in alternating bouts of diarrhea and constipation).

Medical Causes

Hemorrhoids are a common feature in many health conditions, some serious and others not-so-serious. These include:

  • Anal injury, such as from anal sex
  • Ascites (the accumulation of fluid in the abdominal cavity, often seen in advanced liver disease)
  • Inflammatory bowel diseases (IBD), such as Crohn's disease and ulcerative colitis
  • Obesity: Excessive abdomen girth and weight places stress on the muscles of the pelvic floor and, in turn, the hemorrhoid cushion. 
  • Rectal prolapse

Because many of these conditions are serious and/or treatable, it is important not to ignore any hemorrhoid that is either worsening or failing to improve.

While hemorrhoids can sometimes bleed, you should see a doctor if the bleeding is persistent and is accompanied by abdominal pain, changes in bowel habits, bloody stools, and unexplained weight loss.

This may be a sign of colon or rectal cancer, both of which require immediate attention.

The same goes for chronic diarrhea and constipation. Neither should be considered normal, and steps should be taken to identify any underlying cause (such a lactose or gluten intolerance) that might explain or contribute to the condition.

Hemorrhoids Doctor Discussion Guide

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Hemorrhoids are also a common occurrence during pregnancy. While the pressure exerted by the weight of the baby can contribute to their development, hormonal changes can also cause blood vessels to swell excessively.

During the pregnancy itself, the increased size of the uterus can exert pressure on the inferior vena cava, a large vessel on the right side of the body that receives blood from the lower limbs. Doing so impedes the flow of blood back to the heart and causes any vessels below the uterus to dilate, including those of the hemorrhoid cushion.

Childbirth can place further strain by the sheer force of the labor contractions, leading to the development of hemorrhoids after delivery.

It is estimated that as many as 35 percent of women will develop hemorrhoids during the course of her pregnancy.

The risk typically increases with each subsequent birth.


Genetics can also play a role in the development of hemorrhoids. One such example is an inherited disorder called Ehlers-Danlos syndrome (EDS) in which the lack of collagen can lead to the impairment of pelvic floor tissues. Hemorrhoids are a common symptom of EDS and can sometimes foreshadow a more serious complication known as rectal prolapse in which the bowel falls partially or completely out of the body.

Another commonly noted defect is the absence of valves within hemorrhoidal veins, which can lead to excessive vascular pressure and swelling.

Frequently Asked Questions

  • How do you treat hemorrhoids for fast relief?

    For quick relief, ice packs can help with inflammation and sitz baths can soothe irritation and itching. Witch hazel and aloe vera are also useful remedies for flare-ups. Over-the-counter creams and stool softeners will relieve discomfort and make it easier to empty bowels.

  • How do you prevent hemorrhoids?

    Ways to avoid developing hemorrhoids include not holding in your bowels and trying not to strain during bowel movements. Also, do not sit on the toilet for prolonged periods of time as this puts unnecessary pressure on your blood vessels. Finally, consider a diet with a lot of fiber, stay well hydrated, and exercise.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. National Institute of Diabetes and Digestive and Kidney Disorders. Symptoms & Causes of Hemorrhoids.

  3. National Institute of Diabetes and Digestive and Kidney Disorders. Eating, Diet, & Nutrition for Hemorrhoids: What should I eat if I have hemorrhoids?.

  4. Schubert MC, Sridhar S, Schade RR, Wexner SD. What every gastroenterologist needs to know about common anorectal disorders. World J Gastroenterol. 2009;15(26):3201-9. doi:10.3748/wjg.15.3201

  5. Staroselsky A, Nava-ocampo AA, Vohra S, Koren G. Hemorrhoids in pregnancy. Can Fam Physician; 54(2):189-90.

  6. Plackett TP, Kwon E, Gagliano RA, Oh RC. Ehlers-danlos syndrome-hypermobility type and hemorrhoids. Case Rep Surg. 2014;2014:171803. doi:10.1155/2014/171803

  7. Harvard Health Publishing, Harvard Medical School. Hemorrhoids and what to do about them.

  8. Cleveland Clinic. 5 simple ways you can prevent hemorrhoids.

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.