Health experts have not determined the exact cause of hemorrhoids, but they are known to appear because increased pressure within your lower abdomen or rectum stretches the veins in these areas. This leads to the bulging and swelling of these blood vessels. Factors that may affect your risk for having hemorrhoids include:
Straining during bowel movement
People who strain too much during bowel movement increase pressure on the veins located in their anus or rectum, potentially leading to hemorrhoids
Chronic constipation or diarrhea
In connection with the previous risk factor, having these conditions may prompt you to strain hard during bowel movement
Sitting for a long period of time, especially on the toilet
Chronic sitting, especially when you’re on the toilet, puts stress on your veins and consequently increases your risk for hemorrhoids
Family history
Weak veins that run in the family could be considered as a risk factor. Weaker veins tend to be more easily damaged or widened and could possibly trigger hemorrhoids.
Aging
Older people are more prone to have hemorrhoids because the tissues supporting the veins in their rectum and anus stretch and weaken with age. Hemorrhoids are most common among adults aged 45-65. This does not mean, however, that young people and children do not get them.
Obesity
Obese people are more predisposed to hemorrhoids because they don’t get enough high-fiber food in their system, drink less fluids and spend more time sitting instead of working out
Lifting
Regular lifting heavy objects and those who perform strenuous manual labor are at risk of piles.
Low-fiber diet
Not eating enough fiber can make your stools hard, making you strain harder than usual during bowel movement, increase pressure on your rectum and anus and consequently raise your risk for hemorrhoids.
Not enough fluid intake
Not drinking enough water or any other fluids may also result in harder, more compacted stools and this in turn, results in constipation and would cause additional pressure in the anus.
Pregnancy
Pregnancy is associated with hemorrhoid swelling and is likely due to increased pressure of the enlarged uterus on the rectum and anus. In addition, hormonal changes with pregnancy may weaken the muscles that support the rectum and anus. The act of giving birth will also cause tremendous pressure in the area. It is very common for new mothers to experience hemorrhoids.
History of rectum and anal surgery
People who have had surgery of the rectum or anus before are at a similar risk of piles since the muscles of their rectum and anus may be weak and straining may lead to piles.
References
http://articles.mercola.com/hemorrhoids/causes.aspx
http://www.news-medical.net/health/Causes-of-piles-(haemorrhoids).aspx
