What causes haemorrhoids?

What causes haemorrhoids?

The exact caues of hemorrhoids is unknown. What is known is that swelling of veins (a dilation or enlargement of veins which allows an accumulation of blood) in the anus and rectum results in these often highly uncomfortable formations.

When the stretching of veins occurs, pressure and bulging are the result, which in turn lead to the weakening of the connective tissue within haemorrhoid cushions. As the weakness progresses these cushions begin to slide down into the anal canal, producing a haemorrhoid. Swelling is further irritated with increased pressure and straining, especially during bowel movements, which then adversely affects blood flow to the area.

Some other influencing causal factors which can result in vein swelling include:

  • Sitting for long periods of time (especially on the loo / toilet) – this interferes with blood flow, resulting in blood pooling which enlarges veins.
  • Chronic diarrhoea or constipation
  • Obesity (excess weight can place unnecessary pressure on the veins in the colon)
  • A low-fibre diet and low-calibre stool / faeces (loose or narrow stools)
  • Pregnancy (as a woman’s uterus enlarges during pregnancy, pressure can occur on the veins in the colon, resulting in a bulge / swelling. Hormonal changes can also weaken muscles which cushion and support the anus and rectum. Constipation, which is also common in pregnancy may lead cause strain during a bowel movement and lead to hemorrhoids.)
  • Anal intercourse (this may also worsen existing haemorrhoids)
  • Aging (tissues supporting the anal and rectal veins weaken and stretch as the body ages, particularly after the age of 50) (1)
  • Straining when repeatedly lifting heavy objects, standing or sitting for long periods of time without sufficient breaks (i.e. such as in the case of certain occupations)
  • Hereditary factors (some families can pass on certain genes which may predispose a future generation to the development of haemorrhoids)
  • Overuse of laxatives or enemas
  • Colon cancer


1. National Institute of Diabetes and Digestive and Kidney Diseases. October 2016. Definition and Facts of Hemorrhoids: https://www.niddk.nih.gov/health-information/digestive-diseases/hemorrhoids/definition-facts [Accessed 17.10.2017]

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