Causes

Constipation most commonly occurs when waste or stool moves too slowly through the digestive tract or cannot be eliminated effectively from the rectum, which may cause the stool to become hard and dry. Chronic constipation has many possible causes.

Blockages in the colon or rectum

Blockages in the colon or rectum may slow or stop stool movement. Causes include:

• Tiny tears in the skin around the anus (anal fissure)
• A blockage in the intestines (bowel obstruction)
• Colon cancer
• Narrowing of the colon (bowel stricture)
• Other abdominal cancer that presses on the colon
• Rectal cancer
• Rectum bulge through the back wall of the vagina (rectocele)

Problems with the nerves around the colon and rectum

Neurological problems can affect the nerves that cause muscles in the colon and rectum to contract and move stool through the intestines. Causes include:

• Damage to the nerves that control bodily functions (autonomic neuropathy)
• Multiple sclerosis
• Parkinson's disease
• Spinal cord injury
• Stroke

Difficulty with the muscles involved in elimination

Problems with the pelvic muscles involved in having a bowel movement may cause chronic constipation. These problems may include:

• The inability to relax the pelvic muscles to allow for a bowel movement (anismus)
• Pelvic muscles that don't coordinate relaxation and contraction correctly (dyssynergia)
• Weakened pelvic muscles

Conditions that affect hormones in the body

Hormones help balance fluids in your body. Diseases and conditions that upset the balance of hormones may lead to constipation, including:

• Diabetes
• Overactive parathyroid gland (hyperparathyroidism)
• Pregnancy
• Underactive thyroid (hypothyroidism)