Constipation

Constipation: Causes and Physiology of the Problem

Constipation is a common digestive disorder that is defined not so much by the infrequency of bowel movements as by their quality and accompanying symptoms. Constipation is said to occur when defecation happens fewer than three times a week, and the stools are hard, dry, require strong straining, and often there is a feeling of incomplete evacuation. It can be a short‑term issue or a chronic condition that significantly impairs quality of life.

What happens in the intestine?

The main function of the large intestine is to absorb water from the fecal mass, forming it. Constipation arises when this process is disrupted:

• Slowed motility (hypomotor dyskinesia): Contractions of the large‑intestinal muscles become weak and slow. The fecal masses stay too long in the colon. The longer they remain there, the more water is absorbed from them, making them harder and drier.
• Pelvic floor muscle dysfunction (dyssynergic defecation): This is a coordination disorder. For successful defecation a person must contract the abdominal muscles while simultaneously relaxing the pelvic floor muscles and the anal sphincter. In dyssynergia this relaxation does not occur, creating a mechanical obstacle.

Main causes and risk factors

In most cases constipation is functional, i.e., not associated with an organic disease.

• Lifestyle: Insufficient intake of fiber (vegetables, fruits), low fluid consumption, and a sedentary lifestyle are the "big three" causes.
• Ignoring urges: Systematically suppressing the desire to go to the toilet (due to busyness or inconvenient conditions) leads to a weakened reflex.
• Medications: Many drugs can cause constipation, including opioid analgesics, iron supplements, and some antidepressants.
• Pregnancy: Hormonal changes and the mechanical pressure of the uterus are a common cause of constipation in pregnant women.
• Diseases: Constipation can be a symptom of endocrine (hypothyroidism) or neurological (Parkinson’s disease) disorders.

Chronic constipation can lead to complications such as hemorrhoids or anal fissures.