Sigmoid diverticular disease
- Lesion
High pressure inside the colon pushes its lining out through weak spots in the muscle, forming small pouches that can inflame or bleed.
What it is
Colonic diverticula are acquired outpouchings of mucosa and submucosa through the muscularis propria, so they are false diverticula. They form at points where nerves and vasa recta pierce the inner circular muscle, which in the colon is not reinforced by a complete outer longitudinal coat because that layer is gathered into the three taeniae coli. Exaggerated sigmoid contractions with low-fibre diets raise the pressure. Prevalence approaches half of Western adults over sixty.
Structure
- Gross: rows of small outpouchings along the sigmoid between the taeniae; thick muscular wall.
- Micro: diverticular wall of mucosa with muscularis mucosae, separated from serosa by fat; attenuated or absent muscularis propria.
- Diverticulitis: inflammation in the pouch and surrounding fat, sometimes abscess or fistula.
Step by step
- Low-fibre diet leads to small hard stools and strong segmental contractions.
- Intraluminal pressure rises, especially in the sigmoid.
- Mucosa herniates through gaps where vasa recta and nerves cross the inner muscle.
- Stool or debris blocks the diverticular neck; bacteria proliferate.
- Inflammation of the thin wall leads to perforation, abscess or peritonitis.
Clinical notes
- Most people with diverticulosis never have symptoms; about one in five has cramping, discomfort or altered bowel habit.
- Diverticulitis presents with left lower quadrant pain and fever, the so-called left-sided appendicitis.
Test yourself
Think of the answer, then tap the question to see it.
Why are colonic diverticula called false diverticula?
They contain only mucosa and submucosa, which herniate through the muscularis propria.
Why does the colon form diverticula more readily than the small bowel?
Its outer longitudinal muscle is gathered into taeniae, leaving the sites where vessels pierce the inner circular layer unreinforced.
What are the complications of diverticulitis?
Perforation, pericolic abscess, sinus tracts, fistulas and peritonitis; diverticula can also bleed.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Diverticular Disease of the Colon (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.