What Happens

Diverticulitis develops when pouches (diverticula) that have developed in the wall of the large intestine (colon) become inflamed or infected. It is not clearly understood why 20% of people who have these pouches—a condition called diverticulosis—develop diverticulitis and the others do not.

Diverticulitis usually affects the left side of the colon (sigmoid colon).

Mild attacks of diverticulitis, with few symptoms or signs of infection or inflammation, sometimes heal without treatment. In some cases, a doctor recommends oral antibiotics to resolve an infection and a clear liquid diet to rest the bowel until inflammation goes away.

When infection and symptoms are severe, diverticulitis is treated in the hospital. Treatment includes resting the bowel with fluids given through a vein (intravenous, or IV) or a liquid diet and taking IV antibiotics. If severe diverticulitis is not treated, complications such as an abscess or fistula may develop. Surgery often is needed to treat complications.

It is common to have lower abdominal pain after recovering from an attack of diverticulitis. But this pain is not always a return of diverticulitis. Less than half of people ever have a second diverticulitis attack. Of those who do have another attack, about half have the second attack within 1 year of their first one.¹