Diverticulitis

What it means

With age, small pouches called diverticula commonly bulge outward from the wall of the colon; simply having them is called diverticulosis and is usually silent. Diverticulitis is what happens when one of those pouches becomes inflamed or infected. The distinction matters: the first is a harmless structural finding, while the second is an active problem that often needs treatment.

Why it appears on a CT or MRI report

CT is the main test used when diverticulitis is suspected. Reports describe inflamed pouches, thickening of the colon wall, and "stranding" — a hazy look in the fat around the bowel that signals inflammation. Importantly, the scan also looks for complications: a walled-off pocket of pus (abscess), a small perforation with free air, or a blockage. The location is usually the sigmoid colon in the lower-left abdomen, which is where most cases occur.

What it usually means

Most episodes are uncomplicated and improve with treatment — rest, dietary changes, and, when appropriate, antibiotics — often without needing a hospital stay. Complicated diverticulitis, with an abscess, perforation, or blockage, is more serious and may need drainage or surgery. After recovery, doctors sometimes recommend a colonoscopy a few weeks later to confirm the colon lining is otherwise healthy, and long-term prevention focuses on a high-fiber diet. Episodes can recur, though many people have only one.

When to follow up

Seek prompt medical care for persistent lower abdominal pain (especially lower-left), fever, and a change in bowel habits — the typical picture of an attack. Get emergency care for severe or spreading abdominal pain, a rigid or very tender belly, high fever, or inability to keep fluids down, as these can signal a complication needing urgent treatment. Diverticulosis found incidentally, without inflammation, does not need urgent action.

A plain-language way to picture it

Imagine an old inner tube that has developed a few small bulging blisters along its wall. Most of the time the blisters just sit there. But if one gets irritated and inflamed, that single spot becomes hot, sore, and swollen, and the whole tube complains until it calms down. Diverticulosis is the harmless blisters; diverticulitis is one of them flaring up.