What Is Diverticulitis?

Two words that sound almost identical — diverticulosis and diverticulitis — describe two very different situations, and mixing them up causes a lot of unnecessary worry. The short version: one is usually silent, the other is the painful flare that brings people to hospital. The video above, "Diverticula, diverticulosis, & diverticulitis," walks through exactly that distinction in about six minutes, starting from what a diverticulum actually is.

First, the pouches themselves: diverticulosis

Diverticula are small outpouchings that push through the wall of the large intestine, most commonly in the sigmoid colon, the last section before the rectum — that is how the anchor video defines them. Simply having these pouches is called diverticulosis. On its own, diverticulosis usually causes no symptoms at all, and many people only learn they have it because a routine examination found it. If you want to see what the pouches look like from inside, the site's video "Diverticulosis of the Colon" follows a screening colonoscopy as it passes the splenic flexure and reveals a colonic diverticulum along the way. Our guide to what a colonoscopy is and how it is done explains that examination itself.

When a pouch turns troublesome: diverticulitis

Diverticulitis is what happens when one of those pouches becomes inflamed, and sometimes infected. That is when the quiet finding turns into symptoms — most typically pain in the lower left of the abdomen, where the sigmoid colon sits, often with fever, nausea, and a change in bowel habit. The contrast with diverticulosis is the whole point: pouches alone are a finding, pouches that are inflamed are a condition that needs care. A flare can also lead to complications such as an abscess or a tear in the bowel wall, which is why new, persistent lower-abdominal pain with fever deserves prompt in-person assessment rather than a wait-and-see approach at home.

How a flare is sorted out

A clinician will start with your symptoms and an examination of the abdomen, and blood tests can show signs of inflammation or infection. Imaging is often the deciding step — a CT scan of the abdomen can show an inflamed section of colon and reveal whether a complication is present. That matters because the treatment plan depends on whether the episode is straightforward or complicated. Many uncomplicated flares are managed with rest for the bowel, fluids, and medication prescribed by the treating team, with close follow-up; more severe or complicated episodes may need hospital care, and surgery is sometimes part of treatment, particularly when complications occur or flares keep returning. What helps long term, once things have settled, is a conversation with your own clinician about diet, fibre, and your personal risk of another flare — general articles like this one cannot make that call for you.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Frequently Asked Questions

What is the difference between diverticulosis and diverticulitis?
Diverticulosis simply means small pouches (diverticula) are present in the colon wall — usually with no symptoms. Diverticulitis means one of those pouches has become inflamed or infected, which is what causes pain and fever.

Where is diverticulitis pain usually felt?
Most often in the lower left side of the abdomen, because the pouches most commonly form in the sigmoid colon, which sits on that side. Pain location can vary, though.

Can diverticulitis be treated without surgery?
Many uncomplicated flares are managed without surgery, using bowel rest, fluids, and medication from the treating team. Surgery is considered when there are complications or repeated flares — that decision belongs to the team treating you.

How long is the anchor video?
About six minutes (6 minutes 20 seconds). It defines diverticula, explains diverticulosis, and contrasts it with diverticulitis, most commonly in the sigmoid colon.

Educational only — this article is general information about diverticulitis, not medical advice and not a diagnosis. Lower-abdominal pain that is severe, persistent, or accompanied by fever needs prompt in-person medical assessment.