Nobody tells you that the scariest part of a diverticulitis diagnosis is usually the word "itis." The first patient I saw with it asked if his colon was going to burst. It almost never does, but the panic is real. So let's start with the vocabulary, because the difference between diverticulosis and diverticulitis is the difference between having a spare room and having your in-laws move into it. Diverticulosis means you have small pouches — diverticula — in the wall of your colon, usually from years of pressure. Most people with these pouches never know they're there. Diverticulitis is what happens when one of those pouches gets inflamed or infected, and it makes itself known.

These pouches are extremely common. By age 60, about half of people have diverticulosis, and by 80, that figure climbs to roughly 70 percent, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Only a minority ever develop diverticulitis, but nobody can predict who. Risk factors include a diet low in fibre and high in red meat, obesity, smoking, physical inactivity, and regular use of non-steroidal anti-inflammatory drugs. Age is the biggest one, though — this condition tends to show up in middle age and beyond.

Recognising Diverticulitis: Symptoms and When to Worry

The classic symptom is pain in the lower left side of the abdomen, which makes sense because the sigmoid colon — the S-shaped section on the left — is where pouches most often form. The pain can come on gradually or suddenly, and it tends to be constant rather than cramping. Along with it, you might run a fever, feel nauseated, vomit, or notice a change in your bowel habits, usually constipation but sometimes diarrhoea. Some people also get urinary symptoms like urgency or frequency, because an inflamed colon can irritate the bladder sitting next door.

Here's a detail worth knowing: in people of Asian descent, diverticula are more likely to appear on the right side of the colon, so the pain can show up on the right and be mistaken for appendicitis. That's a real diagnostic problem, not a footnote. If the pain is severe, if you can't keep fluids down, if you have a high fever, or if you notice blood in your stool, get medical help promptly. Most episodes are uncomplicated, but complicated diverticulitis can involve an abscess, a perforation, a blockage, or an abnormal connection to another organ called a fistula. And trust me, you'd rather catch a fistula early.

How Doctors Confirm the Diagnosis

A CT scan — computed tomography, which is basically a rotating X-ray that builds a 3D picture — is the standard way to confirm diverticulitis and see whether it's uncomplicated or complicated. Blood tests check for infection and inflammation, and a urine test can rule out other causes. Your doctor may not need all of these if the story and exam are clear enough. The National Institute of Diabetes and Digestive and Kidney Diseases has a plain-language explanation of how the diagnosis works if you want the official version.

One piece of advice I give every patient: after the inflammation settles down, usually six to eight weeks later, get a colonoscopy. The reason is that diverticulitis can look like colorectal cancer on a scan, and the only way to be sure is to look inside. My first patient who needed a CT scan was convinced the machine was going to find something worse. It didn't, but I understood the fear. Nobody enjoys a colonoscopy prep, but it's a lot better than missing something.

Treatment: Not Everyone Needs Antibiotics Anymore

Here's where the research has genuinely changed practice. For decades, the automatic response to uncomplicated diverticulitis was antibiotics for everyone. Then a series of randomised trials — the kind where patients are assigned by chance to different treatments — showed that for selected people with mild, uncomplicated diverticulitis, antibiotics didn't improve recovery or reduce complications. Major guidelines from the American Gastroenterological Association and the American Society of Colon and Rectal Surgeons now say it's reasonable to treat many such patients without antibiotics, as long as they're otherwise healthy, can keep fluids down, and can be followed closely.

That's not a licence to ignore symptoms. It means your doctor should make a judgement call based on your age, other conditions, and how severe the episode looks. If you're prescribed antibiotics, they're usually a short course of oral medication. If you're not, you'll still need pain relief, a short period of clear liquids or low-fibre food, and a plan for what to do if you get worse. The word "uncomplicated" is doing a lot of heavy lifting here, and it only applies to people who meet specific criteria.

For pain, paracetamol is usually the first choice. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen are generally discouraged because some studies link them to a higher risk of diverticular bleeding and complications. Not every doctor agrees on this, but it's a conversation worth having.

Complicated Diverticulitis Needs a Hospital

If the scan shows an abscess, a perforation, a blockage, or a fistula, you'll be admitted to hospital. Intravenous antibiotics, fluids, and bowel rest are the starting points. A small abscess can often be drained by a radiologist using a needle guided by CT; a large or inaccessible one may need surgery. Perforation with peritonitis — infection throughout the abdominal cavity — is a surgical emergency.

The good news is that most people with complicated diverticulitis recover with treatment, and the techniques for surgery have improved enormously. But no one should pretend it's minor. That word again: uncomplicated. Once you cross into complicated territory, the game changes and so does the urgency.

Diet, Fibre, and the Advice That Changed

When I started in clinical practice, I told patients to avoid nuts, seeds, popcorn, and anything with small hard bits, on the theory that they'd get stuck in a pouch. That advice was based on a guess, not evidence, and it turned out to be wrong. Large studies found no link between eating nuts, seeds, or popcorn and diverticulitis. In fact, those foods are often high in fibre, which is protective. I've apologised to my own colon since. The Mayo Clinic confirms that you don't need to avoid these foods.

During an acute episode, you may be told to stick to clear liquids or low-fibre foods for a few days to let the bowel rest. After you recover, the goal shifts to a high-fibre diet — vegetables, fruits, whole grains, legumes — along with enough water to keep things moving. Fibre softens stool and reduces pressure inside the colon, which is the main thing you can do to prevent future episodes. If you can't get enough from food, a fibre supplement like psyllium is a reasonable option, but start slowly or you'll learn about bloating the hard way.

Surgery: When and Why

Surgery for diverticulitis is not the first option, but it has a clear role. The most common operation is a sigmoid colectomy, removing the affected section of the colon and reconnecting the healthy ends. It's usually done laparoscopically — through small incisions with a camera — which means less pain and a faster recovery than open surgery.

Guidelines generally consider elective surgery after a complicated episode that required drainage, after repeated uncomplicated episodes that are affecting your quality of life, or if you develop a fistula or stricture. Emergency surgery is reserved for perforation with peritonitis or a blockage that won't resolve. My first surgical referral for diverticulitis was a man who had ignored symptoms for a week. Don't be that man. The decision is highly individual, and anyone facing it deserves a detailed conversation with a colorectal surgeon about risks, benefits, and alternatives.

Prevention and Long-Term Outlook

The best evidence for prevention points to the boring stuff: a high-fibre diet, regular physical activity, not smoking, and maintaining a healthy weight. Some studies also suggest that limiting red meat and getting enough vitamin D may help, though the evidence is less solid. Probiotics are popular, but the research doesn't yet support a clear benefit for preventing diverticulitis.

Most people who have one episode of uncomplicated diverticulitis recover fully and may never have another. About a third will have a recurrence, and the risk goes up after complicated episodes. The key is to know the symptoms, take them seriously, and work with your doctor on a plan that fits your situation. And if someone tells you to avoid nuts for the rest of your life, ask them for the evidence — then send them to me.

Photo by Ryan Thorpe on Unsplash