Diverticulitis

A diverticulum is a small outpouching. In the setting of diverticulitis this is actually the inner lining of the colon punching through and ballooning from an inherent weakness in the wall of the colon from where the blood vessels penetrate. Over years of pressure, the diverticulum herniates through these weak points. So it is thin walled, which is why it is so prone to complications such as rupture or perforation.

They form most commonly in the sigmoid colon, the last segment before the rectum. That is the narrowest part of the colon, and by simple physics the narrower the tube the higher the wall pressure for a given contraction. That is also why the sigmoid is where nearly all the trouble happens.

Simply having these pouches is called diverticulosis. It is extremely common. By age 60 a large fraction of people in Western countries have them and the overwhelming majority will go their entire lives without any problems. Diverticulosis by itself is not a disease and is not a reason for surgery.

Diverticulitis is what happens when one of those pouches becomes inflamed. What happens following inflammation can be highly variable. An entire segment of colon can just become inflamed and infected. Or a diverticulum or “tic” as we often refer them too can rupture. The mechanism is very close to what happens in appendicitis, which is why the two conditions can look and feel similar, just on opposite sides of the abdomen.

Was it something I ate?

This is a common question and the answer is no. A study in 2008 showed no increase in events with foods commonly feared to instigate diverticulitis such as popcorn, nuts, and seeds.

What does appear to matter over the long run is dietary fiber, physical activity, smoking, and body weight. Those are the same unglamorous levers that matter for most things, and none of them explain any single attack. Most of the time the honest answer to “why now?” is that we do not know.

Uncomplicated versus complicated

We think of diverticulitis in two broad buckets as this informs how we go about treatment: complicated or uncomplicated. Uncomplicated diverticulitis means inflammation without abscess, perforation, obstruction, or fistula. This is the large majority of episodes.

Once a diverticulum perforates, the consequences can range from mild to severe. Complicated diverticulitis means the perforation did something. We classify them using the Hinchey classification system and it ranges from stage 1 through 4. The mildest form is a small collection of inflammation or pus that stays right next to the colon. Most of these are treated with antibiotics alone and settle down.

Next is a larger abscess that has collected somewhere in the pelvis or abdomen. If it is above a certain size threshold and is in a location accessible to drain, the usual answer is antibiotics plus a drain placed by an interventional radiologist through the skin. Whether or not a radiologist can get to an abscess depends on a number of factors such as abscess size and whether there are any vital structures between the skin and the target.

The two most severe patterns are when the contamination is not walled off and spreads through the abdomen, either as pus or as stool. These are often surgical emergencies. Patients in this situation are usually quite ill or can become ill, and an emergency operation is often indicated to decrease the risk of worse complications.

What does the emergency operation involve?

This usually requires an open operation through a midline incision. The diseased segment of colon is then removed. Care has to be taken to often dissect this segment off as it can become stuck to many vital structures through the inflammatory process.

The question then becomes what to do with the two ends afterward.

Traditionally, the answer was a Hartmann’s procedure: remove the sigmoid, bring the upstream end of the colon out to the skin as a colostomy, and staple the rectum closed and leave it inside. This is an operation with a long history and is the go-to as a safe, fast, and reliable operation. Most of all it avoids the most consequential complication: a fresh connection that leaks. The cost is that the patient wakes up with a stoma, and reversing it later is a second operation, and in a minority of patients it becomes permanent.

The alternative is to reconnect the colon at the original operation, often with a kind of temporary ostomy to divert stool away from the fresh connection. Good evidence supports this approach in selected patients, and the practical advantage is that closing this connection (called a loop ileostomy) is usually a smaller operation than reversing a Hartmann’s. The trade-off is that it takes longer and is not appropriate in an unstable patient.

Which one your surgeon chooses depends on how sick you are, how contaminated the abdomen is, the quality of the tissue, and a fair amount of judgment in the moment.

Do I need surgery after I recover?

Historically, patients who have had two bouts often got surgery. The reality is that now the decision is individualized. There are many variables that go into the decision to undergo resection, including how complicated the episode was. Many of the patients that we meet on the surgical service have already self-selected for more severe presentations by sheer fact that we become involved.

One rule that has not changed: after an episode of diverticulitis, patients who have not had a recent colonoscopy should get one once everything has calmed down. Colon cancer can present in a way that is indistinguishable from diverticulitis on a CT scan, and that is not a diagnosis anyone wants to make late.

Fistulas

If a diverticular abscess sits against another structure long enough, it can erode into it and form an abnormal connection called a fistula. The most common is between the colon and the bladder. The symptoms are unmistakable once you have heard them: passing air in the urine, or urine that looks like it has stool in it, along with recurrent urinary infections that never fully clear. Fistulas do not heal on their own and are often an indication for surgery.

How will my body change after a sigmoid resection?

Most people do well. The colon’s main job is absorbing water, and the sigmoid is a small fraction of the whole, so major changes in digestion are uncommon. What patients most often report in the first few months is more frequent or looser bowel movements and a bit less warning before they need a bathroom. For most people this settles substantially by six months to a year as the remaining colon adapts.