Diverticulitis and Crohn’s disease are not the same condition. They can produce similar symptoms, particularly abdominal pain and changes in bowel habits, which is why they’re often confused. But they differ in what causes them, where they strike, how they’re diagnosed, and how they’re treated. In some cases, a person can even have both at the same time.
What Each Condition Actually Is
Diverticulitis starts with diverticulosis, a condition where small pouches (diverticula) form in weak spots along the colon wall. These pouches are extremely common, appearing in roughly 60% of people over age 60. Most people with diverticula never have problems. Diverticulitis happens when one or more of those pouches develops tiny tears, allowing bacteria to cause infection and inflammation. It’s essentially a structural problem that leads to a localized infection.
Crohn’s disease is a chronic autoimmune condition in which the immune system attacks the digestive tract, causing deep inflammation that extends through the full thickness of the intestinal wall. Unlike diverticulitis, Crohn’s isn’t triggered by a structural defect. It’s a systemic disease that can flare and remit over a lifetime, and its exact cause remains unclear, though genetics and immune dysfunction play central roles.
Where They Occur in the Body
Diverticulitis almost always affects the sigmoid colon, the S-shaped section on the lower left side of your abdomen. That’s why the hallmark symptom is left-sided abdominal pain. The inflammation stays localized around the affected pouch or pouches.
Crohn’s disease can involve any part of the gastrointestinal tract, from the mouth to the anus. It most commonly affects the end of the small intestine (the ileum) and the beginning of the colon, but it can appear in patches anywhere along the digestive system. These “skip lesions,” areas of inflammation separated by healthy tissue, are one of its defining features. Crohn’s also frequently causes perianal disease, including pain, swelling, and drainage around the anus, which diverticulitis does not.
How Symptoms Overlap and Differ
Both conditions cause abdominal pain, fever, and changes in bowel habits. That overlap is the main reason people wonder whether they might be the same disease. But the patterns differ in important ways.
Diverticulitis typically comes on suddenly. You feel sharp pain in the lower left abdomen, often with fever and sometimes nausea. It’s an acute episode that, once treated, may never return, though some people do have recurrent bouts. Between episodes, many people feel completely normal.
Crohn’s disease tends to develop more gradually and runs a chronic course with periods of flare and remission. Pain can occur anywhere in the abdomen depending on which part of the GI tract is involved. Crohn’s also produces symptoms you wouldn’t expect from diverticulitis: prolonged diarrhea (sometimes bloody), significant weight loss, fatigue, joint pain, skin rashes, and mouth sores. These “extraintestinal” symptoms reflect the systemic, immune-driven nature of the disease.
How Doctors Tell Them Apart
During a colonoscopy, the two conditions look very different. Diverticulitis shows inflamed tissue around the openings of diverticula, but the diverticula themselves are typically unaffected. The surrounding mucosa may be red and swollen, but the pattern is localized.
Crohn’s disease has a distinctive visual signature: deep longitudinal ulcers running parallel to the intestinal lumen, small shallow ulcers called aphthous ulcerations, and the classic “cobblestone appearance” where islands of swollen tissue sit between crisscrossing ulcer lines. Tissue biopsies in Crohn’s often reveal granulomas, clusters of immune cells that form when the body tries to wall off chronic inflammation. These findings don’t appear in diverticulitis.
CT scans also help. In diverticulitis, imaging typically shows thickening of the colon wall around diverticula with surrounding fat inflammation, and sometimes abscesses or free air from a perforation. In Crohn’s, imaging reveals thickened bowel segments that can appear anywhere, often with narrowing of the intestinal passage.
Different Complications
Both conditions can lead to serious complications, but the patterns differ. Diverticulitis can cause abscesses, perforation, and fistulas (abnormal tunnels connecting the colon to nearby organs). The fistula rate after an episode of acute diverticulitis is around 14%. The most common types connect the colon to the bladder, typically on the left posterior side of the bladder because of its close proximity to the sigmoid colon. Colon-to-small-intestine and colon-to-uterus fistulas also occur.
Crohn’s disease causes fistulas too, but in different locations. Fistulas in Crohn’s typically form between the terminal ileum and the right anterior surface of the bladder, reflecting the disease’s preference for the end of the small intestine. Crohn’s also causes strictures (narrowed sections of bowel from chronic scarring), which can lead to bowel obstruction over time. Perianal fistulas and abscesses are particularly common in Crohn’s and rare in diverticulitis.
Treatment Is Fundamentally Different
The treatment approach for each condition reflects their different underlying causes. Diverticulitis is an infection, so it’s treated like one. Mild cases may resolve with bowel rest and oral antibiotics. More severe episodes with abscesses or perforation can require hospitalization, IV antibiotics, drainage procedures, or surgery to remove the affected section of colon. Once an acute episode resolves, ongoing medication usually isn’t necessary.
Crohn’s disease requires long-term management aimed at calming the immune system. Treatment typically starts with anti-inflammatory medications and can escalate to immunosuppressive drugs, which are effective at inducing and maintaining remission in about 40% of patients after five years. For moderate to severe Crohn’s that doesn’t respond to those options, biologic therapies that block specific inflammatory signals are the standard of care. Combinations of immunosuppressives and biologics often produce better remission rates than either alone. Surgery is sometimes needed for complications like strictures or fistulas, but it doesn’t cure Crohn’s, and the disease frequently recurs at or near the surgical site.
Dietary Management
Dietary strategies differ for each condition, though both benefit from attention to what you eat. For diverticulitis, the long-standing advice has been to increase fiber intake between episodes to keep stool soft and reduce pressure in the colon. During an acute flare, a temporary low-fiber or liquid diet gives the colon time to heal.
Crohn’s dietary management is more complex. During severe flares, some patients benefit from exclusive enteral nutrition, a formula-based liquid diet followed for 4 to 12 weeks that can induce remission, particularly in children. For long-term management, whole-foods-based exclusion diets that eliminate wheat, animal fat, dairy, packaged foods, and artificial additives have shown promise in reducing gut inflammation. Increasing fruit and vegetable intake is generally recommended for Crohn’s patients, with the exception of those who have narrowed sections of bowel where high-fiber foods could cause blockages.
Can You Have Both?
Yes. Diverticula typically form in the sigmoid colon, and when someone with Crohn’s disease has left-sided inflammation in that same area, the two conditions can coexist. This overlap can make diagnosis tricky, since the inflammatory changes from one condition can mask or mimic the other. Doctors rely on the specific colonoscopy findings, particularly the presence or absence of granulomas, cobblestoning, and skip lesions, to sort out which condition is driving the symptoms.