The Dangers of Untreated Crohn’s Disease
Crohn's DiseaseTaking Control of Crohn’s

The Dangers of Untreated Crohn’s Disease

The Dangers of Untreated Crohn’s Disease
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Updated on January 15, 2026
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With Crohn’s disease, a form of inflammatory bowel disease (IBD), uncontrolled inflammation at any point during your illness can lead to dangerous complications. Whether you have symptoms of the condition but haven’t sought diagnosis, opted to go against your doctor’s recommendations and delay treatment, or your medication regimen isn’t working well to control your illness, you should understand the risks — including arthritis, complications that require surgery, and cancer.

That’s why it’s crucial to get a diagnosis for Crohn’s disease and start treatment to achieve remission from active inflammation as early as possible. A gastroenterologist can help you manage and treat the condition, thereby helping to reduce or delay your risk of developing certain complications.

Fistulas and Strictures

The early signs of active Crohn’s inflammation — also known as a flare (or a relapse, if you’ve had active inflammation before) — include diarrhea, abdominal cramping, and rectal bleeding. Over time, other, more serious complications can develop.

That’s because the inflammation caused by Crohn’s disease doesn’t occur in just one layer of the bowel wall. “It can spread throughout all the layers,” says Adam Cheifetz, MD, director of the center for inflammatory bowel disease at Beth Israel Deaconess Medical Center and a professor of medicine at Harvard Medical School in Boston.

This can lead to perianal fistulas — or tunnels that lead from the anal canal (rectum) to an external opening in the skin near the anus. This complication affects around one-third of people with Crohn’s, according to research, while Black people with the disease face even higher rates and often develop more severe fistulas.

Inflammation can also cause strictures, in which scar tissue narrows the intestinal wall, and can eventually lead to bowel obstructions — they occur in up to 54 percent of people with Crohn’s within 20 years of being diagnosed.

Once Crohn’s has progressed to the stage at which fistulas or strictures form, surgery is often necessary. Surgery is not a cure, however, says Dr. Cheifetz.

Surgery may be necessary when scar tissue causes a potentially dangerous situation, as with strictures. “Medicine may work to heal inflammation, but it doesn’t work on scar tissue,” says Michele Rubin, MSN, an inflammatory bowel disease advanced practice nurse at University of Chicago Medicine.

The longer the disease goes untreated, the more dangerous the effects of chronic inflammation become. Without properly managing Crohn’s using medication, you’ll increase the risk of complications, hospitalizations, disability, time off from work, surgery, and a decreased quality of life.

If symptoms lead you to suspect you may have Crohn’s, ask for a referral to a gastroenterologist who specializes in IBD. “[Preventing complications by starting treatment] is why an early diagnosis of Crohn’s disease is essential,” says Rubin.

Colorectal Cancer and Malnutrition

Crohn’s disease, particularly Crohn’s colitis, a type that only affects the colon, also increases the risk of colorectal cancer. The link between the two conditions isn’t as strong as it is for ulcerative colitis and colorectal cancer, but Cheifetz says that untreated inflammation in the colon poses one of the biggest risks for colon cancer.

Malnutrition is another common complication of untreated Crohn’s. It may develop based on the extent and location of bowel inflammation, says Rubin. The symptoms of active inflammation may make it difficult to eat, and its effects on the intestinal lining can reduce the absorption of nutrients.

“Prolonged inflammation also leads to a loss of weight and muscle mass,” Rubin says.

 Nutrient deficiencies resulting from Crohn’s may require diet changes and the addition of dietary supplements. If malnutrition becomes severe, some people may require enteral (through a tube) or parenteral (intravenous) feeding.

As many as 30 to 60 percent of people with Crohn’s also develop low bone density (osteopenia, osteomalacia, or osteoporosis) as the result of prolonged inflammation, malabsorption of calcium and vitamin D, or steroid use.

Many people with Crohn’s disease opt to work with a registered dietitian who specializes in IBD to develop a flexible, nutrient-dense diet plan that can accommodate both its symptoms and the effects of inflammation.

Extraintestinal Complications of Crohn’s

Though Crohn’s inflammation affects the gastrointestinal (GI) system most prominently, it can also impact other organ systems via so-called extraintestinal complications (manifestations). An estimated 25 to 40 percent of people with IBDs experience such complications, which often occur in the skin, joints, eyes, liver, and kidneys.

Extraintestinal complications include:

  • Arthritis Some form of joint inflammation with pain and stiffness may affect as many as 30 percent of people with IBD, regardless of age.
  • Skin Up to 20 percent of people with IBD experience skin complications, such as canker sores, skin tags, lesions that join to form chronic ulcers (pyoderma gangrenosum), or sensitive red bumps, usually on the shins (erythema nodosum).
  • Kidneys Atypical protein buildup (amyloidosis), kidney stones, inflammation (glomerulonephritis), and other renal conditions can also occur in IBD.
  • Liver Conditions Fatty (steatotic) liver disease, chronic inflammation of the bile ducts (primary sclerosing cholangitis), and inflammation (hepatitis), among other liver conditions, can also develop in people with IBD.
  • Eyes Around 10 percent of people with IBD have ocular complications, including dry eyes, corneal inflammation (keratopathy), and inflammation of other eye structures (uveitis).
One research review found that up to 24 percent of people with IBD actually experience extraintestinal complications before they ever experience GI-related symptoms. Researchers noted that, generally, arthritis in the large joints of the arms and legs, canker sores, a type of eye inflammation (episcleritis), and the erythema nodosum rash were all connected with active intestinal inflammation. But other non-GI complications, such as a type of spinal arthritis (ankylosing spondylitis) tend to develop during both remission and relapse, independent of inflammation levels.

Avoiding the Dangers of Untreated Crohn’s

If Crohn’s inflammation isn’t being treated with medication, you may be increasing your risk of serious, potentially life-threatening, complications.

 But even if you have mild Crohn’s without active inflammation and have done fine over a number of years without the disease progressing, Cheifetz says that you still need to be monitored closely, so that any changes in your condition can be addressed quickly.

He also says that it’s important to get treated and be monitored carefully if you have moderate-to-severe Crohn’s, to make sure your medication regimen is working and that the disease isn’t progressing.

“Part of our goal is to treat the disease while it’s inflammatory, when Crohn’s will respond to the medication and we can prevent these progressive changes and complications,” Cheifetz says.

While all medications have potential side effects, you can work with your gastroenterologist to balance the risks and benefits of a treatment regimen that keeps your Crohn’s-related inflammation in check. Maintaining remission from inflammation is key to avoiding complications, and for most people with the illness, medication is an important part of managing it.

The Takeaway

  • Untreated Crohn’s disease and the inflammation it causes can lead to dangerous and even life-threatening complications.
  • Complications that can develop due to inflammation include fistulas and strictures, which often require surgery.
  • Uncontrolled inflammation can also cause malnutrition and increase the risk of colorectal cancer.
  • Crohn’s inflammation can also lead to extraintestinal complications like arthritis, skin conditions, and eye, kidney, and liver issues.

Resources We Trust

EDITORIAL SOURCES
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Resources
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Waseem Ahmed, MD

Medical Reviewer

Waseem Ahmed, MD, is an assistant professor of medicine in the Karsh Division of Gastroenterology and Hepatology at Cedars-Sinai Medical Center in Los Angeles and serves as Director, Advanced Inflammatory Bowel Disease Fellowship and Education within the F. Widjaja Inflammatory Bowel Disease Institute.

He received his undergraduate degree from the University of Michigan and attended medical school at Indiana University. He then completed an internal medicine residency at New York University, followed by a fellowship in gastroenterology and hepatology at Indiana University, and an advanced fellowship in inflammatory bowel disease at the Jill Roberts Center for Inflammatory Bowel Disease at New York-Presbyterian Hospital/Weill Cornell Medicine. Prior to his current role, Dr. Ahmed served as an assistant professor of medicine within the Crohn’s and Colitis Center at the University of Colorado from 2021-2024.

Dr. Ahmed is passionate about providing innovative, comprehensive, and compassionate care for all patients with inflammatory bowel disease (IBD). His research interests include IBD medical education for patients, providers, and trainees; clinical trials; acute severe ulcerative colitis; and the use of combined advanced targeted therapy in high-risk IBD.

He enjoys spending time with his wife and dog, is an avid follower of professional tennis, and enjoys fine dining.

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Jen Laskey is a writer, editor, and content strategist. She has worked on EverydayHealth.com in various capacities since its inception, and her writing has appeared in many major publications, including SAVEUR magazine, EatingWell magazine, NBC, TODAY, and Fodor's Travel guides. She has also served as the senior editorial director of Twill Health, leading editorial strategy and daily operations for Twill's health and mental health apps.

In addition to writing about health, mental health, and wellness, Laskey writes regularly about food, wine/spirits, travel, and the arts. She is the author of Jen’s Candy Jar: Artisanal Candy Recipes for Special Occasions and is the founding executive editor of the multi-award-winning wine & spirits online trade magazine SevenFifty Daily.

She holds bachelor’s and master’s degrees in writing from Bennington College and Columbia University.

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