Crohn’s Disease Complications: What to Know and When to Get Help

By Anna Curran, RN, BSN, PHN · Last reviewed October 2026

Crohn’s disease complications are problems that happen when long-term inflammation damages the bowel or affects other parts of the body. The most common ones include narrowing of the bowel (strictures), tunnels called fistulas, pockets of infection called abscesses, anemia, poor nutrition and bone loss. Many can be prevented or caught early with good treatment and regular checkups.

Here is what each complication is, what it can feel like and when you need help right away.

Why Crohn’s Disease Complications Happen

Crohn’s can inflame the full thickness of the bowel wall. Over time, that deep inflammation can scar the bowel, tunnel through it or keep your body from absorbing food well. It can also affect the eyes, skin, joints, bones and liver.

The best way to lower your risk is to keep inflammation under control with the plan you and your doctor choose. Our guide to Crohn’s disease treatment options explains the choices.

Strictures and Bowel Obstruction

A stricture is a narrowed section of bowel. Mayo Clinic explains that parts of the bowel can scar and narrow over time, which may block the flow of digestive contents.

When food and stool cannot pass through, that is a bowel obstruction, or blockage.

Signs of a possible blockage:

Cramping belly pain that comes in waves
A swollen or bloated belly
Nausea and vomiting
Not being able to pass gas or stool

A blockage is an emergency, so go to the ER for these signs. If you have a known stricture, your care team may suggest a low-fiber diet. Our Crohn’s disease diet guide explains how that works.

Fistulas

A fistula is an abnormal tunnel that connects two places that do not normally connect. Mayo Clinic notes that ulcers can tunnel through the bowel wall and that fistulas near or around the anus are the most common kind.

Fistulas can also connect the bowel to another loop of bowel, the bladder, the vagina or the skin of the belly.

Possible signs of a fistula:

Pain, swelling or drainage near the anus
Pus or stool leaking from an opening in the skin
Passing gas or stool through the vagina
Gas or cloudy urine when you pee, or frequent bladder infections

Call your doctor if you notice any of these. Some fistulas heal with medicine, and others need a procedure.

Abscesses

An abscess is a pocket of pus caused by infection. Cleveland Clinic describes abscesses in Crohn’s as infected, pus-filled pockets in the belly or near the anus. They often form along with a fistula.

Watch for:

Fever or chills
A painful, tender, swollen lump near the anus
Belly pain in one spot that keeps getting worse
Feeling very sick or run down

Mayo Clinic warns that abscesses in the belly can be life-threatening. Abscesses usually need antibiotics, and many need to be drained.

Anemia

Anemia means you do not have enough healthy red blood cells to carry oxygen through your body. The Crohn’s & Colitis Foundation calls it the most common blood-related complication of IBD, affecting up to one in three people with IBD.

In Crohn’s, anemia can come from:

Slow blood loss from the bowel
Poor absorption of iron, vitamin B12 or folate
Ongoing inflammation itself

Vitamin B12 is absorbed in the last part of the small intestine (the ileum). The Crohn’s & Colitis Foundation notes that when part of the ileum is removed in surgery, B12 can be harder to absorb. If your Crohn’s affects that area, your B12 level is worth watching.

Signs of anemia include feeling tired or weak, pale skin, shortness of breath and dizziness. The Foundation’s health checklist suggests checking blood counts, iron and vitamin B12 every year or during flares. Talk with your doctor before starting any supplement.

Malnutrition

Mayo Clinic notes that diarrhea, belly pain and cramping can make it hard to eat or absorb enough nutrients. Watch for weight loss without trying, low energy, muscle loss and, in children, slow growth. A registered dietitian who works with IBD can help you get enough calories and protein.

Bone Loss

People with Crohn’s are more likely to have thin, weak bones (osteoporosis). The Crohn’s & Colitis Foundation lists three main drivers: steroid medicines, inflammation and poor absorption of calcium and vitamin D.

The Foundation recommends a bone density scan (DXA) for people with IBD who have any risk factor for osteoporosis. Risk factors include:

More than three months of steroid use in total
Smoking
Low body weight
Poor nutrient absorption

If your first scan is normal, it is usually repeated in about five years. Walking, enough calcium and vitamin D, and keeping steroid use short all help protect your bones.

Colon Cancer Screening

Long-term inflammation in the colon raises the risk of colorectal cancer. Mayo Clinic notes that the risk goes up when Crohn’s affects more than one-third of the colon, and that screening usually begins about 8 to 10 years after diagnosis.

The Crohn’s & Colitis Foundation says people at higher risk should have surveillance colonoscopies every 1 to 3 years, depending on their risk. You may need yearly exams if you have:

Primary sclerosing cholangitis (PSC), a liver and bile duct disease
Past precancerous changes (dysplasia) or a stricture in the colon
A parent, brother, sister or child who had colorectal cancer before age 50

Ask your gastroenterologist when your next colonoscopy should be.

Eye, Skin and Joint Problems

Some of these problems flare when your gut flares, and some do not.

Eyes

According to the Crohn’s & Colitis Foundation, eye problems affect about 2% to 5% of people with IBD:

Episcleritis causes redness and mild irritation of the white of the eye. It does not usually harm vision and tends to follow gut flares.
Uveitis causes eye pain, blurry vision and pain in bright light. It can happen even when your gut is calm. It needs urgent care from an eye doctor to protect your vision.
Scleritis causes deep, severe eye pain and can threaten vision. It also needs urgent care.

Skin

Erythema nodosum causes red, tender bumps under the skin. It tends to follow gut flares and often improves when your Crohn’s is treated.
Pyoderma gangrenosum causes painful skin ulcers. The Foundation notes it affects fewer than 2% of people with IBD, but it needs prompt treatment.

Mayo Clinic also notes a link with hidradenitis suppurativa, which causes deep, painful lumps in areas like the armpits and groin.

Joints

Arthritis in a few joints often follows gut flares, while arthritis in many joints can flare on its own schedule. Tell your doctor about joint pain, and ask before taking ibuprofen or naproxen, which can worsen Crohn’s.

Other Complications to Know

Blood clots. Mayo Clinic lists Crohn’s disease as a risk factor for deep vein thrombosis (DVT), a clot in a deep vein. Watch for one leg that is swollen, painful, warm or a different color.
Kidney stones. Diarrhea and dehydration can raise your risk.
Liver and bile duct problems. These are less common in Crohn’s but can happen.
Medicine side effects. Some medicines that calm the immune system raise the risk of infections and certain cancers. The Foundation suggests a yearly full-body skin check if you take them.

When to Go to the ER

Call 911 or go to the emergency room if you have:

Signs of a bowel blockage: cramping belly pain, a swollen belly, vomiting, and not passing gas or stool
Severe or constant belly pain
Heavy rectal bleeding or passing blood clots
A high fever with belly pain, or a fever while you take a medicine that weakens your immune system
Vomiting so much that you cannot keep liquids down
Sudden shortness of breath, chest pain that is worse when you breathe in, coughing up blood or fainting, which can be signs of a blood clot in the lungs
Sudden eye pain with vision changes or pain in bright light

Call your doctor the same day for new pain, swelling or drainage near the anus, or a swollen, painful leg.

Frequently Asked Questions

What is the most common complication of Crohn’s disease?

Anemia is one of the most common, affecting up to one in three people with IBD. Strictures and fistulas around the anus are also common complications in the gut.

Can Crohn’s disease complications be prevented?

Not always, but keeping inflammation under control lowers your risk. Take your medicine as prescribed and keep up with lab work and screenings.

How often do I need a colonoscopy with Crohn’s?

It depends on how much of your colon is affected and your other risk factors. Many people with Crohn’s in the colon start screening 8 to 10 years after diagnosis, then repeat it every 1 to 3 years. Your gastroenterologist will set your schedule.

The Bottom Line

Crohn’s disease complications can affect the bowel, the blood, the bones and even the eyes, skin and joints. Strictures, fistulas and abscesses are the main problems in the gut, while anemia, malnutrition and bone loss affect the whole body. Regular lab work, bone scans when needed and colon cancer screening help catch problems early. Know the signs of a blockage, abscess or blood clot, and get emergency care right away when they appear.