Crohn’s disease

Causes

• Genetics:
  • Crohn's disease often runs in families. If you have a close relative with the disease, your risk is significantly higher.
  • Several genes have been identified as increasing susceptibility, including NOD2/CARD15.
• Immune System Reaction:
  • It's thought that a virus or bacterium may trigger an abnormal immune response in genetically predisposed individuals.
  • Instead of fighting off the invading pathogen, the immune system mistakenly attacks healthy cells in the digestive tract, leading to chronic inflammation.
  • This involves an overactive inflammatory response against the normal bacteria in the gut.
• Environmental Factors:
  • Smoking: This is the most significant controllable risk factor for Crohn's disease. Smokers are twice as likely to develop Crohn's disease and tend to have more severe symptoms and a higher risk of relapse.
  • NSAIDs: Nonsteroidal anti-inflammatory drugs (e.g., ibuprofen, naproxen) do not cause Crohn's disease but can worsen inflammation and increase the risk of flare-ups.
  • Diet: While not a cause, a diet high in fat or refined foods may play a role in increasing risk, possibly by altering gut microbiome.
  • Geography: Crohn's disease is more common in developed countries and urban areas, suggesting environmental influences.
  • Oral Contraceptives: Some studies suggest a weak link, but evidence is inconclusive.
• Gut Microbiome: Imbalances in the trillions of bacteria living in the gut may contribute to the development or progression of Crohn's disease, leading to an abnormal immune response.

Symptoms

• Digestive Symptoms:
  • Abdominal Pain and Cramping: Often in the lower right abdomen, but can occur anywhere along the GI tract. Pain can be severe and persistent.
  • Diarrhea: Often chronic, sometimes bloody, especially if the large intestine is involved.
  • Rectal Bleeding: Can occur, though more common in ulcerative colitis.
  • Weight Loss: Due to poor appetite, malabsorption, and inflammation.
  • Fever.
  • Fatigue.
  • Reduced Appetite.
  • Anal or Perianal Problems: (More specific to Crohn's)
    • Fistulas: Tunnels that burrow from the intestine through to the skin around the anus, or to other organs (e.g., bladder, vagina).
    • Abscesses: Collections of pus.
    • Fissures: Tears in the anal lining.
    • Skin tags.
• Complications (Severe Cases):
  • Bowel Obstruction: Caused by scarring and narrowing of the intestine (strictures). Can lead to severe cramping, nausea, vomiting, and constipation.
  • Fistulas and Abscesses: As described above, can lead to infection and pain.
  • Malnutrition and Vitamin Deficiencies: Due to malabsorption, especially of iron, B12, vitamin D.
  • Anemia: From chronic bleeding or malabsorption.
  • Ulcers: Sores can develop anywhere in the GI tract.
  • Inflammation in Other Body Parts (Extraintestinal Manifestations):
    • Joint pain and arthritis.
    • Skin disorders (e.g., erythema nodosum, pyoderma gangrenosum).
    • Eye inflammation (e.g., uveitis, episcleritis).
    • Liver or bile duct inflammation (e.g., primary sclerosing cholangitis, though more common in UC).
    • Kidney stones.
    • Osteoporosis.
  • Increased Risk of Colon Cancer: If the colon is involved for a long duration.

Diagnosis

• Medical History and Physical Exam: The doctor will ask about symptoms, family history, and lifestyle factors. An exam may reveal abdominal tenderness or masses.
• Blood Tests:
  • Complete Blood Count (CBC): To check for anemia (low red blood cells) or elevated white blood cells (indicating inflammation/infection).
  • Inflammatory Markers: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) indicate inflammation.
  • Nutrient Deficiencies: Checks for iron, vitamin B12, vitamin D levels.
• Stool Tests: To rule out infections (e.g., bacterial, viral, parasitic) that cause similar symptoms, and to check for blood or inflammatory markers (e.g., fecal calprotectin).
• Endoscopic Procedures (to visualize and biopsy the GI tract):
  • Colonoscopy: A thin, flexible tube with a camera is inserted into the rectum to view the entire colon and the end of the small intestine (terminal ileum). Biopsies are taken to check for characteristic inflammation patterns (skip lesions, granulomas).
  • Upper Endoscopy: To examine the esophagus, stomach, and upper small intestine if symptoms suggest upper GI involvement.
  • Capsule Endoscopy: You swallow a tiny camera capsule that takes pictures as it passes through the small intestine, useful for areas not reached by traditional endoscopy.
  • Balloon-Assisted Enteroscopy: Allows direct visualization and biopsy of deeper parts of the small intestine.
• Imaging Tests (to identify inflammation, strictures, or fistulas):
  • CT Enterography or MR Enterography (MRE): Specialized CT or MRI scans that provide detailed images of the small intestine. They are excellent for identifying inflammation, strictures, fistulas, and abscesses.
  • Abdominal X-rays or Barium Studies: (Less common now with advanced imaging).

Treatment

• Medications:
  • Anti-inflammatory Drugs:
    • Aminosalicylates (5-ASAs): (e.g., mesalamine) Mild to moderate inflammation, often for colon involvement. Less effective for small intestine Crohn's.
    • Corticosteroids: (e.g., prednisone, budesonide) Used for short-term control of flare-ups due to significant side effects with long-term use.
  • Immunomodulators: Suppress the immune system to reduce inflammation (e.g., azathioprine, mercaptopurine, methotrexate). Take time to work but can maintain remission.
  • Biologics (TNF-alpha Inhibitors, Integrin Inhibitors, Interleukin Inhibitors): Targeted therapies that block specific proteins involved in the inflammatory process. Used for moderate to severe Crohn's, often when other treatments fail. Examples:
    • TNF-alpha inhibitors: infliximab (Remicade), adalimumab (Humira), certolizumab pegol (Cimzia).
    • Integrin inhibitors: vedolizumab (Entyvio).
    • Interleukin inhibitors: ustekinumab (Stelara).
  • Antibiotics: To treat abscesses, fistulas, or bacterial overgrowth (e.g., metronidazole, ciprofloxacin).
  • Anti-Diarrheal Medications: (e.g., loperamide) Used for symptom relief, but with caution during severe flares due to risk of toxic megacolon.
  • Pain Relievers: (e.g., acetaminophen) Avoid NSAIDs unless specifically advised by a doctor.
• Nutritional Support:
  • Dietary Modifications: Identifying and avoiding trigger foods (e.g., high-fiber, fatty foods, dairy for lactose intolerance) during flares. A balanced diet is important during remission.
  • Nutritional Supplements: To correct deficiencies (e.g., iron, B12, vitamin D, calcium).
  • Enteral or Parenteral Nutrition: (Liquid diets or IV feeding) may be needed for severe malnutrition or during severe flares to allow the bowel to rest.
• Surgery:
  • Not a cure, but often necessary for complications. The goal is to remove damaged sections of the bowel while preserving as much healthy intestine as possible.
  • Common surgeries: Strictureplasty (widening narrowed sections), resection (removing diseased sections), draining abscesses, repairing fistulas.
  • Recurrence after surgery is common, so medical therapy usually continues.

Living With Crohn's Disease

Crohn's disease differs from ulcerative colitis in one way that shapes everything: inflammation left to smolder becomes scar, and scar responds to no medication. Getting inflammation controlled early, and proving it rather than assuming it, is what protects the bowel.

Why steroids are a bridge and biologics come early

Prednisone or gut-targeted budesonide settles a flare but does not heal the bowel lining, and needing steroids twice in a year means the maintenance plan is inadequate. For moderate or severe disease, a biologic such as infliximab, adalimumab, or risankizumab, or the oral JAK inhibitor upadacitinib, is now started early rather than held back as a last resort. Mesalamine, useful in ulcerative colitis, does little in Crohn's. Success is judged by a normal stool calprotectin and healed bowel on imaging or endoscopy, not by feeling well.

Smoking is the one factor entirely in your hands

Smokers flare more often, need more surgery, and relapse sooner after it, and quitting improves the course substantially. Treating nicotine dependence with medication is part of Crohn's care; our smoking cessation guide covers the options.

Not every symptom is a flare

Cramping and bloating after high-fiber meals can mean a stricture rather than active inflammation. Watery diarrhea after removal of the last part of the small bowel is often bile acid malabsorption, which responds to a bile acid binder rather than more immunosuppression. Bacterial overgrowth, C. difficile infection, and the overlap with irritable bowel syndrome are tested for before treatment is escalated; our IBS versus IBD article explains the difference. NSAIDs such as ibuprofen can trigger flares and are avoided in favor of acetaminophen.

Deficiencies, bones, stones, and vaccines

Disease or surgery at the end of the small bowel causes vitamin B12 deficiency, checked yearly and replaced by injection when absorption is the problem. Iron deficiency is treated intravenously during active disease, vitamin D deficiency is common, and repeated steroid courses call for a bone density test for osteoporosis. Fat malabsorption raises the risk of kidney stones, which Florida heat compounds. Before a biologic, tuberculosis and hepatitis B are screened for, and live vaccines are avoided while on one.

Emergencies and perianal disease

Vomiting with a swollen abdomen and no gas passing is a bowel obstruction; fever with severe localized pain suggests an abscess; both need same-day assessment. New pain or drainage around the anus means a fistula, mapped by MRI and treated with ciprofloxacin or metronidazole, a biologic, and often a surgical drain together. Our gastrointestinal team coordinates care with gastroenterology and surgery. The NIDDK and the Crohn's and Colitis Foundation publish patient guidance on treatment and living well.

If you have needed steroids more than once this year, still smoke, or have never had a calprotectin or imaging check while feeling well, schedule a visit.