What is Inflammatory Bowel Disease?
 

Inflammatory Bowel Disease (IBD) is a term for chronic, immune-mediated conditions characterized by persistent inflammation of the gastrointestinal (GI) tract.

It involves destructive inflammation, tissue damage, and potential long-term complications. It primarily encompasses two major conditions: Crohn's Disease and Ulcerative Colitis.
 

Crohn's Disease

It can affect any part of the GI tract from mouth to anus. It most commonly involves the terminal ileum and colon. "Skip lesions"—areas of active inflammation interspersed with healthy, normal tissue. Inflammation extends through all layers of the intestinal wall (mucosa to serosa). Perianal Disease is common (fistulas, perianal abscesses, skin tags, and anal fissures). "Cobblestoning" appearance, deep linear ulcerations, and strictures may be seen. Non-caseating granulomas may sometimes be seen on biopsy.

Ulcerative Colitis

It is confined strictly to the colon (large intestine) and rectum. It extends proximally in a continuous fashion. There is continuous inflammation starting at the rectum and extending uniformly upward without skipped areas. Inflammation is limited to the innermost lining of the colon. Continuous mucosal erythema, friability, loss of vascular pattern, and superficial ulcerations may be seen. Crypt abscesses, crypt distortion, and absence of granulomas may be seen on biopsy.

Pathophysiology & Risk Factors
 

• Immune Dysregulation: An overly aggressive T-cell mediated response triggers chronic mucosal inflammation, tissue destruction, and cytokine release (e.g., TNF-alpha, IL-12, IL-23).

• Genetic Susceptibility: Over 200 genes are linked to altered gut immunity and bacterial sensing.

• Environmental & Lifestyle Factors: Smoking significantly worsens Crohn's disease risk and severity, whereas smoking cessation can strangely trigger flares in Ulcerative Colitis. Westernized diets high in ultra-processed foods and low in dietary fiber, as well as frequent NSAID use, can disrupt gut barrier integrity.

Common Symptoms
 

Gastrointestinal Symptoms
 

• Persistent diarrhea (often bloody in Ulcerative Colitis; can be watery or mucus-filled in Crohn's Disease)

• Cramping, severe abdominal pain (frequently right lower quadrant in Crohn's; left lower quadrant or diffuse in UC)

• Urgency to defecate and tenesmus (the painful feeling of incomplete bowel evacuation, classic in UC)

• Unintended weight loss, chronic fatigue, low-grade fever, and growth delay in pediatric patients

Extraintestinal Manifestations (Systemic Involvement)

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• Joints: Peripheral inflammatory arthritis, ankylosing spondylitis, or sacroiliitis.

• Skin: Erythema nodosum (tender red nodules usually on the shins) or pyoderma gangrenosum (painful, necrotic skin ulcers).

• Eyes: Episcleritis, scleritis, or anterior uveitis (causing eye redness, pain, and light sensitivity).

• Hepatobiliary: Primary Sclerosing Cholangitis (PSC)—a chronic liver/bile duct inflammation strongly associated with Ulcerative Colitis.

• Bone: Accelerated osteopenia and osteoporosis from chronic inflammation and corticosteroid use.

Potential Long-Term Complications
 

Crohn's Disease
 

• Strictures & Bowel Obstruction: Transmural scar tissue narrows the intestinal lumen, causing blockages.

• Fistulas & Abscesses: Deep transmural inflammation forms abnormal tunnels connecting the bowel to other bowel loops, bladder, vagina, or skin (especially perianal fistulas).

• Malabsorption & Nutritional Deficiencies: Vitamin B12 deficiency, fat-soluble vitamin (A, D, E, K) deficiencies, and bile acid diarrhea due to terminal ileum involvement.

Ulcerative Colitis
 

• Toxic Megacolon: A life-threatening, acute dilation of the colon accompanied by severe systemic toxicity and risk of bowel perforation.

• Severe Gastrointestinal Bleeding: Profuse mucosal ulceration leading to acute, life-threatening blood loss and severe anemia.

• Colorectal Cancer Risk: Long-standing mucosal inflammation increases dysplasia and colorectal cancer risk, requiring routine surveillance colonoscopies starting 8 years after diagnosis. This does not apply to ulcerative proctitis. 

Diagnostics
 

• Laboratory Studies: Elevated inflammatory markers (CRP, ESR), anemia on CBC, low serum albumin, and elevated fecal calprotectin or fecal lactoferrin (non-invasive stool markers that distinguish active IBD inflammation from functional IBS).

• Endoscopy & Colonoscopy with Biopsy: The cornerstone of diagnosis. Allows direct visualization of mucosal patterns and tissue sampling to evaluate for granulomas, crypt distortion, and depth of inflammation.

• Diagnostic Imaging: CT or MR Enterography is preferred to visualize small bowel wall thickening, strictures, or fistulas in Crohn's disease without exposing patients to repeated radiation.

Management
 

• 5-Aminosalicylates (5-ASAs – e.g., Mesalamine, Sulfasalazine): First-line therapy for inducing and maintaining remission in mild-to-moderate Ulcerative Colitis. Less effective in Crohn's disease.

• Corticosteroids (e.g., Prednisone, Budesonide): Highly effective for rapid control of acute flares. Not used for long-term maintenance due to severe systemic side effects (bone loss, glucose intolerance, infection risk).

• Immunomodulators (e.g., Azathioprine, 6-Mercaptopurine, Methotrexate): Used as steroid-sparing maintenance agents or in combination with biologic agents.

• Biologics & Targeted Small Molecules:

  • Anti-TNF Agents (e.g., Infliximab, Adalimumab): Potent biological agents for moderate-to-severe Crohn's and UC.

  • Anti-Integrin Agents (e.g., Vedolizumab): Gut-selective biological therapies that block lymphocyte migration into the inflamed intestinal mucosa.

  • Anti-IL-12/23 & IL-23 Inhibitors (e.g., Ustekinumab, Risankizumab): Block inflammatory cytokine pathways.

  • JAK Inhibitors (e.g., Tofacitinib, Upadacitinib): Oral small-molecule options for moderate-to-severe UC.

• Surgical Interventions:

  • Ulcerative Colitis: Proctocolectomy with Ileal Pouch-Anal Anastomosis (IPAA / J-pouch) is considered curative for the intestinal manifestations of UC because disease is limited to the colon and rectum.

  • Crohn's Disease: Surgery (strictureplasty, localized bowel resection) is non-curative and reserved for complications like strictures, non-healing fistulas, or severe abscesses, with a focus on conserving as much healthy bowel length as possible.