In-Depth Notes on Inflammatory Bowel Disease, IBS, and Diverticulosis

Inflammatory Bowel Disease (IBD) Epidemiology

• Geographic variability: Higher prevalence in Northern countries, lower rates in Asia/South America.

• Increasing Incidence: Worldwide incidence is rising, including in Asia.

• Demographics: Affects men and women equally.

• Age Distribution: Most commonly diagnosed between 15-30 years, with another peak in the 50-60 range. This results in a bimodal age distribution.

Inflammatory Bowel Disease (IBD) Etiology

• Genetics: Increased risk among family members, indicating a genetic predisposition.

• Microbiome & Enteric Flora: Alterations in gut microbiota contribute to disease development.

• Lifestyle and Dietary Modifications:

  • Smoking: Increases risk of Crohn’s disease and disease flare-ups; decreases risk of Ulcerative Colitis.

  • Diet and Physical Activity: Role in disease modulation.

• External Environment: Higher socioeconomic status associated with IBD prevalence.

Inflammatory Bowel Disease (IBD) Pathophysiology

• Complex Interplay: Involves genetics, immune dysfunction, and the microbiome.

• Genetic Influence: Family history indicates a significant genetic component.

• Immune Dysregulation: Results in inappropriate inflammation due to defects in the cell-mediated and humoral immune systems.

Clinical Presentation of Crohn’s Disease

• Symptoms:

  • Cramping abdominal pain

  • Diarrhea

  • Fatigue

  • Weight loss

  • Palpable masses or phlegmon

  • Perianal disease

• Complications:

  • Fistulas (e.g., enteroenteric, enterovesical)

  • Odynophagia and dysphagia in cases of esophageal involvement.

Clinical Presentation of Ulcerative Colitis

• Symptoms:

  • Colicky abdominal pain

  • Bloody diarrhea

  • Fatigue

  • Weight loss

  • Urgency with frequent, small-volume bowel movements

  • Tenesmus

  • Fever

Presentation Overview

• Crohn’s Disease: Can occur anywhere in the GI tract, most commonly in the terminal ileum, characterized by "skip" lesions, transmural inflammation, and fistulas.

• Ulcerative Colitis: Continuous mucosal inflammation limited to the colon, starting from the rectum without penetrating disease. Can lead to severe complications such as severe bleeding and toxic megacolon.

Physical Examination Findings in IBD

• Assess for:

  • Abdominal pain

  • Blood in stool

  • Perianal skin tags

  • Sinus tracts

• Extra-Intestinal Manifestations (approx. 40% of IBD cases): Includes oral ulcers, arthritis, eye involvement (e.g., uveitis), skin conditions (e.g., erythema nodosum), renal stones, and possible pulmonary involvement.

Objective Evaluation of Crohn’s Disease

• Endoscopy Findings:

  • Discontinuous distribution of lesions.

  • Patchy edema, erythema, aphthous ulcerations.

  • Histopathological findings include transmural inflammation and non-caseating granulomas.

Objective Evaluation of Ulcerative Colitis

• Endoscopy Findings:

  • Continuous lesions from the rectum.

  • Findings include edema, erythema, loss of vascularity, and spontaneous bleeding.

  • Histopathology shows chronic inflammation of the mucosal layer without transmural involvement.

Imaging and Classification

• Patients should undergo small bowel imaging (CT or MRI) to evaluate small bowel involvement.

• About 15% of IBD patients are classified as IBD unclassified (IBDU).

Treatment Goals for IBD

• Focus on improving quality of life, inducing remission, and avoiding surgery.

• Medications:

  • First-line treatment for Ulcerative Colitis: Aminosalicylates (e.g., Mesalamine).

  • Steroids for remission induction in both types.

  • Immunomodulators (e.g., Azathioprine) and Biologics (e.g., Anti-TNF) are used in moderate to severe cases.

Prognosis of Crohn’s Disease

• Chronic and intermittent symptoms.

• Some patients may achieve remission but face a high risk of complications and surgery over time.

• Increased risk of colorectal cancer and slightly higher mortality compared to the general population.

Prognosis of Ulcerative Colitis

• Characterized by intermittent exacerbations; selective patients may not achieve remission.

• Approximately 20-30% may need colectomy, leading to a higher risk of colorectal cancer and slight mortality increase compared to the general population.

Irritable Bowel Syndrome (IBS) Epidemiology

• Prevalence: Affects 5-15% of Western populations; global prevalence is approximately 11.2%.

• Females are more commonly affected than males, typically under 50 years old at diagnosis.

IBS Definition according to Rome IV Criteria

• Characterized by recurrent abdominal pain at least once per week for three months, onset at least six months prior. Symptoms should link to defecation, stool frequency, or stool form changes.

• Symptoms Indicative of Organic Disease: Unexplained weight loss, fever, gastrointestinal bleeding, nocturnal symptoms.

IBS Subtypes

• IBS with constipation.

• IBS with diarrhea.

• Mixed IBS (alternating bowel habits).

• IBS unclassified (cannot be categorized into the above groups).

IBS Etiology

• Psychosocial factors, particularly seen in those under 50 and females.

• Genetic predisposition and history of post-infectious IBS.

IBS Pathophysiology

• Involves the brain-gut axis, GI motility issues, visceral hypersensitivity, and gut microbiome alterations.

• Symptoms can be affected by dietary triggers (e.g. carbohydrates, gluten).

Clinical Presentation of IBS

• Chronic abdominal pain is the primary symptom, along with bloating, diarrhea, constipation, and alternating bowel habits.

IBS Objective Evaluation

• Comprehensive history to assess symptoms associated with dietary triggers and previous GI infections.

• Physical exam typically reveals no significant findings.

Laboratory Evaluation for IBS

• No definitive lab tests for IBS; testing aims to exclude other diagnoses (CBC, stool testing, etc.).

• Appropriate screening for colorectal cancer in patients above specific age thresholds.

IBS Treatment Strategies

• Lifestyle and dietary modifications: Identifying and avoiding trigger foods (e.g., FODMAP diet).

• Pharmacologic treatments vary by subtype: fiber supplements, loperamide for diarrhea, and antispasmodics for pain.

IBS Prognosis

• A chronic relapsing condition with variations in subtype. Outcomes may worsen with prior surgeries, longer disease duration, increased comorbid anxiety/depression, and significantly impacts quality of life.

Diverticulosis Epidemiology

• Prevalence increases with age, with 1/3 of adults under 50 and over 70% of adults greater than 80 in the U.S.

Diverticulosis Etiology

• Divergent contributors: Congenital factors in Asia vs lifestyle factors in Western countries.

• Risk Factors: High fiber diets can be protective, while high-fat diets and inactivity increase risk.

Diverticulosis Pathophysiology

• Develops at weakness points in the colon; chronic constipation increases colonic pressures.

• Diverticulitis occurs when diverticula become obstructed and inflamed, potentially leading to perforation.

Complications of Diverticulosis

• Leading cause of lower GI bleeding, often resolves spontaneously. Rare cases require endoscopic intervention.

Clinical Presentation of Diverticulitis

• Typically presents as left lower quadrant pain, nausea, and altered bowel habits or fever.

Differential Diagnosis for Diverticulitis

• Includes conditions like acute appendicitis, colorectal cancer, and infectious colitis.

Objective Evaluation of Diverticulitis

• Laboratory Findings: Mild leukocytosis; imaging with CT is preferred to visualize inflammation.

• Colonoscopy is avoided during acute episodes to prevent perforation.

Diverticulitis Treatment

• Uncomplicated Diverticulitis: Managed non-operatively with antibiotics.

• Complicated Diverticulitis: May require IV antibiotics, surgical interventions for complications.

Prognosis of Diverticulitis

• 25% of diverticulosis patients develop diverticular disease, with 15% facing complications.