Inflammatory Bowel Disorders

• Crohn's Disease (CD) and Ulcerative Colitis (UC) are inflammatory diseases with distinct characteristics.

Crohn's Disease (CD)

• Can occur anywhere in the GI tract, most commonly in the terminal ileum and colon.
• Pattern of inflammation is discontinuous ("skip lesions").
• Inflammation is transmural, affecting the entire bowel wall.
• Immune response is Th1-dominant (cell-mediated immunity).
• Granulomas are commonly present, and are non-caseating.
• Fistulas and perforations are common due to deep ulcers and transmural inflammation.
• Strictures and obstruction are common due to fibrosis and thickening of the intestinal wall.
• Increased risk of colorectal cancer, especially with longstanding disease.
• Clinical symptoms include crampy abdominal pain, diarrhea (often non-bloody), weight loss, B12 deficiency (ileal involvement), and perianal disease (fissures, abscesses, fistulae).
• Extra-intestinal manifestations include arthritis, uveitis, and skin lesions like erythema nodosum, and gallstones.

Ulcerative Colitis (UC)

• Begins in the rectum and extends proximally in the colon (continuous pattern).
• Inflammation is continuous from the rectum upwards.
• Affects only the mucosal and submucosal layers.
• Immune response is Th2-dominant (humoral immunity).
• Granulomas are rare.
• Fistulas and perforations are rare.
• Strictures and obstruction are less common.
• Increased risk of colorectal cancer correlates with the duration and severity of the disease.
• Clinical symptoms include bloody diarrhea, urgency to defecate, tenesmus, and cramping, often in the LLQ.
• Extra-intestinal manifestations are similar to Crohn's disease, including skin, joints, and eyes.

Diverticulosis

• Defined by the presence of diverticula, which are outpouchings of the mucosa/submucosa through the muscular wall, typically in the sigmoid colon.
• Usually asymptomatic.
• Common in older adults.
• Etiology is linked to increased intraluminal pressure, age, low-fiber diets, obesity, and a sedentary lifestyle, but not primarily caused by fiber deficiency.

Diverticulitis

• Characterized by inflammation or infection of one or more diverticula.
• Affects about 10-15% of individuals with diverticulosis.
• Can lead to complications such as abscess, fistula, obstruction, and perforation.
• Clinical manifestations include LLQ abdominal pain (common in sigmoid disease), fever, leukocytosis, nausea, vomiting, constipation or diarrhea, rebound tenderness, and guarding.

Appendicitis Pathophysiology

• Obstruction of the appendiceal lumen is the most common initiating factor, caused by fecaliths (hardened stool), lymphoid hyperplasia, foreign bodies, or tumors.
• Obstruction leads to bacterial overgrowth, inflammation, and ischemia.
• Can progress to necrosis, perforation, and peritonitis if untreated.

Appendicitis Clinical Manifestations

• Initial vague abdominal pain localizes to the RLQ (McBurney's point).
• Fever, nausea, and vomiting occur.
• Rebound tenderness, guarding, and positive Rovsing's or psoas sign are present.
• Anorexia is common.
• Elevated WBC count with a left shift.
• Pain intensifies with movement or coughing.