9. Disorders of the colon

Introduction

• The presentation is on the pathology of the colon, focusing on high-yield topics, delivered by Rodrigo Vivar Barragán at the Universidad Autónoma de Guadalajara School of Medicine (UAG).
• The presentation covers diverticular disease, inflammatory bowel disease (Crohn's disease and ulcerative colitis), colorectal cancer (adenocarcinoma and squamous cell carcinoma), prevention and early detection, psychosocial impact, and recent advances in the field.

Diverticular Disease

• Definition and Epidemiology: Diverticulosis is the presence of diverticula (small pouches) in the colonic wall. Prevalence increases with age, affecting about 30% of people over 50 and 50-70% of those over 80. Diverticular disease is more common in developed countries due to dietary habits.
• Pathogenesis: Low-fiber diets contribute to altered intestinal motility and increased intraluminal pressure, increasing the risk of diverticular formation. Other risk factors include obesity, sedentary lifestyle, and advanced age.
• Diagnosis: Colonoscopy is used for direct visualization of diverticula. CT scans are helpful in evaluating complications.
• Complications: Diverticular bleeding (painless hematochezia), fistula formation (abnormal connections between the colon and other organs), and perforation (resulting in peritonitis).
• Classification: Hinchey classification system categorizes diverticulitis severity based on the extent of the infection (abscess formation). Hinchey I involves pericolic or mesenteric abscess, Hinchey II involve pelvic abscess, Hinchey III involves purulent peritonitis and Hinchey IV are cases of fecal peritonitis.
• Clinical Manifestations Diverticular disease can be asymptomatic or have symptoms like intermittent abdominal pain (left lower quadrant), bloating, changes in bowel habits.

Inflammatory Bowel Disease: Crohn's Disease

• Description: A chronic inflammatory condition affecting any part of the gastrointestinal (GI) tract.
• Location: Most commonly found in the terminal ileum and colon.
• Epidemiology: Higher incidence in developed countries.
• Pathogenesis: Multifactorial, involving genetics, immunology, and environmental factors. Genetic mutations in NOD2/CARD15 gene and abnormal immune response against intestinal antigens play a role. Environmental factors like smoking, Westernized diet, and antibiotic use during childhood may contribute.
• Diagnosis: Combination of endoscopy with biopsy, imaging studies (CT, MRI), and serological markers (ASCA).
• Complications: Intestinal stenosis, fistulas, abscesses, malabsorption, nutritional deficiencies, and increased risk of colorectal cancer.
• Clinical Manifestations: Symptoms vary depending on location and severity. Common symptoms include abdominal pain, chronic diarrhea, weight loss, fever, and perianal involvement (fistulas and abscesses).
• Treatment: Pharmacologic agents (aminosalicylates, corticosteroids, immunomodulators, biologics) and surgical interventions (for complications like refractory stenosis, fistulas, and severe perianal disease).

Inflammatory Bowel Disease: Ulcerative Colitis

• Description: A chronic inflammatory condition affecting only the colon, always starting in the rectum and extending proximally in a continuous manner.
• Epidemiology: Similar incidence to Crohn's disease in developed countries.
• Pathogenesis: A combination of genetic, immunologic, and environmental factors. Abnormal immune response against intestinal microbiota and alterations in gut microbiota composition are implicated.
• Diagnosis: Colonoscopy with biopsy, histopathology for cryptitis and crypt abscesses, and imaging studies for extent and severity assessment.
• Complications: Toxic megacolon, colonic perforation, massive hemorrhage, and increased risk of colorectal cancer.
• Clinical Manifestations: Typical symptoms include bloody stool, diarrhea, rectal pain, abdominal pain, constant urgency to defecate, weight loss, and chronic fatigue. Extraintestinal symptoms can also occur, including arthritis, uveitis, and primary sclerosing cholangitis.
• Treatment: Pharmacologic (aminosalicylates, corticosteroids, immunomodulators, biologics) and surgical (colectomy in refractory cases or severe complications) approaches.

Colorectal Cancer: Adenocarcinoma

• Description: The most common type of colorectal cancer.
• Epidemiology: High incidence in developed countries.
• Risk Factors: Family history, hereditary syndromes, high-fat diet, smoking, and alcohol use.
• Pathogenesis: Adenoma-carcinoma sequence, where adenomatous polyps undergo malignant transformation. Genetic mutations (APC, KRAS, TP53) play a crucial role.
• Diagnosis: Colonoscopy with biopsy, tumor markers (CEA), and imaging studies (CT, MRI, PET) for staging.
• Staging and Classification: The TNM system (tumor, node, metastasis) and clinical stages (I to IV) categorize the disease severity.
• Clinical Manifestations: Initial symptoms can include changes in bowel habits, hematochezia, iron-deficiency anemia, and weight loss. Advanced symptoms involve intestinal obstruction and abdominal pain.
• Treatment: Surgery (segmental resection or total colectomy), chemotherapy (advanced stages, adjuvant post-surgery), radiotherapy (mainly for rectal cancer), and targeted therapies (bevacizumab, cetuximab).
• Prognosis and Follow-up: Prognosis improves with early diagnosis, and follow-up involves regular colonoscopies and monitoring of tumor markers.

Colorectal Cancer: Squamous Cell Carcinoma

• Description: A less common type of colorectal cancer than adenocarcinoma.
• Risk factors: HPV infection, chronic inflammatory conditions.
• Clinical Manifestations: Symptoms include anal pain, rectal bleeding, and palpable anal masses; presentation varies by tumor location and extent.
• Diagnosis: Visualization using anoscopy, biopsy, and imaging studies. Histological characteristics are key to diagnosis.
• Treatment: Surgery, chemotherapy, and radiotherapy. Treatment response relies on cancer stage and tumor characteristics.
• Prognosis: Generally a worse prognosis than adenocarcinoma, influenced by stage at diagnosis and treatment response. Local invasion and lymph node involvement affect prognosis.

Prevention and Early Detection, Psychosocial Impact, and Recent Advances

• Prevention and Early Detection: Early detection via colonoscopy is crucial for preventing colorectal cancer and removing precancerous polyps.
• Psychosocial Impact: Colon diseases significantly impact quality of life, requiring multidisciplinary management, including psychological support for stress, anxiety, and depression.
• Recent Advances: Recent developments include new biological and targeted therapies, ongoing research on gut microbiota, and the role of biomarkers in personalized diagnosis and treatment.

Test your knowledge on diverticular disease and its association with colorectal cancer. This quiz covers clinical manifestations, diagnostic tools, risk factors, and dietary influences on these conditions. Ideal for medical students and health professionals.