CheatSheet: Gastroenterology

1. Esophageal Disorders

1.1 Gastroesophageal Reflux Disease (GERD)

1.2 Barrett's Esophagus

1.3 Achalasia Cardia

1.4 Esophageal Carcinoma

1.5 Esophageal Varices

2. Gastric Disorders

2.1 Peptic Ulcer Disease (PUD)

2.1.1 H. pylori Diagnosis

• Invasive: Endoscopic biopsy (rapid urease test, histology, culture)
• Non-invasive: Urea breath test (gold standard), stool antigen test, serology (IgG - not for eradication monitoring)

2.1.2 H. pylori Eradication

2.2 Gastric Carcinoma

2.3 Gastric Outlet Obstruction

2.4 Zollinger-Ellison Syndrome

3. Small Intestinal Disorders

3.1 Celiac Disease

3.2 Tropical Sprue

3.3 Whipple's Disease

3.4 Small Intestinal Bacterial Overgrowth (SIBO)

3.5 Meckel's Diverticulum

4. Inflammatory Bowel Disease

4.1 Comparison: Crohn's Disease vs Ulcerative Colitis

4.2 Extraintestinal Manifestations

4.2.1 Related to Disease Activity

• Peripheral arthritis (large joints)
• Erythema nodosum
• Episcleritis
• Aphthous ulcers

4.2.2 Unrelated to Disease Activity

• Ankylosing spondylitis (HLA-B27)
• Sacroiliitis
• Primary sclerosing cholangitis (UC > CD)
• Pyoderma gangrenosum
• Uveitis

4.3 Treatment

4.3.1 Mild-Moderate Disease

• 5-ASA (mesalamine, sulfasalazine): UC first-line; limited role in CD
• Budesonide: ileal/right-sided CD

4.3.2 Moderate-Severe Disease

• Corticosteroids (prednisolone 40-60mg): acute flares, not for maintenance
• Immunomodulators: azathioprine, 6-mercaptopurine, methotrexate (steroid-sparing)
• Biologics: anti-TNF (infliximab, adalimumab), vedolizumab, ustekinumab

4.3.3 Severe UC (Truelove and Witts Criteria)

• IV corticosteroids (hydrocortisone/methylprednisolone)
• Rescue: infliximab or cyclosporine if no response in 3-5 days
• Colectomy if medical therapy fails

5. Malabsorption Syndromes

5.1 Classification

5.2 Lactose Intolerance

5.3 Tests for Malabsorption

6. Colorectal Disorders

6.1 Colorectal Carcinoma

6.2 Polyps

6.3 Hereditary Polyposis Syndromes

6.4 Diverticular Disease

6.5 Anorectal Disorders

7. Intestinal Infections

7.1 Acute Diarrhea

7.2 Intestinal Tuberculosis

8. Gastrointestinal Bleeding

8.1 Upper GI Bleeding

8.1.1 Management of Upper GI Bleeding

• Resuscitation: IV access, crossmatch, crystalloids/blood transfusion (target Hb >7 g/dL)
• Glasgow-Blatchford Score (risk stratification), Rockall Score (mortality prediction)
• PPI: IV bolus followed by infusion (omeprazole 80mg bolus, then 8mg/hr)
• Endoscopy within 24 hours (emergent if ongoing bleeding)
• Forrest Classification: Ia (spurting), Ib (oozing), IIa (visible vessel), IIb (adherent clot), IIc (flat spot), III (clean base)
• Endoscopic therapy: injection (epinephrine), thermal (cautery), mechanical (clips)

8.2 Lower GI Bleeding

9. Pancreatic Disorders

9.1 Acute Pancreatitis

9.1.1 Ranson's Criteria

• ≥3 criteria: severe pancreatitis; each criterion adds 10% mortality

9.1.2 Complications

9.1.3 Management

• Aggressive IV fluid resuscitation (Ringer's lactate 250-500 mL/hr)
• Analgesia, NPO initially, early enteral nutrition (within 24-48 hours, nasojejunal preferred)
• ERCP within 24 hours if acute cholangitis/biliary obstruction
• Antibiotics only if infected necrosis (imipenem, meropenem)
• Necrosectomy for infected necrosis (step-up approach: percutaneous drainage first)

9.2 Chronic Pancreatitis

9.3 Pancreatic Carcinoma

9.4 Pancreatic Neuroendocrine Tumors

10. Hepatobiliary Disorders

10.1 Cholelithiasis

10.2 Acute Cholecystitis

10.3 Choledocholithiasis

10.4 Acute Cholangitis (Ascending Cholangitis)

10.5 Primary Sclerosing Cholangitis (PSC)

10.6 Primary Biliary Cholangitis (PBC)

10.7 Cholangiocarcinoma

11. Gastrointestinal Emergencies

11.1 Intestinal Obstruction

11.1.1 Clinical Features

• Pain (colicky), vomiting (early in proximal, late in distal), distension, absolute constipation
• High-pitched bowel sounds (early), absent sounds (late)
• X-ray: dilated loops, air-fluid levels, absent colonic gas (complete obstruction)

11.1.2 Management

• NPO, NG decompression, IV fluids, electrolyte correction
• Conservative management for partial SBO without strangulation
• Surgery: complete obstruction, strangulation, closed-loop obstruction, LBO

11.2 Volvulus

11.3 Acute Mesenteric Ischemia

11.4 Perforation

11.5 Acute Appendicitis

12. Functional GI Disorders

12.1 Irritable Bowel Syndrome (IBS)

12.2 Functional Dyspepsia

12.3 Gastroparesis

13. Miscellaneous GI Disorders

13.1 Protein-Losing Enteropathy

13.2 Ménétrier's Disease

13.3 Short Bowel Syndrome

13.4 Abetalipoproteinemia

13.5 Gastrointestinal Stromal Tumors (GIST)

13.6 Carcinoid Tumors