Pathology - Digestive System Disorders

Anorexia: Lack of desire to eat. Must distinguish between pathological causes (cancer, chronic disease) and psychological causes (depression).
Nausea and Vomiting: Can be GI-related (gastritis, enteritis) or non-GI (meningitis due to increased intracranial pressure).
- Hematemesis: Vomiting blood; can appear bright red or as "coffee brown" (mixture of blood, mucus, and bile).
Constipation: Increased transit time. Often caused by medications like cholestyramine (treated with applesauce), iron, and opioids (smooth muscle relaxants).
Diarrhea: Sharp increase in frequency and water content.
- Osmotic: Unabsorbed solutes (e.g., lactose in lactose intolerance) pull water into the lumen.
- Secretory: Active secretion of water and electrolytes, often triggered by toxins like Vibrio cholerae.
- Motility: Induced by drugs (like macrolide antibiotics) or hyperthyroidism.
Abdominal Pain:
- Visceral: Dull, diffuse, and poorly localized (stretching/distension).
- Parietal: Sharp and well-localized.
- Referred: Pain felt away from the source (e.g., pancreatitis to the back; gallbladder to the right shoulder blade; appendicitis to the groin or umbilicus).
GI Bleeding:
- Upper GI Bleed: Mouth to duodenum. Often presents as hematemesis.
- Lower GI Bleed: Jejunum to anus.
- Hematochezia: Bright red blood in the stool.
- Melena: Dark, tarry, foul-smelling stool indicating old, metabolized blood.

Pathogenesis: Incompetence of the lower esophageal sphincter (LES) or gastroesophageal sphincter, allowing reverse flow of stomach acid into the esophagus.
Symptoms: Heartburn, acid regurgitation (sour taste), dysphagia (difficulty swallowing), chronic cough, hoarseness, and laryngitis.
Risk Factors: Obesity, pregnancy, hiatal hernia, and delayed gastric emptying (gastroparesis).
Complications: Barrett's esophagus (metaplasia from stratified squamous to columnar epithelium), which increases the risk for adenocarcinoma.
Diagnosis: Upper endoscopy with biopsy is the standard; manometry (pressure measurement) or pH testing may also be used.
Treatment: Proton Pump Inhibitors (PPIs) (drug of choice), weight loss, and fundoplication surgery for hiatal hernias.

General Pathogenesis: Chronic, idiopathic inflammation involving epithelial barrier dysfunction and immune reactions to bacterial flora.
Ulcerative Colitis (UC):
- Limited to the colon and rectum; spreads in a continuous, retrograde fashion.
- Causes mucosal ulceration and bloody diarrhea.
Crohn's Disease:
- Can affect any part of the GI tract (mouth to anus).
- Characterized by skip lesions (patches of diseased tissue separated by normal tissue) and granulomatous inflammation.
- Complications: Malabsorption (B12 and folate deficiency), hypoproteinemia, and fistulas (abnormal connections between organs).
Treatment: Sulfasalazine, glucocorticoids, and immunotherapy.

Portal Hypertension: Increased pressure in the hepatic portal circulation due to liver scarring. Can lead to esophageal varices and Mallory-Weiss syndrome (rupture of esophageal vessels).
Ascites: Accumulation of fluid in the peritoneal cavity due to decreased oncotic pressure (reduced albumin production).
Hepatic Encephalopathy: Personality changes and impaired cognition caused by the accumulation of ammonia that crosses the blood-brain barrier.
Jaundice (Icterus): Hyperbilirubinemia causing yellowing of skin/eyes.
- Prehepatic: Caused by hemolysis (e.g., sickle cell crisis, transfusion mismatch).
- Intrahepatic: Liver damage (e.g., hepatitis, drugs, cancer).
- Posthepatic: Obstruction of the biliary tree (e.g., gallstones, pancreatic cancer).
Alcohol Usage Disorder (AUD):
- Steatosis (fatty liver): Reversible accumulation of fat in hepatocytes.
- Alcoholic Hepatitis: Inflammation and cell death (still reversible).
- Cirrhosis: Irreversible fibrous scarring and end-stage liver failure.

Gallbladder Terminology:
- Cholelithiasis: Gallstones (primarily cholesterol-based).
- Cholecystitis: Inflammation of the gallbladder/cystic duct.
- Choledocholithiasis: Stone in the common bile duct.
Gallstone Risk Factors (The 4 F's): Fat, Forty, Female, Fertile. Also rapid weight loss and Native American ancestry.
Acute Cholecystitis Presentation: Right upper quadrant pain, often triggered by fatty foods which stimulate cholecystokinin (CCK). Diagnosed via ultrasound.
Acute Pancreatitis: Autodigestion of pancreatic tissue by its own enzymes (amylase, lipase, protease).
- Causes: Primarily alcoholism and gallstones.
- Presentation: Severe epigastric pain radiating to the back; fever; nausea.
- Labs: Elevated serum amylase and lipase.
- Management: Nothing by mouth (NPO), bowel rest, nasogastric suction, and IV fluids.