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Approach to the Patient with Gastrointestinal Disease¶

Chapter 332 | Part 10: Disorders of the Gastrointestinal System · Part 10 – Gastrointestinal Disorders · Chapter 332

Key Clinical Points¶

GI diseases involve alterations in nutrient/fluid assimilation, transit, sensation, immune function, vascular supply, and neoplasia.
Disorders of Gut-Brain Interaction (DGBI) include IBS, functional dyspepsia, and functional heartburn; Rome criteria are the primary diagnostic tool.
Abdominal pain is categorized as visceral (midline/vague) or parietal (localized/precise).
Upper GI bleeding presents as melena or hematemesis; lower GI bleeding typically presents as bright red or maroon stools.
Fecal calprotectin and lactoferrin are key markers for inflammatory conditions like IBD.
Fecal fat indicates malabsorption; fecal elastase decrease suggests exocrine pancreatic insufficiency.
Lynch syndrome is an autosomal dominant condition increasing risk for colon and gynecologic cancers.
Endoscopy indications vary by clinical suspicion: Upper (dyspepsia, bleeding), Colon (cancer screening, bleeding), ERCP (jaundice, stones), EUS (staging), Capsule (obscure bleeding).
Heartburn is experienced by 40% of the population and may be caused by acid or non-acidic reflux.
Gastric cancer risk is associated with H. pylori infection; colorectal cancer typically presents after age 45.

DEFINITION & CLASSIFICATION¶

• Overview: GI function is influenced by external factors; gut is in continuity with the environment. • Protective Mechanisms: ◦ Mucosal immune pathways (epithelial/lamina propria lymphocytes, plasma cells, lymph node chains) prevent entry of noxious agents. ◦ Paneth cells secrete antimicrobial peptides to defend against pathogens. ◦ Liver filters and detoxifies substances in portal circulation. • Brain-Gut Axis: Alters function in regions not under volitional regulation; stress disrupts motor, secretory, and sensory activities. • Anatomic Considerations: ◦ Sphincters: Provide compartmentalization. ◦ Layers: Mucosa (barrier/nutrient transfer), Smooth muscle & enteric nerves (propulsion), Serosa (support). ◦ Systems: Pancreaticobiliary conduits (bile/enzymes), Lymphatic channels (immune activity). • Functional Anatomy: ◦ Esophagus: Propulsion via peristalsis; basal tone of lower esophageal sphincter prevents reflux. ◦ Stomach: Trituration, mixing with pepsin/acid; proximal stomach for storage; distal stomach for propulsion. ◦ Small Intestine: Primary site of nutrient absorption; mucosal villi increase surface area. ◦ Large Intestine: Dehydration of stool (1000–1500 mL to 100–200 mL); dense microbiome modulates immune activity. • Classification: ◦ Based on alterations in: Nutrient/fluid assimilation, transit, sensation, immune function, vascular supply, and neoplasia.

EPIDEMIOLOGY¶

• Heartburn: Experienced by 40% of the population. • Celiac Disease: More prevalent in populations of northern European descent. • IBD: More common in Jewish populations. • Colorectal Cancer: Most common in the US; typically presents after age 45. • Gastric Cancer: Prevalent in certain Asian populations (often linked to H. pylori).

ETIOLOGY & PATHOPHYSIOLOGY¶

• Extrinsic Modulation: Gut is exposed to food, meds, toxins, and microbes; protected by mucosal immunity and liver detoxification. • Immune Dysregulation: ◦ Celiac Disease: Result of gluten-containing grain ingestion. ◦ Eosinophilic conditions: Eosinophilic esophagitis/gastroenteritis show prominent eosinophil infiltration. ◦ IBD: Ulcerative colitis and Crohn's disease (lower gut injury). ◦ Microbiome: Dysbiosis may trigger IBD, celiac, or contribute to pancreatic cancer oncogenesis. • Genetic Influences: ◦ IBD: Family members show genetic predisposition. ◦ Lynch Syndrome: Autosomal dominant; increased risk for colon and gynecologic cancers. ◦ DGBIs: Show familial clustering (potentially learned behavior). • Ischemia: ◦ Causes: Arterial embolus, thrombosis, hypoperfusion (dehydration, sepsis, hemorrhage, low cardiac output). ◦ Consequences: Mucosal injury, hemorrhage, perforation, or stricturing. • Neoplasia: ◦ Colorectal: Most common in US; usually >45 years old. ◦ Gastric: Linked to H. pylori infection. ◦ Esophageal: Linked to chronic acid reflux, alcohol, or tobacco. ◦ Pancreatic/Biliary: Characterized by severe pain, weight loss, and jaundice.

CLINICAL FEATURES¶

• Pain Types: ◦ Visceral: Midline location, vague character (e.g., biliary colic, mesenteric ischemia). ◦ Parietal: Localized, precisely described; associated with inflammation (e.g., appendicitis, diverticulitis, pancreatitis). • Heartburn: Burning substernal sensation; caused by acid reflux or non-acidic reflux/heightened nerve sensitivity. • Nausea & Vomiting: Caused by GI disease, meds, toxins, infection, endocrine disorders, or CNS disease. ◦ Note: Mechanical obstruction must be excluded in chronic cases. • Bowel Habits: ◦ Constipation: Result of obstruction, motor disorders, medications, or endocrine diseases (hypothyroidism/hyperparathyroidism). ◦ Diarrhea: Result of infection, inflammation, malabsorption, or medications. ◦ IBS: Characterized by constipation, diarrhea, or alternating patterns; often includes fecal mucus. • GI Bleeding: ◦ Upper: Melena or hematemesis (brisk bleeding can cause red rectal bleeding). ◦ Lower: Bright red or maroon stools (slow ascending colon bleed may cause melena). ◦ Chronic: May present as iron deficiency anemia. • Jaundice: Result of prehepatic, intra1intrahepatic, or posthepatic disease. ◦ Posthepatic causes: Biliary (choledocholithiasis, cholangitis) and pancreatic (pancreatitis, malignancy).

DIFFERENTIAL DIAGNOSIS¶

• Table 332-1: Common Causes of Common Gastrointestinal (GI) Symptoms → Abdominal Pain: Appendicitis, Gallstone disease, Pancreatitis, Diverticulitis, Ulcer disease, Esophagitis, GI obstruction, IBD, Functional bowel disorder, Vascular disease, Gynecologic causes, Renal stone. → Nausea and Vomiting: Medications, GI obstruction, Motor disorders, Functional bowel disorder, Cyclic vomiting syndrome, Cannabinoid hyperemesis syndrome, Enteric infection, Pregnancy, Endocrine disease, Motion sickness, CNS disease. → Diarrhea: Infection, IBD, Poorly absorbed sugars, Microscopic colitis, Functional bowel disorder, Celiac disease, Pancreatic insufficiency, Hyperthyroidism, Ischemia, Endocrine tumor. → GI Bleeding: Ulcer disease, Esophagitis, Varices, Vascular lesions, Neoplasm, Diverticula, Hemorrhoids, Fissures, Infectious colitis. → Obstructive Jaundice: Bile duct stones, Cholangiocarcinoma, Cholangitis, Sclerosing cholangitis, Ampullary stenosis/carcinoma, Pancreatitis, Pancreatic tumor.

DIAGNOSTIC APPROACH¶

History & Physical Examination: ◦ History: Assess duration (acute vs. chronic), timing (relation to meals), and triggers (stress, travel). ◦ Physical Exam: Check for fever (inflammation/neoplasm), orthostasis (blood loss/dehydration), and specific signs like jaundice or skin/joint findings.
Laboratory Testing: ◦ Anemia: Iron-deficiency suggests mucosal blood loss; B12 deficiency suggests intestinal/gastric/pancreatic disease. ◦ Inflammatory Markers: Leukocytosis, ESR, and CRP indicate inflammation. ◦ Metabolic/Endocrine: Thyroid, cortisol, calcium, and pregnancy tests. ◦ Tumor Markers: CEA, CA 19-9, CA 125, α-fetoprotein.
Luminal Contents: ◦ H. pylori: Fecal antigen test for ulcer disease or dyspepsia. ◦ Stool Analysis: Culture (bacteria), microscopy (parasites/leukocytes). ◦ Malabsorption: Fecal fat (increased) and fecal elastase (decreased). ◦ Inflammation: Fecal calprotectin or lactoferrin elevation.
Radiography & Nuclear Medicine: ◦ Esophagography: Initial step to exclude rings, strictures, or achalasia in dysphagia. ◦ Small-bowel contrast: Detect tumors, strictures, and fistulae.
Endoscopy (Based on Table 332-2): → Upper Endoscopy: Dyspepsia (despite treatment/with organic signs), Reflux, Vomiting, Dysphagia, Bleeding, Anemia, Weight loss, Malabsorption, Biopsy, Barrett's surveillance. → Colonoscopy: Cancer screening, Lower GI bleeding, Anemia, Diarrhea, Polypectomy, Obstruction. → ERCP: Jaundice, Postbiliary surgery complaints, Cholangitis, Gallstone pancreatitis, Pancreatic/biliary/ampullary tumor, Unexplained pancreatitis, Fistulas. → EUS: Staging malignancy, Submucosal mass biopsy, Bile duct stones, Chronic pancreatitis, Drain pseudocyst, Anal continuity. → Capsule Endoscopy: Obscure bleeding, Suspected Crohn's of small intestine, Ablation of small-intestinal bleed sources.

MANAGEMENT & TREATMENT¶

Nutritional Modification: ◦ Specific diets: Lactose restriction, gluten-free (celiac), low-FODMAP (IBS). ◦ Specialized needs: Liquid meals for gastroparesis; enteral/parenteral nutrition for gut failure.
Over-the-Counter Agents: ◦ Antacids, PPIs, fiber, and laxatives.
Prescription Drugs for Symptom Control: ◦ PPIs (GERD), Baclofen (reflux), Prokinetics (gastroparesis).
Prescription Drugs for Disease Modification: ◦ Immunomodulators (IBD), Biologics (IBD), H. pylori eradication.

KEY PEARLS & HIGH-YIELD POINTS¶

• Rome Criteria: Best accepted symptom-based criteria for DGBIs; sensitivity/specificity of 55–75% against structural findings. • Fecal Markers: ◦ Calprotectin/Lactoferrin \uparrow → Inflammatory conditions (IBD). ◦ Fecal Fat \uparrow → Malabsorption. ◦ Fecal Elastase \downarrow → Exocrine pancreatic insufficiency. • Clinical Differentiation: ◦ Visceral pain = Midline/Vague; Parietal pain = Localized/Precise. ◦ Upper GI Bleed = Melena/Hematemesis; Lower GI Bleed = Bright red/Maroon. • Lynch Syndrome: Autosomal dominant → increased risk for colon and gynecologic cancers.

Reference Tables¶

TABLE 332-1 Common Causes of Common Gastrointestinal (GI) Symptoms¶

Harrison's 22e, p.2460

ABDOMINAL PAIN	NAUSEA AND VOMITING	DIARRHEA	GI BLEEDING	OBSTRUCTIVE JAUNDICE
Appendicitis	Medications	Infection	Ulcer disease	Bile duct stones
Gallstone disease	GI obstruction	Poorly absorbed sugars	Esophagitis	Cholangiocarcinoma
Pancreatitis	Motor disorders	Inflammatory bowel disease	Varices	Cholangitis
Diverticulitis	Functional bowel disorder	Microscopic colitis	Vascular lesions	Sclerosing cholangitis
Ulcer disease	Cyclic vomiting syndrome	Functional bowel disorder	Neoplasm	Ampullary stenosis
Esophagitis	Cannabinoid hyperemesis syndrome	Celiac disease	Diverticula	Ampullary carcinoma
GI obstruction	Enteric infection	Pancreatic insufficiency	Hemorrhoids	Pancreatitis
Inflammatory bowel disease	Pregnancy	Hyperthyroidism	Fissures	Pancreatic tumor
Functional bowel disorder	Endocrine disease	Ischemia	Inflammatory bowel disease
Vascular disease	Motion sickness	Endocrine tumor	Infectious colitis
Gynecologic causes	Central nervous system disease
Renal stone

TABLE 332-2 Common Indications for Endoscopy¶

Harrison's 22e, p.2462

UPPER ENDOSCOPY	COLONOSCOPY	ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY	ENDOSCOPIC ULTRASOUND	CAPSULE ENDOSCOPY	DOUBLE-BALLOON ENDOSCOPY
Dyspepsia despite treatment Dyspepsia with signs of organic disease Refractory vomiting Dysphagia Upper GI bleeding Anemia Weight loss Malabsorption Biopsy radiologic abnormality Polypectomy Place gastrostomy Barrett’s surveillance Palliate neoplasm Sample duodenal tissue/fluid Remove foreign body Endoscopic mucosal resection or endoscopic submucosal dissection for dysplasia or early cancer Place stent across stenosis Endoscopic myotomy for achalasia or gastroparesis Endoscopic bariatric procedures	Cancer screening Lower gastrointestinal (GI) bleeding Anemia Diarrhea Polypectomy Obstruction Biopsy radiologic abnormality Cancer surveillance: family history prior polyp/cancer, colitis Palliate neoplasm Remove foreign body Place stent across stenosis	Jaundice Postbiliary surgery complaints Cholangitis Gallstone pancreatitis Pancreatic/biliary/ampullary tumor Unexplained pancreatitis Pancreatitis with unrelenting pain Fistulas Biopsy radiologic abnormality Pancreaticobiliary drainage Sample bile Sphincter of Oddi manometry	Staging of malignancy Characterize and biopsy submucosal mass Bile duct stones Chronic pancreatitis Drain pseudocyst Anal continuity Direct stent placement	Obscure bleeding Suspected Crohn’s disease of the small intestine	Ablation of small- intestinal bleeding sources Biopsy of suspicious small-intestinal masses/ ulcers