Approach to the Patient with Gastrointestinal Disease¶
Chapter 332 | Part 10: Disorders of the Gastrointestinal System
KEY CLINICAL POINTS¶
- The gastrointestinal tract serves dual functions: nutrient assimilation and waste elimination, with extrinsic modulation by the brain-gut axis and immune pathways.
- GI diseases range from mild functional disorders (e.g., IBS) to severe organic conditions (e.g., cancer), with classification based on etiology (malabsorption, motility, immune, neoplastic).
- Diagnostic evaluation integrates history, physical exam, endoscopy, imaging, and functional tests, with specialized tools like the Rome criteria for functional disorders.
1. DEFINITION & OVERVIEW¶
The gastrointestinal (GI) tract extends from the mouth to the anus, performing nutrient absorption and waste elimination. It interacts with extrinsic systems (e.g., brain-gut axis, liver, pancreas) and is protected by mucosal immune pathways, antimicrobial peptides, and intrinsic/extrinsic neural control. GI dysfunction can arise from altered secretion, transit, immune dysregulation, or genetic factors.
1.1 Anatomic Considerations¶
The GI tract includes sphincters, distinct layers (mucosa, smooth muscle, serosa), and interactions with pancreaticobiliary systems. The colon's microbiome modulates immunity and fermentation of undigested carbohydrates.
1.2 Functional Roles¶
The GI tract absorbs nutrients, regulates fluid balance, and eliminates waste. Motility is controlled by intrinsic nerves and extrinsic vagus/splanchnic pathways. The brain-gut axis influences non-volitional gut function.
2. EPIDEMIOLOGY¶
GI diseases vary in severity from mild functional disorders (e.g., IBS, functional dyspepsia) to life-threatening conditions (e.g., cancer). Risk factors include age, genetics (e.g., Lynch syndrome), and environmental exposures. Functional disorders (DGBIs) show familial clustering but may reflect learned behaviors rather than true genetic inheritance.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Pathophysiology includes altered secretion (e.g., gastrinoma, celiac disease), impaired transit (obstruction, pseudoobstruction), immune dysregulation (IBD, eosinophilic disorders), and genetic factors (e.g., hereditary cancer syndromes). The gut microbiome influences immunity and metabolism.
3.1 Altered Secretion¶
Gastric acid hypersecretion occurs in gastrinoma, while atrophic gastritis reduces acid. Intestinal hypersecretion causes diarrhea in infections (e.g., Giardia) or malabsorption syndromes (e.g., lactase deficiency).
3,2 Altered Gut Transit¶
Obstruction (e.g., adhesions, tumors) or pseudoobstruction (e.g., enteric nerve injury) disrupts motility. Delayed propulsion causes constipation (e.g., slow-transit colon) or rapid transit (e.g., dumping syndrome).
3.3 Immune Dysregulation¶
Inflammatory conditions (e.g., IBD, celiac disease) result from immune responses to dietary antigens or pathogens. Eosinophilic disorders (e.g., eosinophilic esophagitis) involve mucosal infiltration.
4. CLINICAL FEATURES¶
Symptoms include abdominal pain (visceral/parietal), heartburn, nausea/vomiting, altered bowel habits, GI bleeding, jaundice, and weight loss. Physical findings may reveal distension, tenderness, or masses.
Table 332-1 Common Causes of Common Gastrointestinal (GI) Symptoms¶
| 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 |
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include functional disorders (e.g., IBS, functional dyspepsia), organic conditions (e.g., IBD, cancer), infections (e.g., Giardia), and systemic diseases (e.g., lupus, diabetes). DGBIs (e.g., IBS) require exclusion of structural/organic causes.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnostic tools include endoscopy (upper/lower), imaging (CT, MRI, ultrasound), functional tests (manometry, breath tests), and lab studies (fecal calprotectin, serology for celiac disease). The Rome criteria guide functional disorder diagnosis.
Table 332-2 Common Indications for Endoscopy¶
| UPPER ENDOSCOPY | COLONOSCOP Y | ENDOSCOPIC RETROGRADE CHOLANGIOPA NCREATOGRA PHY | ENDOSCOPIC ULTRASOUND | CAPSULE ENDOSCOPY | DOUBLE-BALL OON ENDOSCOPY |
|---|---|---|---|---|---|
| Dyspepsia despite treatment | Cancer screening | Jaundice | Staging of malignancy | Obscure bleeding | Ablation of small-intestinal bleeding sources |
| Dyspepsia with signs of organic disease | Lower gastrointestinal (GI) bleeding | Postbiliary surgery complaints | Characterize and biopsy submucosal mass | Suspected Crohn’s disease of the small intestine | Biopsy of suspicious small-intestinal masses/ulcers |
| Refractory vomiting | Anemia | Cholangitis | Bile duct stones | Staging of malignancy | |
| Dysphagia | Diarrhea | Gallstone pancreatitis | Chronic pancreatitis | Direct stent placement | |
| Upper GI bleeding | Polypectomy | Pancreatic/biliar y/ampullary tumor | Drain pseudocyst | Anal continuity | |
| Anemia | Obstruction | Unexplained pancreatitis | Pancreatitis with unrelenting pain | Place stent across stenosis | |
| Weight loss | Biopsy radiologic abnormality | Pancreatitis with unrelenting pain | Fistulas | Endoscopic myotomy for achalasia or gastroparesis | |
| Malabsorption | Cancer surveillance: family history prior | Fistulas | Biopsy radiologic abnormality | Endoscopic bariatric procedures | |
| Biopsy radiologic abnormality | Polypectomy | Biopsy radiologic abnormality | Pancreaticobiliar y drainage | ||
| Polypectomy | Palliate neoplasm | Sample bile | Sphincter of Oddi manometry | ||
| Place gastrostomy | Remove foreign body | Place stent across stenosis |
| UPPER ENDOSCOPY | COLONOSCOP Y | ENDOSCOPIC RETROGRADE CHOLANGIOPA NCREATOGRA PHY | ENDOSCOPIC ULTRASOUND | CAPSULE ENDOSCOPY | DOUBLE-BALL OON ENDOSCOPY |
|---|---|---|---|---|---|
| Barrett’s surveillance | Endoscopic mucosal resection or endoscopic submucosal dissection for dysplasia or early cancer | Place stent across stenosis |
6.1 Laboratory Tests¶
Iron deficiency anemia suggests chronic blood loss; fecal occult blood tests detect GI bleeding. Fecal calprotectin and lactoferrin aid in IBD diagnosis. Serologic tests screen for celiac disease and atrophic gastritis.
6.2 Imaging and Endoscopy¶
Endoscopy is the gold standard for evaluating ulcers, tumors, and inflammation. Capsule endoscopy and EUS assess small-bowel and pancreaticobiliary disease. CT/MRI detect tumors, strictures, and complications.
7. MANAGEMENT & TREATMENT¶
Management includes dietary modifications (e.g., low-FODMAP, gluten-free), medications (PPIs, prokinetics, immunomodulators), endoscopic interventions, and surgery. Complementary therapies (e.g., ginger, acupressure) may aid symptom control.
7.1 Nutritional Modifications¶
Lactose restriction for lactase deficiency, low-FODMAP diets for IBS, and enteral nutrition for malabsorption. Parenteral nutrition is reserved for generalized gut failure.
7.2 Pharmacotherapy¶
PPIs for GERD, prokinetics for gastroparesis, immunomodulators (e.g., biologics) for IBD, and antispasmodics for IBS. H. pylori eradication reduces gastric cancer risk.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis varies from benign (e.g., IBS) to poor (e.g., pancreatic cancer). Complications include malnutrition, dehydration, and severe bleeding. Early diagnosis and treatment improve outcomes for inflammatory and neoplastic diseases.
9. SPECIAL CONSIDERATIONS¶
Pregnancy requires cautious medication use; pediatric patients may present with atypical symptoms. Elderly patients face higher risks of complications (e.g., ischemia). DGBIs often involve psychosocial factors requiring multidisciplinary care.
10. KEY POINTS & CLINICAL PEARLS¶
- History and physical exam are critical for distinguishing functional vs. organic causes. 2. Endoscopy is the gold standard for evaluating structural abnormalities. 3. The Rome criteria guide diagnosis of functional disorders. 4. Early intervention for IBD and neoplasms improves prognosis. 5. Complementary therapies may aid symptom management but should not replace evidence-based treatments.