37 Patho

Disorders of Gastrointestinal Function

Overview

This chapter reviews the major disorders affecting gastrointestinal (GI) function, emphasizing the microbiological and physiological mechanisms underlying symptoms, disease progression, and clinical management. Understanding these disorders is essential for recognizing the interplay between host defenses, microbial pathogens, and environmental factors in GI health.

Common Symptoms and Protective Responses in GI Disorders

Anorexia, Nausea, Retching, and Vomiting

These symptoms are common responses to various GI problems and serve as protective mechanisms to remove harmful substances and signal underlying pathology.

• Anorexia: Loss of appetite, often associated with systemic illness or GI irritation.

• Nausea: Sensation of unease and discomfort in the upper stomach, often preceding vomiting.

• Retching: Repeated spasms of the diaphragm, chest wall, and abdominal muscles without actual vomiting.

• Vomiting: Forceful expulsion of stomach contents, coordinated by the vomiting center in the dorsal medulla and the chemoreceptor trigger zone (CTZ) on the floor of the fourth ventricle.

The vomiting center integrates signals and triggers the reflex, while the CTZ detects toxins/drugs in blood and cerebrospinal fluid, activating vomiting for protection.

Disorders of Swallowing

Mechanism and Types

Swallowing requires coordinated action of the mouth, pharynx, and is controlled by cranial nerves V, IX, X, and XII.

• Dysphagia: Difficulty swallowing, often due to neuromuscular or structural abnormalities.

• Odynophagia: Painful swallowing.

• Achalasia: Failure of the lower esophageal sphincter to relax, causing food retention.

Gastroesophageal Reflux Disease (GERD)

Pathophysiology and Management

GERD is characterized by the backward flow of acidic stomach contents into the esophagus, leading to mucosal irritation and symptoms such as heartburn and epigastric pain.

• Symptoms typically occur 30 to 60 minutes after meals.

• Pain may radiate to the throat, shoulder, or back.

• Complications include metaplasia (Barrett's esophagus) and increased cancer risk.

Patient Teaching:

• Avoid large meals, alcohol, and smoking.

• Eat meals sitting up and avoid recumbent position after eating.

• Avoid bending for long periods and sleep with the head elevated.

• Lose weight if overweight.

Esophageal Diverticulum

Definition, Symptoms, and Complications

An esophageal diverticulum is an outpouching or pocket in the wall of the esophagus.

• Symptoms: Dysphagia, regurgitation of undigested food, nocturnal coughing, halitosis, aspiration, and choking.

• Complications: Aspiration pneumonia, inflammation, or ulceration of the esophagus.

Esophageal Cancer

Types and Clinical Features

Esophageal cancer includes:

• Squamous cell carcinoma: Originates in the lining of the upper/middle esophagus.

• Adenocarcinoma: Arises from mucus-secreting glands, usually in the lower esophagus, often linked to GERD and Barrett's esophagus.

Symptoms:

• Progressive dysphagia (first solids, then liquids)

• Unintentional weight loss

• Chest pain or discomfort

• Hoarseness or chronic cough

• Regurgitation of food

• Fatigue/weakness

Gastric Mucosa Protection Barrier

Structure and Function

The gastric mucosa is protected by a specialized barrier:

• Protective lining: Epithelial cells block harmful substances.

• Transport control: Hydrogen (H+) and bicarbonate (HCO3-) are regulated to maintain pH balance.

• Mucus layer: Thick gastric mucus coats and protects the stomach wall from acid and enzymes.

Types of Mucus

• Soluble mucus: Washed from the surface, mixes with stomach contents, acts as a lubricant.

• Insoluble mucus: Forms a stable gel layer, protects against pepsin, contains bicarbonate for an alkaline microenvironment.

Causes of Gastric Irritation (Gastritis) and Ulcer Formation

Major Etiological Factors

• Aspirin & NSAIDs: Irritate the stomach lining and block prostaglandins that normally protect the mucosa.

• Helicobacter pylori infection: Spread via person-to-person contact, contaminated food/water. Colonizes mucus-secreting cells, releases enzymes/toxins, weakens mucosal defenses, and triggers strong inflammation.

Diagnostic Tests for H. pylori

• C-Urea Breath Test

• Stool Antigen Test

• Endoscopic Biopsy

• Blood Test for antibodies

Gastritis

Types and Pathogenesis

• Acute gastritis: Transient inflammation, often due to local irritants (bacteria, alcohol, aspirin).

• Chronic gastritis: Absence of visible erosions, chronic inflammatory changes, glandular atrophy.

• Chronic atrophic gastritis: Widespread thinning of the stomach lining.

• Immune gastritis: Autoimmune attack on stomach lining.

• Gastropathy: Damage from bile reflux, NSAIDs, or other irritants.

Peptic Ulcer Disease

Definition, Causes, and Treatment

Peptic ulcers are open sores in the stomach or duodenum where acid and pepsin cause damage.

• Most common cause: H. pylori infection

• Other causes: NSAIDs, warfarin

• Treatment: Antibiotics for H. pylori, acid reduction (proton pump inhibitors), protective medications, lifestyle changes (stop smoking, avoid irritants)

Complications

• Hemorrhage (bleeding)

• Obstruction (blockage)

• Perforation (ulcer breaks through wall)

Gastrointestinal Tract Bleeding

Types and Manifestations

• Hematemesis: Blood in vomitus (bright red or coffee ground appearance)

• Melena: Blood in stool (bright red to tarry black, may be occult)

Stress Ulcers

Risk Factors

• Severe burns

• Trauma

• Sepsis

• ARDS

• Liver failure

• Major surgery

• Zollinger-Ellison syndrome (tumor causing high acid production)

Gastric Cancer

Risk Factors

• Genetic predisposition

• Carcinogenic diet factors

• Autoimmune gastritis

• Gastric adenomas or polyps

Altered Intestinal Function

Major Conditions

• Irritable Bowel Syndrome (IBS): Functional disorder with abnormal bowel movements, abdominal pain, bloating, and linked to stress.

• Inflammatory Bowel Disease (IBD): Chronic inflammation (Crohn's disease, Ulcerative Colitis).

• Diverticulitis: Infection/inflammation of small pouches in the colon wall.

• Appendicitis: Inflammation of the appendix.

• Altered bowel motility: Abnormal speed of intestinal contents movement.

• Malabsorption syndrome: Poor absorption of nutrients (e.g., celiac disease).

• Colon & rectal cancer: Tumors affecting bowel function.

Intestinal Infections

Major Pathogens

• Viral: Rotavirus (common cause of diarrhea in children)

• Bacterial: Clostridium difficile (post-antibiotic, severe diarrhea), Escherichia coli O157:H7 (foodborne, bloody diarrhea, kidney damage)

• Protozoal: Entamoeba histolytica (amoebic dysentery)

Irritable Bowel Syndrome (IBS)

Characteristics

• Functional disorder with no known cause

• Abdominal pain, changes in bowel habits (constipation, diarrhea), gas, bloating, nausea, loss of appetite

• Symptoms may worsen with stress, anxiety, or depression

Inflammatory Bowel Disease (IBD)

Types

• Crohn's Disease: Chronic granulomatous inflammation, can affect any part of the GI tract (mouth to anus)

• Ulcerative Colitis: Inflammation limited to the colon, always involves the large intestine

Diverticulitis

Symptoms and Complications

• Abdominal pain (often left lower side), fever, vomiting, constipation or diarrhea, elevated white blood cell count

• Complications: Abscess, perforation, peritonitis, fistula, bowel obstruction

Appendicitis

Pathogenesis and Triggers

• Appendix becomes inflamed, swollen, and may perforate if untreated

• Triggers: Blockage by fecalith, gallstones, tumors, parasites, swollen lymph tissue

Diarrhea Types

Large Volume vs. Small Volume

• Large Volume: Osmotic (water pulled into intestine, e.g., lactose intolerance), Secretory (excess fluid secretion, e.g., infections, toxins)

• Small Volume: Linked to inflammation or irritation (IBD, infections, IBS)

Celiac Disease

Pathogenesis and Manifestations

Celiac disease is a chronic autoimmune disorder triggered by gluten ingestion, leading to damage of the small intestine lining and malabsorption.

• Villi become blunted and flattened, causing poor nutrient absorption

• Symptoms: Diarrhea, bloating, abdominal pain, weight loss, constipation, anemia, fatigue, osteoporosis, skin rash, mouth ulcers, irritability, delayed growth in children

• Treatment: Lifelong gluten-free diet

Constipation and Fecal Impaction

Common Causes

• Failure to respond to urge to defecate

• Inadequate fiber/fluid intake

• Weakness of abdominal muscles

• Immobility, bed rest, malignancy, debility

• Use of constipating medications, antacids, bulk laxatives, low-residue diet, drug-induced colonic stasis

Intestinal Obstruction

Types and Effects

• Mechanical: Physical blockage (tumor, hernia, scar tissue)

• Paralytic (ileus): Muscles stop contracting, no movement of contents

• Effects: Abdominal distention, loss of fluids/electrolytes, dehydration, imbalance

Peritoneal Cavity and Peritonitis

Pathogenesis and Clinical Importance

• Peritoneal cavity absorbs toxins quickly, allowing infection to spread rapidly

• Strong inflammatory response produces thick fibrin (protective coating)

• Causes: Perforated peptic ulcer, ruptured appendix, perforated diverticulum, gangrenous bowel, pelvic inflammatory disease, gangrenous gallbladder, abdominal trauma

Intestinal Malabsorption

Definition and Manifestations

• Failure to absorb nutrients from the intestine into the body

• Causes: Celiac disease, inflammation, tumors, cancer

• Symptoms: Diarrhea, steatorrhea (fatty stools), gas, bloating, abdominal pain, cramps, weight loss, muscle weakness, abdominal distention

Colorectal Cancers

Diagnostics and Risk Factors

• Family history, ulcerative colitis, familial adenomatous polyposis

• Diagnostic tests: Stool occult blood, digital rectal examination, X-ray with barium enema, flexible sigmoidoscopy, colonoscopy

Summary Table: Major GI Disorders and Features

Disorder	Main Features	Key Microbial/Pathological Factor
GERD	Heartburn, acid reflux, mucosal irritation	Acid, pepsin, lifestyle
Peptic Ulcer	Epigastric pain, bleeding, perforation	H. pylori, NSAIDs
Gastritis	Inflammation, atrophy	Bacteria, alcohol, drugs
IBS	Abdominal pain, altered bowel habits	Functional, stress-related
IBD	Chronic inflammation, ulceration	Autoimmune, genetic
Diverticulitis	Pain, fever, abscess, perforation	Bacterial infection
Celiac Disease	Malabsorption, villi atrophy	Autoimmune, gluten
Colorectal Cancer	Obstruction, bleeding	Genetic, chronic inflammation

Additional info: These notes expand on the original slides and text, providing definitions, mechanisms, and clinical context for each disorder. All major microbiological and pathophysiological aspects relevant to a college-level microbiology course are included.