Week 12 Gastrointestinal Disorders

GI Tract is divided up into portions

• Mouth

• Esophagus

• Stomach

  • Fundus, cardia, body, pylorus

• Small intestine

  • Duodenum, jejunum and ileum

• Large intestine

  • Cecum, ascending, transverse,

    descending, sigmoid colon and rectum

What is the purpose of the GI tract?

Ingestion, digestion, and absorption

Categories of nutrients

Carbohydrates, Proteins, and Lipids

Nutrients - Carbohydrates

Amylase in oral cavity; amylase from pancreas; enzymes from brush border.

Nutrients - Proteins

• Gastrin; hydrochloric acid converts pepsinogen to pepsin (chyme)

• Cholecystokinin in small intestine- pancreatic enzymes (e.g., trypsinogen)

Nutrients - Lipids

Cholecystokinin stimulates the gallbladder (bile) and pancreas and small intestine (lipase)

Peptic Ulcers

• Break in mucosa in stomach or duodenum - Potential of perforation

• Duodenal and gastric ulcers are commonly caused by Helicobacter pylori

  • Stimulates the inflammatory process

  • Increase in hydrochloric acid

  • Production of urease

Peptic Ulcers Transmission

person-to-person, fecal-to-oral, and contaminated food

Peptic Ulcers Laboratory considerations

Gastroscopy, breath tests, stool antigen tests, and serological tests

GI Ulcers - Diagnosis (Gastroscopy)

Tissue samples, Rapid urease test (phenol red; changes in colour), Microbiological cultures and Histologic tests.

GI Ulcers - Diagnosis (Urea breath test)

• High sensitivity (94%) and high specificity (98%)

• Most widely used test (noninvasive)

• Commonly uses urea with carbon-13

• Pathogenic H. pylori produces urease

  • Breaks down urea and release CO2

• Elevated levels of labeled CO2 indicate H. pylori

  • Detect active infections

GI Ulcers - Diagnosis (Stool test for H. pylori antigen)

• Reliable, convenient, and noninvasive test

• High sensitivity and specificity (>90%)

• Detect active/ recent infections

• Use of immunoassays (ELISA)

GI Ulcers - Diagnosis (Serological tests)

Antibodies (IgM, IgA, IgG) to H. pylori

Zollinger-Ellison Syndrome

Associated with mutations; Benign, non-beta-islet cell, gastrin-secreting tumours; Gastrinomas (pancreas or duodenum).

A rare condition characterized by gastrin-secreting tumors (gastronomas) that lead to excessive gastric acid production. This overproduction can cause severe peptic ulcers and gastrointestinal symptoms due to high acidity levels.

Zollinger-Ellison Syndrome (symptoms/signs)

• Gastric pain

• Fulminant peptic ulcers

• Massive gastric hypersecretion

• Hypergastrinemia

• Diarrhea

• Steatorrhea

Zollinger-Ellison Syndrome - Diagnosis

• Gastrin levels

  • Gastrin levels >10 X RI + gastric acid hypersecretion (diagnostic-gastrinoma)

• Imaging techniques (CT scan)

• Gastroscopy

• H. pylori investigation is negative

Malabsorption Syndrome

• Defective absorption of nutrients

• Single nutrient malabsorption (i.e., lactose)

• Widespread nutrient deficiency (i.e., Crohn disease, Celiac disease)

• Common symptoms: diarrhea, abdominal discomfort, and weight loss

Malabsorption Syndrome- Diagnosis

• CBC

• Prothrombin time

• Vitamin and mineral assays

• Serologic tests (celiac disease)

• Pancreatic elastase-1 (maldigestion Vs. malabsorption)

• Stool cultures (bacteria? Parasites?)

• Fecal fat test (nonspecific)

• Lactose tolerance test

  • No significant increase in blood glucose

Diarrhea

• Loose, watery, and frequent stools

  • Chronic if >4 wks

Diarrhea (Acute)

Bacterial, parasitic, viral causes, antibiotic

Diarrhea (Chronic)

• May lead to: dehydration and low potassium levels

• Causes

  • Inflammatory bowel disease

  • Irritable bowel syndrome

  • Celiac disease

  • Food intolerances (E.g., lactose)

  • Chemotherapy, radiation

Laboratory Tests for Diarrhea

• Stool cultures

• Immunoassays

  • C. difficile, rotavirus, and E. coli strains

• Ova and parasite test

• Fecal fat test (nonspecific)

Inflammatory Bowel Disease (IBD)

Primarily including Ulcerative colitis and Crohn disease; Unknown cause; Both exhibit bouts of remission and exacerbations.

Cause chronic inflammation in the digestive tract, leading to symptoms such as abdominal pain, severe diarrhea, weight loss, and fatigue.

Symptoms of Inflammatory Bowel Disease (IBD)

Abdominal pain, Cramping, Anorexia, Bloody diarrhea and Anemia.

Characteristic of Crohn Disease

• Area affected: More common in terminal ileum and colon

• Stool: Loose, semiformed

• Lesion distribution: Transmural, all layers and skip lesions

• Presence of granuloma: Common

• Fistula, fissure, abscess: Common

• Stricture, obstruction: Common

• Malabsorption: Yes

Characteristic of Ulcerative colitis

• Area affected: Rectum, colon

• Stool: Frequent, watery, with blood and mucus

• Lesion distribution: Mucosa only diffuse

• Presence of granuloma: No

• Fistula, fissure, abscess: No

• Stricture, obstruction: Rare

• Malabsorption: Not Common

Inflammatory Bowel Disease - Diagnosis

• CBC (WBC)

• C-reactive protein

• Calprotectin stool test

  • High because of inflammation

• Fecal examination

  • Red and white blood cells

• Occult blood tests

• Imaging (e.g., MRI) and endoscopy / biopsy

Celiac Disease

Autoimmune disease: Antibodies to gluten (gliadin); Inflammation, malabsorption; Avoided through a gluten-free diet

An autoimmune disorder that occurs in genetically predisposed individuals where the ingestion of gluten—a protein found in wheat, barley, and rye—leads to damage in the small intestine.

Celiac Disease - Diagnosis

• Signs and symptoms are important

• Biopsy (gold standard) -invasive

  • Endoscopy

  • Villus atrophy

• Serological tests

Signs and Symptoms of Celiac Disease

Diarrhea, weight loss, abdominal pain, bloating, fatigue, and anemia. In children, it can also cause delayed growth and development.

Celiac Disease- Diagnosis

• Serological tests:

  • (EMA) IgA-antiendomysial antibody

  • (AGA) IgA-antigliadin antibody

  • (tTG) IgA-antitissue transglutaminase antibody

  • (DGP) IgA-deamidated gliadin peptide antibody

IgA-antiendomysial antibody (EMA)

Immunofluorescence on monkey esophagus or human umbilical cord

Quantitative ELISA

• IgA-antigliadin antibody (AGA)

• IgA-antitissue transglutaminase antibody (tTG)

• IgA- deamidated gliadin peptide antibody (DGP)

Gastrointestinal Function Tests

• Evaluate the function of the digestive system

• Fecal fat test

  • E.g., pancreatitis, celiac disease, cystic fibrosis

• 24-hour pH monitoring

• D-Xylose absorption test

  • Easily absorbed in intestine

  • E.g., celiac disease, small intestinal bacterial overgrowth, pancreatic insufficiency