GI_and_Hepatology_Lecture__1___1_

GASTROENTEROLOGY

Course Title: GASTROENTEROLOGYCourse Code: NURS 5315 Advanced PathophysiologyInstructor: Kristin Hittle Gigli, PhD, RN, CPNP-AC

OBJECTIVES

Students will:

• Examine the intricate anatomy and physiology of the GI system, focusing on the interconnectedness of various organs.

• Differentiate between upper and lower GI organs, emphasizing their distinct roles and functions in digestion.

• Explain hepatoportal circulation and its critical importance in nutrient processing and detoxification.

• Analyze pathologic bases for GI disorders, including:

  • Diarrhea (osmotic, secretory, and motility-related) and its implications for hydration and electrolyte balance.

  • Upper and lower GI bleeds, their causes, symptoms, and management strategies, focusing on ulcerative and malignant processes.

  • Conditions such as ulcerative colitis, Crohn’s disease, and IBS, with special attention to their nutritional implications and patient management.

  • Diverticulitis and diverticulosis, focusing on their prevalence and impact on the aging population.

  • Small and large bowel obstructions, including causes and consequences, such as ischemia and perforation.

  • Appendicitis, with emphasis on diagnostic criteria and common outcomes.

  • Acute pancreatitis, cholecystitis, and cholelithiasis, analyzing their etiology and treatment options.

• Evaluate age-related changes in the GI system, noting alterations in function and health outcomes in the elderly.

• Analyze the etiology, manifestations, and pathophysiology of:

  • Pyloric stenosis, focusing on its pediatric presentation and management.

  • Anorexia of aging, discussing its multifactorial causes and effects on health.

FUNCTIONS OF THE GI TRACT

Key Functions:

• Ingestion of food: The process of taking in nutrients through the mouth.

• Propulsion of food and waste from mouth to anus: Involves peristalsis and segmentation movements within the GI tract.

• Secretion of mucous, water, and enzymes: Essential for lubrication and digestion.

• Mechanical and chemical digestion: Breakdown of food into absorbable nutrients through physical and enzymatic processes.

• Absorption of nutrients: Transfer of nutrients from the intestines into the bloodstream.

• Elimination of waste: Removal of indigestible substances from the body.

• Immune and microbial protection against infection: The gut serves as a barrier to pathogens and supports immune responses.

CONTROL OF GI TRACT FUNCTION

Control Mechanisms:

• Muscle control: Involuntary muscle contractions (e.g., chewing, swallowing, defecation).

• Hormonal control: Influences of the autonomic nervous system on motility and secretion, including gastrin, secretin, and cholecystokinin (CCK).

ANATOMY

Division of GI Tract:

• Upper GI: Mouth, esophagus, stomach, duodenum. Each organ performs specific digestive functions.

• Lower GI: Small intestine, large intestine, colon; key areas for nutrient absorption and waste formation.

• Sphincters: Control compartmentalization between organs, preventing backflow and regulating flow (e.g., lower esophageal sphincter, pyloric sphincter).

• Gut wall: Structured into layers (mucosa, submucosa, muscularis, serosa) that support its diverse functions.

GI BLOOD FLOW

Arterial Supply:

• Celiac artery: Supplies blood to the stomach, liver, spleen, and proximal duodenum.

• Mesenteric artery: Supplies blood to the small intestine and part of the large intestine.

Venous Blood Supply:

• Blood flows to hepatic circulation via the portal vein, facilitating the detoxification process in the liver before returning to the inferior vena cava (IVC) through hepatic veins.

HEPATIC CIRCULATION

Functionality of Liver:

• Blood flows through liver sinusoids, allowing for nutrient processing and detoxification.

• Kupffer cells: Specialized macrophages in the liver that remove pathogens and debris from blood.

• Reticuloendothelial cells and hepatocytes: Involved in absorption and storage of nutrients, and in metabolism.

COUNTERCURRENT BLOOD FLOW IN VILLI

Unique Flow Mechanism:

• Arterial and venous vessels flow adjacent but in opposite directions, enhancing oxygen exchange.

• Decreased perfusion can lead to villi ischemia, necrosis, and reduced absorptive capacity, creating a risk for bacterial translocation into the bloodstream.

GI DISORDERS

Introduction to GI disorders and their impact on health

• Understanding the vast array of GI disorders is crucial for effective patient management and improving health outcomes.

MOTILITY DISORDERS - CONSTIPATION

Definition & Classification:

• Difficult or infrequent stooling classifies as constipation. Understanding the underlying causes is essential for effective treatment.

• Primary: Includes functional, slow-transit, and pelvic floor dysfunction.

• Secondary: Can occur due to opioid use, spinal cord injuries, strokes, Parkinson’s disease, and Hirschsprung disease.

• Symptoms persist for over three months and may involve straining, hard stools, and sensations of incomplete emptying.

MOTILITY DISORDERS - DIARRHEA

Definition & Types:

• Defined as three or more loose stools per day, which can be acute, persistent, or chronic.

• Types: Includes osmotic (substances increase intestinal water), secretory (increased secretion due to infection), and motility-induced (accelerated bowel movements).

• The consequences of prolonged diarrhea include dehydration, electrolyte imbalances, and potentially metabolic acidosis.

GI BLEEDING

Classification based on bleeding origin:

• Upper GI: Causes include esophageal and gastric varices, cancers, and peptic ulcers.

• Lower GI: Polyps, inflammatory bowel disease, and diverticular disease.

• Symptoms may comprise hematemesis, melena, and hematochezia, guiding the diagnosis and management.

ULCERATION

Types of Peptic Ulcers:

• Occur in the lining of the esophagus, stomach, or duodenum. Risk factors include H. pylori infection, NSAID use, alcohol intake, and advanced age.

• Types:

  • Gastric Ulcers: More frequent in individuals aged 50-70, with a heightened risk of gastric cancer.

  • Duodenal Ulcers: Typically seen in younger patients, linked to increased gastric acid secretion.

INFLAMMATORY BOWEL DISEASE

Characteristics:

• A chronic relapsing condition influenced by genetic and environmental factors.

• Increased risk of colorectal cancer and requires ongoing management strategies.

• Ulcerative Colitis: Presents with continuous lesions restricted to the mucosal layer of the colon.

• Crohn’s Disease: Can affect any segment of the gastrointestinal tract and is characterized by “skip lesions.”

IRRITABLE BOWEL SYNDROME

• Involves an interaction of the brain-gut axis leading to abdominal pain and altered bowel habits. Stress and psychological factors may exacerbate symptoms.

• Commonly affects women and manifests as pain, bloating, and urgency without disrupting sleep quality.

DIVERTICULAR DISEASE OF COLON

• Diverticulitis: An inflammatory condition that manifests with abdominal pain, diarrhea, and cramping. Management may involve dietary adjustments and antibiotic therapy.

• Diverticulosis: Characterized by outpouching of the mucosa through the muscle layer, typically asymptomatic but may lead to complications.

BOWEL OBSTRUCTIONS

Definition and causes:

• Defined as any blockage affecting intestinal flow, which can be acute or chronic, intrinsic or extrinsic (e.g., hernias, adhesions, intussusception).

• Symptoms may include colicky pain, distension, and additional signs that depend on the obstruction's location.

APPENDICITIS

• Inflammation of the appendix is the most common cause of abdominal surgical emergencies.

• Presentation typically begins with epigastric pain that migrates to the right lower quadrant, often accompanied by nausea and vomiting, requiring prompt diagnosis and treatment.

CHOLELITHIASIS (GALL STONES)

• Associated risks include obesity, female sex, and increasing age.

• Leads to obstruction or inflammation in the gallbladder; symptoms include episodic pain after fatty meals, often requiring surgical intervention.

PANCREATITIS

• Acute inflammation of the pancreas presenting with severe epigastric pain, which can be complicated by fever and jaundice. Diagnosis often utilizes pancreatic enzymes (amylase and lipase) for assessment.

DISEASE OF AGE

• Pyloric Stenosis: A condition in infants caused by hypertrophy of the pyloric sphincter, typically presenting in early life and usually treated with surgical intervention.

• CHANGES IN GI TRACT WITH AGING: Key changes include diminished secretory function, reduced motility, and alterations in gut flora composition.

• ANOREXIA OF AGING: Involves a reduced appetite tied to a blend of psychological and physiological factors, leading to risks of malnutrition and frailty.

HEPATOLOGY

• Focuses on mechanisms of liver injury, patterns of chronic liver failure, and implications for patient management and care strategies.

ACUTE LIVER INJURY / FAILURE

• Characterized by hepatocyte necrosis without a prior history of liver disease. Potential causes include medication overdose and viral hepatitis, necessitating immediate evaluation.

CHRONIC LIVER FAILURE (CIRRHOSIS)

• Irreversible disease marked by fibrotic changes in liver architecture, attributable to diverse etiologies such as chronic alcoholism and viral infections.

LIVER FAILURE MANIFESTATIONS

• Symptoms encompass jaundice, portal hypertension, ascites, and hepatic encephalopathy, indicating systemic impacts of liver dysfunction.

JAUNDICE

• Manifestation of yellowing of the skin due to hyperbilirubinemia, classified into categories based on causative factors, including obstruction and hemolysis.

PORTAL HYPERTENSION

• A condition characterized by elevated pressures in the portal venous system, leading to complications like varices and splenomegaly.

ASCITES

• Accumulation of fluid in the peritoneal cavity due to various underlying conditions, impacting fluid dynamics and increasing infection risk through peritoneal fluid change.

HEPATIC ENCEPHALOPATHY

• Neurologic complications arising from liver failure, attributed to altered metabolism and the accumulation of neurotoxins, demanding rigorous monitoring and management.

ALCOHOLIC LIVER DISEASE

• A spectrum of conditions ranging from simple steatosis to advanced cirrhosis, caused by chronic alcohol consumption, emphasizing the importance of early intervention.

HEPATITIS

• Various types including Hepatitis A (transmitted via fecal-oral), Hepatitis B (via blood/serum), and Hepatitis C (via blood and sexual contact), each with distinct risk factors and management strategies.

NEONATAL JAUNDICE

• A common, usually benign, condition in newborns requiring careful monitoring to prevent severe complications, highlighting the need for pediatric awareness.

SUMMARY

The complex interaction of GI and liver disorders underlines the necessity for a comprehensive understanding of their distinctive presentations and implications for blood flow as we age, guiding effective treatment and patient care.