GI DISORDERS

Digestive System Structure and Function

• The digestive system is responsible for the chemical digestion of food particles, absorption of nutrients, and the elimination of waste products via defecation.
• It also provides immune and microbial protection against infection.

Gastrointestinal Tract

• The gastrointestinal tract (GI tract) is a continuous tube that extends from the mouth to the anus.
• It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• Accessory organs of the digestive system, including the liver, gallbladder and pancreas, play a vital role in digestion and absorption.

Stomach

• The stomach produces gastric juices containing mucus, acid, enzymes, hormones and intrinsic factor, as well as gastroferrin.
• The lining of the stomach has several layers, including the mucosa, submucosa, muscularis externa and serosa.
• The stomach plays a part in the digestion of proteins via gastric hydrochloric acid and pepsin.
• The stomach has special mechanisms to protect itself from its own digestive secretions.

Intestinal Digestion and Absorption

• Digestion of food begins in the stomach and continues in the small intestine.
• Pancreatic enzymes, intestinal enzymes, and bile salts are instrumental in this process.
• Carbohydrates, proteins, and fats are broken down and absorbed.
• Nutrients are absorbed by active transport, diffusion, or facilitated diffusion.

Gastric Secretion

• The stomach secretes large volumes of gastric juices.
• Mucus, acid, enzymes, and hormones, including intrinsic factor, and gastroferrin, are secreted.
• The stomach has specialized cells (like parietal and chief cells), each responsible for specific secretions.

Gastric Glands

• Gastric glands are located in the stomach lining (mucosa), and produce several secretions crucial for digestion.
• Different types of cells in these glands, such as surface mucous, mucous neck, parietal, chief, and G cells, each perform distinct functions in producing mucus, acid, enzymes and hormones for digestion.

Gastric Acid

• Secreted by parietal cells.
• Essential for dissolving food fibers and acting as a bactericide.
• Converts pepsinogen to pepsin.
• Pepsin is a proteolytic enzyme crucial for protein breakdown within the stomach.
• The stomach has mechanisms to protect the lining from its own acidic environment.

Normal Protective Mechanisms of the Stomach

• Mucus secreted by superficial mucosal cells forms a protective layer.
• The presence of bicarbonate neutralizes the acid in the lumen of the GI tract (stomach).

Peptic Ulcer Disease (PUD)

• A condition characterized by ulceration of the stomach and/or duodenum.
• Occurs when the protective mucosa cannot protect itself from corrosive substances and back-diffusion of acid.
• Helicobacter pylori (H. pylori) is a major cause.
• Other causes include hyperacidity, use of ulcerogenic drugs, cigarette smoking, genetic/environmental factors, and stress.

Gastritis

• An inflammatory disorder of the gastric mucosa.
• Acute gastritis is caused by injury of the protective mucosal barrier due to various factors such as nonsteroidal anti-inflammatory drugs (NSAIDs) or chemicals.
• Chronic gastritis is an older adult condition, and can include chronic fundal gastritis (type A, immune) or chronic antral gastritis (type B).

Intestine Disorders

• The intestines and the digestive system can be involved in several disorders, including intestinal and gastric obstructions, and diseases like paralytic ileus and hypokalemia.
• These conditions may affect the functions of normal intestinal movements and absorption.

Diagnostic Tests

• Endoscopy and biopsy aid in identifying lesions, H. pylori, and ruling out gastric cancer.
• Diagnostic tests for H. pylori include serum antibody testing and urea breath testing.
• Barium swallow is an alternative to endoscopy if contraindicated

Treatment

• Protein pump inhibitors (PPIs) and H2-receptor antagonists are common treatments for PUD.
• Treatment for H. pylori typically involves a combination of antibiotics and PPIs.
• Antacids are frequently used to neutralize gastric contents and decrease discomfort.

Complications

• Potential complications of PUD include hemorrhage (bleeding), perforation (hole) leading to peritonitis (inflammation), and reduced blood supply to the intestines from strangulation.

Stress-Related Mucosal Disease

• Ischemic ulcers, Curling ulcers, and Cushing ulcers are types of peptic ulcers related to trauma, sepsis or burns.

Proximal Colon

• The proximal colon encompasses the ascending and transverse colon and cecum.

Disorders of Motility

• Intestinal obstruction and paralytic ileus are conditions that block the passage through the intestines.

Clinical Manifestations of Intestinal Obstruction

• Abdominal pain (colicky), nausea and vomiting, abdominal distension and leukocytosis are typical signs.

Diagnostic Tests for Intestinal Obstruction

• Abdominal X-rays and CT scans, sigmoidoscopy, and colonoscopy can aid in diagnosis and visualize the obstruction.

Treatment of Intestinal Obstruction

• Decompression with NG tube and suction, fluid and electrolyte correction using IV (intravenous) fluids, and surgery (resection, colostomy or ileostomy) are typical treatments following the medical diagnosis.

Accessory Organs of Digestion

• The liver, gallbladder, and pancreas are accessory organs of digestion that have critical roles contributing to digestion and absorption.

Liver Functions

• The liver carries out several important functions, including metabolism of nutrients (fats, proteins, carbohydrates), detoxification, and storage of minerals and vitamins.

Vascular and Hematological Liver Functions

• The liver stores blood and synthesizes clotting factors which are necessary for appropriate blood clotting.

Metabolism of Bilirubin

• Bilirubin metabolism involves several steps, progressing from red blood cell breakdown to the excretion of bilirubin in bile and urine.

Portal Hypertension

• A significant complication of cirrhosis, characterized by abnormally high blood pressure in veins leading to the liver can lead to several related disorders.

Liver Disorders

• Fatty liver disease, hepatitis B & C are the most common causes of liver damage, also a major cause of liver transplants.

Cirrhosis

• Liver inflammation, necrosis followed by fibrosis and scarring are the key components of cirrhosis.
• The loss in liver function can lead to several other related complications—portal hypertension, hypoalbuminemia, ascites, hepatic encephalopathy, and others.

Pathophysiology of Cirrhosis

• Ischemia and necrosis (death) of liver cells are followed by regeneration leading to scarring.
• This process disrupts the normal architecture of the liver (make-up of the organs) and causes problems with blood flow and liver function.

Clinical Manifestations of Cirrhosis

• Early symptoms are mild, but they can worsen over time and include fatigue, weight loss, anorexia, jaundice, constipation, and abdominal pain.
• Symptoms include portal hypertension, esophageal varices, ascites, and blood and clotting problems.

Portal Hypertension

• Increased resistance to blood flow through the liver's vasculature results in portal hypertension.
• This can cause several critical complications.

Portal Venous System

• The portal venous system is crucial for carrying blood from the digestive organs into the liver for processing and filtering.

Esophageal Varices

• Varices are enlarged and swollen veins in the esophagus.
• They can rupture and bleed profusely, leading to potentially life-threatening complications.

Ascites

• Ascites is the accumulation of serous fluid in the peritoneal cavity (around the abdomen).

Pathophysiology of Ascites

• Increased pressure in the portal venous system, low albumin in the blood, and elevated aldosterone levels may all lead to fluid leaking into the tissues.

Complications of Cirrhosis

• Complications of cirrhosis include varices, splenomegaly, hepatopulmonary syndrome, hepatorenal syndrome and others.

Vomiting of Blood

• Vomiting blood, due to ruptured esophageal varices, is a critical symptom that should be addressed immediately.

Hematological Problems

• Disorders affecting the production, function, or destruction of blood cells (RBCs, WBCs, platelets) are related to problems with portal hypertension, splenomegaly etc.

Hepatic Encephalopathy

• A neuropsychiatric disorder characterized by impaired behavior, cognition, and motor function, caused by liver dysfunction.

Hepatorenal Syndrome

• A critical complication that involves kidney failure due to low blood volume, and advanced azotemia and intractable ascites.

Hyperbilirubinemia

• Excessive bilirubin levels cause jaundice which is characterized by a yellowing of skin and eyes and may also indicate poor liver function.

Hyperestrogenemia

• Impaired liver function leads to the body accumulating estrogen, potentially causing gynecomastia in males and other related symptoms

Diagnostic Testing for Liver Disorders

• Liver Function Tests (LFTs), such as aminotransferase or AST/ALT tests, Prothrombin Time (PT), INR, and bilirubin tests, give a detailed assessment for liver functionality.

Treatment of Liver Disorders

• Treatment for liver problems often includes rest, nutritional dietary adjustments, vitamin supplements and in severe cases, liver transplant.

Disorders of the Pancreas

• Pancreatitis includes acute (often resolved spontaneously) or chronic (progressive) forms, characterized by inflammation of the pancreas.
• Often related to gallstones or alcohol abuse—either of which can obstruct the outflow of pancreatic enzymes.

Clinical Manifestations of Pancreatitis

• Epigastric or midabdominal pain, ranging from mild to severe, and other symptoms including fever, leukocytosis, nausea, vomiting, and jaundice, may occur.

Diagnostic Tests for Pancreatitis

• Elevated amylase and lipase levels in the blood, and abdominal X-rays, ultrasounds, and CT scans can detect the appropriate diagnoses.

Treatment of Pancreatitis

• Treating the symptoms and mitigating causes are the typical goals, including pain relief medication, electrolyte balancing with IV fluids, NPO and NG tubes (if needed), and antibiotics (if infection is suspected).

Gallbladder

• The gallbladder is a sac-like organ that lies on the inferior surface of the liver, and functions to store and concentrate bile between meals.
• It begins to contract 30 minutes after eating, facilitated by both the vagus nerve and cholecystokinin.

Gallstones

• Gallstones are formed when the biochemical composition of bile leads to supersaturation of cholesterol or bilirubin.
• Types of stones include cholesterol and pigmented brown and black gallstones.
• They can cause obstruction or inflammation leading to complications.

Disorders of the Gallbladder

• Cholecystitis, an inflammation of the gallbladder, is frequently caused by gallstones lodged in the cystic duct.
• Gallstones can also obstruct the common bile duct causing pain that is similar to other disorders, such as epigastric or right hypochondrium pain and intolerance to fatty foods.

Case Study Notes

• A 55-year-old male with a history of alcohol abuse and smoking reports pain and burning pressure around his stomach two to three hours after eating along with a 4.5-kg weight loss in two months.
• His examination with an esophagogastroduodenoscopy (EGD) reveals stomach ulcers and biopsy confirms H. Pylori bacteria.

Discussion Questions

• Potential risk factors for PUD and how this might happen.
• Treatment options.
• Potential complications of PUD.
• Lifestyle modifications necessary for healing.