Gastrointestinal Tract Disorders PDF

## Disorders of the Gastrointestinal Tract - **Anorexia**, **loss of appetite**, **vomiting**, **constipation**, **diarrhea**, **abdominal pain**, and **evidence of gastrointestinal bleeding** are clinical manifestations of many disorders of the gastrointestinal tract. - **Vomiting** is the forcefu...

## Disorders of the Gastrointestinal Tract - **Anorexia**, **loss of appetite**, **vomiting**, **constipation**, **diarrhea**, **abdominal pain**, and **evidence of gastrointestinal bleeding** are clinical manifestations of many disorders of the gastrointestinal tract. - **Vomiting** is the forceful emptying of the stomach effected by gastrointestinal contraction and reverse peristalsis of the esophagus. It is usually preceded by **nausea** and **retching** with the exception of **projectile vomiting**, which is associated with direct stimulation of the vomiting center in the brain. - **Primary constipation** is defined in three categories: - **Functional**: associated with low-residue, low-fluid diet. - **Slow-transit**: related to impaired colonic motor function. - **Pelvic floor dyssynergia-anismus**: decreased intestinal motility. - **Secondary constipation** results from a **neurogenic disease**, **drugs that decrease intestinal motility**, **endocrine or metabolic disorders**, or **obstruction**. - **Diarrhea** can be caused by: - **Osmosis**: excessive fluid drawn into the intestinal lumen. - **Secretion**: excessive secretion of fluids by the intestinal mucosa. - **Motility**: excessive gastrointestinal motility. - **Abdominal pain** is caused by **stretching**, **inflammation**, or **ischemia** and originates in the **peritoneum** (parietal pain) or in the organs themselves (visceral pain). Visceral pain is often referred to the back. - **Gastrointestinal bleeding** can occur in the **upper** or **lower gastrointestinal tract**. - **Hematemesis**: vomiting of blood. - **Melena**: dark, tarry stools. - **Hematochia**: frank bleeding from the rectum. - **Occult bleeding**: can be detected only by testing stools or vomitus for the presence of blood. - **Dysphagia** is difficulty in swallowing or perception of obstruction during swallowing. It can be caused by a **mechanical** or **functional obstruction** of the esophagus. Functional obstruction is an impairment of esophageal motility. - **Achalasia** is a form of functional dysphagia caused by **loss of esophageal innervation** or **relaxation of the lower esophageal sphincter**. - **Gastroesophageal reflux disease** is the **regurgitation of chyme from the stomach into the esophagus**, causing **esophagitis** from repeated exposure to acids, enzymes, or bile salts in the regurgitated gastric contents. - **Hiatal hernia** is the **protrusion of the upper part of the stomach through the hiatus** (esophageal opening in the diaphragm) at the gastroesophageal junction. Hiatal hernia can be **sliding**, **paraesophageal**, or **mixed**. - **Gastroparesis** is **delayed gastric emptying in the absence of mechanical gastric outlet obstruction**. - **Pyloric obstruction** is the **narrowing or blockage of the pylorus**, which is the opening between the stomach and the duodenum. It can be caused by a **congenital defect**, **inflammation and scarring secondary to a gastric ulcer**, or **tumor growth**. - **Intestinal obstruction** can occur in the **small or large intestine** and prevents the normal movement of chyme through the intestinal tract. It is usually **mechanical**: caused by **torsion**, **herniation**, or **tumor**. **Functional obstruction** is caused by **paralytic ileus**. - The most severe consequences of intestinal obstruction are: - **Fluid and electrolyte losses**. - **Hypovolemia**. - **Shock**. - **Intestinal necrosis**. - **Perforation of the intestinal wall**. - **Gastritis** is an **acute or a chronic inflammation of the gastric mucosa**. - **Regurgitation of bile**, **use of antiinflammatory drugs or alcohol**, **H. pylori infection**, and **some systemic diseases** are associated with gastritis. - **Chronic fundal gastritis** is rare and associated with **autoantibodies to parietal cells and intrinsic factor**, resulting in **gastric atrophy** and causing **pernicious anemia**. - **Chronic antral gastritis** is the most common gastritis and is associated with **H. pylori and NSAIDs**. - **Alkaline reflux gastritis** is stomach inflammation caused by the reflux of bile and pancreatic secretions from the duodenum into the stomach. These substances disrupt the mucosal barrier and cause inflammation. - **A peptic ulcer** is a **circumscribed area of mucosal inflammation and ulceration** caused by **excessive secretion of gastric acid**, **disruption of the protective mucosal barrier**, or **both**. - The three types of peptic ulcers are: - **Duodenal**. - **Gastric**. - **Stress ulcers**. - Duodenal and gastric ulcers are associated with **H. pylori infection and chronic use of NSAIDs**. - **Duodenal ulcers**, the most common peptic ulcers, are associated with: - **Increased numbers of parietal** (acid-secreting) cells in the stomach. - **Elevated gastrin levels**. - **Rapid gastric emptying**. - Pain occurs when the stomach is empty, and pain is relieved with food or antacids. Duodenal ulcers tend to heal spontaneously and recur frequently. - **Gastric ulcers** develop near parietal cells, generally in the antrum, and tend to become chronic. Gastric secretions may be normal or decreased, and pain may occur after eating. - **Zollinger-Ellison syndrome** is associated with a **gastrinoma**, **chronic secretion of gastric acid**, and **gastric and duodenal ulcers**. - **Stress ulcer** (stress-related mucosal disease) is an acute form of peptic ulcer associated with severe illness or extensive trauma. - **Ischemic stress ulcers** develop suddenly after severe illness, systemic trauma, neural injury, or burns (Curling ulcer). Ulceration follows mucosal damage caused by ischemia (decreased blood flow to the gastric mucosa). - **Cushing ulcer** is a stress ulcer caused by head trauma. Ulceration follows hypersecretion of hydrochloric acid caused by overstimulation of the vagal nuclei. - **Postgastrectomy syndromes** are a group of signs and symptoms that occur after gastric resection for the treatment of peptic ulcer,_ gastric carcinoma_, or_ bariatric surgery_ for extreme obesity. - **Dumping syndrome** causes malabsorption by the rapid emptying of hypertonic chyme from the surgically created residual stomach into the small intestine. It causes an osmotic shift of fluid from the vascular compartment to the intestinal lumen, which decreases plasma volume. - **Malabsorption syndromes** result in impaired digestion or absorption of nutrients. - **Pancreatic insufficiency** causes malabsorption associated with insufficient amounts of the enzymes that digest protein, carbohydrates, and fats into components that can be absorbed by the intestine. - **Deficient lactase production** in the brush border of the small intestine inhibits the breakdown of lactose. This prevents lactose absorption and causes osmotic diarrhea. - **Bile salt deficiency** causes fat malabsorption, including fat-soluble vitamins, and steatorrhea (fatty stools). Bile salt deficiency can result from inadequate secretion of bile, excessive bacterial deconjugation of bile, or impaired reabsorption of bile salts caused by ileal disease. - **Ulcerative colitis** is an inflammatory bowel disease that causes ulceration, abscess formation, and necrosis of the colonic and rectal mucosa. Cramping pain, bleeding, frequent diarrhea, dehydration, and weight loss accompany severe forms of the disease. A course of frequent remissions and exacerbations is common. - **Crohn disease** is similar to ulcerative colitis but it affects entire GI tract, including the large and small intestines. Ulceration tends to involve all layers of the lumen. "Skip lesion" fissures and granulomas are characteristic of Crohn disease. Abdominal tenderness, nonbloody diarrhea, and weight loss are the usual symptoms. - **Microscopic colitis** involves two histologic forms of the disease, lymphocytic and collagenous, with both resulting in frequent diarrhea. - **Irritable bowel syndrome** is a disorder of brain-gut interaction characterized by abdominal pain with altered bowel habits (diarrhea, constipation, or both). - **Diverticula** are outpouchings of colonic mucosa through the muscle layers of the colon wall. **Diverticulosis** is the presence of these outpouchings; **diverticulitis** is inflammation of the diverticula. - **Appendicitis** is caused by obstruction of the lumen and leads to increased pressure, ischemia, and inflammation of the appendix. Without surgical resection, inflammation may progress to gangrene, perforation, and peritonitis. - **Vascular insufficiency in the intestine** is associated most often with acute or chronic occlusion or obstruction of the mesenteric vessels or insufficient mesenteric arterial blood flow. The resulting ischemia and necrosis produce abdominal pain, fever, bloody diarrhea, hypovolemia, and shock. ## Disorders of the Accessory Organs of Digestion 1. **Portal hypertension**, **ascites**, **hepatic encephalopathy**, **jaundice**, and **hepatorenal syndrome** are complications of many liver disorders. 2. **Portal hypertension** is an elevation of portal venous pressure to at least 10 mmHg. It is caused by increased resistance to venous flow in the portal vein and its tributaries, including the sinusoids and hepatic vein. 3. Portal hypertension is the most serious complication of liver disease because it can cause fatal complications, such as bleeding varices, ascites, hepatic encephalopathy, and renal failure. 4. **Varices** are distended, tortuous, collateral veins associated with portal hypertension. 5. **Splenomegaly** is an enlargement of the spleen resulting from increased splenic vein pressure caused by portal hypertension. 6. **Hepatopulmonary syndrome** is pulmonary hypertension related to the release of vasodilators that affect pulmonary arterioles and is associated with portal hypertension and severe liver disease. 7. **Ascites** is the accumulation and sequestration of fluid in the peritoneal cavity, often as a result of portal hypertension, decreased concentrations of plasma proteins, and sodium retention. 8. **Hepatic encephalopathy** (portosystemic encephalopathy) is impaired cerebral function caused by blood-borne toxins (particularly ammonia) not metabolized by the liver. 9. **Jaundice** (icterus) is a yellow or greenish pigmentation of the skin or sclera of the eyes caused by increases in plasma bilirubin concentration (hyperbilirubinemia). 10. **Obstructive jaundice** is caused by obstructed bile canaliculi (intrahepatic obstructive jaundice) or obstructed bile ducts outside the liver (extrahepatic obstructive jaundice). Bilirubin accumulates proximal to sites of obstruction, enters the bloodstream, and is deposited in the skin and other connective tissues. 11. **Hemolytic jaundice** is caused by destruction of red blood cells at a rate that exceeds the liver's ability to metabolize unconjugated bilirubin. 12. **Hepatorenal syndrome** is functional renal failure caused by advanced liver disease, particularly cirrhosis with portal hypertension. Renal failure is caused by a sudden decrease in blood flow to the kidneys, usually as a result of massive gastrointestinal hemorrhage or liver failure. Its chief clinical manifestation is oliguria. 13. **Acute liver failure** can be caused by toxic overdose of acetaminophen or complications of viral hepatitis. 14. **Autoimmune hepatitis** is T-cell mediated inflammatory liver disease with hypergammaglobulinemia, elevated transaminases, and absence of viral hepatitis. 15. **Viral hepatitis** is an infection of the liver caused by strains of the hepatitis virus. Modes of transmission are HAV and HEV, fecal-oral route; and HAV, HBV, HCV, HDV, and HEV, parenteral and sexual transmission. The hepatitis viruses can cause hepatic cell necrosis, Kupffer cell hyperplasia, and infiltration of liver tissue by mononuclear phagocytes. These changes obstruct bile flow and impair hepatocyte function. 16. The clinical manifestations of viral hepatitis depend on the stage of infection. Fever, malaise, anorexia, and liver enlargement and tenderness characterize the prodromal phase (stage 1). Jaundice and hyperbilirubinemia mark the icteric phase (stage 2). During the recovery phase (stage 3), symptoms resolve. Recovery takes several weeks. 17. Chronic active hepatitis can occur with HBV and HCV with predisposition to cirrhosis and hepatocellular carcinoma. ## Cancer of the Digestive System 1. Cancer of the esophagus is rare and tends to occur in people older than 60 years. Alcohol and tobacco use, reflux esophagitis, radiation exposure, and nutritional deficiencies are associated with esophageal carcinoma. There are two types, squamous cell and adenocarcinoma. 2. Dysphagia and chest pain are the primary manifestations of esophageal cancer. Early treatment of tumors that have not spread into the mediastinum or lymph nodes results in a good prognosis. 3. Gastric carcinoma is associated with H. pylori (CagA), high salt intake, food preservatives (nitrates and nitrites), and atrophic gastritis. 4. Gastric cancers are commonly located in the prepyloric antrum. Clinical manifestations (weight loss, upper abdominal pain, vomiting, hematemesis, anemia) develop only after the tumor has penetrated the wall of the stomach. 5. Cancer of the colon and rectum (colorectal cancer) is the third most common type of cancer and cancer death in the United States. Small intestinal cancers are rare. Familial adenomatous polyposis coli and hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome) are inherited forms of colon cancer. Preexisting large and numerous polyps are highly associated with sporadic (acquired) adenocarcinoma of the colon. 6. Tumors of the right (ascending) colon are usually large and bulky; tumors of the left (descending, sigmoid) colon develop as small button-like masses. Manifestations of colon tumors include pain, bloody stools, and change in bowel habits. 7. Rectal carcinoma is located up to 15 cm from the opening of the anus. The tumor spreads transmurally to the vagina in women or to the prostate in men. 8. Metastatic invasion of the liver is more common than primary cancer of the liver. 9. Primary liver cancers are associated with chronic liver disease (cirrhosis and hepatitides B and C). Hepatocellular carcinomas arise from the hepatocytes, whereas cholangiocellular carcinomas arise from the bile ducts. Primary liver cancer spreads to the heart, lungs, brain, kidney, and spleen through the circulation. 10. Cancer of the gallbladder is relatively rare and tends to occur in women older than 50 years. Adenocarcinoma is most common. Because clinical manifestations occur late in the disease, metastases to lymph channels have usually occurred by the time of diagnosis, and the prognosis is poor. 11. Cancer of the pancreas represents about 2.6% of all cancers in the United States. Most tumors are adenocarcinomas that arise in the exocrine cells of ducts in the head, body, or tail of the pancreas. Symptoms may not be evident until the tumor has spread to surrounding tissues. Treatment is palliative, and mortality is nearly 100% for advanced tumors.