GIT

• Agenesis


  Absence of the esophagus - extremely rare

  
• Atresia


  Development is incomplete, more common
• Atresia


  1. Occurs most commonly at or near the tracheal bifurcation

  2. Usually associated with a fistula connecting the upper or lower esophageal pouches to a bronchus or the trachea

  3. Segment of the esophagus does not develop, leaving only a thin, noncanalized cord and causing a mechanical obstruction

  
• Imperforate anus


  The most common form of congenital intestinal atresia; due to a failure of the cloacal diaphragm to involute
• Stenosis


  Incomplete form of atresia in which the lumen is markedly reduced in caliber as a result of fibrous thickening of the wall
• Omphalocele


  • Occurs when closure of the abdominal musculature is incomplete
  • The abdominal viscera herniate into a ventral membrane covered by amnion and peritoneum separated by Wharton jelly
  • Often associated with other birth defects as well as chromosomal abnormalities
• Gastroschisis


  • Involves all of the layers of the abdominal wall, from the peritoneum to the skin
  • Usually limited to the intestine
  • Occurs as an isolated defect without other abnormalities
• Ectopic gastric mucosa


  Most frequent site is the upper third of the esophagus, where it is referred to as an inlet patch
• Ectopic pancreatic tissue


  Occurs less frequently and is found in the esophagus or stomach

  
• True diverticulum


  A blind outpouching of the alimentary tract that communicates with the lumen and includes all three layers of the bowel wall
• Meckel diverticulum


  • The most common true diverticulum, occurs in the ileum
  • The "rule of 2s" is often used to help remember characteristics: occur in approximately 2% of the population, are generally present within 2 feet (60 cm) of ileocecal valve, are approximately 2 inches (5 cm) long, are twice as common in males, are most often symptomatic by age 2

  
• Acquired diverticula


  Lack muscularis entirely or have an attenuated muscularis propria, the most common site is the sigmoid colon
• Congenital hypertrophic pyloric stenosis

  • Generally, presents between the third and sixth weeks of life as new-onset regurgitation, projectile, nonbilious vomiting after feeding
  • Firm, ovoid, 1 to 2 cm abdominal mass
  • Surgical splitting of the muscularis (myotomy) is curative

  
• Hirschsprung disease (congenital aganglionic megacolon)


  • Caused by the absence of Meissner submucosal and the Auerbach myenteric plexus ("aganglionosis") within the colon
  • The aganglionic region may have a grossly normal or contracted appearance
  • The normally innervated proximal colon undergoes progressive dilation and may become massively distended (megacolon) as a result of distal obstruction
  • The colonic wall may be stretched to the point of rupture, which occurs most frequently near the cecum
  • Typically presents with a failure to pass meconium in the immediate postnatal period
  • Treatment consists of surgical resection of the aganglionic segment

  
• Acquired megacolon


  • Chagas disease - only one that is associated with loss of ganglion cells
  • Obstruction by a neoplasm
  • Complication of ulcerative colitis

  
• Nutcracker esophagus


  Describes functional obstruction of the esophagus by intense, high amplitude, uncoordinated contractions of the smooth muscle

  
• Diffuse esophageal spasm


  Known as corkscrew esophagus due to the appearance on barium swallow, characterized by repetitive, simultaneous contractions of the distal esophageal smooth muscle

  
• Lower esophageal sphincter dysfunction


  Includes high resting pressure or incomplete relaxation
• Zenker diverticulum (pharyngoesophageal diverticulum)


  Occurs when impaired relaxation and spasm of the cricopharyngeus muscle after swallowing can result in increased pressure within the distal pharynx
• Esophageal mucosal webs


  Idiopathic ledge-like protrusions of mucosa that may cause obstruction, may be accompanied by iron-deficiency anemia, glossitis, and cheilosis as part of the Paterson-Brown-Kelly or Plummer-Vinson syndrome, semi-circumferential lesions that protrude less than 5 mm, and are composed of a connective tissue and overlying epithelium

  
• Esophageal rings, or Schatzki rings


  Similar to webs, but are circumferential, include mucosa and submucosa and occasionally, hypertrophic muscularis propria
• Achalasia


  Characterized by 1) incomplete lower esophageal sphincter (LES) relaxation, 2) increased LES tone, and 3) aperistalsis of the esophagus

  
• Primary achalasia


  The result of distal esophageal inhibitory neuronal, that is, ganglion cell, degeneration

  
• Secondary achalasia


  May arise in Chagas disease, in which Trypanosoma cruzi infection causes destruction of the myenteric plexus
• Mallory-Weiss tears


  Longitudinal mucosal tears near the gastroesophageal junction and are most often associated with severe retching or vomiting secondary to acute alcohol intoxication, usually cross the gastroesophageal junction and may also be located in the proximal gastric mucosa
• Boerhaave syndrome


  A serious disorder characterized by transmural tearing and rupture of the distal esophagus, produces severe mediastinitis and generally requires surgical intervention

  
• Esophagitis


  Reflux of gastric contents into the lower esophagus is the most frequent cause and the most common outpatient GI diagnosis in the US

  
• GERD


  Transient LES relaxation is thought to be a major cause
• Esophageal varices


  Portal hypertension results in the development of collateral channels at sites where the portal and caval systems communicate resulting in congestion and dilation of the veins within the mucosa and submucosa of the distal esophagus and proximal stomach, develop in the vast majority of cirrhotic patients, most commonly in association with alcoholic liver disease, worldwide, hepatic schistosomiasis is the second most common cause

  
• Barrett esophagus


  A complication of chronic GERD that is characterized by intestinal metaplasia within the esophageal squamous mucosa, increased risk of esophageal adenocarcinoma

  
• Types of esophageal cancers

  • Squamous cell carcinoma - more common worldwide, half occur in the middle third
  • Adenocarcinoma - typically arise from Barrett esophagus in the distal third

  
• Gastritis


  A mucosal inflammatory process, when neutrophils are present, the lesion is referred to as acute gastritis
• Gastropathy


  When inflammatory cells are rare or absent
• Stress-related mucosal disease


  Occurs in patients with severe trauma, extensive burns, intracranial disease, and other forms of severe physiologic stress, includes Curling ulcers, Cushing ulcers, and acute stress ulcers, most often related to local ischemia due to systemic hypotension or reduced blood flow caused by stress-induced splanchnic vasoconstriction, most critically ill patients admitted to the ICU unit have histologic evidence of gastric mucosal damage

  
• Dieulafoy lesion


  Caused by a submucosal artery that does not branch properly within the wall of the stomach, results in a mucosal artery with a diameter of up to 3 mm, usually found within the lesser curvature

  
• Gastric antral vascular ectasia (GAVE)


  Can be recognized endoscopically as longitudinal stripes of edematous erythematous mucosa that alternate with less severely injured, paler mucosa, sometimes referred to as watermelon stomach

  
• Chronic gastritis


  Most common cause is infection with the bacillus H. pylori - most often presents as a predominantly antral gastritis with normal or increased acid production, virulence factors include flagella, urease secretion, adhesins and toxins (CagA), autoimmune gastritis is the most common cause of diffuse atrophic gastritis in patients without H. pylori infection
• Autoimmune gastritis


  Characterized by diffuse damage to the oxyntic (acid-producing) mucosa within the body and fundus, spares the antrum and is associated with marked hypergastrinemia, characterized by antibodies to parietal cells and intrinsic factor, Vit B12 deficiency manifested by megaloblastic anemia, and defective gastric acid secretion (achlorhydia)
• Peptic ulcer disease (PUD)


  Refers to chronic mucosal ulceration affecting the duodenum or stomach which is due to increased gastric acid secretion, and decreased duodenal bicarbonate secretion, associated with H. pylori infection, NSAIDs, or cigarette smoking, predominantly located along the lesser curvature, solitary in more than 80% of patients, a round to oval, sharply punched-out defect that is usually level with the surrounding mucosa, the epigastric pain tends to occur 1 to 3 hours after meals during the day, is worse at night (usually between 11 PM and 2 AM), and is relieved by alkali or food
• Hypertrophic gastropathies


  Uncommon diseases characterized by giant "cerebriform" enlargement of the rugal folds due to epithelial hyperplasia without inflammation