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Gastrointestinal Tract (Effective February 2007) (1%-5%) Anatomy of GI Tract Esophagus • bulls-eye or “target” • EG junction seen on sagittal scan posterior to left lobe of liver and anterior to aorta Anatomy of GI Tract Stomach – stores food and aids in digestion • Fundus • body or corpus – lesser curvature – greater curvature • Pylorus – Antrum – canal or bulb 1 supporting ligaments greater curvature • greater omentum • gastrophrenic ligament • gastrosplenic ligament • lienorenal ligament. lesser curvature • gastrohepatic ligament • lesser omentum. Small intestines Most of the digestion and absorption of food takes place (pancreatic enzymes and bile) • three parts: duodenum, jejunum, and ileum. – • about 23 feet long and 1 inch wide avalvulae conniventes (valves of Kerckring) – linear echoes representing mucosal folds spaced 3 – 5mm apart that slow down the passage of food to create a greater absorbing area → “Keyboard sign” duodenum is divided into four parts • #1 pylorus and runs upward and backward on the right side of the first lumbar vertebra #2 runs anterior to the right kidney on the right side of the second and third lumbar vertebrae • – The common bile duct and main pancreatic duct pierce the duodenal wall midway down its posterior aspect. 2 duodenum is divided into four parts • • #3 horizontally to the left, following the inferior margin of the pancreatic head #4 runs upward and to the left, and then runs forward at the duodenojejunal junction. – ligament of Treitz ascends to the right crus and holds the junction in position Jejunum and Ileum • jejunum arises from the duodenum and extends for 2 m • inner walls – – circular folds of the mucous membrane, – villi; the valvulae conniventes are large folds of mucous membrane • ileocecal orifice – marks the entry into the large intestine and serves as a landmark to find the appendix. Large Intestine • divided into the – – – – – – – vermiform appendix Cecum ascending (to hepatic flexure) Transverse descending (to splenic flexure) colon, rectum. The colon is divided into segments called haustra.Ψ 3 Vascular Supply Esophagus • inferior thyroid branch supplies the upper esophagus. • The descending thoracic aorta supplies the midesophagus • The left inferior phrenic artery supplies the lower end of the esophagus. Varices may arise from gastroesophageal arteries. Vascular Supply Stomach • branches of the hepatic artery, – • right gastric arterial branch, the pyloric and right gastroepiploic left gastric artery. Gastrointestinal Tract The five layers of bowel: • Mucosa: directly contacts intraluminal contents; line with epithelial folds, echogenic • Submucosa: contains blood vessels and lymph channels • Muscularis: contains circular and longitudinal bands of fiber • • Serosa: thin, loose layer of connective tissue Mesothelium: covers intraperitoneal bowel loops 4 Measurements • wall of the GI tract should measure <5 mm, or <3 mm when distended – from the edge of the echogenic core to the outer border of the anechoic halo Stomach • Could look like cystic mass in LUQ • GE Junction seen to the left of the midline as a bull’s-eye or target structure • gastric antrum can be seen as a target in the midline Duodenum • Usually, a gas- or fluid-filled duodenal cap is seen lateral to the pancreatic head. 5 Small Bowel • fluid or contrast media filled small bowel can visualize the valvulae conniventes – seen as linear echo densities spaced 3 to 5 mm apart – known as a keyboard sign – The small bowel wall is <3 mm thick. Appendix • located on the abdominal wall under McBurney’s point. – McBurney’s point - drawing a line from the right ASIS to the umbilicus—at the midpoint of this line lies the root of the appendix. Ψ • Fusiform structure <6 mm in caliber, 8 to 10 cm long Ψ Appendix Technique • high-resolution linear array transducer should be used • Graded compression over the area of maximum tenderness • visibility of the retrocecal and paracecal areas is improved by displacing gas and other bowel loop contents from the scanning field 6 Abnormalities of the Appendix • appendicitis – lesion in the RLQ. – noncompressible mass – diameter is >6 mm – muscular wall thickness is >3 mm. Abnormalities of the Appendix • Perforation or Abscess – loculated pericecal fluid – prominent pericecal fat – circumferential loss of the submucosal layer of the appendix. • Crohn’s Appendicitis – With Crohn’s ileocolitis the appendix may be involved 25% of the time Abnormalities of the Appendix Appendiceal Tumors • Primary adenocarcinomas of the appendix are rare. • A primary adenocarcinoma may manifest as acute appendicitis with perforation. • Often only seen by pathologist 7 Colon • haustral markings 3 to 5 cm apart in the ascending and transverse colon When fluid filled • descending colon appears as a tubular structure with an echogenic border. • Layers of the colon : – mucosa, submucosa, muscularis propria, serosa, and subserous fatty tissue. Benign Tumors Polyp • seen with fluid distention of the stomach – solid masses adherent to the gastric wall • Leiomyomas – most common tumor of the stomach – hypoechoic mass continuous with the muscular layer of the stomach Malignant Tumors Gastric Carcinoma • 90-95% malignant tumors of the stomach are carcinomas • ½ of the tumors occur in the pylorus, and ¼ in the body and fundus. • ultrasound study will show – a target or pseudokidney sign Ψ – possibly gastric wall thickening. 8 Malignant Tumors • Leiomyosarcoma – second most common gastric sarcoma – globular or irregular and may become huge – outstrips blood supply → central necrosis → cystic degeneration and cavitation. • Metastatic Disease – rare - originates as melanoma or lung or breast cancer. Crohn’s Disease Ψ • AKA regional enteritis – recurrent granulomatous inflammatory disease that affects the terminal ileum and/or any level of the colon. • involves entire thickness of the bowel wall. • Physical symptoms include diarrhea, fever, and RLQ pain.Ψ • There is rigidity to pressure exerted from the transducer. • Peristalsis is absent or sluggish. • There is dilation with hyperperistalsis and water and air stasis. 9 Laboratory values Gastrin • blood hormone – stimulates intestinal movement and secretion of juices – elevates in acute and chronic peptic ulcer disease Serum Amylase • elevates in intestinal obstruction, perforated ulcers; pancreatitis Feces • examined for presence of blood, fat, bile, and • parasites Hernia Peritoneal Fluid (including Inflammatory Fluid Collections) 10