1. also called the small bowel. is the part of thegastrointestinal tract following the stomach and followed by the large intestine. extends from the pyloric sphincter of the stomach to the ileocecal valve, where it joins the large intestine at a right angle. Digestion and absorption of food occur in this portion of the alimentary canal .

2. Size Adult human male> average length 6.9 m (22 feet 6 inches) Adult human female > 7.1 m (23 feet 4 inches) Its diameter gradually diminishes from approximately 1 inches (3.8cm) in the proximal part to approximately 1 inch (2.5 cm) in the distal part. 3. Intestinal wall The normal intestinal wall is seen as a multilayered area withhyperechoic bowel content at the center. Five distinct layers can be depicted on sonography: 1. inner hyperechoic layer - which is the interface between the mucosa and the bowel contents. 2. second hypoechoic layer- which is the deep mucosa. 3. third hyperechoic layer - which is the submucosa 4. fourth hypoechoic layer - which is the muscle proper 5. last outer hyperechoic layer - which is the serosa and the serosal fat 4. Division The smallintestine is divided into three portions: > Duodenum > Jejunum > Ileum 5. Duodenum The name duodenum is from theLatin duodenum digitorum, or "twelve fingers' breadth". is 8 to 10 inches (20 to 24 cm) in length. It is retroperitoneal and relatively fixed in position. The duodenum is divided into four sections: first (superior), second (descending), third (horizontal or inferior), and fourth (ascending) portions. 6. The segment of the first portion is called the duodenalbulb because of its radiographic appearance when it is filled with an opaque contrast medium. The second portion is about 3 or 4 inches (7.6 to 10cm) long. This segment passes inferiorly along the head of the pancreas and in close relation to the undersurface of the liver. The third portion passes toward the left at a slight superior inclination for a distance of about 2 1/2 inches (6 cm) and continues as the fourth portion on the left side of the vertebrae. The duodenal loop, which lies in the second portion, is the most fixed part of the small intestine and normally lies in the upper part of the umbilical region of the abdomen; however, its position varies with body habitus and with the amount of gastric and intestinal contents. 7. The duodenum is largely responsible for thebreakdown of food in the small intestine, using enzymes. The duodenum also regulates the rate of emptying of the stomach via hormonal pathways. Secretin and cholecystokinin are released from cells in the duodenal epithelium in response to acidic and fatty stimuli present there when the pylorus opens and releases gastric chyme into the duodenum for further digestion. 8. Jejunum is the middle section of the small intestine. is wider, its diameter being about 4 cm., and is thickerand more vascular.Ileum is the final section of the small intestine is narrow, its diameter being 3.75 cm. and its coatsthinner and less vascular than those of the jejunum. The jejunum and ileum are attached to the posterior abdominal wall by an extensive fold of peritoneum, the mesentery, which allows the freest motion, so that each coil can accommodate itself to changes in form and position. 9. The large intestine is about 5 feet ( 1 .5 m) long and is greater in diameter than the small intestine. It begins in the right iliac region, where it joins the ileum of the small intestine, forms an arch surrounding the loops of the small intestine, and ends at the anus. The wall of the large intestine contains the same four layers as the walls of the esophagus, stomach, and small intestine. The main functions of the large intestine are reabsorption of fluids and elimination of waste products. The large intestine takes about 16 hours to finish the digestion of the food. It removes water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum. 10. The large intestine has four main parts: Cecum Colon Rectum Anal canal 11. Cecum - is the pouchlike portion of the large intestine and is below the junction of the ileum and the colon . - is approximately 2 1/2 inches (6 cm) in length and 3 inches (7.6 cm) in diameter. The vermiform appendix is attached to the posteromedial side of the cecum. The appendix is a narrow, wormlike tube that is about 3 inches (7.6 cm) long. The ileocecal valve is just below the junction of the ascending colon and the cecum. The valve projects into the lumen of the cecum and guards the opening between the ileum and the cecum. 12. Left colic flexure right flexureDescending colon Ascending colonTaenia coli HaustraIleocecal valveCecumSigmoid colonAnus 13. Colon- is subdivided into ascending, transverse, descending, and sigmoid portions. Transverse colonSigmoid colon rectum 14. The ascending colon passes superiorly from its junctionwith the cecum to the undersurface of the liver, where it joins the transverse portion at an angle called the right colic flexure (formerly hepatic flexure). The transverse colon, which is the longest and most movable part of the colon, crosses the abdomen to the undersurface of the spleen. The transverse portion then makes a sharp curve, called the left colic flexure (formerly splenic flexure), and ends in the descending portion. The descending colon passes inferiorly and medially to its junction with the sigmoid portion at the superior aperture of the lesser pelvis. The sigmoid colon curves to form an S-shaped loop and ends in the rectum at the level of the third sacral segment. 15. Rectum extends from the sigmoid colon to the anal canal. is approximately 6 inches (15 cm) long. The distal portion, about 1 inch (2.5 cm) in length, is constricted to form the anal canal . Following the sacrococcygeal curve, the rectum passes inferiorly and posteriorly to the level of the pelvic floor and then bends sharply anteriorly and inferiorly into the anal canal, which extends to the anus. 16. Anal Canal The anal canal terminates atthe anus, which is the external aperture of the large intestine It forms an angle with the lower part of the rectum, and measures from 2.5 to 4 cm. in length. Just above the anal canal is a dilation called the rectal ampulla. The rectum and anal canal thus have two anteroposterior curves, a fact that must be remembered when an enema tube is inserted.Rectal ampullacanal Anus 17. Adults: Do not eat or drink 8 hours before exam. Children: Do not eat or drink 4 hours before studyor skip 1 meal. Necessary medications may be taken with a small amount of water only. No chewing gum. 18. Severe abdominal pain Inflammatory Bowel Diseases Neoplastic Bowel Diseases Management of intestinal obstruction 19. The choice of transducer for bowel assessment largely depends on the patient's body habitus and the distance between the probe and the object of study.For a regular scan of the abdomen: > abdominal transducer (2-5 MHz) For a detailed examination of the intestine: > A 2.5- to 5.0-MHz curvilinear probe is used for a heavy patient. > A 7.0- to 12.0-MHz linear transducer, which facilitates high-resolution sonography, is used for an average-size or thin patient and generally for assessment of superficial abnormalities. 20. In patients with localized abdominal pain, the sonographic examination can be started at the point of maximum tenderness. An area of interest is carefully analyzed with a high-resolution linear probe and graded compression sonography if possible. The compression resembles palpation of the abdomen. Gentle but adequate graded compression is applied to decrease the distance between the probe and the area of interest and to displace gas and fecal material. For average-size and thin patients, a 7.0- to 12.0-MHz linear probe normally is sufficient for detailed evaluation of the area of interest and assessment of the peristalsis, compressibility, and rigidity of the segment in question. For obese patients and patients in whom the affected bowel segment is distant from the abdominal surface, a lower-frequency curvilinear probe should be used, and a fair amount of pressure must be applied to obtain images of diagnostic quality. 21. Appendicitis > is an inflammation of the appendix. It occurs when the appendix becomes blocked, often by stool, a foreign body, or cancer. Blockage may also occur from infection, since the appendix swells in response to any infection in the body. 22. Ultrasound of appendicitis: The normal appendix presents as a small, easily compressible, concentrically layered, mobile, blindending, sausage-like structure. The diameter is usually less than 7 mm, but is incidentally large. The normal appendix is mobile, may have a collapsed lumen, but also may contain air or some fecal material, and rarely a little fluid. Power Doppler reveals scarce or no vascular signal and there is no hyperechoic, non-compressible inflamed fat around the appendix. The typical appearance of an inflamed appendix is that of aconcentrically layered, non-compressible sausage-like structure demonstrated in a fixed posi-tion at the site of maximum tenderness. The average maximum diameter is 9 mm with a variation from 7 to 17 mm. 23. AB20-year-old man with acute nonperforating appendicitis. Long-axis (A) and transverse (B) sonograms of appendix typically situated in right iliac fossa show enlarged (9.6 mm) appendix (long arrows) and prominent hyperechoic inflamed periappendiceal fat (short arrows). 24. Diverticulitis Is a common digestive disease whichinvolves the formation of pouches (diverticula) within the bowel wall. Diverticulitis results when one of these diverticula becomes inflamed. Doctors aren't sure what causes diverticula in the colon (diverticulosis). But they think that a low-fiber diet may play a role. Without fiber to add bulk to the stool, the colon has to work harder than normal to push the stool forward. The pressure from this may cause pouches to form in weak spots along the colon. Diverticulitis happens when feces get trapped in the pouches (diverticula). This allows bacteria to grow in the pouches. This can lead to inflammation or infection. 25. On sonography, inflamed diverticula appear as bright echogenic fociwith acoustic shadowing or a ring-down artifact within or beyond the thickened gut wall.56-year-old man with acute sigmoid diverticulitis. Transverse gray-scale image through left lower quadrant shows wall thickening of sigmoid colon (arrowheads) with associated diverticulum (calipers). Adjacent mesenteric and omental fat (F) is abnormally echogenic and attenuating, obscuring deeper structures. 26. Crohns Disease Crohn's disease is an inflammatory bowel disease (IBD). Itcauses inflammation of the lining of your digestive tract, which can lead to abdominal pain, severe diarrhea and even malnutrition. Inflammation caused by Crohn's disease can involve different areas of the digestive tract in different people. Sonographically, there is marked mural thickening of the ileum, which shows decreased or no peristalsis and is not compressible. Classically, all layers are involved and layer structure is often locally disturbed, the earliest sign being echolucent changes in the submucosa. There is inflammation of the fatty mesentery and omentum, recognizable as hyperechoic, noncompressible tissue adjacent to the ileum. 27. Fig. 4 6-year-old boy with Crohn disease. Gray-scale ultrasound image shows dramatic circumferential wall thickening of two adjacent small-bowel loops (arrowheads). Note also increased echogenicity of adjacent mesenteric fat (F), indicating inflammation. 28. Fig. 8 17-year-old girl with Crohn disease. Power Doppler image of terminal ileum (arrowheads) shows wall thickening and mural hyperemia, indicating active inflammation. Note also enlarged adjacent mesenteric lymph node (arrow) surrounded by echogenic fat. 29. Ulcerative colitis is a disease that causes inflammation and sores(ulcers) in the lining of the large intestine (colon ). It usually affects the lower section (sigmoid colon) and the rectum. Cytomegalovirus is the most commonly associated pathogen in colitis in post-transplant patients. Other causes for colitis include ischemic factors, parasites, and radiation. Sonographic findings include long segment, concentric, regular thickening of the colonic wall. 30. 45-year-old womanwith ulcerative colitis. Long-axis sonogram of sigmoid colon (arrows) in left lower quadrant shows concentric diffuse wall thickening (12 mm, calipers) of entire sigmoid colon, mainly due to thickening of mucosa. 31. 52-year-old woman withinfectious colitis. Grayscale ultrasound image shows concentric wall thickening and blurring of normal mural stratification (arrowheads) in colon. Power Doppler image (inset) reveals marked hyperemia (arrow) in affected segment. 32. THE END. Reported by: JOAN C. VARGAS JONATHAN MANAOIS