Stomach And Small Bowel Anatomy (PDF)

Stomach AND SMALL BOWEL Mariam Mohamed Ali  The stomach is a muscular organ that lies between the esophagus and duodenum in the upper abdomen. It lies on the left side of the abdominal cavity caudal to the diaphragm at the level of T10.  Erect abdominal radiograph Radiographic features...

Stomach AND SMALL BOWEL Mariam Mohamed Ali  The stomach is a muscular organ that lies between the esophagus and duodenum in the upper abdomen. It lies on the left side of the abdominal cavity caudal to the diaphragm at the level of T10.  Erect abdominal radiograph Radiographic features stomach outlined on fluoroscopy Related pathology neoplastic benign gastric leiomyoma gastric lipoma malignant gastric adenocarcinoma gastric lymphoma gastrointestinal stromal tumor  nflammatory gastritis infections phlegmonous gastritis  congenital gastric condition gastric duplication cyst other gastric volvulus gastric varix gastric diverticulum gastric emphysema  Gastric leiomyomas Gastric leiomyomas are rare benign mesenchymal tumors, usually asymptomatic and found incidentally. Radiographic features CT It usually presents as a well-defined solid mass with smooth contours and showing low homogeneous contrast enhancement. Calcifications, intratumoral hemorrhage, and cystic degeneration are rare  Gastric lipoma Gastric lipomas are a location-specific subtype of gastrointestinal lipomas and represent a rare benign mesenchymal tumors of the stomach. They can be definitively diagnosed on CT. Radiographic features: CT Gastric lipomas present as well-defined, homogeneous fat-density lesions (-70 to -120 HU is diagnostic)  Gastric adenocarcinoma Gastric adenocarcinoma, commonly, although erroneously, referred to as gastric cancer, refers to a primary malignancy arising from the gastric epithelium. It is the most common gastric malignancy. It is the third most common GI malignancy following colon and pancreatic carcinoma.  Radiographic features Endoscopy is regarded as the most sensitive and specific diagnostic method in patients suspected of harboring gastric cancer. Endoscopy allows direct visualization of tumor location, the extent of mucosal involvement, and biopsy (or cytologic brushings) for tissue diagnosis. But radiological methods are often the initial examination that raises suspicion for gastric carcinoma, besides being used in the staging of the disease.  Fluoroscopy: polypoid or fungating mass filling defect in barium pool. ulcerated carcinoma (penetrating cancer): 70% of all gastric cancers  Ultrasound Not useful, unless a large epigastric mass is present or in an endoscopic ultrasound study. CT is currently the staging modality of choice because it can help identify the primary tumor, assess for the local spread, and detect nodal involvement and distant metastases  Gastric lymphoma Gastric lymphoma may either represent secondary involvement by systemic disease or primary malignancy confined to the stomach. CT scan: Typically gastric lymphoma demonstrates marked thickening of the stomach wall (2-4 cm) with a large lateral extension of the tumor (i.e. along the wall of the stomach) representing submucosal spread  The mass is usually homogeneous in attenuation, but may contain focal areas of low density representing necrosis. Extensive retroperitoneal and local nodal enlargement is often seen.  Gastritis: refers to any form of mucosal inflammation of the stomach and can sometimes be part of a wider gastroenteritis. It may have acute or chronic forms. Radiographic features CT scan: While it may not often be needed for routine workup, gastritis may be seen as thickening of the gastric folds and wall.  Small bowel The small bowel (or small intestine) is the section of bowel between the stomach and the colon. It has distinctive mucosal folds, valvulae conniventes, and is made up of three functional units: duodenum jejunum ileum  Related pathology small bowel obstruction small bowel ischemia small bowel adenocarcinoma small bowel lymphoma diffuse small bowel disease Small bowel obstruction Small bowel obstruction (SBO) accounts for 80% of all mechanical intestinal obstruction, the remaining 20% results from a large bowel obstruction. It has a mortality rate of ~5%. Radiographic features Abdominal radiograph Abdominal radiographs are only 50-60% sensitive for small bowel obstruction. In most cases, the abdominal radiograph will have the following features: dilated loops of small bowel proximal to the obstruction (predominantly central dilated loops three instances of dilatation > 2.5 - 3 cm gas-fluid levels if the study is erect, especially suspicious if >2.5 cm in width in the same loop of the bowel but at different heights (> 2 cm difference in height)  CT CT is more sensitive than radiographs and will demonstrate the cause in ~80% of cases. Features on CT may include: dilated small bowel loops >2.5 cm up from outer wall to outer wall normal caliber or collapsed loops distally small bowel feces sign  Small bowel ischemia Small bowel ischemia may be a life- threatening condition, arising from any one of numerous causes of disturbance of the normal blood flow through the small bowel wall.  Adenocarcinoma of the small bowel Primary adenocarcinoma of the small bowel is about 50 times less common than colonic carcinoma. Radiographic features CT CT shows a soft-tissue mass with heterogeneous attenuation, usually with moderate enhancement after intravenous administration of contrast material. The mass may manifest as an annular narrowing with abrupt concentric or irregular “overhanging edges,” a discrete tumor mass or an ulcerative lesion.  Small bowel lymphoma Small bowel lymphoma is one of the most common small bowel malignancies, accounting for ~25% of all primary small bowel malignancies, and ~40% of all primary gastrointestinal lymphomas.  Radiographic features Typically, small-bowel lymphoma involves a single loop of bowel, with 5-20 cm of its length demonstrating bowel wall thickening. Regional lymph node enlargement in approximately 50% of cases.