Gastrointestinal Tract Conditions

Study Notes

Gastrointestinal Tract Conditions

Abdomen (Gastrointestinal): Carcinoid tumors are rare cancers starting in the lining of the GI tract, often in the appendix or small bowel. They're usually slow-growing but can spread. Symptoms are often vague (abdominal pain, bleeding, bowel obstruction). Imaging shows a mass, sometimes calcified, with fibrous strands radiating from it, characteristically resembling a "sunburst" pattern.
Colorectal Cancer: This is a malignancy affecting the GI tract originating as polyps (which may become malignant). Risk factors include heredity, inflammatory bowel disease, physical inactivity, obesity, diabetes, and diet. Common symptoms include rectal bleeding, blood in stool, cramping pain, and changes in bowel habits. Imaging might reveal a tumor (greater than 1 cm) with central low attenuation potentially indicating hemorrhage or necrosis.
Crohn's Disease: A chronic inflammatory condition affecting any part of the alimentary tract, frequently the terminal ileum. Factors associated include genetics, immunology, and infectious elements. Common symptoms may include diarrhea, abdominal pain, and weight loss. CT imaging characteristics of Crohn's disease include bowel wall thickening (greater than 1 cm) and involvement of a large segment of bowel (more than 15 cm).
Free Intraperitoneal Air (Pneumoperitoneum): A collection of air within the abdominal cavity. Causes include iatrogenic perforation (from procedures), disease processes (ulcers, foreign bodies, ruptured intestines), or penetrating trauma. Symptoms commonly include pain and tenderness in the abdominal region. CT imaging best detects free air using lung windows.
Gastric Carcinoma (Adenocarcinoma): A frequently malignant stomach cancer (95% adenocarcinomas). Risk factors include diet (nitrates, pickled foods, salted fish, smoked foods), and smoking. Symptoms include pain, bloating, vomiting, and weight loss. Imaging, especially CT scan, shows potential tumors as thick markings or masses affecting the stomach wall.
Intussusception: A telescoping of one part of the bowel into another, commonly seen in children. Idiopathic in most cases, though other factors can cause this. Symptoms in infants may include sudden abdominal pain, vomiting, and bloody stools (currant jelly). Imaging shows a "bowel-within-bowel" appearance.
Ischemic Bowel: Reduced blood flow to the intestinal tract (often the superior or inferior mesenteric vessels). Acute cases may result from emboli, nonocclusive ischemia, or thrombosis. In older patients, atherosclerosis often plays a role. Symptoms include abdominal pain, nausea, and vomiting. CT is the key modality for imaging this condition, especially CTA to assess vascular involvement.
Large Bowel Obstruction (LBO): A blockage of the colon, typically due to mechanical issues (tumors, diverticulitis) or, less commonly, due to acute pseudo-obstruction (from trauma, infections). Symptoms may include abdominal pain, distention, vomiting, and constipation. CT is the modality to diagnose LBO and locate the obstruction.
Mesenteric Adenitis: Inflammation of the mesenteric lymph nodes, often caused by bacterial infection (Yersinia enterocolitica). Typically occurring in the right lower quadrant of the abdomen, symptoms can mimic appendicitis. Imaging may show enlarged mesenteric lymph nodes, but CT should be employed to exclude other causes.
Mesenteric Ischemia: Inadequate blood flow to the mesenteric vessels. Risk factors include atherosclerotic narrowing, embolism, or thrombosis. Symptoms primarily involve abdominal pain, distention, and nausea. CT angiogram (CTA) is helpful to evaluate the superior and inferior mesenteric vessels when evaluating this condition.
Volvulus: A twisting of a portion of the bowel on its mesentery. Most commonly involving the sigmoid colon or cecum. Symptoms often include colicky abdominal pain, distention, and vomiting. Imaging is key, with CT commonly showing the twisted bowel.