No Disclosures. Approach to Abdominal Radiographs

Transcription

1 Approach to Abdominal Radiographs Tapas K. Tejura, M.D. Assistant Professor of Clinical Radiology Keck Medical Center of USC No Disclosures 34-year-old male with acute abdominal pain Normal obstruction series Now what? Multiple studies have found the role of abdominal radiography to be limited in the adult emergency department setting Retrospective study of 1000 consecutive patients with abdominal pain in Emergency Department (ED) 871 had abdominal radiographs 23% normal 10% abnormal (bowel obstruction, urolithiasis, ileus, foreign body, gallstones) 68% nonspecific 188 had abdomen computed tomopgrahy (CT) scan 20% normal 80% had specific diagnosis Ahn, et al. Radiology 2002 Prospective study of 91 patients All had unenhanced CT and three-view abdominal series Abdominal Series Unenhanced CT 30.0% sensitivity % sensitivity 87.8% specificity % specificity 56.0% accuracy % accuracy MacKersie, et al. Radiology 2005 Retrospective study of 874 patients with abdominal pain in ED 34% normal, 46% nonspecific, and 19% abnormal Normal results led to additional imaging (CT, US, upper GI) in 42% of patients 72% of patients with normal abdominal radiographic findings had abnormal findings on further imaging Kellow, et al. Radiology 2008

2 Role for abdominal radiography With the exception of catheter placement assessment, this study suggests that the appropriate work-up of a patient presenting to the emergency department with abdominal symptoms (without a history of trauma) should not include radiographic imaging. Rather, if the patient requires investigation beyond the clinical history, physical examination, and lab results, the emergency physician should be encouraged to immediately request more definitive imaging techniques. Kellow, et al. Radiology 2008 Abdominal radiographs frequently obtained as initial imaging examination for evaluation of acute abdominal pain Most common indications in ED: Bowel obstruction Renal colic General abdominal pain ED physicians did not seek advanced imaging following normal abdominal radiograph interpretation 20% of the time Kellow, et al. Radiology 2008 Role for abdominal radiography Technique Catheter placement Foreign Bodies Bowel perforation Acute bowel obstruction History of kidney stones, evaluate change in position Anterior-posterior (AP) Supine Left lateral decubitus Sandström S, Ostensen H, Pettersson H et al. The WHO Manual of Diagnostic Imaging, Radiographic Technique and Projections. Diamond Pocket Books (P) Ltd.; Radiation Dose Search Pattern Demographics Technical assessment Systematic review Implanted devices/catheters Stomach and bowel gas pattern Organs (liver, spleen, kidneys, urinary bladder) Abnormal calcifications Bones and soft tissues Mettler FA, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):

3 R Kidney L Kidney Spleen Liver Psoas muscles Nasogastric / Orogastric tube Implanted Devices/Catheters and Foreign Bodies Can be used for feeding, gastric sampling, gastric decompression, and medication administration Tip and sideport should be in stomach Sideport can extend up to 10 cm from tip of the tube Commonly malpositioned Can enter trachea or curl up in esophagus Indewlling tube can lead to gastroesophageal reflux and cause esophagitis and stricture

4 Dobhoff Tube Typically used for nutrition Weighted, radiodense tip Tip should be in 2 nd or 3 rd portion of the duodenum Most are in the stomach If tip located proximal to gastroesophageal junction, can lead to aspiration Gastrostomy tube Can be of varying length and appearance Should be overlying the expected location of the stomach An inflated balloon tip may be seen, preventing the tube from pulling out Intraluminal position can be confirmed with contrast administration

5 Other Implanted Devices

6 Foreign Bodies Many foreign bodies, including glass, metal, and stone are radiopaque and can be detected on plain film CT is more sensitive to detect foreign bodies surrounded by air (ie; in bowel) Bowel Gas Pattern

7 Normal Gas Pattern Distinguishing Large and Small Bowel Stomach Almost always has air Small Bowel Normal diameter ~ 3 cm Large Bowel Almost always has air in rectum or sigmoid Normal diameter ~ 6 cm Cecum up to ~ 10 cm Distention vs. Dilatation Bowel containing sufficient amount of air to fill lumen completely Bowel filled beyond normal size Large Bowel Peripheral Haustral folds usually do not extend across lumen Small Bowel Central Valvulae conniventes usually extend across lumen Spaced more closely Air-Fluid Levels Can be seen on upright views Stomach Almost always Small Bowel No more than 2 or 3 levels Should be < 3 cm long Large Bowel Usually none Abnormal Bowel Gas Patterns Ileus Small and large bowel obstruction Volvulus 3 Questions: 1) Is there gas in the rectum or sigmoid colon? 2) Are there dilated segments of small bowel? 3) Are there dilated segments of large bowel? Abnormal Bowel Gas Patterns Generalized ileus Dilated small AND large bowel Localized ileus (sentinel loop) Several persistently dilated segments of large or small bowel Gas in rectum/sigmoid Mechanical small bowel obstruction Dilated small bowel with little/no gas in large bowel Mechanical large bowel obstruction Dilated small and large bowel

8 Generalized Ileus Refers to disruption in the normal coordinated propulsive motor activity of the gastrointestinal tract in the absence of a mechanical bowel obstruction Suggests that the muscle of the bowel wall is transiently impaired and fails to transport intestinal contents Lack of coordinated propulsive action leads to the accumulation of both gas and fluids within the bowel Common causes: Surgery Inflammation Neural Metabolic Generalized Ileus Radiographic features Generalized, uniform, gaseous distension of both the large and small bowel No discrete transition point to decompressed distal segments of bowel Localized Ileus Can be the result of an adjacent inflammatory or infectious process Focal cluster of 1-3 distended and/or mildly dilated segments of small bowel Termed sentinel loops Location can help suggest underlying etiology Localized Ileus Cholecystitis Pancreatitis Ulcer Appendicitis Diverticulitis

9 Small Bowel Obstruction (SBO) Common clinical condition that occurs secondary to mechanical or functional obstruction of the small bowel Represents 20% of all surgical admissions for acute abdominal pain Proximal dilatation of the intestine due to accumulation of gastrointestinal secretions and swallowed air Bowel distal to the point of obstruction empties over time Small Bowel Obstruction Eventually leads to increased intraluminal pressures Causes compression of mucosal lymphatics Microvascular changes in the bowel wall allow translocation of gut bacteria to mesenteric lymph nodes Increase in incidence of bacteremia due to E. coli Mortality and morbidity are dependent on the etiology, the early recognition and correct diagnosis of obstruction Diagnosis of Small Bowel Obstruction Small bowel diameter > 2.5 cm (usually > 3 cm) KEY: Disproportionate dilatation of small bowel Gas-fluid levels > 2.5 cm wide and at different levels Small bowel feces sign - Often seen near transition point Relative paucity of gas in the colon Presence of residual colonic gas after 6-12 hours is suggestive of partial SBO Early SBO may resemble ileus need follow-up Lappas et al. AJR 2001; 176: May-Smith et al. Clin Radiol 1995; 50:

10 Causes of Small Bowel Obstruction Extraluminal Adhesions Hernias Volvulus Intraluminal Foreign bodies Gallstones Inspissated meconium Intramural Crohn s disease Tumor Radiation Hematoma SBO DDx: Adhesions, Bulges, Crohn s, Cancer

11 Gasless Abdomen Refers to little or no bowel gas This is nonspecific and can be seen in a variety of etiologies Clinical history plays a key role in distinguishing between benign and threatening etiologies Diagnosis of Large Bowel Obstruction Dilated segments of colon to the point of obstruction Little or no gas in the rectum/sigmoid colon Little or no gas in the small bowel (assuming competent ileocecal valve) Causes of Large Bowel Obstruction Tumor, tumor, tumor. Diverticulitis/stricture Hernia Volvulus Intussusception

12 Volvulus Sigmoid More common in older patients Surgical emergency, as can lead to colonic strangulation and bowel necrosis Classic findings include coffee bean or inverted U appearance of sigmoid colon Distal large bowel obstruction Cecal Less common than sigmoid Displacement of massively dilated cecum away from right lower quadrant Proximal large bowel obstruction Can lead to small bowel dilatation

13 1 limb 1 limb Coffee Bean Ogilvie Syndrome / Acute colonic Pseduo-obstruction Refers to clinical picture of large bowel obstruction without any demonstrable evidence of mechanical obstruction Risk factors Medications which decrease motility Recent surgery Infection Debilitation High mortality rate if perforation occurs

14 Constipation and Fecal Impaction Clinical diagnosis that cannot be made on imaging alone Be aware of fecal impaction, typically referring to large obstructing mass of hardened stool in the distal colon or rectum that can occur in the setting of constipation Fecal impaction can lead to stercoral colitis and perforation Normal Haustral Folds Normally are ~3-4 mm in thickness Thickened haustral folds can be seen on radiographs Etiologies include inflammatory bowel disease, infectious colitis, hematoma, ischemia

15 Lead pipe Colon Term used to describe complete loss of normal haustration Presumably due to alterations in muscle tone of the teniae coli from chronic inflammation Reflects burned-out disease Toxic Megacolon Life threatening condition characterized by severe colonic dilatation without obstruction in the setting of systemic toxicity (fever, tachycardia, leukocytosis) Most often seen in infectious or inflammatory bowel disease Pathologic Gas Pneumoperitoneum Pathologic Gas Pneumoretroperitoneum Pneumatosis Portal venous gas Emphysematous pyelpenphritis, cystitis, or cholecystitis Looking for Erect view Pneumopertioneum Air-fluid levels Substitute Left lateral decubitus

16 How Sensitive? Plain films can be 85% sensitive for free air Theoretical threshold is 1 ml CT is much more sensitive and is considered the Gold Standard Best views Erect chest and left lateral decubitus abdomen Supine abdomen is insensitive Signs for pneumoperitoneum Rigler s visualization of air on both sides of the bowel wall Flaciform ligament appearance of a linear opacity from the liver to the midabdomen Double bubble subdiaphragmatic gas outlining the wall of the stomach and diaphragm Miller, et al. Am J Roentgenol Radium Ther Nucl Med 197 Roh, et al. Am J Surg, 1983 Extraluminal Air Spontaneous Pneumoperitoneum Gastric or duodenal ulcer perforation Colonic perforation Diverticulitis Appendicitis Cancer Other causes Thoracic disease (pneumothorax, pneumomediastinum) Iatrogenic

17 Post-operative Pneumoperitoneum Usually presents 3-7 days When to worry? When volume of air increases over time Erect view can be used to evaluate quantity of air Pneumatosis Can occur in variety of conditions, including bowel ischemia, iatrogenic, chemotherapy, collage vascular disease, and chronic obstructive pulmonary disease Concomitant presence of gas in the portal venous circulation is suspicious for bowel ischemia Pneumoretroperitoneum Sites of origin Duodenum Ascending colon Descending colon Rectum Look for Linear air along margins of psoas muscle Gas surrounding kidneys Gas under medial surface of diaphragm

18 Abscess Small bubbles/collections of air Straight or triangular margins of air collections Unusually large collections of air Soft Tissue Masses Hepatosplenomegaly Mass (tumor, abscess, cyst, aneurysm, bladder) Bowel displacement Paucity of gas Focal region of increased density Extrinsic compression of bowel

19 Plain film diagnosis of ascites Gray abdomen: diffuse increase density Indistinct margins liver, spleen, psoas Medial displacement of colon, liver and spleen away from properitoneal stripe Bulging flanks Separation of gas-filled small bowel loops ASCITES NORMAL

20 Calcification Patterns Rimlike Linear or track-like Lamellar Rimlike Calcification Hollow viscus wall Cysts Aneurysms Saccular organs Porcelain gallbladder Amorphous Walls of a tube Ureters Arterial walls Vas Deferens Linear or Track-like

21 Lamellar Formed in lumen of a hollow viscus Renal stones Gallstones Bladder stones Amorphous, Cloudlike Popcorn Formed in solid organ or solid mass Leiomyomas of uterus Chronic pancreatitis Lymph nodes Summary Abdominal radiographs are often the first imaging examination performed in patients with abdominal pain Understand role of abdominal radiographs in clinical management of patients Recognize range of abdominal radiograph findings, including Implanted devices/catheters, bowel gas patterns, pathologic gas, abdominal organs, and calcifications

22 Thank You