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Imaging of Bowel Obstruction
This document discusses imaging techniques for evaluating bowel obstruction, including radiography and CT. It covers the clinical presentation, imaging features, and causes of gastric, small bowel, and large bowel obstruction. Key points include using CT to identify the location and cause of obstruction, assess for complications like strangulation or closed loop obstruction that may require emergent surgery. The most common causes of small bowel obstruction are adhesions, hernias, and malignancies, while large bowel obstruction is usually due to malignancy, volvulus, or diverticulitis in older patients.
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Imaging of Bowel Obstruction
- 1. Imaging of BowelObstruction Rathachai Kaewlai, MD Ramathibodi Hospital, Mahidol University, Bangkok Emergency Radiology Minicourse 2015
- 2. What to Cover… Imagingtechniques Gastric obstruction Small bowel obstruction Large bowel obstruction
- 3. Bowel Obstruction Lack oftransit of bowel contents Small bowel obstruction: high or low Large bowel obstruction Simple (intact blood supply) vs. strangulated
- 4.
- 5. Clinical Presentation Depend uponsite of obstruction High SBO – vomiting early, profuse, rapid dehydration Low SBO – pain with distension LBO – constipation Strangulation – shock, rigidity/rebound (localized/diffuse)
- 6. Treatment Conservative Surgery: Early – Strangulation Closed loop obstruction Obstructed/strangulated hernia Delayed – Adhesive obstruction without pain
- 7. Aims of Investigations Isobstruction present? Where is the location? What is the cause? Is emergent surgery needed? Strangulation Closed loop Obstructed hernia Radiography CT
- 8. CT Techniques Helical scan,thinnest collimation Coronal reformats IV contrast, single venous phase No need for oral contrast. May be neutral contrast No rectal contrast needed May be helpful if LBO, neutral contrast preferred
- 9. Gastric Outlet Obstruction(GOO): Etiology Malignancy benign (PUD) Extrinsic: pancreatitis with pseudocyst, hematoma Intrinsic: malignancy, PUD with stricture Intraluminal: bezoars, FB, GS Acute incarceration or strangulation: obstructed paraesophageal hernia, gastric volvulus
- 10. Radiography Markedly dilated stomach, airor fluid filled Filling defect (cancer) Calcified gallstone (Bouveret syndrome)
- 11. CT Marked distension Etiology Enhancing softtissue mass Focal thickening of gastric wall with mucosal hyper- enhancement and/or ulcers Pancreatitis w/wo pseudocyst Acute cholecystitis Filling defects (polyp, gallstone, bezoar) Stomach
- 12. GOO: Malignant Etiologies Ampullary,duodenal, cholangiocarcinoma, gastric cancer Pancreatic cancer with extension to duodenum/ stomach 15-25% with GOO Usually have biliary obstruction Stomach Mass Gastric cancer with GOO
- 13. GOO: Benign Etiologies PUD(acute vs scarring/fibrosis) Polyps, caustic ingestion, web, GS, pancreatic pseudocyst, bezoar
- 14. Gastritis vs. Neoplasm Difficultdifferentiation on imaging. Endoscopy necessary to differentiate neoplasm Gastritis Layered (halo) appearance Diffuse, segmental, or annular Neoplasm Nodal disease Metastasis Pseudothickening of antrum
- 15. Diagnostic Approach Dilated stomachmay contain up to 5L of fluid Functional disturbance Postoperative, severe trauma, immobilization, inflammatory disease of abdomen, neurogenic, diabetes Mechanical obstruction (stomach, duodenal, high SB) Differentiate benign from malignant processes
- 16. Gastric Volvulus Abnormal rotationaround its axis Surgical emergency if acute Organo-axial, mesenteroaxial, or both Organoaxial Stomach rotates around axis connecting EGJ and pylorus Mesenteroaxial Less common Stomach rotates around axis bisecting both lesser and greater curvatures Image: Differen-al diagnosis in conven-onal gastrointes-nal radiology. Burgener FA, Kormano M.
- 17. Gastric Volvulus Diaphragmatic defectm.c. causative factor Intrathoracic stomach Transverse lie with single air- fluid level = organoaxial Spherical lucency with beak in distal stomach + differential air fluid levels = mesenteroaxial Case courtesy of Radiopaedia.org Case courtesy of Dr Maxime St-Amant, Radiopaedia.org Organoaxial volvulus Mesenteroaxial volvulus * *
- 18. Gastric Volvulus “Organoaxial volvulus”Case courtesy of Dr David Cuete, Radiopaedia.org “Mesenteroaxial volvulus” Case courtesy of Dr Maxime St-Amant, Radiopaedia.org
- 19. Superior Mesenteric ArterySyndrome Dilatation of 1st and 2nd part of duodenum with abrupt narrowing at 3rd portion Relieved by changing position Aorta-SMA distance 8-10 mm Aortomesenteric angle 22 degrees (compression of LRV – renal vein thrombosis, pneumatosis, PVG,AAA) Narrow aortomesenteric angle and compression at 3rd portion of duodenum
- 20. Small Bowel Obstruction(SBO) Dilated small bowel proximal to the site of obstruction with distal decompression
- 21. Radiography Diagnostic in 50-60% Non-diagnostic or misleading in 40% Poor predictor of Location Cause Complications * * Dilated small bowel loops with relative absence of colonic gas
- 22. Radiography Dilated small bowel3 cm Paucity of colonic gas Air fluid levels Multiple Differential Longer than 2.5 cm String of beads sign Multiple air fluid levels in dilated small bowel loops
- 23. CT Quick and accurate Noneed for luminal contrast Bowel wall assessment Extraluminal abnormalities * * * * Diffuse, fluid-filled, dilated loops of small bowel Free fluid
- 24. CT: Indications Non-diagnostic radiographybut clinical suspicion Virgin abdomen History of abdominal malignancy Suspected complications
- 25. Indications for CTin SBO: Non-diagnostic Radiography SBO due to gallstone obstruction Normal bowel gas pattern despite SBO shown on CT because of fluid-filled small bowel loops
- 26. Indications for CTin SBO: Virgin Abdomen Known diseases Metastasis (54%) Crohn disease (46%) No known diseases Adhesions (75%) Metastasis (10%) Rare: sclerosing encapsulating peritonitis, Meckel diverticulum, gallstone ileus Beardsley C, et al. Am J Surg 2014
- 27. Indications for CTin SBO: History of Abdominal Malignancy Spread/extent of tumor around bowel Pre-operative planning for bypass/debulking procedures
- 28. Transition Point Dilated loopschange in caliber to decompressed loops Trace rectum ! colon ! small bowel Small bowel feces Scroll images on workstation (difficult on hardcopy films) Multiplanar reformats
- 29. Transition Point Adhesions inferredwhen no cause identified Abrupt tapering Beak External hernias Tumors, esp. metastasis to bowel/peritoneum Inflammation/infection, gallstones CT accuracy 63-95% for identifying transition point
- 30. Transition Point TellsEtiology of Obstruction Cecal cancer Femoral hernia Transition point Transition point
- 31. Small Bowel FecesSign Gas bubbles and particulate matter within dilated SB Usually just proximal to transition point Secondary to prolonged stasis Transition point
- 32. Small Bowel FecesSign Suggestive of preserved SB function Negative predictor of failure of conservative Rx Unlikely to be ischemic Longer segment, less chance of getting surgery SB feces
- 33. Etiology of SBO Adhesions 50-75% Hernias 8-15% Malignancies 10-15% Others: Crohn, intussusception, volvulus, trauma, iatrogenic conditions
- 34. Adhesions Most common sites= omentum to incision site Most problematic adhesions = involving small bowel Appendectomy, colorectal surgery and gynecology Most common to produce adhesive obstruction Anytime from operation 20% 1m 20% 10y Dayton MT et al. 2012 Curr Probl Surg
- 35. External Hernia 2nd mostcommon cause of SBO Inguinal femoral Umbilical = m/c congenital hernia Incisional and parastomal = m/c iatrogenic hernia Others: spigelian, lumbar, Richter, Littre Umbilical hernia, obstructed strangulated
- 36. SBO: Internal Hernia Defectsin mesentery or peritoneum Post surgical cong Adhesive bands Most common around duodenum Paraduodenal internal hernia, obstructed
- 37. Obstructing Tumors Adenocarcinoma Irregular, nodularmass Carcinoid rarely obstructive GIST Lymphoma rarely obstructive Peritoneal carcinomatosis Ovary, colon, stomach, pancreas, breast, endometrium Small bowel adenocarcinoma, obstructed Diagnologic.com
- 38. Others Intussusception Inflammatory bowel TB verycommon inflammatory cause of SBO, ileocecal, local nodes with hypodense center Acute Crohn Chronic Crohn Pancreatitis, diverticulitis and appendicitis Radiation enteropathy Stone and bezoar
- 39. Is Emergent SurgeryNeeded? YES IF: Strangulation = SBO + Ischemia Closed loop obstruction
- 40. Closed-loop SBO Obstructed at2 adjacent locations Bowel between 2 points more dilated than upstream to the proximal obstruction Risk of torsion/volvulus Hernia and adhesion (usu. Single) Roux-en-Y gastric bypass
- 41. Closed-loop SBO U-, C-or coffee bean Radial orientation of dilated loops Beak Balloons on a string Whirl sign Sensitivity 60% PPV 80%
- 42. Ischemia Complicating SBO Twomechanisms Inc. pressure in bowel wall Direct occlusion of mesenteric vessels 2/2 torsion, hernia or tight adhesion Mortality 25% (only 2% for non-strangulated SBO) Need high suspicion
- 43. Ischemia Complicating SBO Enhancement– hyper ! hypo ! absent Reduced bowel wall enhancement 11x probability of strangulation Wall thickening – nonspecific Wall thinning can be 2/2 transmural infarction Pneumatosis and portomesenteric gas Millet I, et al. Eur Radiol 2014
- 44. Mimics of SBOon AXR Ileus Mesenteric ischemia Obstruction of cecum/ ascending colon (cecum filled with mass or fluid) SMA occlusion
- 45. Large Bowel Obstruction(LBO): Etiology More in elderly Malignancy 60% Volvulus 15% Diverticulitis 10% Others: incarcerated hernia, fecal impaction, adhesion 15-20% of colorectal malignancy present with LBO
- 46. Radiography Marked colonic dilatation withdisproportionate distension of cecum (10 cm) Competent IC valve Functional closed loop Risk of perforation * * * Colonic dilatation to the sigmoid colon due to distal LBO
- 47. Radiography Incompetent IC valve DilatedSB and colon Cecum dilated v. non- dilated Difficult Dx on AXR Poor sensitivity, specificity and interobserver agreement * * Colonic and small bowel dilatation to the splenic flexure colon due to distal LBO *
- 48. Colon Cancer CT sensitivityand specificity 90% Imaging of choice = CT 60% of LBO Mostly adenocarcinoma Mass, involvement of adjacent structures, lymphadenopathy, intraperitoneal metastasis Cancer of the splenic flexure colon
- 49. Extrinsic Neoplasm Direct invasion Intraperitonealseeding Hematogenous metastasis Lymphatic extension
- 50. Sigmoid Volvulus Twist aroundsigmoid mesocolon Massive distension Lack of haustration Coffee bean shaped classic- Rt dome Central stripe
- 51. Sigmoid Volvulus Diagrams fromsurgeonsblog.blogspot.com and pmj.bmj.com Beak sign
- 52. Cecal Volvulus Dilated cecum Dilatedcecum Beak sign
- 53. Volvulus: CT? Classic picture Colondilatation alone LBO Toxic megacolon Pseudo-obstruction Colon + SB dilatation LBO Ileus CT Rx CT
- 54. Mimics of LBO Toxicmegacolon Clinical toxicity Colonic pseudo-obstruction CT often needed to exclude a mass Diffuse colonic dilatation. CT confirmed no evidence of obstruction
- 55. Summary Investigative questions: Obstructionpresent? Where? Cause? Surgery? Radiography still has a limited role in bowel obstruction CT is the mainstay imaging: Quick and safe No luminal contrast Confirm obstruction, site, etiology, surgical need Extraluminal abnormalities