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Approach to PFA Interpretation

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An introduction to abdominal radiograph interpretation for medical students.

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Approach to PFA Interpretation

  1. 1. Approaching the PFA David Murphy FRCR, FFRRCSI Radiology SpR St Vincent’s University Hospital Dublin, Ireland
  2. 2. Terminology PFA=Plain Film of the Abdomen AXR=Abdominal X-Ray
  3. 3. Terminology PFA=Plain Film of the Abdomen AXR=Abdominal X-Ray These terms are interchangeable!
  4. 4. Technique Nearly all PFAs are now acquired as supine antero- posterior (AP) radiographs Erect PFAs are not routinely performed anymore in adults Lateral decubitus (patient lying on their side) abdominal x- rays are rarely performed in adults-occasionally in children
  5. 5. Radiation Dose Average radiation dose for a PFA is 0.7mSv (Sieverts). Approximately 35 times the dose of a standard chest x-ray (CXR), which is 0.02mSv. Portable PFAs are not routinely performed due to the problem of radiation dose to surrounding patients
  6. 6. Indications Suspected bowel obstruction Suspected bowel perforation (along with an erect CXR) Suspected abdominal mass Ingested foreign body Evaluation of possible toxic megacolon Follow up of renal tract calculi
  7. 7. PFA is not routinely indicated in… Vague abdominal pain Constipation Uncomplicated appendicitis Gastroenteritis Haematemesis
  8. 8. Normal Structures Visible on PFA Gas in stomach, colon, rectum +/- small bowel Renal outlines Outline of right lobe of liver +/- outline of spleen Psoas shadows Costal margin, lumbar vertebrae, pelvic bones
  9. 9. Bowel gas pattern Any part of the bowel will be visible if it contains gas in the lumen Upper limit of normal for bowel diameter -3/6/9 rule 1. 3cm - Small Bowel 2. 6cm - Large Bowel 3. 9cm - Caecum
  10. 10. Stomach May be visible if it contains gas/fluid Usually visible in the left upper quadrant Can cross the midline May see pattern of gastric rugae Rugae
  11. 11. Small bowel Usually central in the abdomen Has valvulae conniventes (arrows) that cross the entire width of the small bowel Normally <3cm in diameter
  12. 12. Large Bowel Peripheral position Has incomplete transverse folds called haustra (arrow) Contains faeces Large bowel should be <6cm, caecum <9cm
  13. 13. Liver Lies in the RUQ Superior portion forms the right hemidiaphragm contour Gallbladder not usually visible (can see gallstones if calcified, 10-20% of cases)
  14. 14. Kidneys Often visible on PFA Lie at T12-L3 Lateral to psoas muscles Right kidney slightly lower due to liver T12 L1 L2 L3 Psoas outline
  15. 15. Normal Bones Visible Sacrum Iliac bone Femoral head T12 L1 L2 L3 L4 L5 11th and 12th ribs Acetabulum Superior pubic ramus
  16. 16. Normal PFA
  17. 17. Normal PFA-Liver & Spleen
  18. 18. Normal PFA-Kidneys
  19. 19. Normal PFA- Psoas shadows
  20. 20. Normal PFA-Colon
  21. 21. Interpretation Major areas to assess on the PFA: 1. Bowel gas pattern 2. Soft tissues 3. Bones 4. Calcifications
  22. 22. 10 practice cases Read the history, look at the PFA and try and formulate a differential diagnosis before clicking ahead
  23. 23. Case 1 60 year old man with abdominal pain, distension and vomiting
  24. 24. 1. Mechanical Small bowel obstruction Multiple air filled dilated loops of bowel in the center of the abdomen with valvulae conniventes
  25. 25. 1. Mechanical Small bowel obstruction Coronal CT confirms mechanical small bowel obstruction.
  26. 26. 1. Mechanical Small bowel obstruction Coronal CT confirms mechanical small bowel obstruction. Axial CT shows the site of obstruction (zone of transition, arrow) in the right iliac fossa. Obstruction caused by ileal stricture from Crohn’s disease.
  27. 27. Case 2 78 year old man with sudden onset severe abdominal pain
  28. 28. 2. Perforation Multiple dilated loops of large bowel Generalised central lucency in the abdomen Air underneath the liver, outlining the falciform ligament (arrow)
  29. 29. 2. Perforation Zoomed up image of the right upper quadrant shows air outlining both sides of the bowel wall (arrows) Allows for exact deliniation of the bowel wall Called Rigler’s sign-very sensitive for perforated large or small bowel CT confirmed perforation due to a colonic tumour
  30. 30. Case 3 80 year old woman with abdominal pain and distension
  31. 31. 3. Sigmoid Volvulus Large dilate loop of large bowel centered in the pelvis Has an inverted U configuration, with its axis pointed towards the right upper quadrant (arrow) Dilated loops of large bowel are seen in the left upper quadrant Also note the EVAR stent
  32. 32. 3. Sigmoid Volvulus This appearance is often called the coffee bean appearance and is typical for a sigmoid volulus
  33. 33. 3. Sigmoid Volvulus Coronal CT shows the swirled sigmoid mesentery around which the sigmoid colon has twisted (arrows) This is called the whirlpool sign
  34. 34. Case 4 50 year old man with painless abdominal swelling and a history of alcohol excess
  35. 35. 4. Ascites General paucity of aerated bowel loops Homogenous increased density throughout the abdomen Visible bowel loops tend to be in the centre of the abdomen (imagine them floating!)
  36. 36. 4. Ascites CT shows a shrunken, nodular liver consistent with cirrhosis with large volume ascites Note the calcified gallstones (arrow)-Did you spot them on the PFA?
  37. 37. Case 5 80 year old woman with a painless, pulsatile abdominal mass
  38. 38. 5. Abdominal Aortic Aneurysm There is round structure in the lower abdominal midline with faint peripheral calcification (arrows) Classical appearance of an abdominal aortic aneurysm (AAA) on PFA with mural calcification
  39. 39. 5. Abdominal Aortic Aneurysm CT angiogram confirms the presence of the large infrarenal AAA (arrows) Significant amount of thrombus (low density material) within the aneurysm sac
  40. 40. 5. Abdominal Aortic Aneurysm 3D reconstructions shows the relationship of the aneurysm to the kidneys and can help with operative planning
  41. 41. Case 6 60 year old man with difficulty urinating and severe back pain
  42. 42. 6. Bone Metastases There is a generalised increased density of the pelvic bones and lumbar spine (compare the density to the previous PFAs) Appearances are those of diffuse sclerotic bone metastases
  43. 43. 6. Bone Metastases Sagittal whole spine CT confirmed diffuse bone sclerosis Classical appearance of prostate cancer with diffuse sclerotic osseous metastases Always check the bones on a PFA!
  44. 44. Case 7 70 year old woman with severe abdominal pain
  45. 45. 7. Bowel ischaemia Generalised increase in lucency with positive Rigler’s sign in the RUQ and free air under the right hemidiaphragm consistent with perforation
  46. 46. 7. Bowel ischaemia Close up of large bowel loops in the RIF shows bubbles of gas within the bowel wall (arrows), known as pneumatosis
  47. 47. 7. Bowel ischaemia Close up of large bowel loops in the RIF shows bubbles of gas within the bowel wall (arrows), known as pneumatosis Pneumatosis is highly suggestive of ischaemic bowel
  48. 48. 7. Bowel ischaemia CT abdomen on lung windows (to look for air) shows bubbles of gas within the bowel wall, confirming pneumatosis. Bowel ischaemia was confirmed at surgery.
  49. 49. Case 8 65 year old woman with altered bowel habit
  50. 50. Case 8 Nonspecific bowel gas pattern No cause for the patient’s acute symptoms is identified
  51. 51. 8. Splenic Artery Aneurysms Did you spot the several peripherally calcified lesions in the left upper quadrant? (arrow) This appearance is typical of multiple splenic artery aneurysms
  52. 52. 8. Splenic Artery Aneurysms CT confirmed the presence of multiple peripherally calcified splenic artery aneurysms at the splenic hilum Important diagnosis as they are prone to rupture, especially during pregnancy.
  53. 53. Case 9 50 year old man with chronic lower back pain
  54. 54. 9. Sacral tumour There is a large lytic, expansile, destructive abnormality in the sacrum (arrow) consistent with a tumour. The foreign body in the left lower quadrant is a spinal cord stimulator to help treat chronic pain
  55. 55. 9. Sacral tumour Coronal CT abdomen on bone windows confirms the large destructive soft tissue mass in the sacrum (arrow) Biopsy confirmed a primary bone tumour
  56. 56. Case 10 60 year old woman with abdominal pain and reduced mobility
  57. 57. Case 10 At first look this PFA looks normal Do you spot any abnormality?
  58. 58. Case 10 Always look at the edge of the film
  59. 59. 10. Displaced Left Femoral Fracture The left femoral shaft is in an abnormal position
  60. 60. 10. Displaced Left Femoral Fracture Pelvic X-ray shows an old non-united left femoral neck fracture with superior migration of the left femoral shaft (arrow). Always look at the edge of the x-ray for ‘hidden’ abnormalities, especially in exams!
  61. 61. Summary Major areas to look at on the PFA: 1. Bowel gas pattern (3/6/9 rule) 2. Soft tissues 3. Bones 4. Calcifications Always look at the edges of an x-ray for ‘hidden’ abnormalities
  62. 62. svuhradiology.ie David Murphy FRCR, FFRRCSI Radiology SpR St Vincent’s University Hospital Dublin, Ireland

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