Ultrasound Normal Anatomy of Major Organs

Normal sonographic anatomy of abdominal and pelvic organs

1. Basic Sonographic Anatomy of Major Organs Presented by: Anish Dhakal (Aryan) MBBS, Patan Academy of Health Sciences

2. What hapens to ultrasound wave? 1 . Transmission (Small difference in acoustic impedance = greater transmission) 2. Reflection : source for ultrasound image 3. Scattering: mostly occurs with RBCs 4. Attenuation: resulting in heat production 5. Refraction: can result in double image artifacts due to difference in acoustic impedence between body tissues

3. Fluid: most acoustical energy is transmitted Gas or bone: most energy reflected back, not enough energy to define deeper structures Hyperechoic Hypoechoic/ Sonolucent /Anechoic Longitudinal & Transverse Plane Patient’s head: your left, Patient’s feet: your right Anterior is up & Posterior is down

4. Preparation Patient preparation: Patient should be NPO for at least 8 hours unless there is possibilities of dehydration In that case water should be given As the examination proceeds and there is no clinical contraindication, water should be given especially when scanning pancreas, lower abdomen and pelvis

5. Preparation Patient position: Supine Pillow under head If much tenderness one pillow should be under the knee Choice of transducer: For adult 3.5 MHz For children and thin adults 5 MHz

6. Scanning technique Apply coupling agent Start by placing the probe centrally at the top of the abdomen (at xiphoid angle) Slowly move the transducer from the midline across the abdomen to the right, stopping to check the image approximately every 1 cm. Repeat at different level Examine the left side in the same way when right side is completed. Ask the patient to take deep breath and hold it.

7. Liver scan Normal liver: Liver parenchyma appears homogenous, interrupted by portal vein and its branches Portal vein and its branches appears tubular structure with reflecting walls (bright) The thinner hepatic veins are non-reflective It is possible to follow hepatic veins to their confluence with the inferior venacava Hepatic veins can be made dilated by Valsalva maneuver

8. Scanning technique for liver:

9. Oblique (upper) and transverse (lower) scans of the liver showing portal vein and inferior venacava

10. Transverse scan: fissure of ligamentum teres hepatis ( falciform ligament)

11. Right and left lobes of lever can be recognized by identifying the falciform ligament fissure Caudate lobe is recognized by identifying the inferior venacava. Caudate lobe is limited posteriorly by inferior venacava and separate antero -superiorly from the left lobe by a highly reflective line. Caudate lobe must be identified because it may be mistaken for a mass.

12. The normal echogenicity of liver parenchyma is mid way between pancreas (more echogenic) and spleen (less echogenic)

13. Gall bladder and biliary tree scanning technique Start with longitudinal scan, then transverse scan and intercostal scan if necessary Then turn the patient on the left and make oblique scans at different angles If there is excess bowel gas, examine the patient standing erect. Hand knee position can be used to demonstrate gallstone more clearly allows the stones to move more anteriorly.

14. Normal anatomy of gall bladder On longitudinal scan, it appears echo free, pear shaped structure. It is very variable in shape, size, position but normal gall bladder is seldom more than 4 cm wide. Longitudinal scan

15. The thickness of gall bladder wall can be measured by transverse scan In a fasting patient, it is 3 mm Distended gall bladder has 1 mm thickness Transverse section: Full gallbladder (wall thickness 1mm)

16. Longitudinal (upper) and transverse (lower) scans of a contracted gallbladder (wall thickness less than 3 mm)

17. Non-visualization of gallbladder The patient has not been fasting: re-examine after an interval of at least 6 hours without food and drink The gall bladder lies in an unusual positions: Scan low down in the right abdomen, even as low as the pelvis Scan to the left of the midline and in the patient in the oblique position with the right side down Scan high under the costal margin

18. Non-visualization of gallbladder The gallbladder is congenitally hypoplastic or absent It is shrunken and full of stones with associated acoustic shadowing It has been removed surgically: examine the abdomen for scars and ask the relatives The examiner is not properly trained or experienced: ask the colleague to examine the patient

19. Biliary ducts It is not always easy to identify the normal main left and right hepatic bilary ducts, but when visible they are within the liver and appear as thin walled tubular structure Common hepatic duct can be recognized just anterior and lateral to the crossing portal vein. Its cross-section at this point should not be more than 5 mm The diameter of common bile duct is variable but should not exceed 9 mm near its entrant into pancreas

20. Oblique scan: normal common bile duct Transverse scan: normal common bile duct at porta hepatis

21. Oblique scan: normal common bile duct at porta hepatis

22. Pancreas scan Pancreas can be very difficult to find out especially the tail Start with transverse scan across the abdomen moving downwards towards the feet until the splenic vein is seen. Splenic vein is seen as a linear, tubular structure with the medial end broadened. This is where it is joined by superior mesenteric vein at the level of the neck of the pancreas The superior mesenteric artery will be seen in cross section just below the vein. By angling and rocking the transducer, the head and tail of the pancreas can be seen

23. Scanning Technique:

24. If bowel gas obscures the image:

25. Transverse scan: splenic vein, superior mesenteric artery and body of pancreas seen

26. Continue transverse scan downward to visualize the head of the pancreas and uncinated process between the inferior venacava and portal vein Transverse scan: head of the normal pancreas scanned through the left lobe of the liver

27. Transverse scan: tail of the normal pancreas Transverse scan: Normal pancreatic duct

28. Longitudinal scanning of the pancreas Start just to the right of the midline and identify the tubular pattern of the inferior vena cava with the head of the pancreas anteriorly, below the liver The vena cava should not be compressed or flattened by normal pancreas. Longitudinal scan: Inferior vena cava and head of the pancreas

29. Continue longitudinal scan moving to the left Identify the aorta and superior mesenteric artery This will help identifying body of pancreas Longitudinal scan: The aorta and body of pancreas

30. Normal pancreas Pancreas has about the same echogenicity as the adjacent liver and should appear homogenous. However, the pancreas echogenicity increases with age The outline of normal pancreas is smooth.

31. Essential landmarks while scanning pancreas Aorta Inferior vena cava Superior mesenteric artery Splenic vein Superior mesenteric vein Wall of the stomach Common bile duct Note: The most essential land marks are superior mesenteric artery and splenic vein

32. The average diameter of head of the pancreas is 2.8 cm The average diameter of medial part of the body of pancreas is less than 2 cm The average diameter of tail of the pancreas is 2 cm The diameter of pancreatic duct should not exceed 2 mm. it is normally smooth and wall and lumen can be identified The accessory pancreatic duct is seldom visualized.

33. Spleen scan Technique: Scan with the patient in the supine position and then oblique position

34. Scan from below the costal margin, aligning the beam towards the diaphragm, then in the 9 th intercostal space downwards. Repeat through all intercostal spaces, first with the patient supine and then with the patient lying obliquely (30 degree) on right side.

35. Also perform longitudinal scans from anterior to posterior axillary lines and transverse upper abdominal scans. Scan the liver also, particularly when spleen is enlarged

36. Normal spleen It is important to identify: Left hemi-diaphragm Splenic hilus Splenic vein and relationship to pancreas Left kidney and renal-splenic relationship Left edge of liver Pancreas

37. When spleen is normal size , it is difficult to image completely The splenic hilus is the reference point to ensure correct identification of the spleen Identify the spleen as the entry point of splenic vessels Oblique scan: normal spleen and left kidney

38. Echo pattern of spleen The spleen should show a uniform pattern of homogenous echogenicity It is slightly less echogenic than lever

39. Common errors in scanning the spleen

40. Full bladder is required Scanning is always done in deep suspended inspiration Start with the longitudinal scan over the right upper abdomen and then follow with the transverse scan to visualize the right kidney in the coronal view Kidney and ureter scanning

41. If the left kidney is not visualized generally with bowel gas, try to visualize in the right decubitus position Bowel gas can also be displaced by drinking 3-4 glasses of water

42. Normal kidneys In newborns, the kidneys are about 4 cm long and

43. Longitudinal scan of normal right kidney

44. Longitudinal scan of normal right kidney with bifid renal sinus

45. Anterior transverse scan through the right renal sinus showing pelvis

46. Longitudinal scan of normal left kidney

47. Transverse scan of normal left kidney

48. Transverse scan of a normal renal sinus (renal pelvis, fat and vessels)

49. Bladder: Scanning Technique

50. Thank you