1. Hepatic Doppler Didactic objectives  Review Doppler principles  Review hepatic function/disease  Discuss hepatic arterial and venous anatomy  Review grey scale findings of hepatic disease  Normal and abnormal Doppler findings  Define elements of Hepatic Doppler exam  billing  patient prep  protocol

2. Hepatic Doppler Doppler principles  The shift in sound frequency is proportional to the speed of flowing blood:  f = 2f i v cos   Practical implications of the principle:  faster flow (v) results in bigger Doppler shift  higher incident frequency (f i ) results in bigger Doppler shift  smaller angle of insonation (cos  ) results in bigger Doppler shift

3. Hepatic Doppler Align the ultrasound beam in the direction of flow (small angle)  Shallow angle results in bigger Doppler shift  Shallow angle minimizes errors introduced by inaccurate angle correction

4. Hepatic Doppler Technologist controlled variables  Machine settings:  power output  transducer frequency  system gain  sample volume (gate size)  angle assignment  pulse repetition frequency (velocity scale)  display size  sweep speed  wall filter

5. Hepatic Doppler Technologist controlled variables  Transducer frequency  Select for best gray scale image  3.5 curved is the workhorse for the liver  When imaging superficial structures (left portal vein, recanalized umbilical vein, hepatic capsule) use higher frequency and linear transducers  2.5 sector may provide best fit in small window  Use a lower frequency transducer for high velocity flow in a deep vessel (avoids aliasing)

6. Hepatic Doppler Technologist controlled variables  System gain  Gray scale and Doppler gain are set independently  Gain used to amplify weak signal (don’t use gain to compensate for inappropriate transducer selection, wall filter, or PRF)  When performing Doppler, narrow the imaging window to permit identification of the vessel, but eliminate extraneous noise

7. Hepatic Doppler Technologist controlled variables  Sample volume  Enlarge sample volume when searching for flow in small or obstructed vessels and in main portal vein  Sample volume should be kept as small as reasonably possible when recording Doppler signal to minimize extraneous signals from adjacent tissue and vessels  Use color Doppler to assist sample volume position in flow stream (center of the vessel in most cases)  Listen to the Doppler signal to assist in sample volume placement

8. Hepatic Doppler Technologist controlled variables  Angle assignment  May be performed during acquisition or on frozen/stored image  Angle correction aligned parallel to vessel walls in most cases  Angle correction oriented to the direction of flow (color may assist in demonstrating flow direction in a curving or stenotic vessel)

9. Hepatic Doppler Technologist controlled variables  Pulse repetition frequency (PRF) “velocity scale”  PRF controls how frequently the machine sends a Doppler pulse  Aliasing occurs if the Doppler frequency shift is more than twice of the sampling rate (PRF)  The PRF and baseline should both be adjusted so the spectral signal (unidirectional or bidirectional) occupies 2/3 of the window  Adjust color baseline to avoid (or exaggerate) aliasing

10. Hepatic Doppler Technologist controlled variables  Display size  Gray scale images should be enlarged or magnified (zoomed) so the region (vessel) of interest occupies half the image  Gray scale and spectral Doppler windows should each occupy half of the monitor display

11. Hepatic Doppler Technologist controlled variables  Sweep speed  Use slow sweep speed to demonstrate pulsatility of flow (e.g. cardiac or respiratory pulsatility)  Use fast sweep speed for measurements (acceleration time, peak systolic, diastolic, RI, PI, etc.)

12. Hepatic Doppler Technologist controlled variables  Wall filter  Used to eliminate low frequency vibrations of the vessel wall and solid tissue around vessels  Typical preset 25 kHz (optional 25-150 kHz)  Set as low as possible to permit identification of low velocity flow

13. Hepatic Doppler Doppler Options  Continuous wave  Pulsed (spectral)  Duplex  Color  Triplex imaging  Power (amplitude)

14. Hepatic Doppler Pulsed Doppler  Machine sends pulses of sound energy at intervals to allow sound to travel to the sample gate and return to the transducer before sending the next signal  Returning signal is analyzed (FFT) to separate the different frequencies (velocities) of flowing blood  The sample is displayed on the monitor to demonstrate the range of velocities and their change over time

15. Hepatic Doppler Doppler spectrum  Time is displayed on the X axis; Doppler frequency on Y  Blood flow towards the transducer is conventionally displayed as an upwards deflection  At any moment in time, the entire range of RBC velocities within the sample volume is displayed in the spectrum  Pulsatility Index = S-D/mean  Resistive Index = S-D/S

16. Hepatic Doppler Duplex Doppler  Combines grey scale image with pulsed Doppler in “real time” (time sharing)  Machine acquires a grey scale image, stores it, then acquires a pulsed Doppler signal and displays it  Machine can prioritize grey scale or Doppler acquisitions

17. Hepatic Doppler Optimize the duplex exam  Narrow the grey scale image to only include structures necessary to identify the anatomy  For deep vessels with high velocity, decrease transducer frequency to minimize aliasing  Decrease frame averaging (persistence) to minimize aliasing; increase frame averaging for slow flow  Lower wall filter for low flow states (veins)  Listen to the Doppler signal for optimal gate placement

18. Hepatic Doppler Color Doppler  A “duplex” examination of flow in a large area  Because multiple vessels imaged simultaneously, Doppler shifts are displayed in color, not spectra  Displays flow direction by color (e.g. red and blue) and flow velocity by color saturation  Doppler sampling of large area slows the frame rate and maximal pulse repetition frequency (velocity)  Gray scale image is frozen (or periodic refresh) during color/spectral Doppler acquisition

19. Hepatic Doppler Optimize the color exam  Attempt to image from a position that aligns the ultrasound beam in the direction of flow of the vessel of interest  Adjust focal zone to the level of primary interest  Adjust color sample volume so that vessel(s) of interest occupies 1/2 of box  Adjust PRF and baseline to fill vessel lumen (slow flow along walls) without aliasing

20. Hepatic Doppler Hepatic Blood Supply  Portal vein  75% of blood flow to the liver  Deoxygenated but nutrient rich  Hepatic artery  25% of blood flow to the liver  Oxygenated  Sole source of flow to bile ducts

21. Hepatic Doppler Hepatic Sinusoids  Functional unit of liver  Parallel columns of hepatocytes surrounded by portal triads  Portal triads include branches of the portal vein, hepatic artery, bile ducts  Portal venous and hepatic arterial blood mixes in sinusoids and drains into central vein

22. Hepatic Doppler Hepatic venous drainage  Central veins empty into hepatic veins  Right, middle, left  No valves in hepatic veins therefore reflect cardiac pressures and pulsatility

23. Hepatic Doppler Hepatic Physiology  Processes dietary amino acids, carbohydrates, lipids, to synthesize fats (cholesterol) and proteins  Metabolizes toxins  Glycogen storage  Produces clotting factors  Blood markers of liver function:  AST/AST (aspartate transaminase/alanine transaminase)  Alkaline phosphatase  GGT  (  glutamyl-transferase)  Albumin  Bilirubin (direct, indirect, total)  PT (prothrombin time)  CBC (platelets)

24. Hepatic Doppler Hepatic pathology  Acute injury (hepatitis) results in influx of inflammatory cells, cytokine release and cell death  Chronic injury leads to parenchymal fibrosis (cirrhosis) with focal areas of hepatic repair called regenerating nodules  Fatty liver (steatosis) may be related to excess triglycerides (diet, diabetes) or response to injury

25. Hepatic Doppler Cirrhosis – common causes  Alcohol (60%)  Viral hepatitis B, C, and D (10%)  Non-alcoholic fatty liver disease (10%)  Biliary obstruction (5%)  Others  Hemochromatosis  Drugs/toxins  Genetic metabolic  Chronic heart failure

26. Hepatic Doppler Child-Pugh Cirrhosis Classification  Class A: score 5-6  Class B: score 7-9  Class C: score >9 ScoreBilirubinAlbuminINR Enceph- alopathy Ascites 1<2 mg/dl>3.5 gm/dl<1.7None 22-3 mg/dl2.8-3.51.7-2.21-2Mild 3>3 mg/dl<2.8 gm/dl>2.23-4severe

27. Hepatic Doppler Gray scale diagnosis of diffuse liver disease  Acute hepatitis  Hepatomegaly (normal 15 -17 cm)  Starry night - not useful  Mottled or normal texture (without nodules)

28. Hepatic Doppler Gray scale diagnosis of diffuse liver disease  Fatty liver (two or more findings)  Liver echogenicity exceeds that of renal cortex and > spleen  Attenuation of the ultrasound wave (difficult to image the diaphragm)  Poor definition of the intrahepatic architecture  Often focal or areas of fatty sparring  Intra- and interobserver reproducibility 76% and 72%

29. Hepatic Doppler

31. Gray scale diagnosis of diffuse liver disease  Cirrhosis  Surface nodularity (linear transducer right and left lobes)  Mottled texture  Loss of fine architectural detail  Normal size or hepatomegaly  Caudate lobe hypertrophy

32. Hepatic Doppler

33. Portal vein dynamics  Normal PV pressure 5-10 mm Hg  Normal flow direction is towards the liver (hepatopetal)  Portal volume 20-1500 cc/min  Flow influenced by:  Eating/fasting  Abdominal pressure (inspiration/expiration, Valsalva, ascites, obesity)  Patient position (supine, LPO, sitting)

34. Hepatic Doppler PV Doppler - Normal  Hepatopetal  Peak velocity 20-30 cm/sec (Haktanir)  Mild cardiac pulsatility (Pulsatility Index 0.2 to 0.5) (Barakat)  Moderate spectral broadening (preservation of 30% window) (Barakat)

35. Hepatic Doppler Portal Venous hypertension (wedged hepatic vein pressure 5mm Hg greater than IVC pressure)  Obstruction to PV flow  Prehepatic (PV thrombosis, pancreatitis)  Intrahepatic (cirrhosis)  Posthepatic(right heart failure, Budd-Chiari)  Increased PV flow  Arterioportal shunt (hepatic artery-PV fistula following trauma, surgery, AVM)

36. Hepatic Doppler PV hypertension – “soft” findings  Decreased PV velocity (<20 cm/sec) (Haktanir)  Spectral broadening  Decreased pulsatility  PV diameter >15mm  Diminished response to inspiration (<20% change in diameter)

37. Hepatic Doppler PV hypertension – “hard” findings  Reversed flow (hepatofugal)  Portosystemic collaterals  Splenomegaly  Ascites

38. Hepatic Doppler PV hypertension  PV flow reverses (hepatofugal) when extra-hepatic collateral pathways develop between PV branches and systemic veins  Requires examination of splenic and superior mesenteric veins

39. Hepatic Doppler Portosystemic collaterals  Gastric-esophageal most important – from coronary and gastrosplenic veins  10-20% spontaneous splenorenal shunt  Paraumbilical  Inferior mesenteric- hemorrhoid  Look for common collateral pathways

40. Hepatic Doppler Portal venous hypertension  Intrahepatic shunts complicate detection of flow reversal  Examination of intrahepatic left and right PV branches required

41. Hepatic Doppler Hepatic Artery Doppler - Normal  Hepatopetal  Peak systolic velocities 30 – 60 cm/sec  Low impedance (RI = 0.60 – 0.68) (Haktanir)  Rapid acceleration time (<0.08 sec)  Intrahepatic branches more sensitive to disease states

42. Hepatic Doppler Hepatic Artery - Abnormalities  Hepatitis (inflammation) and cirrhosis  Increased flow  Increased impedance (RI >0.72) (Haktanir)  PV thrombosis  Increased flow  Decreased impedance (RI <0.68) (Platt)

43. Hepatic Doppler Hepatic Artery - Abnormalities  Hepatic artery stenosis  Decreased flow  Tardus/parvus downstream from stenosis  High velocity jet at stenosis

44. Hepatic Doppler Hepatic Vein Doppler – Normal  Triphasic  Antegrade (hepatofugal) peaks during atrial diastole and ventricular diastole  Retrograde (hepatopetal) flow during atrial systole  Affected by respiration

45. Hepatic Doppler Hepatic Vein Doppler – Altered flow  Hepatic “stiffness” prevents hepatic veins from distending during atrial systole  Hepatofugal flow maintained  Biphasic or monophasic  Nonspecific response to steatosis, acute or chronic injury

46. Hepatic Doppler Hepatic Vein Doppler – Occlusion  Budd-Chiari syndrome (abdominal pain, ascites, hepatomegaly)  75% associated with hypercoagulable conditions (polycythemia, antiphospholipid disease, protein S or factor V Liden deficiency, postpartum)  25% secondary to extrinsic compression of IVC (tumors) or vascular webs  Complications include cirrhosis, hepatic necrosis, encephalopathy,  Treated with paracentesis, anticoagulants, transplant for liver failure

47. Hepatic Doppler Hepatic Vein Doppler – Thrombosis  Color Doppler demonstrates absent flow in one or more hepatic veins (+/- IVC)  Intrahepatic shunts and subcapsular collaterals  Secondary findings:  Failure to visualize hepatic veins  High velocity venous jets  Hepatofugal portal flow  Hepatomegaly and ascites

48. Hepatic Doppler Transjugular Intrahepatic Portosystemic Shunt (TIPS)  High rate of obstruction (25-75% within 12 months)  Thrombosis or pseudointimal hyperplasia

49. Hepatic Doppler TIPS obstruction  Absent color flow (good angle, low flow settings)  Decreased peak velocity (<50 cm/sec) mid stent  Focal jet (>250 cm/sec)

50. Hepatic Doppler Liver Transplant  Mechanical complications at sites of anastomosis  Bile duct obstruction, stenosis, leak (25%)  Hepatic artery thrombosis, stenosis, pseudoaneurysm (4- 12%)  Portal and hepatic vein thrombosis or stenosis (1%)

51. Hepatic Doppler Hepatic Doppler Protocol  Limited Abdominal US (76705)  Prep  Technique  Documentation  Abdomen Doppler Complete (93975)  Technique  Documentation

52. Hepatic Doppler Hepatic Doppler Protocol Fasting 6 hours Supine or LPO, suspended inspiration  Abdominal imaging  liver (13 images)  biliary system (3 images)  spleen (2 images)  Color and spectral Doppler  portal venous system (8 images)  hepatic artery (3 images)  hepatic veins (4 images)  inferior vena cava (1 image)