Exam 1: Validity Testing, Mesenteric Doppler, Liver Doppler, Liver Pathologies, Liver Transplant, Renal Doppler, Renal Transplant

Gold Standard

Well-established, reliable diagnostic method used as a reference

Gold Standard for Vascular Imaging

Angiography

Validity

Ability of a test to distinguish between who has the disease and who does not

True Positive (TP)

Those who have disease and a positive test

Ultrasound shows disease, gold standard shows disease

True Negative (TN)

Those who do not have disease and a negative test

Ultrasound shows no disease, gold standard shows no disease

False Positive (FP)

Those who do not have disease and a positive test

Ultrasound shows disease, gold standard shows no disease

False Negative (FN)

Those who have disease and a negative test

Ultrasound shows no disease, gold standard shows disease

Sensitivity

Ability of test to correctly detect patients with disease compared to the gold standard - positive sonogram with positive gold standard

Sensitivity Formula

Number of true positive tests

Number of all positive tests by gold standard

Specificity

Ability of test to correctly detect patients without disease compared to the gold standard - negative sonogram with negative gold standard

Specificity Formula

Number of true negative tests

Number of all negative tests by gold standard

Positive Predictive Value (PPV)

Probability that a positive test result reflects the actual presence of disease

Portion of patients with a positive test that have disease

Positive Predictive Value (PPV) Formula

Number of true positive tests

Number of all positive noninvasive tests

Negative Predictive Value (NPV)

Probability that a negative test result reflects the actual absence of disease

Portion of patients with a negative test that do not have disease

Negative Predictive Value (NPV) Formula

Number of true negative tests

Number of all negative noninvasive tests

Accuracy

Degree of closeness of a test result to the actual value

Percentage of overall correct results

Must lie between sensitivity & specificity and PPV & NPV

Accuracy Formula

Total number of correct tests

Total number of all tests

Reliability

Consistency of obtaining similar results under similar conditions - reflects accuracy over time

Increasing Cut-Off Values

Improves specificity

More true negatives

Decreasing Cut-Off Values

Improves sensitivity

More true positives

Why is Validity Testing Important?

Required part of accreditation for labs

Ensures reason, quality, & completeness of exams

Ensures lab follows protocol & quality standards

Patient Prep for Mesenteric Study

NPO ≥ 6 hours - schedule early to avoid bowel gas

No smoking or gum chewing

Medications with water only

Patient supine

Low frequency curved transducer

Protocol for Mesenteric Study

RUQ first - eliminate GB as pain source

Pre and post-prandial images - 2D, color, spectral

Aorta at level of celiac axis and SMA

Origin of celiac axis

Origin of SMA

Origin of IMA

Celiac Artery Doppler Waveform

Low resistant

Celiac Artery PSV

101 cm/sec

Celiac Artery RI

0

70% Celiac Artery Stenosis PSV

≥ 200 cm/sec

Celiac Artery Occlusion

Results in SMA collaterals diverting blood through gastroduodenal artery toward the liver and spleen

Replaced Right Hepatic Artery

Right hepatic artery branches off something else besides celiac artery - usually SMA

Hepatic Artery Retrograde Flow

Due to celiac artery occlusion

Blood flows towards splenic artery - RABT color pattern

Pre-Prandial SMA Doppler

Post-Prandial SMA Doppler

SMA PSV

113 cm/sec

SMA Stenosis

High velocity jet

Distal tardus parvus flow

70% SMA Stenosis PSV

≥ 275 cm/sec

SMA Dissection

Common Trunk Variant

Celiac and SMA come off common trunk

IMA

IMA PSV

141 cm/sec

IMA Stenosis PSV

> 200 cm/sec

Prominent IMA

Due to SMA occlusion

Acute Mesenteric Ischemia

Thrombosis of one or more mesenteric vessels

Life threatening - requires immediate intervention

Severe cramping/pain - disproportional pain

Chronic Mesenteric Ischemia

Low resistant pre-prandial doppler signals

70% occlusion of 2/3 splanchnic arteries required for diagnosis (celiac, SMA, IMA)

Epigastric pain after eating - fear of food, weight loss, decreased nutrition

Compensatory Flow

Elevated velocities in normal collateral vessels

No stenotic profile seen

Aneurysm

Most common in splenic artery

Life threatening if ruptured

Dissection

Separation of channels - flap line

To and fro flow

Bypass Graft Protocol

Inflow artery

Proximal anastomosis

Length of graft

Distal anastomosis

Outflow artery

Median Arcuate Ligament Syndrome (MALS)

Compression of celiac axis during exhalation by median arcuate ligament

Pain relieved by inhalation

Evaluate in supine & upright positions and with inspiration & expiration

Celiac Artery PSV with MALS

> 250 cm/sec during expiration that normalizes with inspiration

Patient Prep for Liver Doppler

Fasting 8-12 hours

No smoking or chewing gum

Pre-Hepatic/Inflow Vessels

Portal Vein

Hepatic Artery

Intrahepatic/Sinusoidal Vessels

Sinusoids/capillaries

Hepatocytes

Post-Hepatic/Outflow Vessels

Central Veins

Sublobular Veins

Hepatic Veins

IVC

Left Gastric Vein (coronary vein) Diameter

> 6 mm

Left Gastric Vein (coronary vein) Doppler Flow

Hepatofugal

Main Portal Vein

Junction of splenic vein & SMV

Brings blood from bowel and spleen into liver

Main Portal Vein Diameter

≤ 13mm (resting)

≤ 16 mm (deep inhalation/valsalva)

Main Portal Vein Doppler Waveform

Monophasic continuous waveform

Hepatopetal flow (antegrade flow)

Main Portal Vein PSV

16-31 cm/sec

Slight respiratory variation

-> breath in = decreased velocity

-> breath out or eating = increased velocity

Hepatic Vein Diameter

6 mm

≤ 9 mm (when CHF is present)

Hepatic Vein Doppler Waveform

Triphasic

Antegrade & retrograde flow - cardiac pressure changes

Hepatic Vein Doppler

S wave: ventricular systole

D wave: atrial filling

A wave: atrial contraction

Inspiration depresses systolic wave

Exhalation augments systolic wave

Valsalva diminishes pulsatility

Hepatic Vein PSV

20-39 cm/sec

Hepatic Artery

Right branch of celiac trunk

Hepatic Artery Doppler Waveform

Hepatopetal

Low resistant monophasic pan-diastolic forward flow

Hepatic Artery PSV

70-120 cm/sec

Hepatic Artery RI

0.5 - 0.7

Hepatic Buffer Response

When PV flow increases, HA flow decreases (post-prandial)

Splenic Vein Diameter

10 mm

Splenic Vein Doppler Waveform

Hepatopetal flow

Continuous monophasic with slight respiratory variation

Splenic Vein PSV

9-30 cm/sec

SMV Diameter

10 mm

SMV Doppler Waveform

Hepatopetal flow

Continuous monophasic with slight respiratory variation

SMV PSV

8-40 cm/sec

IVC Diameter

15-25 mm

valsalva = max diameter

IVC PSV

44-118 cm/sec

Increases with inspiration

Sub-Xiphoid/Transverse Epigastric & Left Sagittal

Left Hepatic V at IVC: blue

Ascending Left Hepatic V: red

Hepatic Artery: red

Porta Hepatis: red

Portal Confluence: blue

Splenic Vein: red

Right Subcostal Margin

Porta hepatis, MPV, anterior RPV, HA: red

Posterior RPV : blue

Right Intercostal

Porta hepatis: red

Portal-Splenic confluence: red

Left Coronal Oblique

Splenic vein: blue

Splenic artery: red

Portal Pressure Formula

IVC pressure - portal vein pressure

Portal Vein Pressure

5-10 mmHg

≥ 15 mmHg = clinically significant

Portal HTN

Increased pressure in portal venous system

Not diagnosed with spectral Doppler -> diagnosed with gray scale & color

Causes of Portal HTN

Hepatitis C

Hepatitis B

Alcoholic cirrhosis

Primary Biliary Cirrhosis

Autoimmune Hepatitis

Hereditary Hematochromatosis

Schistosomiasis

Portal HTN 2D Findings

Large pulmonary vein

Collaterals

Splenomegaly

Ascites

Enlarged hepatic artery

Portal HTN Doppler Findings

Slow, hepatofugal flow in portal vein

Cirrhosis

End-stage liver disease

Cirrhosis Findings

Portalization of hepatic veins

Collaterals

Hepatofugal flow in portal vein & splenic vein

Coronary Vein Collateral

Can lead to esophageal varices

Recanalized Paraumbilical Vein

Ligamentum teres recanalizes

Courses from left portal vein to anterior abdominal wall

Hepatofugal flow

Recanalized Paraumbilical Vein Diameter

> 3 mm

Recanalized Paraumbilical Vein PSV

> 5 cm/sec

Splenorenal Shunt

Prominent veins at splenic hilum

Hepatofugal flow in splenic vein

Gastroesophageal Veins/Esophageal Varices

Originate from gastroesophageal junction posterior to left liver lobe

Due to hepatofugal flow in coronary vein shunt

High risk of rupture

Gallbladder Varices

Serpentine anechoic structures along GB wall

Gallbladder Varices Diameter

3-8 mm

AV Fistula

Arterialized portal vein flow - hepatic artery to portal vein shunting

Leads to portal HTN

AV Fistula Causes

Trauma

Penetrating trauma

Iatrogenic trauma- biopsies, invasive imaging procedures

AV Fistula Findings

Large anechoic spaces

Increased portal vein pulsatility & velocities

Aterialization of the Liver

Max portal vein pressure leads to increased hepatic artery flow