Abdominal Ultrasonography

David A. Masneri, DO, FACEP, FAAEM

Assistant Professor of Emergency MedicineAssistant Director, Emergency Medicine Residency

Medical Director, Operational Medicine Division Center for Applied LearningWake Forest University School of Medicine

Disclosure

None:

I do not have any significant financial relationships to disclose.

Outline of Topics:

• Detection of intra-abdominal free fluid and Aorta

• Clinical Application

• Anatomy

• Technique

• Normal US

• Pathologic US

• Pitfalls/Take Home Points

Clinical Application

Question:

Why learn how to identify intra-abdominal free fluid?

Answer:

Clinically significant – Trauma patient assessment

– Part of US evaluation of a hypotensive patient• Component of RUSH Exam

– Ascites assessment

– Assist in US Guided Paracentesis

How good is US for detection of free fluid?

• Detection of Intraperitoneal fluid - Excellent

• Increased sensitivity with – Increasing number of views– Positioning (Trendelenburg) – Serial examinations

• Important to visualize as much of the areas as possible and not just obtain one quick view– Multiple windows may be required to fully evaluate for

free fluid

US is POOR for assessing:

• Solid organ disruption without significant bleed

• Hollow viscus injury

• Retroperitoneal injury or hemorrhage

Appearance of Free Fluid

• Anechoic collections

– Free flowing blood

– Urine, bile, ascites, peritoneal dialysate

• Echogenic

– Clotted blood

– Bowel contents

Peritoneal Windows - Dependent Spaces

• LUQ: Perisplenic space

• RUQ: Morison’s pouch

• Pelvic:– Retrovesical space

– Retrouterine space

1

2

6

34 5

7 7

liver

RUQ (Hepatorenal) View

• Mid-axillary line in 10, 11 interspaces

• Must see junction of right kidney and liver – “Morison's pouch”

• Visualize subdiaphragmatic space

• Visualize the pleural space

8

RUQ View

• Liver cephalad

• Kidney inferiorly

• Morison’s Pouch *

*

**

Normal

Morison’s Pouch

Free fluid in

Morison’s

Pouch

Positive RUQ

Pelvic (Suprapubic or Bladder) View

• Probe should be placed in the suprapubic position

• Full bladder is window

– Helpful to image before placement of a Foley

• Trick of trade:

– If bladder is empty or Foley already placed:

– IV bag on abdomen

– Scan through bag

Pelvic View

• Where to look?– Behind bladder in men

• Retrovesicular space

– Behind uterus in women

• Retrouterine space

• Reduce far gain

• Sagittal and transverse

7

Sagittal Pelvic View

Positive Sagittal Pelvic View

Transverse Pelvic View

Positive Pelvis Transverse View

LUQ (Perisplenic) View

• Probe at left posterior axillary line at Left 8th or 9th Intercostal space

• Angle probe obliquely (avoid ribs)

• Spleen is a smaller window

• Close attention to perisplenic area:– Diaphragm – spleen interface

– Splenorenal space not as important

Normal LUQ

spleen

kidney

diaphragm

Positive LUQ View

Assessment for Intra-peritoneal Free Fluid

Interpretation:

– Exam positive

• If any one abd view positive

– Exam negative

• All three abd views negative

– Indeterminate

• Cannot adequately visualize any one view– Window not available

– Technically limited study

– Body habitus

OK the FAST is positive, but home much fluid is in the belly?

• 1cm stripe 1 L of fluid

• 0.5 cm stripe 500 mL

• Thin stripe 250 mL

Aorta Ultrasound Clinical Application

Question:

Why learn Aorta Ultrasound?

Answer:

Clinically significant in assessing or AAA

– Flank or back pain in the elderly patient

– Part of US evaluation of a hypotensive patient

• Component of RUSH Exam

– Good screening study

Aorta Ultrasound

• Excellent sensitivity for presence of AAA

• High degree of accuracy with brief training

• Improve time to diagnosis and OR vs. CT

• Poorly identifies retroperitoneal rupture

Aorta - Anatomy

• Courses from Xyphoid to umbilicus

• Originates at diaphragm and extends to iliacs

• Main branches– Celiac (CA)– Superior Mesenteric

(SMA) – Renal (RA)– Inferior Mesenteric (IMA)

From: Gray, H. Anatomy of the Human Body 20th ed. 2000

Aorta - Anatomy

• Maximal diameter– Proximal:

• 2.1 cm for males, 1.8 cm for females > 55 yrs

– Distal: • 1.5 cm

• Aneurysm considered when diameter 3 cm– Measure diameter from outer surface of walls

Aorta Technique

• Curved or phased array probe

• Supine position preferred

Aorta Technique

Transverse Aorta

• Anterior to vertebral body

• Ao vs IVC:

– Aorta on pt’s left

– IVC on pt’s right

IVC Aorta

Abd wall

Back

Right Left

Normal Appearance - Transverse

• Vertebral body posterior,– Hyperechoic arch

• Aorta and IVC anechoic circles anterior to vertebral body

• Aorta “divides” at bifurcation

IVC Aorta

Abd wall

Back

Right Left

Bifurcation- Transverse

Aorta Technique

Longitudinal images

• Rotate probe 90°

• Rock and slide technique

Abd Wall

Head Feet

Back

Normal Appearance - Longitudinal

• Longitudinal Aorta – Courses left to right

• Branches– Celiac

– Superior Mesenteric

– Course anterior to Ao

Abd Wall

Head Feet

Back

SMACA

Ao

Technically Difficult Studies

• Bowel gas and obesity may obscure images

• Maneuvers:

–Gentle pressure with probe

– Left lateral decubitus position

–Coronal plane images from right flank

Coronal

Right

Head Feet

Left

Aorta

Cava

IVC Aorta

• On patient’s right

• Undulating motion

• Thin walled

• Compressible

• Collapses with negative intrathoracic pressure– “Sniff”, Valsalva

• On patient’s left

• Pulsatile motion

• Thick walled

• Non-compressible

• Non-collapsing

Color Doppler to Differentiate

AAA

• Best visualized in transverse view– Many AAAs have greater transverse than AP diameters– If you see the aorta VERY WELL it is probably a AAA

• Fusiform– Symmetric, concentric dilatation– More common

• Saccular– Localized out-pouching

• 90 % occur at and below level of renals (region of SMA)– MUST visualize Ao bifurcation for complete scan

AAA – Transverse View Fusiform

Abd wall

Back

LeftRight

AAA - Longitudinal View Fusiform

Abd Wall

Head Feet

Back

AAA – Transverse View Saccular

AAA - Transverse View with Thrombus

Intro to RUSH Exam

• Rapid Ultrasound for Shock and Hypotension

• Assess the Pipes, Pump, Tank

• “HI MAP”

– Heart

– IVC

– Morison’s Pouch (Abdominal FAST views)

– Aorta

– Pneumothorax

Thank You