1/15/20

1

Ultrasound of the Equine Abdomen

Liara M. Gonzalez, DVM, PhD, DACVS-LAAsst. Prof. of Gastroenterology & Equine Surgery

Large Animal Models Core- Co-DirectorNC State University

Lmgonza4@ncsu.edu

Gonzalez Lab: http://go.ncsu.edu/GonzalezLab

Why Ultrasound?

• Indications– Colic– Weight loss– Fever of unknown origin– Abnormal rectal

palpation• Limitations

– Depth 22 to 26 cm– Gas obstructs view of GI

contents/deep structures

Principles of US

• Acoustic impedance– Energy à sound wave (piezoelectric effect)– Sound waves reflected back (acoustic impedance)– Sound à energy (image generated)

Incident wave Transmitted wave

Reflected wave

1/15/20

2

• Scattering– Heterogeneous material (i.e organs)– Echogenicity = ability of tissue to reflect US wave

• spleen > liver > kidney > fat > fluid

Principles of US

• Field of view– Closer structures

• Top of image– Deeper structures

• Bottom of image

Principles of US

• Transducer frequency

– Low frequency (2-5 mHz)

• Better penetration/depth – up to 30 cm

• Less detailed image

– High frequency (8-10 mHz)

• Less penetration/depth – up to 10 cm

• More detailed image. Why..?

Principles of US

1/15/20

3

• Transducer shape– Curvilinear

• Sector shaped image• Wide field of view

– Linear• Rectangular image• Narrow field of view

– Gets worse as depth increases

Principles of US

• Maximizing your image– Alcohol

• More is usually more• To clip or not to clip...

– Depth: Change it frequently• Superficial structures: 6 – 12 cm

– Improves detail

• Deep structures: 20 – 30 cm

Principles of US

Preparation/Technique

• 2.5-5 MHz curvilinear probe

• Clean coat/ clip hair• Alcohol/ US gel• Systematic scanning

– Top to bottom– Rostral to caudal– Left and right

orFlash Ultrasound

1/15/20

4

Normal Intestine US Anatomy

• Typically see 3 layers:1. Hyperechoic serosa2. Hypoechoic muscularis to

mucosa3. Hyperechoic lumen

http://vetultrasoundgroup.com.au/wp-content/uploads/2015/09/layer-git-2.png

Interior

Exterior

Intestinal Layer

Echogenicity

Lumen HyperechoicMucosa HypoechoicSubmucosa HyperechoicMuscularis HypoechoicSerosa Hyperechoic

Abdominal Anatomy: Left Side• Liver: 6th-9th ICS, best imaged on R side• Stomach: 9th-13th ICS• Spleen: 8th ICS – paralumbar fossa

https://www.studyblue.com

Abdominal Anatomy: Left Side• Small intestine: inguinal and ventral midline• Kidney: 17th ICS to paralumbar fossa medial

to spleen• Small colon: Caudal medial to spleen • Large colon: ventral caudal to spleen

1/15/20

5

Scanning Left Side

Busoni et al., 2011; LeJeune & Whitcomb., 2014

Abdominal Anatomy: Right Side

• Liver: 6th-15th ICS, b/t diaphragm and RDC• Kidney: 14th-17th ICS• Duodenum: B/t liver/RDC and caudal to kidney• Right colon: Ventral to liver• Cecum: Paralumbar fossa extending ventral

https://www.studyblue.com

Scanning Right Side

Busoni et al., 2011; LeJeune & Whitcomb., 2014

1/15/20

6

Emergency US Exam for Colic

• FLASHFast LocalizedAbdominal Sonography of Horses

Liver• Indications: icterus, weight loss, liver enzymes• Normal:

– Echogenicity: homogenous, > kidney, < spleen– bile ducts not visible– No gallbladder

• Disease:– Acute hepatic necrosis/ hepatitis: enlarged, round edges– Chronic liver dz: small, echogenicity (focal or diffuse)– Cholelithiasis: Dilated ducts containing hyperechoic

contents– Fatty liver: Enlarged, diffuse echogenicity – Abscess/Cancer: rare

Image courtesy of Amy Stuart

Stomach

• Normal:– Thickness: 7-9mm

• Disease:– Gastric distension: >13 ICS– Gastric impaction: may cause

distension, no def. dx with US– Ulcers: Use endoscopy

http://fourwaysequine.co.za/wp-content/uploads/sites/11/2015/12/Ultrasound3.png

1/15/20

7

Small intestine• Normal:

– Inguinal & ventral midline

– Small tubular/circular

– Most visibly motile of all GI

– Wall thickness ≤4mm (ileum up to 5mm)

– Short axis diameter <3cm

• Disease:

– Enteritis: wall thickened, fluid distension, variable motility

– Obstruction (Mechanical/Functional): >3cm diameter with N wall- wall thickness, motility

– Inflammatory bowel: variable changes

– Intussusception: “bulls-eye” or target lesion

Colon

• Normal:– Thickness: ≤4mm– poor motility– LVC sacculated– RDC cd to liver, no sacculations– RVC ventral to RDC, sacculations

• Disease– Colitis: >4mm wall– LDC displacement- No left kidney

Diver & Orsini Equine Emergencies

Kidney

• Indications: Azotemia, polyuria, stranguria• Normal:

– Cortex & pelvis hyperechoic– L: 15-18cm long, 11-15cm wide, 5-6cm thick– R: 13-15 cm long, width/thickness same

• Disease:– Acute renal failure: enlarged, medullary rim sign-

echogenic line in outer zone of the medulla, parallel to corticomedullary junction, associated with NSAID toxicity

– Chronic renal failure: echogenicity (fibrosis), loss of corticomedullary junction, decreased size

– Nephrolith: hyperechoic with anechoic acoustic shadowImage courtesy of Amy Stewart

1/15/20

8

Case 1 – NSE

• Signalment– Warmblood

• Or other large breed– Gelding– +/- previous history of recurrent colic

Rectal Palpation

• Cannot palpate kidney• Spleen displaced medially or ventrally• LC tracking into NSS…

US Findings

1/15/20

9

Case 2 – Strangulating SI Lesion• Types

– Strangulating lipoma• > 10 years of age

– Epiploic foramen entrapment• Cribbing• Poorer prognosis

– Rents• Mesenteric• Gastrosplenic ligament

– Segmental or root volvulus

Strangulating SI Lesion

Oral to lesionAboral to lesion

Surgical Findings

Strangulated loop (thick)

Aboral loop (normal)

Incarcerated loop (white)

1/15/20

10

Surgical Findings

Case 3 – Diaphragmatic Hernia • 15 yo Welsh pony gelding

• 2 hour history severe colic– Rolling, thrashing

• Initial exam at NCSU

– HR 72 bpm

– No borborygmi– NGT, no reflux

– Rectal, within normal limits

Case 3 – Diaphragmatic Hernia

• What’s next?– US the abdomen

• No significant findings– Now what?

• DON’T FORGET THE CHEST!

1/15/20

11

Case 4 – Diaphragmatic Hernia

Case 4 – Diaphragmatic Hernia• Treatment?

– Surgery!• Challenges

– Diaphragm is hard to access– Tears are often dorsal – Hemodynamic instability

• Repair options?– Stapling– Mesh– Open vs. laparoscopic approach

Case 4 – Mini Badonkadonk

• 1yo mini donkey colt• 1 week history of colic

– Intermittent and severe– Resolves with time, but recurs

• Now unrelenting colic!

1/15/20

12

Case 4 – Mini Badonkadonk

• HR 120 bpm

• No borborygmi

• Reflux = 3L (that’s a lot in a yearling donkey!)

• Abdominocentesis

– Normal color

– Lactate 5.0 mmol/L (vs. 1.5 mmol/L in blood)

• Rectal evaluation?

– PATIENT TOO SMALL!

Case 4 - US

Case 4 – Target Lesion

1/15/20

13

Case 4 - Intussusception

• Typical signalment– Young horse, usually < 2 years

• What can intussuscept?– Jejunojejunal– Ileocecal– Cecocecal– Cecocolic

Intussusceptum

Intussuscipiens

Case 4

Take Home Points

• US– Max of 30cm penetration– Gas blocks US waves

• US is USUALLY adjunctive diagnostic– Almost never the reason we go to surgery– Exceptions?

• Diaphragmatic hernia• Intussusception• Chronic strangulated SI

1/15/20

14

Questions

Gonzalez Lab: http://go.ncsu.edu/GonzalezLab

email: Lmgonza4@ncsu.eduphone: 919-513-6919

Acknowledgements

• NC State University College of Veterinary Medicine• For images:

– Amy Stuart, DVM, PhD, DACVIM – Megan Burke, DVM, DACVS