1. Abdominal Positioning & Small Animal Special Procedures
Chapters 18 & 25

2. Learning Objectives: Abdomen & Soft Tissue
Understand radiographic concerns associated with the abdomen
Properly and safely position a small animal for two common radiographic views, with the ability to:
Measure accurately
Center the x-ray beam appropriately
Image with correct borders
Properly position the patient
Understand alternate views
Identify normal abdominal anatomy, including major differences between cats and dogs

3. Small Animal Abdomen: Anatomy

4. SA Abdomen: Radiographic Concerns
Less natural contrast than thorax
Similar densities & multiple organ systems
GI gas & fat provide contrast
Contrast media often required
Generally use a higher kVp and lower mAs
Try for higher mA and lower time to shorten exposure
May need two views in deep-chested dogs
Can average measurements on smaller animals
Higher kVp = More shades of grey
Lower mAs = Shorter exposure less motion artifacts

5. SA Abdomen: Radiographic Concerns
Use nonmanual restraint whenever possible
Expose at end of expiration during pause
Allows maximum space for abdominal organs
Minimize intestinal artifacts by:
Fasting 12 hours
Cleansing enema 3-4 hours prior
Abdominal compression can reduce thickness
Can use a compression paddle
Moves underlying organ to aid in visualization
Reduces thickness so lessens scatter
Usually a brief pause at end of expiration
Maximum space for stomach contents as lungs contract & diaphragm relaxes
The Pneumatic Compression Paddle is used for guided compression during radiographic studies of the gastro-intestinal tract. The paddle is inflated beneath the patient to increase pressure in a concentrated area.

6. Radiographing the Abdomen: Positioning

7. Lateral Abdomen – Dog vs Cat

8. Abdominal Positioning: Lateral
L/R marker at ventral aspect
Sternum & spine on same plane
Aim is symmetry & superimposition
Hind limbs caudal to prevent superimposition of femoral muscles
Center the beam differently in dogs & cats
Cats more caudal than dog
Right lateral separates kidneys better
Left lateral is preferable in vomiting patients
Gas in pylorus can highlight a foreign body
Left lateral may be required in contrast studies

9. Liver Mass

10. Abdominal Mass – Lateral View

11. Gastric Trichobezoar
A trichobezoar is a bezoar (a mass found trapped in the gastrointestinal system) formed from the ingestion of hair.

12. Gastric Dilitation & Volvulus (GDV)
“Double bubble”

13. Uterine Inertia/Rupture

14. Abdominal Positioning: Ventrodorsal
Measure at liver
Central ray positioning differs between cat & dog
Imagine a straight line connecting nose & caudal midline
* DV can be used as alternative if animal is compromised by VD
Dog
Cat

15. Abdominal Mass – VD View

16. Abdomen: Modified Lateral & Lateral Oblique
Used when radiographing the entire male urinary tract
Moves hind limbs so they don’t overlap penile urethra or bladder

17. Abdominal Anatomy: Notes
Fat animals image better than emaciated ones
Fat serves as a contrasting opacity
Many normal structures hidden radiographically
Ureters, urethra, adrenals, pancreas, etc.
Abnormalities can make them visible
Liver –
Normally lies beneath ribs
Best evaluated via lateral radiograph
Stomach –
Normally within rib cage – include caudal ribs in radiograph
Food images as granular material of mixed opacity
Can be 2-3 times larger after a meal
Gas rises and fluid moves with gravity

18. Chocolate Ingestion
Chloe - Full stomach

19. Abdominal Anatomy: Kidneys
Dogs:
Canine kidneys elongated
Only the left kidney & part of the right can be seen
Bladder is cranial to the pelvis
Cats:
Feline kidneys more rounded
Both kidneys can generally be seen
Bladder more rounded & cranial than dog
Both
Left kidney is generally more caudal

20. Bladder Stones

21. Switching gears now to…
Small Animal Special Procedures

22. Special Procedures: Learning Objectives
Understand the differences between types of contrast media
Understand the appropriate patient preparation for contrast studies
Know procedures & protocols for various studies
Understand the additional modalities that can be used in addition to contrast studies
ID normal contrast anatomy

23. Special Procedures: General Principles
Contrast media attenuates the x-ray beam & can show previously unseen differences in abdominal structures.
2 types of contrast media:
Positive-contrast: Appears white or radio-opaque
Negative-contrast: Appears dark or radiolucent
Contrast agents are used in 2 ways:
Demonstrate anatomy by outlining or filling
Demonstrate physiology via excretion through an organ
Attenuates = lowers the intensity of the x-ray beam

24. Special Procedures: General Principles
Contrast studies are used to:
Provide information to make a diagnosis
Evaluate a suspected lesion
Determine proper treatment
Injected contrast substance: Used to cause a difference in density & organ visibility yet still be harmless to patient
Higher kVps typically needed in contrast studies
Should never replace a simple survey radiograph
Ultrasound & other imaging has replaced contrast radiography in many evaluations
Barium can be USED as a treatment

25. Positive-Contrast Media: Barium Sulfate
Used to radiograph the GI tract
Administer orally or rectally
Low cost & palatable
Does not alter normal physiologic function
Delineates mucosal walls well
Not absorbed in intestines
Cautions:
Cannot be used if a gastric perforation is suspected
Aspiration in lung can be fatal
Atomic numbers of barium & iodide higher than tissues/bones

26. Barium Aspiration: Lungs

27. Positive-Contrast Media: Iodine
Use for suspected gastric perforation or obstructions
Instead of barium
Used for functional studies
Oral or injectable forms
Has a bitter taste
Nonirritating if aspirated or leaked into body cavities
Mixes with blood or body fluids & is excreted via the kidneys
More expensive than barium
Functional/physiology vs anatomic

28. Negative & Double-Contrast Media
Negative-contrast media:
Low atomic number or low-density agents
Air, nitrous oxide, oxygen, and carbon dioxide
Absorb fewer x-rays & appear dark on radiographs
Less mucosal detail with negative vs positive-contrast
Be careful not to over-inflate organs (bladder, etc.)
Air embolism can lead to cardiac arrest
Double-contrast procedures:
Use both positive & negative agents
Normally used to image the urinary bladder, stomach, or colon
Negative-contrast administered first to avoid air bubbles

29. Negative Contrast

30. GI Tract Studies Patient preparation: Indications:
Fasting + a cathartic/laxative and enema
Take a survey radiograph prior
Take required number of radiographs
4 views generally needed
Oblique views or compression may be required
Indications:
Vomiting, diarrhea, or constipation
Hematochezia or melena
Masses or foreign bodies
Abdominal pain
Post-abdominal trauma
Cathartic - laxative
Barium spill behind the screen

31. GI Tract Studies Contraindications: Contrast agents:
Fluid-filled esophagus or stomach
Atonic bowel
Gastric torsion
Gastric perforation
Contrast agents:
Barium is typically used because it doesn’t separate
Shake prior to use
Chilling barium for upper GI series speeds up transit time
Possibility for contamination once opened
Spilling barium on the coat will cause a radiographic artifact
Barium-impregnated polyurethane spheres (BIPS) – A way to quantify gastric emptying
Dosage is number of large & small spheres
Gastric emptying rate is calculated based on number in areas of GI tract
Large spheres are designed to stop at obstruction
Pics on p.384 in book

32. Esophagography
Contrast radiography of the esophagus to identify lesions
Evaluates morphological or structural alterations
Uses a paste of positive contrast media
Indications:
Dysphagia
Regurgitation, gagging, or retching
Megaesophagus
Abnormal swallowing
Esophageal dysfunction
Foreign bodies
Blockage d/t neoplasm in a cat

33. Esophagography Precautions: Patient preparation: Comments & tips:
Patients with dysphagia are at risk for aspiration
Contrast may not be needed if esophagus is fluid or food-filled
Patient preparation:
If evaluating megaesophagus – empty prior to administration
Fast if further GI studies are planned
Comments & tips:
Avoid barium artifacts
Pharyngeal issues are best evaluated mid-swallow

34. Esophagography

35. Megaesophagus

36. Upper GI Study
Barium is given orally, then images are taken during transit through stomach and small bowel
Studies can be done for:
Morphology – Form & structure of organs
Size, shape, and position or organs
Character of stomach wall & contents
Lesions in the GI tract
Function – How organ works
Gastric motility
Intestinal function
Indications:
Any GI irregularities (vomiting, diarrhea, anorexia, weight loss, etc.)
Inconclusive results of survey radiograph

37. Upper GI Study Precautions: Patient preparation:
For suspected perforation or rupture, use iodides
Unless dehydrated or compromised – ultrasonography preferred
Delay study if full stomach
Gastric distention is not recommended immediately after gastric surgery
Patient preparation:
GI tract should be empty – fast at least 12 hours prior
Administer enema 2-4 hours prior
If using orogastric tube - verify placement in esophagus
Before removing, clear with small amount of air and kink to prevent aspiration

38. Upper GI Study Procedure: Comments & tips: Administer barium (slowly)
Take 4 radiographs centering over cranial abdomen
Both VD and lateral views at 15, 30, and 60 minutes post
Hourly radiographs until study is completed
Label films carefully
Comments & tips:
If slow GI emptying is suspected, start study early in the day
Give a sufficient volume of barium
Gastrogram is finished when the majority of barium is no longer visible in the stomach
Upper GI is complete when the barium is in the colon
Ultrasound is safer in compromised patients
Barium doses:
8-10 mls/kg in dogs < 10 kg
5-8 mls/kg in dogs kgs
3-5 mls/kg in dogs > 40 kg

39. Barium Upper GI Study: Dog
15 minutes
30 minutes
60 minutes
2 hours: Stomach, complete small intestine, cecum
4 hours: Small & large intestine
(Stomach, duodenum)
(Stomach, duodenum, jejunum)

40. Lower GI Study Used for examination of the cecum, colon, and rectum
Evaluates for masses and lesions
Full distention with removal of feces is required
Rectal administration of barium may be required
Sedation is usually warranted
Used when lumen narrowing prevents passing an endoscope
Indications (examples):
Abnormal defecation
Excessive mucus or bright red stool
Strictures or obstructions
Neoplasia
Colitis

41. Lower GI Study Precautions: Patient preparation:
No barium if a perforation is suspected
Transient spasms may occur
Patient preparation:
Fast for hours (water allowed until 4 hours prior)
Colon should be free of fecal matter
Cathartic & warm water enemas the night before
Avoid soapy-water enemas
Sedate or anesthetize
Take survey lateral & VD radiographs

42. Lower GI Study Procedure: Comments & tips:
Exposure factors may need to be increased
Have chemically restrained patient on the table
Insert catheter rectally & inflate cuff
Stop infusion if any resistance
Take 3-view radiographs
Oblique view may be required in males
Process the films, then remove as much contrast medium as possible before removing catheter
Comments & tips:
Remove catheter away from x-ray table
Give barium in small increments

43. Lower GI Study (barium)

44. Links to Case Studies
Barium Study in a Dog (Virtuavet) /26/barium-study-in-a-dog/
8-Year Old Curly-Coat Retriever Takes a Long Road to a Simple Answer (Virtuavet)-
“Titus”