AGR 324 Exam 3: Special Procedures

Why do we perform contrast studies?

To highlight things we can't see otherwise by changing the density and organ visibility without harming the patient.

What should you ALWAYS do before giving contrast media?

Always take survey radiographs prior to giving your contrast media

What do positive contrast agents look like on radiographs - and why do they look that way? (Hint: it has to do with atomic numbers.)

Positive contrast agents appear white (radiopaque)

What do negative contrast agents look like on radiographs - and why do they look that way?

Negative contrast agents appear black (radiolucent)

What are some examples of positive contrast media?

Barium, Water-soluble organic iodides (ionic and nonionic)

What contrast media should NEVER be used in the urinary tract or given IV or used if bowel perforation is suspected?

Barium

What forms is barium provided in?

What is it used for?

Comes as a powder, liquid, or paste, given orally or rectally, Used only for the GI tract

How are Water-soluble organic iodides (ionic and nonionic) given?

Typically injected IV or into body cavities

How is iodine contrast excreted?

via the kidneys

In Water-soluble organic iodides (ionic and nonionic), why do we care about concentration?

The iodine molecules are what interact with the x-ray beam so concentration is important

• Higher concentration=more contrast

Which iodine based contrast media is the SAFEST?

Water-soluble organic nonionic dimers

What are some examples of negative contrast media?

Low atomic number, or low-density agents

Air, nitrous oxide, oxygen, carbon dioxide

What does negtive contrast media enchance?

Enhances contrast between the soft tissue structures

What is an disadvantage of negative contrast studies?

Less mucosal detail than seen with positive-contrast UNLESS you use double-contrast media, can over inflate tissues - might cause an air emboli or rupture the organ

How should you position the patient if you are concerned about an air emboli after a negative contrast study?

IF strange things happen, place the patient in LEFT lateral and elevate the caudal part of the body to trap gas in the RIGHT ventricle

In a double contrast procedure, which contrast do you give FIRST?

Give POSITIVE contrast FIRST, then give the negative contrast SECOND

What structures are looked at in a double contrast procedure?

Stomach, colon, bladder

Should you administer an enema prior to a GI study?

yes

Should the patient be fasted prior to a GI study?

Yes they should

What are the indications for a GI tract study?

Vomiting, diarrhea, constipation, hematochezia, melena, abdominal masses, abdominal pain, foreign bodies, trauma

What are the contraindications for a GI tract study?

• Fluid-filled esophagus

• Ileus

• Torsions (GDV)

(could cause aspiration if given barium)

What is the first choice of GI contrast agents?

Barium unless there is a perforation

What can be used if theres a perforation but ISNT the safest choice?

Diatrizoate meglumine + diatrizoate sodium iodinated water-soluble organic iodine can be used if there's a perforation - but you still worry about the hyperosmolality of these!

Again which is the safest GI contrast agent?

Isomolar nonionic compounds - safest choice if a perforation, but cost limiting

Why would you perform an esophagram?

• Dysphagia

• Regurgitation

• Vomiting

• Megaesophagus

• Foreign bodies

• Abnormal swallowing

• Excess salivation

What are the precautions that go along with an esophagram study?

Aspiration is possible

• Use organic iodine if possible perforation

What views do you take for an esophagram?

Lateral image of the neck, lateral and DV thorax for evaluating anatomy

What is the best for evaulating function in an esophagram?

Fluoroscopy

What contrasts can you use in a esophagram?

-Oral aqueous iodine solution

• Barium paste

What are the indications for Upper GI studies?

• Vomiting

• Diarrhea

• Hematemesis

• Anorexia

• Melena

• Obstructions/foreign bodies

• Wall distortions

• Chronic weight loss

• Persistent abdominal pain

• Inconclusive survey rads

What are the precautions for Upper GI studies?

• Use water-soluble organic iodide if perforation is suspected

• Do endoscopy or US if available

• Avoid barium if going to surgery

• Don't give barium if a GDV suspected

• Remember anesthetics slow GI transit time, as do anticholinergics

How long should you ideally fast a patient before an upper GI study?

Fast at least 12 hours, preferably 24 hours

What dose of barium is used in an upper GI study?

-Cats, dogs<10kg: 8-10mL/kg

• Dogs 10-40 kg: 5-7mL/kg

• Dogs >40kg: 3-5mL/kg

What radiographic views to you take in an upper GI study and how often do you take them?

• Immediately: VD, DV, RL, LL

• 15 minutes: RL, VD

• 30 minutes: RL, VD

• 60 minutes: RL, VD

• Hourly: RL, VD

What can you do to make barium move through faster in an upper GI study?

fast patient prior, use lower concentrations

What does the cecum look like in cats vs dogs?

- cat: pointed

- dog: corkscrew

Why do a double contrast study of the upper GI tract?

• Evaluating the stomach wall and looking for extramural lesions

• Does not tell you anything about motility or emptying

Why do a study of the lower GI tract?

• Abnormal defecation, especially if also seeing mucous or blood

• Straining

• Suspected intussusception or obstruction

What are precautions for lower GI study?

Do not give barium enema if perforation is suspected

• Reflux into the distal SI can happen

How do you prep the patient for a lower GI tract study?

• Fasted 24-36 hours

• Cathartic/warm water enemas the night before

• Take survey rads

• Sedate/anesthetize

Can you do a double contrast study of the lower GI tract?

yes you can

What's another name for a negative contrast study of the lower GI tract?

pneumocolon or pneumocolonogram

What are BIPS and why do we use them?

Barium-Impregnated Polyethylene Spheres,

Evaluate motility and intestinal transit time

If the patient is in RIGHT lateral recumbency, what part of the stomach/GI Tract is filled with air?

gas (air) in fundus "Right Lateral, the Fundus Flies!"

(fluid will be in P)

If the patient is in LEFT lateral recumbency, what part of the stomach/GI tract is filled with air?

Air/gas in Pylorus "Left Lateral, the Fundus Falls."

(fluid will be in f)

If the patient is in VENTRAL recumbency/DV view, what part of the stomach/GI Tract is filled with air?

gas/air in fundus and cardia (fluid in P and body)

If the patient is in DORSAL recumbency/VD view, what part of the stomach/GI Tract is filled with air?

Air/gas in Pylorus and body (fluid in cardia and fundus)

What contrast agent is used in the urinary system?

Water soluble nonionic organic iodide

What is NEVER used in contrast studies of the urinary system?

never use barium

Why do you take survey rads of the urinary tract?

Evaluate kidneys, bladder, ureters, prostate, urethra

How is the contrast media administered in retrograde cystography?

-Infusion of contrast media through a urinary catheter

• Can be positive (Water-soluble nonionic organic iodide), negative, or double contrast

What are the indications in retrograde cystography?

• Hematuria

• Crystalluria

• Abnormal urination

• Trauma

• Masses

What are the precautions in retrograde cystography?

-Trauma, infection secondary to catheter placement

• Gas embolism can be fatal if doing negative or double contrast

Can you a do a negative contrast study of the bladder?

yes, you can

Can you a do a double contrast study of the bladder?

yes, you'll use a positive nonionic contrast

What should you infuse into the bladder prior to administering your contrast?

Infuse 2-5mL lidocaine (without epinephrine)

-reduces bladder spasms and pain

Should you ever put in a greater volume of contrast media than the volume of urine you removed?

no, don't want bladder to burst

What is an excretory urogram and why is it done?

• Determine size, shape, location, and integrity of the kidneys

• Assess relative function of the kidneys

• Sterile, water-soluble, iodinated contrast given IV

• US without media is better when/were possible

What are the precautions when performing an excretory urogram?

• Do NOT do if anuric, severely dehydrated, or known urethral obstruction

• Temporary decrease in renal function may occur

• Check BUN/CRE prior to procedure

• Be prepared for an adverse reaction (most severe in the first 5 minutes)

Which contrast media should be used in an excretory urogram?

• Water-soluble organic iodide 600-700mg/kg up to 880 mg/kg body weight

• Nonionic compounds highly preferred

What is the max dose of contrast media used in an excretory urogram in cats?

15mL

What is the max dose of contrast media used in an excretory urogram in dogs?

90mL

How do you prep the patient for an excretory urogram?

• No food for 24 hours prior to study, do not restrict water

• Perform an enema the night before (minimum of 2 hours prior to procedure)

• Collect urine samples prior to administering medium - Remove as much urine as possible

• Place IV catheter

• Sedate/anesthetize patient

• Take survey radiographs

• Give bolus over 2 minutes

Which images do you take for an excretory urogram?

Take VD and RIGHT lateral images immediately, in 5 minutes, 15-20 minutes, 30-40 minutes

What imaging modalities have largely replaced myelograms? Why do we perform them?

-CT or MRI is used instead

-Localize spinal lesions or compression

What are the precautions for myelography?

• General anesthesia required

• CSF should be examined prior to administering contrast

• Aseptic technique

• May make neuro signs worse

Where is the contrast media placed in myelograms? Is it positive or negative?

Placement of radiopaque (positive) contrast into the subarachnoid space

-Organic nonionic positive-contrast iodine

What contrast media is used for Ultrasound?

Water or saline

What contrast media is used for CT?

Nonionic contrast agents

What contrast media is used for MRI?

Gadolinium Based Contrast Agents - given IV to enhance T1 and FLAIR images

What contrast media is used in nuclear medicine studies?

• Radioactive contrast agents used in PET scans (Positron Emission Tomography)

• Technetium-99mTc is the most commonly used