Contrast radiology–not a dying art (Proceedings)

Definition: A medical contrast medium (or contrast agent) is a substance used to enhance the contrast of structures or fluids within the body in medical imaging.

Agents used most frequently:

Studies to be discussed:

     • Digestive system

     • Urogenital system

     • Intra-cavitary

     • Water soluble iodinated contrast medium-

          o ionic and non-ionic

          o non-ionic tend to me less toxic

          o basic configuation of all of them-benzene ring that has iodine attached to it.

http://en.wikipedia.org/wiki/Radiocontrast

http://hsc.uwe.ac.uk/idis2/contrast_agents/CM%20Zip/ContrastMedia_Schering.pdf

High osmolar (ionic) Ionic contrast media have higher osmolarity and more side-effects

Commonly used iodinated contrast agents

Low osmolar (non-ionic)

Commonly used iodinated contrast agents

Non-ionic contrast media, have lower osmolarity and tend to have less side-effects, such as Omnipaque, Ultravist, Visipaque, etc.

Commonly used iodinated contrast agents

Barium (gastro-intestinal)

Properties

Digestive system

What I have learned from doing digestive system contrast studies:

     o Be positive about the procedure even if you use negative contrast medium.

     o Prepare the patient and the owner.

     o You cannot determine esophageal motility status if the pet is sedated or anesthetized.

     o You may not be able to determine gastric or bowel motility status if the pet is sedated or anesthetized.

     o Administer the contrast medium any place in the hospital except with the patient on the x-ray table.

     o If you get barium on your clothing-especially the shoes-wash it off immediately as it is much harder to remove later on.

     o A barium/contrast study is either normal or abnormal.

     o If it is normal-be happy for the patient-however, it does not mean the GI system is normal.

     o If it is abnormal-decide if it is related to a non-obstructive or an obstructive disease process:

           Non obstructive:

          √ Altered bowel dynamics

          √ Bowel not pathologically distended.

          √ Bowel wall thickened

          √ Bowel mucosa irregular

          √ Barium flocculates

           Obstructive:

          √ Pathological distention of the bowel

          √ Contrast may not traverse the bowel

     o Twenty-five percent of the time your exploratory will not reveal a definitive lesion-then biopsy the bowel!

     o A negative contrast gastrogram is a good way to define gastric pliability, wall thickness/contour and gastric luminal content.

     o A barium enema is a good way to distinguish between the large and small bowel.

     o Endoscopy, ultrasound and exploratory surgery are often required to make a definitive diagnosis.

Esophogram:

     o No sedation or anesthesia

     o Obtain survey lateral and VD or VD oblique radiographic projections.

     o Place contrast in oral cavity and allow animal to swallow it

     o Contrast- General evaluation-Barium sulfate-1 ml/lb. If you suspect esophageal perforation use water soluble medium

     o Any water soluble iodinated contrast medium should be good- 1 ml/lb.

     o Repeat the radiographic projections immediately

Negeative Contrst Gastrogram:

     o Sedation recommended:

          √ Acepromazine IV in Dogs

          √ Ketamine/Valium IV or SQ in cats

     o Obtain survey lateral and VD radiographic projections

     o Pass the orogastric tube

     o Inflate the stomach with room air—6 ml/lb

     o Remove the tube and repeat the radiographic projections.

Positive Contrast Gastrointestinal Series:

     o If sedation needed use acepromazine IV in dogs and ketamine/valium in cats

     o Obtain survey lateral and VD radiographic projections.

     o Place contrast in the esophagus or into the stomach with an orograstric tube

     o Contrast- General evaluation-use barium sulfate-4ml/lb

If suspect GI perforation use water soluble iodinated contrast medium-2 ml/lb

     o Radiographic projections repeated after contrast administration at the following times

     o General comments:

        √ A GI series is not completed until a lesion is defined or the majority of the contrast has traversed the bowel. In the canine, radiographs may need to be taken eight hours post-contrast administration or the next day and in the cat, radiographs may need to be taken two hours post-contrast administration to complete the study.

Urogenital

Intravenous urogram:

     o Make sure colon and urinary bladder are empty

     o Obtain survey lateral and VD radiographs

     o Place a catheter in the cephalic vein

     o Place a catheter in the urinary bladder

     o Inject water soluble contrast medium intravenously-1ml/lb

     o Obtain radiographs within one to two minutes after injection (lateral, VD and oblique projections as needed)

     o Distended the urinary bladder with gas-4ml/lb

     o Obtain radiographs five minutes after the bladder is distended (lateral, VD and oblique projections as needed)

     o Obtain radiographs ten-fifteen minutes after bladder is distended.

Negative contrast cystogram:

     o Make sure the colon is empty

     o Obtain survey lateral and VD oblique radiographs

     o Place catheter in the urinary bladder

     o Distend the bladder with gas-4 ml/lb.

     o Obtain lateral and VD oblique radiographs

Positive contrast cystogram

     o Make sure the colon is empty

     o Obtain survey lateral and VD oblique radiographs

     o Place catheter in the urinary bladder

     o Distend the bladder with water soluble iodinated contrast medium –2 ml/lb.

     o Obtain lateral and VD oblique radiographs

Double contrast cystogram

     o Make sure the colon is empty

     o Obtain survey lateral and VD oblique radiographs

     o Place catheter in the urinary bladder

     o Place a small amount of water soluble iodinated contrast medium into the bladder 1 ml for cat, 2 ml for small dog, 3 ml for medium size dog, 4 ml for large size dog or 5 ml for giant size dog (note this is total volume, not per pound)

     o Distend the urinary bladder with gas-4 ml/lb

     o Obtain lateral and VD oblique radiographs

Positive contrast urethrogram:

     o Make sure the colon is empty

     o Obtain survey lateral and VD oblique radiographs

     o Fill the catheter with positive contrast medium

     o Place the catheter into terminal portion of urethra

     o Secure the catheter in place

     o Inject positive contrast medium 5 ml for small dog or cat10 ml for medium size dog; 15 ml for large or giant size dog

     o Obtain lateral radiograph while completing injection

     o Repeat the injection

     o Take VD oblique radiograph while completing the injection

Positive contrast vaginogram

     o Make sure the colon is empty

     o Obtain survey lateral and VD oblique radiographs

     o Fill the catheter with positive contrast medium

     o Place the catheter into terminal portion of the vagina

     o Secure the catheter in place

     o Inject positive contrast medium 5 ml for small dog or cat10 ml for medium size dog; 15 ml for large or giant size dog

     o Obtain lateral radiograph while completing injection

     o Obtain VD oblique radiograph.

Positive Contrast Peritoneogram

     o Obtain survey lateral and VD radiographs

     o Sedate the animal

     o Place a catheter into the abdominal cavity-catheter should be inserted adjacent to the umbilicus and just to the right of the midline.

     o Inject sterile water soluble contrast medium into the peritoneal cavity-1 ml/lb

     o Remove the catheter

     o Massage the abdomen to distribute the contrast medium.

     o Obtain lateral and VD or DV radiographs.

General comments:

     o If free fluid is present in the abdomen, remove as much of the fluid as you can before injecting the positive contrast medium

     o If you suspect a hernia, position the animal for three minutes so that the positive contrast medium will flow towards the suspected hernia site.

     o The positive contrast medium will be absorbed and you will eventually see it in the kidneys and urinary bladder.