Venogram Procedure (Step By Step)
Following is an in-depth description of the steps taken to perform the digital venogram. I encourage you to follow each of these steps to achieve consistent, informative venograms.
- Work Area
1. Choose a safe, quiet area.
2. A flat surface such as concrete is necessary.
a. Radiograph machine
b. Minimum of five cassettes
d. Barium paste for dorsal hoof wall marker
e. Alcohol saturated gauze to remove barium from wall
f. Protective aprons and gloves
g. Wooden blocks with wires imbedded on the top surface
a. Equipment to pull shoe
b. Hoof knife to clean and prepare the foot for radiographs
a. Elastikon®-3” or 4”, and 2”
b. Inner-tube tourniquet
c. Mosquito hemostat
d. Dry 4x4 gauze
e. 21 gauge, .75 inch butterfly catheter with 12 inch tubing
f. Two to three, 12ml luer lock syringes
1. Detomidine hydrochloride
2. Mepivicaine 2%
3. Renografin® 76 or Hypaque® 76, 20-24 ml. Fill two, 10cc luer lock syringes. If you attempt to use a 20 ml syringe you will not be able to feel the pressure changes if you become perivascular.
1. Assess the palmar digital vein. Decide if it is prominent on the pastern, or if you will catheterize the vein at the level of the sesamoids. The following procedure will describe catheterization of the palmar digital vein at the pastern.
2. Tranquilize the horse with Detomidine. The horse must be quiet, but not overly sedated so that it will stand still without wobbling.
3. Prepare the foot for radiographs and take baseline radiographs (DP and Lateral) to assess technique needed for the foot. On initial presentation, a chronic laminitic horse is radiographed barefoot. If a horse has acute laminitis, or if it has been in a therapeutic shoe, the foot is cleaned and placed in a Redden Modified Ultimate shoe for the procedure.
4. Perform local anesthesia of the medial and lateral palmar digital nerves at the level of the proximal sesamoid. Do not use an excess of mepivicaine, as it may make the application of a tight tourniquet difficult.
5. Clip the medial and lateral pastern in the area of the palmar digital vein.
6. Perform a light surgical scrub on the medial and lateral pastern.
- Podiatry Team
1. Horse holder
a. Observes the behavior of the horse, not the venogram procedure. Warns if the horse is going to strike, move, etc.
b. Keeps the horse standing in place on the radiograph blocks during the venogram.
c. Does not allow the head to drift to either side, because it causes uneven loading of the feet and artifactual changes in the venograms.
a. Performs venogram
b. Takes radiographs and changes technique settings on machine
a. Hands venographer syringes of contrast as needed.
b. Places cassettes in correct position.
c. Removes barium from dorsal wall while venographer changes machine from lateral to dorsal position.
II. PERFORMING THE VENOGRAM
1. Standing squarely on radiograph blocks. Blocks are positioned in the normal stance of the horse so the horse is comfortable.
2. Sedation assessed before beginning procedure.
3. Palmar digital vein assessment-is it visible before the tourniquet is applied?
- Radiograph equipment
1. Machine distance for DP view marked on floor.
2. Machine placed in position for lateral radiographs.
3. Unexposed cassettes are fanned in a location for the assistant to immediately access. All marker windows are in the same location. The grid is in place with the second cassette.
4. Barium is applied to the dorsal wall.
5. The alcohol preps are placed near the foot.
6. The veterinarian is comfortable with the technique chart used for the radiographs, and the assistant understands which views will require the grid.
1. Veterinarian kneels dorsolateral to the foot. The machine is lateral to the foot, and the assistant is palmolateral.
2. 3” Elastikon is wrapped around the fetlock. If the veterinarian is right handed, the Elastikon® is wrapped in a clockwise direction when viewed from the front. The Elastikon® does not come down onto the pastern. Care is taken to not distort the skin or underlying tissue. The Elastikon® is cut on the lateral aspect of the leg.
3. The inner tube tourniquet is taped beneath the tag of Elastikon®.
4. After tightly applying the tourniquet, it is taped in place with several wraps of 2” Elastikon®. The free tag end is on the lateral aspect, and enough is present to tape the hemostat up out of the way.
5. The butterfly catheter cap and needle cover are removed.
6. The veterinarian’s inside arm wraps around the leg, and the catheter is inserted into the vein.
7. When blood flows freely from the vein, the assistant lightly attaches a syringe of contrast.
8. The veterinarian injects the contrast with the inside hand while the outside hand lightly applies digital pressure to the vein and needle to prevent the vein from blowing as the valves are forced open.
9. The assistant removes the empty first syringe and lightly attaches the second syringe. He then grabs the hemostats with the tips of his fingers or palm, and readies the first cassette.
10. The veterinarian gently rocks the leg to unload the foot with his inside arm. When he is done injecting the second syringe, the assistant clamps the tubing with the hemostat. The veterinarian removes the syringe and tapes the catheter and hemostat under the Elastikon® tag.
11. The veterinarian takes a lateral, increases the technique, takes a lateral grid shot, and then moves the machine to the DP position. The assistant removes the barium from the dorsal wall.
12. A DP without the grid follows the DP grid shot. A final lateral is then taken.
13. The tourniquet is removed. The palmar digital vein is covered with dry gauze in a light pressure bandage.
III. TROUBLESHOOTING THE VENOGRAM
- Horse movement
1. If the horse steps off the block with the off leg, the holder must continue to hold the head. The assistant should quickly replace the off foot on the block. (If the holder lets go of the head, the horse will naturally try to remove the second foot from the block.)
2. If the horse is moving the venogram foot, the veterinarian should control that foot. He will feel movement in his shoulder, which is in contact with the forearm. The arm that is wrapped around the inside of the leg will control the leg movement and replace the foot on the block without interrupting the procedure.
3. When the veterinarian bumps the knee as he injects the second syringe, he must be careful to unload the leg, but not signal the horse to pick up the foot.
1. Identify the vein before you apply the tourniquet. If you cannot see the vein once the tourniquet is applied, you may need to catheterize before applying the tourniquet.
2. Consider the skin thickness-draft horses are more difficult to catheterize than Thoroughbreds, and require a deeper angle of the needle.
3. Older horses have more tortuous, fragile veins and require finesse.
4. If you catheterize the vein and the blood starts to flow from the syringe then stops, DO NOT attempt the venogram. Instead, back the needle out 1-2mm, hoping you are just against the opposite wall of the vein. You may need to redirect the needle; remember that subsequent venipunctures will leak contrast into the subcutaneous tissue.
5. If you must catheterize the medial vein, position the venographer palmolateral to the foot. The assistant will attempt to control movement of the foot so the horse doesn’t pick the foot up and hit the venographer in the head.
- Injecting the contrast media
1. Don’t screw the luer lock syringe on tight—you will not be able to remove it quickly.
2. Don’t stretch the tubing on the catheter tight and pull the needle from the vein; be especially careful when changing syringes or clamping the catheter.
3. If the catheter comes out and the vein starts to blow, take the pictures quickly before you lose volume of contrast in the foot as it runs out the vein.
4. If you are injecting the second syringe and you believe you have blown the vein (coolness under your fingers on the skin and needle, distension of the skin perivascular), release pressure on the plunger on the syringe. If the catheter back-fills with blood you are still in the vein. If it doesn’t back-fill, you have probably blown the vein: discontinue injection and take radiographs immediately.
5. The assistant must lightly hold the hemostats in his fingertips, or by the palm. Don’t get them “stuck” on your fingers and waste time or pull the catheter.
6. If you finish the injections and the horse is not totally weight bearing on the block, take the radiographs anyway.
Redden, R.F. A Technique for Performing Digital Venography in the Standing Horse. Equine Veterinary Education, Vol3, No 3, 2001; pp 172-178.
Redden, R.F. Equine Podiatry 101, Short Course 2001.
Redden, R.F. Radiography of the Equine Foot; Techniques for Enhancing the Quality of Your Films. Equine Podiatry Monograph Series, Nanric 2001.
About the Author
Amy Rucker, DVM, works in the equine ambulatory practice in the College of Veterinary Medicine at the University of Missouri-Columbia.
POLL: Laminitis Experience