How to Fashion a Probe-Extender for Your Equine Ultrasound Probe (For Your Miniatures)

It's obviously not at all safe to use traditional ultrasound procedures meant for large horses when working with your much, much smaller miniatures. (I've seen one video online showing someone performing a transrectal ultrasound exam, inserting their hand and arm into the little mare — and that is just NOT WHAT YOU SHOULD BE DOING.)

I strenuously urge you to follow the instructions below in preparing a probe-extender for your ultrasound probe. Scanning your miniatures with a device such as this will be extremly safer for your mares. And obviously far less shocking an experience for them.

We will assume that you are using either the CTS-3300V or CTS-5500V equine ultrasounds with a 50mm, 56mm, or possibly 65mm probe. The images below feature a 50mm probe. The approach is the same with the other probe sizes, though each might require a slightlly different overlap.

Note: While the extender below is made from a thin wooden dowel (a process demonstrated here by Dr. Jim Kubiak, of The Breeder's Assistant in California), I have also heard of probe-extenders being fashioned of thin PVC tubing, and if anyone has any images of such a probe, I would love to see them. You can email me at: shawn [at]

Step 1: Prepare the Wooden Dowel ...

Either a 5/8-inch or 1/2-inch diameter wooden dowel cut down to 12-14 inches in length will work.

wooden dowel

wooden dowel with ruler

... With a Shaped Point (Made to Hold the Upper Edge of the Probe)

The end near the probe needs to be filed to fit the probe and cord, where the portion that will extend onto the probe is fashioned in such a way as to fit smoothly over the edge of the probe (in order to aid in insertion and to avoid puncturing the rectum). This "overlap" also needs to be long enough to be taped to the probe, yet short enough that the tape will not cover the viewing surface of the probe.

Keep going back and forth between your whittling job on the stick and the probe and cord, fitting it in place, and deciding where you might need to carve the dowel some more. Your result might not look as pretty as the one here, but you'll get close enough if you keep going back and forth. Checking the stick against the probe and cord repeatedly will also help ensure that you don't whittle too much off of the dowel. Remember, in the end you're aiming for a nice smooth transition from the probe to the cord, creating a nice straight line.

dowel close up

close up 2

fitting the ultrasond probe


Step 2: Carefully and Securely Tape the Dowel to the Probe and Cord

Dr. Kubiak likes to use black electrical tape as it matches the color of the probe and will last a long time if you start with a nice brand new fresh roll of tape. The electrical tape will of course need to be replaced periodically depending on the frequency of use, however given that most people do not have a lot of miniature mares to scan, it will likely only need to be replaced after the end of each breeding season.

Tip: Don't skimp on the tape. Use plenty of tape, especially to cover the leading edge of the shaped dowel. And wrap it well — really take your time getting it right, and cover it extremely well, being careful to keep the entire probe and cord nice and straight. (Once wrapped, you don't want to notice you botched the job halfway through, and have to unwind and start over!

wrapping the probe extender

... Be careful to wrap it securely, avoiding the actual scanning surface of the probe as much as possible.

tape on probe

tape on probe from side


The Finshed Article:

equine probe extender for miniature horses


And Two Final Tips ...

My original concern when I saw one of these was that, being rigid, it can't really bend or dip the way one handles the probe in a full-size mare. So I checked with Dr. Kubiak on this, and here's what he replied: Interestingly the flexibility is not needed. Because of the small body size of the miniature mare, all that you need to do is to rotate the probe along the rectal wall. I and a local breeder have done many this way and haven't had the need to angle the probe at all.

And also keep in mind: It is important for the rectal channel to be clear enough for the probe to be inserted, so sometimes you need to wait for the horse to pass some manure or a finger or two can be inserted in an effort to clear a few fecal balls before beginning your exam.


Good luck! Be patient! And always treat your miniature mares with gentleness and love!