the linear probe for IUP confirmation

Sometimes, despite some vigorous pressure on the abdomen and asking for some more bladder filling you just can’t see the yolk sac or fatal pole you need to really confirm an IUP with the curvilinear 3-5Mhz probe.  You may have the option of a trans-vaginal scan but nobody wants that, as well as increased time for signed consent, emptying bladder, chaperone and cost/time of processing the TV probe.  Since reading this blog post and looking at the article, I have been using the linear probe occasionally and it really works beautifully.

A classic sagittal view, seen with bladder, vaginal stripe and uterus in line.  There is the decidual ring but no definite IUP
On the transverse view there is something there – a gestational sac with a double ring, more than 8mm myometrial thickness but no yolk sac or fetal pole that can confirm a true IUP.

And then a quick swap to the GE 9L (2.5-8Mhz) and a classic engagement ring yolk sac is seen, safely confirming an IUP.




So it really works – there does seem to be some tricks. This starts when you swap the probes – the machine will default to 1-3cm focal range, small parts pre-sets.  On my machine (GE V2) you can still change to Ob pre-sets using the linear probe.  You will have to wind the depth down, move focus and re-balance the gain (all things I am doing better since attending the UTS course).  You may have to lower the frequency a bit as well to punch down to the pregnancy.  That tiny footprint of the linear probe also gives you a very tiny torch light to see down to the pregnancy, it is easy to lose the pregnancy even with small movements and then hard to find it again.  You don’t get that classic sagittal slice of bladder/vagina/uterus to orientate yourself.  With the linear I have found it easier to orientate in transverse and sweep up from some bladder.

So if you have the option, a linear high frequency probe is a great option, helping you and the woman avoid a TV scan. This is what is exciting about POCUS – new, lateral thinking about how to leverage the machine to get better outcomes for patients.

Here is another set to wind up:


This is a zoomed view – with the eye of faith you could probably be happy this is a true yolk sac, but if that is all you can see maybe you would be safer going to TV
However with the utility of the linear scanner this is definitely the engagement ring of a yolk sac – IUP confirmed!

Author: gppocus

Urban general practioner in Melbourne, Australia

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