Early First Trimester Pitfalls - HD

Introduction and Disclosures

Thank you everyone for coming back after lunch and not going shopping.

I do have to disclose, I get royalties from Elsevier for educational products.

Common Pitfalls in First Trimester Ultrasound

Where can you go wrong in the first trimester and how can you get into trouble?

As always, with radiology, you have to know your anatomy.

You have to communicate clearly to the people ordering the study.

And in certain circumstances, in the first trimester, math becomes very important.

One of the key things to make as a diagnosis of failed pregnancy and there are rules and milestones for that.

And of course the thing none of us want to miss is the ectopic pregnancy because even today you can kill a healthy woman if you send her out to go hiking in the back country with an undiagnosed ectopic.

And her tube ruptures and she bleeds.

I work in Salt Lake City and the church teaches that you should choose the right thing in the ultrasound world.

That means choosing the right transducer.

The machine package presets, the multi hertz option on your transducer lets you go from nine megahertz down to four.

Sometimes you adjust your depth of field and you have to adjust your focal zone.

Overview of Key Themes

This is a poster I did some years ago and I'm not going to go through it in detail, but it is in the syllabus for you all to look at.

And you'll see again there are themes, there's normal anatomy, there's knowing pathology from normal anatomy.

There's a scan technique and there's recognizing which types of inter cavitary fluid actually represent a pregnancy.

Case Examples and Scanning Pitfalls

I'm gonna start out with the case example and here's a transabdominal ultrasound positive pregnancy test, pain and bleeding.

This is the uterus, this is an IUD.

And there's all of this stuff around the outside of the uterus.

The vaginal scan done by a resident on call caused all sorts of terror.

He was completely lost, which is what I refer to as being lost in the fog.

And what I want to share with you is the pitfall about being lost in the fog and what you do.

So actually if you look at this picture, you can see up here in this corner, a little bit of the endometrium comes through, but it's really hard to tell where you are.

Blood in the pelvis is very confusing.

So that's pitfall number one.

Be aware that either blood or pus is echogenic.

It coats all the normal organs in there and it disrupts your normal pattern of recognition of structures.

So if you have a situation like that and your patient is stable, think could this be blood?

Am I looking at a bleeding ectopic?

And then you go back to using your equipment to the best of its abilities.

So what we did was we increased the field of view, we decreased the megahertz transducer frequency, adjusted the focal zone.

And now you can see that this is the uterus, that is the cavity with an IUD.

And all of this is echogenic fluid and these are bowel loops.

So immediately you're in a situation where you don't see anything in the uterus except an IUD, which increases your risk for ectopic.

You keep looking and using color out in the ad nexa.

In the midst of all of this fog of blood products in the pelvis is this very echogenic, very vascular tissue, which is the adnexal ring or the ring of fire that's described in ectopic pregnancy.

So pitfall number one, blood and pos can be very confusing in the normal first sub trimester blood is what you're most concerned about.

Pitfall: Enlarged Uterus with Fibroids

Another example, positive pregnancy test and pain.

And this is a different pitfall. This is the uterus.

It's enormous, it's full of fibroids.

So the person scanning went, I can't see anything here.

I'm just gonna go do a vaginal ultrasound.

And they turned in these extremely rased up pictures of part of the endometrium and said, well, there's an IUP and there were no pictures of the adnexa.

So this is the second pitfall is not looking from side to side and top to bottom through the pelvis.

If the uterus is enlarged, the adnexal structures get pulled up sometimes outta the pelvis.

And I call this LA liar pants on fire because you didn't not see the Aden so you didn't go look for them.

And what we have here in a transabdominal picture is the corner of the fibroid uterus, the ovary and the adnexal ring of the ectopic pregnancy.

So although we all love vaginal ultrasound for OB and for GYN, we need the lights down.

Remember sometimes transabdominal is better.

You have to scan from side to side of the pelvis.

Communication and Differential Diagnosis in Early Pregnancy

I mentioned that communication was very important and I'd like to think that we're all a little bit smarter than our kindergarten children, but we're gonna talk a lot about using our words.

First of all, in the setting where you have a patient in the emergency room with vaginal bleeding in early pregnancy, what are the options that you have to consider?

One is it's a normal pregnancy and it's just too early to see anything which is our pregnancy of unknown location.

Or sometimes you see something but you don't know about the viability.

It can be a failed pregnancy and you can have no embryo or you can have a dead embryo.

Sometimes you can be an above situation and have a sub chorionic hemorrhage as well.

You may have had a complete abortion, in which case there's nothing in the uterus, but you have that single point in time, so you don't know what went before.

And again, you may have a pregnancy of unknown location which can end up being a normal pregnancy or an ectopic pregnancy.

So those are the all the options you have to have in your mind when you start scanning.

Not only that, but all pregnant people are susceptible to all of these other conditions as well.

So you may have a perfectly okay pregnancy and have the patient have pain because of a hemorrhagic ovarian cyst or appendicitis.

So there's a lot of things to get into trouble with.

Nomenclature and Terminology for Early Pregnancy

If we go back to that nomenclature, this is a very busy slide, but it's from this article published in 2011 in Infertility and sterility, which is a journal that our O-B-G-Y-N colleagues place great importance upon.

And essentially here what I want you to take home is there's a pregnancy of unknown location.

When you can't see anything, you can have an IUP, an intrauterine pregnancy, which can be probable or definite and you can have an ectopic pregnancy that can be probable or definite and we'll look at some examples of those.

We also need to be aware of the criteria for what's a viable pregnancy.

And I'll be quoting Dr. dLee quite a bit in this talk because he's a very quotable sort of chap.

And we all heard yesterday at the fellows meeting that he has a math PhD from MIT.

So I'm even more impressed than I used to be in this consensus statement which was held by the UM SRUA couple of years ago.

The definition of a viable pregnancy is a pregnancy that can potentially result in a live born baby.

And that's something to just keep in mind as we go through examples.

So looking at our recommended technol TE terminology, all these items are here.

Instead of calling things a gestational sac, sometimes it's better.

I teach my residents go from the generic to the specific and use your words carefully.

So if you describe an intrauterine sac like structure that essentially says there's fluid in the uterine cavity, then you can move on to describing the shape and whether there are any contents.

So a definite intrauterine pregnancy contains a sac and there has to be a yolk sac or an embryo in that gestational sac.

If you have an intrauterine satellite structure that has no internal content, that's when you're looking at the probable IUP, the pregnancy of unknown location, we'll discuss in more detail and also the ectopics.

So all of these signs that we learned when I was young, like the intertidal and double decid sac sign are not very reproducible.

And again, that's another study that Dr. Dubay and his colleagues did.

So if you stick to describing an intrauterine fluid collection, these ones are round, that one is more pointy edged.

Signs of Intrauterine Pregnancy

What are the signs of an intrauterine pregnancy?

What do we see? Remember you take a single sperm and a single oum and you have to build an entire human being outta that in the first 13 weeks in pregnancy.

So you start out with the intrauterine fluid collection and a pregnancy is an actively growing dynamic process.

So it's rounded out, it should be convex borders toward the uterus, be round and oval and space occupying.

So you see rounded fluid collections.

Then you start to see a little fluid collection inside the gestational sack that is the yolk sack.

And then you see the embryo as a little re essence on the side of the yolk sack, which I call the diamond ring sign.

And this is a 3D of that.

As the embryo grows, it elongates and eventually it becomes more kidney bean shaped, which I'm gonna show you a picture of there.

And at the time that all this growth is happening, various embryological events are happening like the abdominal wall closes and the oak sac separates from the embryo.

So there are very predictable appearances to a normal early IUP.

Irregular Fluid Collections

So let's go back to our intrauterine fluid collection.

And what about this one? This is not round or oval.

It is not pressing out and growing and actively expanding.

You can see that that it's flat, irregular and it has pointy edges.

This is the thing that we used to call the pseudo sac and we want to move away from that term because it causes confusion.

If you use the term sac, people think you are talking about a gestational sac in the uterus.

So you can say an intrauterine fluid collection intrauterine sac like structure and describe that it's flattened, irregular and pointy edged.

Statistics and Probability in Diagnosis

We're also going to go now from kindergarten maybe to middle school and do some statistics and probability.

This is another quote from a Dr. Dubay paper and in this one they show that if you have a round or oval, remember that shape intrauterine fluid collection in a patient with a positive pregnancy test, you have to assume that that is a gestational sac and an intrauterine pregnancy until proven otherwise.

The key thing is the round or oval and that's the pitfall.

If you don't characterize your intrauterine fluid collection, you will make mistakes.

They also did some probability testing and came up with the fact that if you have this nice intrauterine smooth walled ana coexisting structure and here's the kicker and no adnexal mass, then there's a 0.02% probability of ectopic pregnancy and a 99.98% probability of an IUP.

But this no adnexal mass is key.

Just having the intrauterine fluid collection is one part.

If you don't look at the ad nexa, you will get into trouble.

So pitfall is not looking at the entire pelvis, so yay from ahan probability we're talking about measurements here and criteria.

Measurements and Criteria for Viability

So if you are going to determine a live or death situation based on a measurement, you really need to do your measurements correctly.

So with the mean sac diameter, we look at the gestational sac and that has this echogenic chorionic ring.

But the sac diameter is just the fluid component.

So you do orthogonal diameters in the three planes, measure the three of them and do the average.

That is your mean sac diameter.

You do not include the corion.

If you do, you will have the pitfall of overestimating the sac size and therefore deciding something is nonviable when it's actually potentially viable.

Here's the crown rum length and this is a little video clip.

This is the embryo.

You can see the flicker of cardiac activity.

You can see, see that the amni and is expanded around the embryo here visible within the chorionic sac surrounded by the chorionic membrane.

And this is a measurement.

This is 10.7 millimeters and this is above the threshold.

So if there were no cardiac activity in this embryo, it would indeed be dead.

So the criteria for viability are a mean sac diameter greater than 25 millimeters without an embryo is a failed pregnancy as long as you've measured it correctly.

If the embryo is greater than seven millimeters in length and does not have cardiac activity, it is a dead embryo as long as you've measured it correctly to demonstrate cardiac activity.

Video clips are great and mode is nice and you can use color doppler if you absolutely have to.

But we generally try and stay away from using doppler in early pregnancy because of energy deposition.

The only caveat to that rule is if you have a study from last week that you can see cardiac activity in a tiny embryo and now you have a measurable embryo that does not have cardiac activity, if that embryo is less than seven millimeters, it can definitely be called dead because of the cessation of cardiac action.

Follow-Up Guidelines

What do you do when you don't quite meet these criteria?

You have to have some rules about when to follow up because another pitfall is falling up too soon or following up daily ultrasounds and terrorizing this patient and yourself.

So the consensus statement had very clear criteria and if you see a sac without a yolk sac, so it's just your intra in gestational sac slike structure, no visible yolk sac or embryo, and the patient is stable, you wait two weeks, 14 days after 14 days, the absence of an embryo means that pregnancy has failed.

It is not viable. There is not going to be a live born baby.

If you have the definite IUP, which is your intrauterine slike structure that contains a yolk sac, then you only wait 11 days because you're further along.

Anatomic Pitfalls and Variants

Embryologically, one of the other signs that we used to use is called the empty amnion sign.

And I'm gonna show you an example of that in a minute that was actually published as definitive for pregnancy failure.

But at the consensus statement there was quite a bit of discussion and it was decided that it should be characterized as being suspicious for pregnancy failure but not diagnostic of.

Here's an example. And again this comes down to anatomy, right?

Here's your gestational sac, this is your chorionic membrane, this is the amn.

And the amnion usually surrounds the embryo and has completely koic fluid.

The fluid that's beyond the amnion between it and the choon is echogenic because it's protein tenacious.

And this is the yolk sac.

And the yolk sac is clearly separated outside the ion.

So embryologically, if the ambient is expanded and the yolk sac is separated from the embryo, the embryo has undergone gas ration, it has created its cardiac tube, its GI tube and its neural tube and it should be alive, but it's suspicious, not diagnostic.

That's what it looks like.

You scan through the entire AM and you see no embryo.

Subchorionic Hemorrhage vs. Normal Structures

What other anatomic problems can you run into?

People get very confused about sub chorionic hemorrhage versus that echogenic fluid in the chorionic cavity that I just showed you.

So sub chorionic hemorrhage means you have bleeding underneath the choon outside of that gestational sac, which is walled by the chorionic membrane.

So here's an early percent of the choon front doum.

This is the choic sac surrounding an embryo.

And this echogenic fluid is outside of the choon or under it.

So this is a subc chorionic hemorrhage.

This is another example where you have myometrium, you have choon and you have blood under the choon.

You have fluid inside the cavity.

This is subc chorionic hemorrhage.

And this example has a chorionic bump as well, which I'll show you more of later.

This like I showed you earlier, the embryo is inside the ion, which is koic.

That's that little bubble of fluid around the embryo.

The extra embryonic thoma space or the cho cavity is echogenic fluid.

Then you see the placenta, then you see the choon and there is no fluid around the outside.

So this is normal embryological structures.

This is a subchorionic hemorrhage.

Chorionic Bump

Here's another example of a pitfall.

This is a uterus on a vaginal scan and we have an intrauterine slike structure.

It's a little bit pointy edged.

And then there's a structure here that was measured.

And this measures nine millimeters.

And this was said to be a nine millimeter embryo nor cardiac activity.

This is a failed pregnancy.

But what's the problem with the structure is it is continuous with the choon.

It is not encased within amni and in its little bubble inside the gestational sack.

This patient wanted to wait, she came back for a follow-up scan.

Here is the choon, here is the embryo.

This was a live baby and she went ahead to have a term delivery.

So this is an example of the chorionic bump.

It's just a protuberance from the choon.

It's always directly in continuity with the wall of the gestational sac.

An embryo is separate from the wall of the gestational sac.

Here's a normal early embryo one I showed you earlier.

And you can see there is the embryo, there is the amnion, there is the T extra embryonic thoma space.

This is a cho bump bulging out from the wall of the gestational sac, not separate within the sac.

Maternal Anatomic Variants

Another anatomic pitfall that you can have.

That was embryologic anatomy. This is maternal anatomy.

And so here's an image, this ladies 13 weeks, two days by her LMP and there's a uterus and there's some genic endometrium.

Here's a transverse section. There is the uterus.

And the person taking these pictures didn't notice this thing over here.

And when I asked what it was, they said, oh, that must be an ovarian cyst.

So we went back and looked and as I said before, you have to scan side to side, front to back and top to bottom of the maternal pelvic structures because this was a delphis uterus and there was no pregnancy in the right horn and there was the perfectly normal 13 week pregnancy in the left horn.

And you might think that could never really happen.

This had to be a very inexperienced student doing the study.

It was in this case.

But we were asked to provide a legal opinion on a case in which a patient was given methotrexate because a vaginal scan was done and empty uterus was seen and it was a bicornuate uterus and the six week embryo was in the other horn, not identified.

And giving methotrexate to an IUP is catastrophic.

Heterotopic Pregnancy

More about location, location.

So here's a transabdominal scan in a patient who's pregnant with pain and bleeding.

There's the uterus, there is the gestational sac.

This is actually an MO showing a tiny flicker of cardiac activity.

So we have a live IUP. So great, right?

We have pregnancy and the uterus we're done.

Well, not really because we have to explain all of this free fluid in the abdomen.

So we go over to the right atxa, here's the ovary forming a claw around this structure, which doesn't look that dissimilar to that one, but it's in the ovary.

And unless you have donated eggs in an IVF pregnancy, someone who's pregnant has to have ovulated, therefore has to have a corpus lutetium.

So you have to recognize the myriad appearances of the corpus lutetium.

This was the right ad nexa.

We go over to the left ad nexa 'cause you've got to go side to side, front to back, top to bottom here is the ovary.

And here is this big amorphous thing.

This is more of the famous what you do when you're lost in the fog.

Think about blood.

And this was a large blood clot around a ruptured left tube ectopic in a patient with a heterotopic pregnancy.

So don't get satisfaction of search, don't be happy when you find an IUP.

It certainly decreases your concern for an ectopic, but especially in the IVF population, you still can have a tubal in the setting where you have a heterotopic pregnancy.

Ectopic Pregnancies: Descriptors and Findings

So now that we're talking about ectopics, let's think about our descriptors and the nomenclature that we use.

In that 2011 paper, they said that a probable ectopic was an in homogeneous adherent mass or an extrauterine sac like structure.

So both fairly amorphous descriptors.

The definite ectopic, like we see here, was an extra uterine gestational sac in which you can see a yolk sac or an embryo.

The problem is that nowadays we are seeing people earlier and earlier and earlier, you get a pregnancy test, day 29 of your cycle, start bleeding on day 30 and people come to the emergency room.

So this study, again by Dr. Dubay and his colleagues, this is Mary Frais, as the first author here, looked at actual findings in a current series of ectopics.

And what they found is that a non-specific mass was actually by far and away the commonest observation.

The echogenic tubal ring, which I showed you earlier, was also very common.

Seeing a ring of fire in the trophoblast with color doppler was pretty fire common, sorry, not pretty fiery.

However, identifying a live embryo.

Now remember the criteria for definite doesn't say live embryo, but it does say embryo.

An embryo was seen in a live one in less than 10% of cases in modern series.

And it used to be that we saw them more frequently because we saw people further along in their pregnancy.

Another series looked at the types of tubal pregnancy in 339 cases.

And they saw, if you look at this, 47.8 and 38.3, so this is the vast majority of cases had either a sat like structure or an in homogeneous mass.

And the criteria that we would use to say definite ectopic were present in only 13% of cases.

So an extra uterine gestational sac with a yolk sac or embryo, which is the definition of a definite ectopic pregnancy, is highly specific but not very sensitive.

And these authors said, you know, we really ought to be in a situation where we say that if you have any adnexal mass, other than a simple cyst.

So remember you may see a tiny simple cyst in the ovary.

You may see parat tubal cyst.

And those are things that are normal anatomic structures that you need to be aware of and not get fooled by.

But if you have a mass in the adx, that's not a simple cyst in a patient with a positive pregnancy test without anything in the uterus that is very, very concerning for an ectopic pregnancy.

Blob and Bagel Signs

So I'm Irish and I'm irreverent as most of you know, that know me.

But I have some Australian friends who I love because they're more irreverent than I am.

And George Kda is an Australian chap who works in Australia, sorry, he's he's, he's Australian, he's very funny.

He's probably descended from an Irish sheep farmer.

But he wrote this paper and I thought the title was very funny.

Morphological ultrasound known as Blob and bagel Signs should be reclassified.

And I thought, I read the OB literature, I've never heard of the blob and bagel sign, but I did Google it and go to PubMed and I found a paper written by George himself describing those two signs, which was probably a precursor to writing this one.

But basically it's all about that in homogeneous mass or the sac like structure without definite entities in it.

At this point, we should be able to say that is a definite topic.

I want to show you the difference between a corpus lutetium and the blob.

The corpus lutetium is in the ovary, the blob is beside.

And if you use your tools correctly, you can push the blob away from the ovary.

Therefore, this is an adnexal mass and this is an ectopic pregnancy of unknown location.

It's not in, it's not out, it's not seen.

Pregnancy of Unknown Location

Why does that matter? Because half of them spontaneously resolve.

So we never figure out where they are.

But 34%, become viable pregnancies and 11% result in ectopic pregnancies.

So that is not a diagnosis, that is an observation.

I know the patient's pregnant, I don't know where the pregnancy is.

Is this a pregnancy of unknown location? No.

You see a sack with a yolk sack and an embryo.

So if you don't know where it is, it doesn't mean it's an unknown location.

You have to see nothing at all.

And what this is, is a cesarean scar pregnancy.

It's here centered on the anterior myometrium touching the back wall of the bladder.

So that is an intrauterine pregnancy sort of, but it's not really viable because it's not going to continue.

And that again, is the example in the anterior myometrium.

Other Ectopic Locations

Another in pregnancy that causes confusion because it's technically in the uterus, is in the interstitial portion of the tube.

We do not use the term cornal pregnancy anymore.

This is interstitial ectopic and you need to be careful with an angular pregnancy, which is in the cavity versus a pregnancy in the tube.

The pregnancy in the tube looks like this.

It is very, very eccentrically located.

That is transverse through the uterus. That's the cavity.

This is the gestational sac 3D Reconstruction, again, shows you there's the cavity.

Here's the gestational sac.

This is a cervical ectopic, the twin pregnancy, the way you know it bulges the cervix out and thins the myometrium.

It's implanted into the cervix.

It's not a twin pregnancy up in the cavity of the uterus.

The caveat there is you have to be careful between a cervical ectopic that's embedded and a pregnancy that's in the process of aborting.

And you look at the anterior posterior lips of the cervix, those should be symmetric.

The sac should be flattened.

And obviously if the embryo is alive, that is not an abortion in progress because it will be falling out of the uterus and be a dead embryo already by this time.

Conclusion

So in the first trimester, there's a lot of things going on.

If your patient is stable, there's absolutely no harm in waiting to see.

You need to be aware of normal anatomy.

You need to use all of your scan techniques that you can.

You must scan the entire uterus.

And when you're out in the fog, remember what you need to do.

Thank you.