Pitfalls and Practical Challenges in Sonographic Imaging of the Uterus - HD

Introduction

My name is Dr. Nancy Bedor from the State University of New York and Stony Brook.

Today I'll be talking about pitfalls and practical challenges and sonographic imaging of the uterus.

To me this means what are particularly challenging cases regarding ultrasound imaging of the uterus.

I'd like to run this in sort of a quiz format to help you think the same way I think without a complete history looking at the images firsthand.

Case 1: Cervical Fibroid

So we'll start with a relatively straightforward and easy case.

What is the first thing you think about? An imaging this lower uterine segment of a first trimester gravid uterus.

The fetus is not shown here, but the cervix and lower uterine segment are seen in this region.

What is the first thing that comes to your mind on the transverse view and the longitudinal view?

We see there's a large hypoechoic mass facing the cervical canal.

It's a posterior cervical fibroid, so the first thing that will come out of your mouth or come to your head is labor dystocia.

This patient's clinician knew about the lower uterine and cervical fibroid planned a cesarean section and got an MRI late in the second trimester or third trimester showing the same thing we saw in the first trimester, a large posterior cervical mass, which would obstruct the pelvis.

Here's the cervical canal.

This patient had an uneventful cesarean section, so the first thing that would come to your mind with the initial image is pelvic impaction by a fibroid.

So it was a known cervical fibroid followed throughout pregnancy, obstructed the pelvis and the patient had a planned C-section uneventful.

Case 2: Diffuse Uterine Fibroids

Now how about this case?

This is a case with diffuse uterine fibroids.

The patient presented at eight weeks, six days for bleeding.

She has an early pregnancy sometime in the first trimester, eight weeks, six days longitudinal.

We see a bit of the urinary bladder.

This is the lower uterine segment.

Here is the gestational sac in the upper uterus.

This is later 11 weeks, four days.

The patient came for nuchal translucency.

Here's longitudinal fundal uterus.

We see diffuse fibroids and the gestation is confined to the fundus of the uterus.

Here's the lower uterine segment and the cervix measured.

We see that this is a very thickened myometrium diffusely infiltrated with fibroids.

This patient had diffuse fibroids.

She also had a prior open fundal, multiple myomectomy with a Pfannenstiel skin incision.

The surgery was stopped due to blood loss and the lower uterus was never cleared of fibroids.

The current pregnancy demonstrated multiple sonograms describing all the fibroids, but no clear description of confinement of the fetus to the upper uterine segment.

The fetus was never seen in the lower uterine segment on any exam, however, and it also presented with persistent transverse lie in the third trimester.

This patient did not have an MRI.

She was delivered at 34 weeks with severe preeclampsia and it was a very difficult delivery initially with a Pfannenstiel and low vertical uterine incision, the fetus could not be reached.

This was extended superiorly to a classic uterine incision and still the fetus could not be reached because it was confined in the fundus.

The Pfannenstiel skin incision was then converted to a T incision on the skin and the fetus delivered via transverse incision in a myoma free zone.

So this was quite an ordeal and quite a difficult delivery.

Fibroids in Pregnancy

So we know that fibroids in pregnancy may grow and may lead to infarction, and this may lead to pain.

Degeneration of the fibroid may lead to pain as well as torsion of a subserosal.

Fibroid impaction can happen not only because of a focal fibroid as we saw in the first case, but also because of diffuse fibroids.

The fetal head cannot engage for delivery.

Fibroids are associated with increased rates of spontaneous miscarriage, preterm labor, placental abruption, postpartum hemorrhage, and cesarean delivery, mostly due to malpresentation and labor dystocia.

Evaluation Recommendations for Lower Uterine Segment and Cervix in Patients with Fibroids

So what should we really do with lower the lower uterine segment and cervix in a patient with fibroids?

Continue evaluation of the lower uterine segment and the cervix until delivery or until cesarean section and the approach of either the lower uterine segment or fundus are decided.

An MRI may be helpful for you to decide what approach.

This is a different patient with diffuse myomas.

This fetus was not confined to the upper uterus, but we see that this clinician astutely recommended an MRI and because he wanted to be sure that there was no confinement of the uterus.

So just remember that diffuse fibroids can result in confinement of the fetus in the upper uterus, resulting in difficulty extracting the fetus.

If it's not recognized, consider prior MRI prior to delivery for fibroid mapping and planning of the uterine incision.

And we're looking for specifically a fibroid free zone in which the fetus can be delivered by cesarean section.

Case: Interstitial Ectopic Pregnancy

Next case, this is a first trimester gestation.

We see a yolk sac, a gestational sac, and the LMP is unknown.

What is one of the first things that comes to your mind?

We see a gestational sac.

We see the myometrium, we see the endometrium.

A little fluid in the endometrium.

Here's the endometrial canal. This is sagittal.

Here's the gestational sac.

And notice that the peripheral myometrial mantle is thinned.

It's 4.5 millimeters.

What is something that comes to your mind later?

Four weeks later, we see that this was continued this pregnancy and it looks like a normal intrauterine gestation.

So initially it's an asymmetrically implanted gestational sac And one of the things that should come to mind is could this be an interstitial ectopic pregnancy?

Obviously this one was not.

Similar Case and Sonographic Features

How about this similar case? This is very old.

It looks very pixely, but it's a good demonstration.

We see the endometrium separate from the gestational sac.

We see a bulging contour of the eccentrically, the lateral aspect of the myometrium.

We see a little line between the endometrium and the gestational sac.

Who knows what we call this line?

This is the interstitial line.

It's the line between the empty endometrium and the ectopically implanted gestational sac in the interstitium.

It's something that's more definitive than the peripheral myometrial mantle measurement.

So the sonographic features of interstitial pregnancy are an empty appearing lower endometrium, an asymmetric or incomplete myometrial mantle around the gestational sac, specifically less than five millimeters, a gestational sac eccentric to the empty endometrium by a centimeter and the interstitial line sign.

Also, we have found in our institution that a bulging uterine contour can also help us decide if a pregnancy is implanted.

Interstitial vs. Cornual Pregnancy

In the interstitial interstitial pregnancy accounts for two to 4% of ectopic pregnancies.

It has a higher morbidity and mortality, in fact, two times the mortality due to its later presentation and access to better blood supply and tendency for massive hemorrhage.

Traditionally, we have used the words interstitial and cornual pregnancy interchangeably, but cornual pregnancy really refers to a pregnancy in a rudimentary horn of a congenitally abnormal uterus such as bicornuate or septate.

Here we see the interstitial of the fallopian tube.

It's the interstitial portion of the tube.

As we see here, it's one to two centimeters in length and notice it has a very thick muscular layer, which gives it a greater capacity to expand and also a greater capacity for the trophoblast to access better blood supply before rupture than the more distal tube which has very little muscular layer.

MRI for Interstitial Pregnancy

MRI is not always recommended.

This happens to be one that got an MRI because was uncertain if this was an interstitial pregnancy or not.

Here we see the empty endometrium and we see the gestational sac eccentric to the endometrium.

An MRI has its own specific sign for interstitial gestation other than this appearance and that is that it's eccentric to the junctional zone.

So here we see the junctional zone and the gestational sac is eccentric to the junctional zone.

So if you need to go to MRI to decide whether you have an interstitial pregnancy and this would ordinarily be in a pregnancy that's not desired, you need to know that the gestational sac is eccentric to the junctional zone for the diagnosis.

Differential Diagnosis for Eccentrically Located Gestational Sac

So this problem for me is an eccentrically located gestational sac, eccentrically located, but normal gestational sac, or is it an interstitial pregnancy?

Could it be a cornual pregnancy in a duplication anomaly?

And if it's in the lower uterus, it could be either a cervical or a cesarean scar ectopic, which we'll also cover.

So another instance, transverse through the uterus.

Here's an asymmetrically implanted early gestational sac.

In this image, it looks separate from the endometrium.

Is it an interstitial pregnancy?

Is it a cornually implanted pregnancy in a bicornuate or septate uterus?

What can help us? We're measuring only 2.7 millimeters of a peripheral myometrial mantle.

Is this the empty endometrium?

Is there an interstitial line here?

It's a little difficult to tell.

We have found that three dimensional ultrasound is very helpful in deciding these cases.

Remember that the cornual segment of a partially duplicated uterus may be thinned in the myometrial measurement of five millimeters may not be as reliable.

So in this 3D ultrasound, we see that the gestational sac is confined in the endometrium.

It's not an ectopically implanted early gestation, but this is a partially duplicated, probably a septate uterus.

So the myometrial mantle in the cornual region may be slightly thinner than five millimeters in an early pregnancy.

So 3D ultrasound can help to distinguish eccentrically located gestational sacs from a cornual pregnancy in a duplication anomaly from an interstitial pregnancy.

Scar Ectopic and Cervical Ectopic Pregnancies

Now what about this case positive beta first trimester empty endometrium and we see a mass in the lower uterine segment.

What is your differential diagnosis?

Could it be a cesarean scar ectopic, or scar ectopic as we call it?

Is it a cervical ectopic or could it be an ongoing SAB?

What do we look for?

A scar ectopic is a cesarean scar pregnancy before 2002, only 19 cases were reported estimate one in 2,230 to one in 10,000 of all pregnancies.

The rate is 0.15% in women with a prior C-section and 6% of all ectopic accounts for 6% of all ectopic in women with prior C-section.

Some say it's different from accreta in that it has an absent myometrium between the bladder and the gestational sac, but this is not always easy to distinguish.

So the differential diagnosis includes spontaneous abortion in progress, cervical ectopic pregnancy, and a scar ectopic.

Kovacs has described criteria in 2003 of having an empty endometrial cavity, a gestational sac located anteriorly at the level of the internal os covering the site of the prior C-section.

Scar evidence of functional placental trophoblastic circulation on doppler and no sliding sign.

Here's the same case we see that there is one of the signs here.

The gestational sac is located anteriorly at the level of the internal os covering the site of the prior C-section site.

The uterus is empty on color doppler.

There's evidence of functional trophoblastic tissue with vigorous flow surrounding the mass.

There's also bulging outside of the cervix as we see in the lower portion of this image.

And on M mode.

This one even had a heartbeat, which demonstrated a live ectopic pregnancy.

This patient went to MRI.

We see that the fundal endometrium, the whole endometrium actually is empty.

We see this heterogeneous mass obscuring the cervix.

Here's part of the posterior cervix.

The anterior is not even seen.

It's facing the bladder wall.

And this patient went to embolization pre embolization.

Here is the vigorous flow in the region of the cervical ectopic post embolization.

We see there's virtually no flow in this region at surgery.

Here is the cervical ectopic.

Here is the anterior uterus, the cervical ectopic bulging outward, which popped out easily according to the surgeon and there was successful repair of the anterior cervix.

So in our hands, you can't always immediately distinguish by imaging a scar ectopic from placenta accreta, especially if early in pregnancy and even a cervical ectopic can appear similar if very early in pregnancy.

Here we see a gestational sac insinuating into the cesarean section scar.

Cervical Ectopic Pregnancy

Now what is this entity?

This appears a little bit different than the other.

So here we have an anterior and a posterior cervix.

This is a cervical ectopic pregnancy.

It accounts for less than 1% of all ectopic pregnancies.

The risks are multiparity, prior abortion, prior instrumentation of the cervix or the endometrium.

The features are a gestational sac with a live embryo or trophoblastic flow in the cervix.

If there is a gestational sac without live embryo, then you have a different differential diagnosis.

Is it a cervical ectopic with a demise embryo or an ongoing spontaneous abortion?

So we look for trophoblastic flow.

If there's peritrophoblastic flow, it's most likely going to be a cervical ectopic implanted in the cervix.

We look for serial changes in the sac shape and position and that is the sliding sac sign that would tell us it's a spontaneous abortion in progress.

What are the sonographic features?

Well, the cervix is enlarged as we see here.

The uterine enlargement takes an hourglass shape also as we see here with a waist at the lower cervical LUS junction.

There's no intrauterine pregnancy within the endometrium and the placenta and entire chorionic sac must be below the internal os and the level of the uterine arteries.

The cervical canal should be dilated and barrel shaped as we see here, and we will not see a sliding sign, AKA.

This will not move in serial imaging of this cervix.

Here's the enlarged cervix, also barrel shaped.

Here is trophoblastic flow.

That tells us this gestational sac is implanted in the cervix.

The uterus is hourglass shaped, better seen here with a waist at the lower uterine segment slash cervical junction.

So you cannot always distinguish, especially if early in pregnancy.

Scar ectopic from placental invasion from cervical pregnancy.

Uncommon Entities

So we have reviewed the common challenges in imaging the uterus, fibroids, and eccentrically located gestational sacs.

Let's look at some uncommon entities.

Uterine Rupture

This is a patient who came at 25 weeks of gestation for left upper quadrant pain.

What do you think when you see this image?

How about this image?

We see a foot in a sac, a fluid filled sac in the left upper quadrant, two feet.

Here's some bones. We know this is the foot, this is the uterus.

This is a uterine rupture.

Here's the MRI image of the fetus in the uterus with the feet protruding through the ruptured uterus into an intact amniotic sac.

Here's the transverse image.

We see a little debris in the sac protruding.

We see the fetus is relatively confined because a lot of the fluid is pushed out into the extrauterine amniotic sac.

Here's the bones and the limbs.

Portions of the limbs protruding through this large defect, relatively large defect.

And then on the sagittal image we see it protruding a little superiorly.

Here's the defect. We even have a three dimensional image of the feet protruding quite a shocking image.

So an uncommon challenge may be uterine rupture.

This was chronic uterine rupture with intact amnion.

This patient had a prior missed abortion at 15 weeks with subsequent D&E after the D&E, she had subsequent persistent bleeding and hysteroscopy that, in which they removed quote placenta pathology showed that this was actually a fallopian tubal segment, so she must have had a prior perforation at the initial D&E and the fallopian tube ended up partially protruding into the endometrium.

She underwent a subsequent laparoscopic repair and it was unclear if this was cauterized or stitched, the defect.

And then she got pregnant within a year, with IVF.

So she had a reason to have a rupture on this side.

She had prior surgery and complication and probable rupture at A D&E.

This patient had no cord prolapse at 25 weeks on the MRI only the feet were prolapsing.

She was admitted she was tocolyzed with magnesium and then the cord prolapsed in the next week.

Follow-up ultrasounds were performed daily for umbilical artery doppler monitoring.

She presented then at with abdominal pain at 30 weeks gestation in which she was discovered to have rupture of membranes and was precipitously delivered with a classical C-section.

The infant's legs were slightly swollen at delivery.

This spontaneously resolved and there was a good outcome for both the patient and the fetus.

Here we see the cord prolapsing Around the limb and we monitored with umbilical artery doppler until her membranes ruptured.

So uterine rupture is about 0.05% has an incidence of about 0.05% during pregnancy.

It's usually through a prior C-section scar greater than 90%.

It may be limited to dehiscence of the ends of the scar with intact overlying serosa.

It may be full thickness rupture with direct communication of the uterus and peritoneal cavities.

Full thickness rupture carries a high fetal and maternal morbidity and mortality and classical scars are prone to rupture prior to labor, whereas lower uterine scars are prone to rupture after labor.

What is the presentation?

Abdominal pain, as we saw here, abdominal discomfort and hemodynamic instability.

The imaging features are some of which we saw here, protruding portion of sac or contents, endometrial or myometrial defect, which we did eventually see an extrauterine hematoma we didn't see.

And hemoperitoneum or free fluid, which we only saw after the membranes ruptured.

Bandl's Ring

This is a different case. This is a case at 22 weeks.

Gestation was in labor and delivery for termination by induction due to a severe Chiari two malformation.

I was called for an MRI because the patient failed to progress with Laminaria and Cytotec, an ultrasound which we don't have recorded images.

The uterus was dilated in the lower, in the lower portion, but the cervix wouldn't open.

And at the time they wondered if there was a focal rupture or if it had possibly been misdiagnosed as an abdominal pregnancy.

Here we see a transverse image on MRI.

Here's the Laminaria.

In the relatively horizontal appearing uterus, this is a Foley catheter in the urinary bladder.

On serial longitudinal images, we see that there is a dilated lower uterus.

Here's the fetus confined in the upper uterus.

There is myometrium around here and there is a cervical canal.

We can see a portion of the Laminaria on transverse imaging.

We see the placenta anterior, we see the fetus pushing against this constricting region and we see the membrane of the myelocele.

So what is, what would you think of if you see a fetus with this type of configuration of the uterus?

With induction of labor, we went back retrospectively and looked and we had actually imaged this patient in the second trimester.

Here we see a cervix. Here we see the lower uterus.

There's no constriction here either on the longitudinal or the transverse.

Here's the right and left adnexal region, the left adnexal region and the lower uterus.

And there's no such constriction deformity.

So what are we thinking? This can't be a synechia.

It wasn't present prior to labor induction.

What is something that can present like this that can happen with labor induction?

This is a Bandl's ring.

This is a pathologic retraction ring at Barnes boundary line.

It's a constriction at the junction of the thin lower uterus with the thick retracted upper uterine segment.

It results in obstructed labor.

It's one precursor to uterine rupture.

This patient was then delivered by C-section hysterotomy.

So here we see the contraction, the constriction deformity at the Barnes boundary line and it forces the lower uterus into the pelvis and there is inadequate pressure on the cervix to open.

So there's just a fluid filled sac above the cervix and the fetus can't get to the internal os to push the cervix open.

And we also see the dilated ventricles of the Chiari malformation.

Uterine Incarceration

So uncommon entities in challenges of imaging the uterus are rupture and Bandl's ring.

Now I ask you, why is this not a uterine incarceration?

What is different about uterine incarceration than this image here in uterine incarceration?

Portions of the uterus can be confined in the deep pelvis, but what is different about this picture here is the bladder with a Foley.

This was a little bit of free fluid around this uterus.

This is the same myelocele patient.

This is the cervix.

So what is different about the position of the uterus or the cervix in a patient with Bandl's ring versus uterine incarceration?

Here's the cervix.

Here's a normally oriented cervix.

So the cervix is within the pelvis and is flexed.

It can be mildly flexed as we see here, or more flexed as we saw in this prior case of the Bandl's ring.

What about this case? This is a case borrowed from Dr. Hertzberg's group. Here is the lower uterine segment.

Here is the fetal head. This is the cervix.

This cervix is displaced superiorly and anteriorly to the fetal head.

So we're thinking could this be rupture?

Could this be a duplicated uterus with another uterus next to it?

MRI can be very helpful if the, if you have no prior ultrasound and no prior documentation of what the fetus and the uterus looked like previously on MRI, we see this is the effaced uterus anterior to the rest of the effaced cervix anterior to the rest of the uterus.

And on transverse imaging we see the cervix anterior to the uterus.

So this is a patient who presented in the second trimester with persistent pelvic pain.

This is a classic picture of uterine incarceration.

It's entrapment of a portion of the uterus and displacement of the cervix such that the fetus can never get out early in the first trimester.

This is a non gravid uterus, but patients who have retro positioned uterus are prone to uterine incarceration.

And you can imagine that as the gestational sac would enlarge this fundal uterus, it comes more superiorly and can get stuck at the sacral promontory.

If it doesn't pop out, it may spontaneously correct and pop out.

If it doesn't pop out, you can result in long-term uterine incarceration.

If it occurs in the first trimester, it's usually associated with transient urinary retention because the cervix is then pushed anteriorly and it's hard for the detrusor muscles to work because there is mass effect on the urinary bladder.

Rarely a portion of the uterus can be entrapped in the uterus between the sacral promontory and the pubic symphysis.

Long term, the symptoms can be vague, diffuse pain, urinary retention, or even incontinence.

Here we see another, a beautiful diagram also by Hertzberg's group to clearly delineate what is going on here.

Here's a portion of the uterus that is stuck between the sacral promontory and the symphysis.

It never popped out and corrected.

The cervix is pulled up anteriorly and effaced and here is the vagina.

So you can see why this would result in pain.

And also there's pressure as the fetus grows and the uterus enlarges upon the urinary bladder and so the patient can have urinary symptoms.

Predisposing factors are not only a retro positioned uterus prior to pregnancy, but pelvic masses posterior or fundal fibroids can trap portions of the uterus.

Endometriosis can create adhesions that can prevent the uterus from moving normally.

And uterine structural abnormalities are also associated with uterine incarceration.

What do we look for? One is difficulty finding the cervix because it's anterior and superiorly displaced relative to the trapped gravid, uterus or uterine segment.

There may be coexisting mullerian duct anomalies which may predispose or simulate incarceration and it may result in sacculation, which is functional malformation of the gravid uterus where there's a transitory pouch or sac in the posterior pelvis caused by the inverted uterine polarity.

Here the uterine wall can become thinned in its prone to rupture.

Conclusion

So in pitfalls and practical challenges and sonographic imaging of the uterus, I encourage you to try to recall the characteristic sonographic features of both the common and uncommon entities and don't be afraid to utilize three dimensional ultrasound and MRI to help you come to a more complete diagnosis to spare the patient any catastrophic outcomes.

Thank you for your attention.