Controversies in Sonography: Placenta Accreta – Percreta - HD

Introduction

My name is Dr. Lena Poer, and I work at UCSF. Today, I will be talking to you controversies regarding morbidly adherent placenta. I spend my time between ultrasound and abdominal imaging and women's imaging as well. Particular placental imaging is one of my areas of great interest.

At this time, I have nothing to disclose, and when I was asked to talk about this topic, and the title of the plenary was controversies in Sonography, I was rather excited because I realized that there's a lot of controversies regarding the spectrum of morbidly adherent placenta accreta versus percreta and the spectrum of disease.

However, when I started to put the talk together, I realized that perhaps there's a little more controversy that I wanted to get into. And there's a little bit more to it than one can cover in 15 to 20 minutes. But we'll look at some of the issues.

There's even controversies regarding spelling and terminology, presentation and risk factors of those patients. And interestingly, even pathology and underlying mechanisms. And of course, as far as what really mostly relates to US controversies in imaging, and also then controversies in treatment.

Spelling and Terminology

So starting out with spelling and terminology, the term placenta accreta really comes is derived from a Latin term accreta, accreta creta, which means encased in or grow o overgrown with.

And first it was described or defined in 1937 by Irving and Herig as abnormal adherence of the afterbirth in whole or in parts to the underlying uterine wall.

And there are some controversy whether that time really that meant that there was a defect in the wall or that was just difficulties delivering the placenta.

So overall think that this is the definition means a defect individual sali and a chorionic villa will grow into the myometrium. However, there are some controversy regarding that as well. When we get to the pathology section, and when we look at those illustrations in anatomy books or on the internet or in articles, it seems so clear and clean and beautiful when you could just see the appearance of normal.

When it's accreta, the residual is gone, but the placental mass is not really invading into the myometrium. If you have in increta, it's invading into the myometrium. But when it invades all the way through the myometrium as well as the uterine cytes called percreta, and of course, there's some overlap or spectrum of disease.

However, most commonly we encounter, of course, accreta because it's some controversy in imaging as well as particularly in pathology. It's a little difficult to address this topic. And some people have come up with the term morbidly adherent placenta, which includes all three types.

And but some people don't like that term, some groups because perhaps this does not really have the correct terminology and also suggest that perhaps we should be talking about placental attachment disorder.

So that terminology really remains to be determined. What would be the common language for all of us. However, at this time, most important is that whatever terminology you use would be important that your surgeons and your pathologists are using the same terms at your institution.

Presentation and Risk Factors

So what about controversies regarding presentation and risk factors? We know it's iatrogenic really a 20th century disorder, and the numbers are really increasing up to one in 500 in large cohort studies.

The main risk factors we believe are due to patients getting increasing number of C-sections. And we know that with the increase of number of c-sections in the same patient, we also increase the risk of developing placental desat detachment disorder.

Also, it's related to anterior placenta, previous or low lying, or combination of both of those two. Also, there is relationship with previous uterine trauma, some sort of instrumentation ablation, even uterine artery embolization.

Also, interestingly, advanced maternal age high gravity parody and also underlying benign disease such as submucosal fibroids, ments, and other uterine anomalies, and even smoking and hypertension in patients.

So usually when those patients present, it's either they are asymptomatic and they're picked up incidentally, or they present with second trimester, third trimester vaginal bleeding.

There are some clinical laboratory abnormalities one can look at, and there has been some discussion about elevated alpha vita protein as well as beta a CG in second trimester. However, it's only helpful if they truly are elevated and they don't. And there are other conditions which are associated with that, and that this is sort of beyond the scope of our discussion today, but that's something to keep in mind.

Pathology and Underlying Mechanisms

What about the pathology and the underlying mechanisms? They're not well understood as we have stated before. We believe it's a either a primary defect in trophoblastic function versus a failure of normal decentralization or combination of both.

Defective digitalization is related usually to prior surgery or due to anatomic factors such as placenta being low over the endo cervix or lower urine segment. In cases of placenta previa, however, there are other theories such as excessive extra villous invasion or defective maternal vascular remodeling in the area of hysterectomy, scar and or focal abnormalities of oxygen tension deficient formation of placental SEPTA and so forth.

There's also some recent evidence which focuses on c-section scar pregnancy, as is believed to be a precursor to morbidly adherent placenta.

What are the experts say in pathology? It's really regarded as an orphan topic. The radiology pathology correlation is not well studied, and one of the main reasons is because in order to be absolutely sure that we are looking at the whole placenta in the invasion, you actually have to have a hysterectomy. And not all those patients actually will get a hysterectomy, especially for just dealing with mild attachment abnormalities.

Other limitations, the definition is not standardized across disciplines as well as within pathology itself. For instance, percreta could be defined as extra uterine trophoblast without extra uterine vili versus only with a presence of extra uterine vili.

It's very important that there should be, which is not at this point a standardized protocol for path sectioning and sampling of the specimen. For instance, in our institution, when every time a patient goes to surgery, we as radiologists send a note or talk to in person with a pathologist who will be receiving the specimen, what in our opinion would be the best way to sample this, whether axial or sagittal?

Also their scanned attention in pathology literature on nose unresolved issues.

Imaging Controversies

Let's move on to imaging. We all know that ultrasound is primary antenatal modality, and primarily we evaluate the fetus as well as the placenta in second or third trimester.

However, since there's this raising awareness that we could potentially pick up abnormalities of placenta earlier, and especially if it's related to C-section scar pregnancy, we could see abnormalities as early as 11 or 16 weeks.

We all know that all imaging, especially ultrasound as well as MRI really depends on operator experience, equipment and inter observer variability. There are a lot of signs, and we'll review them some, but there's some thoughts.

So what are all the signs? Is one sign enough and or is there one most sensitive or specific sign? And how many do we need to define the accurate diagnosis? Do we actually need a scoring system?

And it's sort of just as an amusement where there are a lot of scoring systems in other areas in radiology, such as for regarding prostate and liver, the rads and rads. Do we really need the scoring system such as placental rads?

Despite all these controversies, what is agreed upon on ultrasound on the gray scale, there is loss of placental homogeneity, inter placental launa, loss of hypoechoic retro placental space, reduced myometrial thickness to less than one millimeter bladder wall abnormalities, placental bulging into internal OSS or posterior bladder wall.

It's very important also to evaluate with a color. Doppler, we are looking for increased placental vascular flow, increased sub placental vascularity bladder, uterine cirr interface, hyper vascularity and particularly vessels crossing and bridging from placenta to the edge into the mucosa of urinary bladder.

So here's a case example of where you could really see the intra placental lacuna. You see the increased vascularity, and if you really squint your eyes, you could actually see that on this axial view here where I have drawn the line, you could see that there is loss of focal loss of retro placental clear space, and you could actually see the echogenic mass of placenta almost invading into the wall or fo invading into the wall of myometrium.

And also notice the engorged bladder wall vascularity. Now when you look at this case, and when I, we did in our institution, we suggested that there has to be at least some element of in increta, and we don't see any obvious bladder wall invasion or placental mass invading into the bladder. So there is likely no percreta, however, would be fairly impossible to tell on all imaging, whether the, there is a little bit of adherence of the uterine serosal surface to the bladder cirr.

So the pathology one, they got their sectioning, which was done in axial plane in this case, they said that there was presence of accreta chorionic vii, where beyond and into the myometrium and they were, the distance was 0.06 centimeters from uterine serosa.

Now this is a very fine line and I think this is sort of beyond the resolution of imaging and this time. So I think even knowing this, it would be fairly impossible still in retrospective even to tell based on this case and knowing that there was some distance between this bladder cirr rosa that, you know, is it really through or is it just, does it just stop at the level of the bladder cirr rosa?

But we have to kind of look at the big picture and not to get stuck on the minute details because we, once we know that there's a at least in increta, we should describe that and communicate to the clinical team, but also let them know that we have these are our limitations. We are not able to a hundred percent tell you that once they open up and go in and try to do the C-section, repeat C-section, that they might not find adherence of placenta or score down to the urinary bladder. That's all possible and they should be in fact prepared for that.

So since we've been doing ultrasound for a long time and looking at all these different signs for possible morbidly adherent placenta, lots of studies have been perform, but they usually most of those studies are all retrospective and this is a multi this is a meta-analysis looking at the sensitivity and specificity of ultrasound overall as well as all the signs.

And again, because of the time constraints, we're not able to dissect all the different numbers here. However, if you look at the sensitivity and specificity, we see that ultrasound is doing pretty good. However, you have to remember that likely all those studies had these limitations of having the limited devaluation of the histology and pathology because there likely were no standardized reporting in most of those cases.

So ultrasound, we know ultrasound is a first study. We talked a little bit about when, but I just wanted to reemphasize that it evidence of accreta if whether we have the clinical history or not should be sort of the signs or should be in the back of our minds to evaluate for it in the even in the first trimester and also during the anti screening because it can be seen in the first trimester.

So usually however the women and risk at risk are screened during first anatomy scan and then serial follow up starting at 28 weeks to plan the best treatment.

MRI in Imaging

Now we're getting to the next big controversy regarding this topic that is MRI. Should we get an MRI and why?

So when is MRI indicated usually when ultrasound is ecal, but more and more, at least in our institution and many study other places out there are using MRI for surgical approach planning because in a lot of the cases, the main question really is, is it going to be a hysterectomy or is it going to be a uterus sparing surgery?

And even if it is going to be a hysterectomy, they wanna be prepared of the blood loss and who else needs to be present during the surgery. The knowledge of precise topography on an MRI is superior than ultrasound and increasingly the surgeons would like to know whether the placenta is involving or the invasion is most significant in the superior aspect of the inferior aspect of low uterine segment.

And this significantly can alter the surgical approach. There might be need for al stenting, vascular clamping or embolization all depends on the this resources and surgical expertise available in a particular institution.

Also, there are studies out there which have demonstrated that MR shows better to is better to assess the depth of invasion in reclassifying the extent of invasiveness. And it's reported to be up to 30% of patients.

However, I personally don't feel that this is the case in our institution and ultrasound as well as MRI really should be used together as complimentary modalities, not one versus the other.

So what are the signs and imaging what we can actually agree upon regarding MRI? So all these findings are quite similar to what we are assessing On the ultrasound. There might be just called slightly different.

We're looking for the inter placental T two dark bands, which likely correlate to the placental lacuna, abnormal inter placental vascularity, heterogeneous signal, focal myometrial interruption and loss of retro placental clear space, lower ute segment, bulging and bulging of placenta into internal OS and tenting of the urinary bladder.

All of these signs should not be interpreted in isolation and like with the ultrasound as well, this has actually been more documented with in MR literature that observation of one of these signs is likely to lead to detection of other signs also, which I found quite interesting.

However, it's sort of stating the obvious is that readers with greater than five years of experience in abdominal MRI demonstrated greater diagnostic accuracy and inter observer agreement. And that kind of makes sense that it is sort one of those areas that every time you see a case and then you follow up the pathology, you learn from it.

So the more you do and see those cases, the better you get. Also, it's very important to emphasize standardized reporting and that would be for both MRI and MRI and ultrasound.

So when we are looking at those imaging studies that we have a list of findings in our report and we kind of just check off is it present, not present and all of them, this is sort of to help us all to follow the algorithm and look at everything what we're supposed to. And also this helps to retrospectively and prospectively go forward and look at the signs, evaluate the signs independently and study the cases what we have done or will be doing in the future.

There are some meta analysis out there who are actually looked at MRI versus ultrasound. And again, I'd like to emphasize that I really wouldn't wanna refer to those two modalities as one versus the other. It's more so one in combination with the other.

And you notice that the sensitivity and specificity, it is really fairly similar for both of those. And it sort of kind of goes along the lines like in many other parts of the body or specifically since I do a lot of women's imaging and the adnexal imaging, you really don't wanna say ultrasound versus MRI, which one is better, it's more so if I see something with ultrasound, can I further evaluate this with MRI rather than using just one or the other modality against each other.

So here's a case which illustrates why MRI could be helpful. This is the same patient which I showed you an ultrasound image earlier. So there's an anterior placenta, there is pre, and you could see normal myometrium in the upper aspect of the uterus. And we are losing the retro placental clear space, quite a long segment anteriorly.

And that was pretty clear on the ultrasound as well as we confirmed it with the MRI and we didn't really add any extra information on the sagal planes. However, look at the imaging on the axial planes and you could see this is normal myometrium and there is complete lack of any myometrium noted laterally and posteriorly.

And that would be a very important information to convey to the clinical, the surgical team to be prepared. If they're dissecting down, putting clamps in there, they could very easily, very soon cut into the placenta there. Might not be even cirr overlying at that point. So be very careful and pre-prepared and that's really most importantly what they wanna know. What should they be prepared for?

And this is the same case in pathology. They did axial lysis and they reported that in the inferior left uterine segment there is near a hundred percent through invasion. And there was also some interruption of the specimen surface and it was very important that the pathologist actually had to call back, talk to the clinical team immediately and ask them was there through, through and through invasion or was there an artificial or iatrogenic interruption, which it was in this case.

So this ca and again, this case illustrates how important it is to communicate between all different specialties and make sure that this wound not be called in isolation as you know, a true interruption due to a placenta.

So when we do decide to get the MRI, when should we do it? There are always some controversy regarding those cases when they come through, you know, is it too early, is it too late? Should we follow it up?

And there are some studies out there, and I do believe that actually looking and from the experience what we've had at UCSF, that it would be better to get the MRI between 20 28 to 30 weeks. And the literature said that says that if MRIs done before 24 weeks, it really has unacceptable accuracy, sensitivity, positive predictive value and so forth.

But it basically applies if it's negative. But if it is positive already at 24 weeks, you clearly just have to keep in mind that perhaps it's only gonna be worse. So depends on what purposes you actually will be using that. MRI Also, it's important to be careful when the M MRI is done later and perhaps the patient was not sent to you as a referral earlier and so you don't have the ability to look, you know, get the MRI earlier.

So you have to remember that, you know, the thinning, the physiologic thinning of the myometrium is really the greatest after 35 or around 35 weeks. So it might be quite difficult to tell is it true loss of retro placental clear space or is it actually the physiologic thinning? I find those cases most frustrating and most difficult.

And obviously you have to look at each case individually that and there are exceptions to the room.

So here's a case when the patient was going through an abortion and it was noted during the ultrasound that there's increased vascularity denoted anteriorly, and it was highly suspicious that perhaps there are some early morbidly adhere placenta already developing.

And just to confirm, because of course this patient could have, could not have had a DNC for this evacuation and had to actually have a hysterectomy. And since we're committing this patient to a hysterectomy, we wanted to have proof and confirmation and that's truly in her best interest.

And so as you can see on those SAG T two and post contrast images that really we confirmed that there's high suspicion for at least in Increta, and again, this patient had a hysterectomy and had definitely near a hundred percent invasion of the myometrium, but fortunately not through the wall and not into the urinary bladder. So not a true perret.

Treatment Controversies

So what are the other controversies and what and we need to know about it as imaging because that's very important. How we time and how we do give the advice to those clinical teams. And that is what is the timing of delivery And usually it's 34 to 35 weeks and where it comes from is the balance between fetal maturation and occurrence of unexpected maternal bleeding.

But it's unfortunately not objectively established in randomly controlled trials. However, this is sort of the scan standard of care at this point. The general rule really is that it's better to have a scheduled C-section in a controlled setting with some degree of fetal immaturity than an opposite situation.

So what about the surgical approaches? There are also no randomized controlled trials comparing different tragedies published at this time. Is it hysterectomy versus uterus sparing treatment? And it really depends on several factors, experience team specific surgical skills and of course hospital resources.

And why is it such a big deal? Is because really this can be a life threatening to mother and the fetus. And we have been going to the operating room in some of our cases to guide the hyster otomy incision to avoid cutting into the placenta.

And you know, we're as images don't get to go to the operating room as often and there's some excitement to being at the in the operating room during the time of the delivery. However, there's also an element of tension because things can go down and if they go downhill, they go downhill really fast.

And you think that, you know, morbidity from childbirth does not exist in 20th century, but I have to all remember that it actually does and it can be quite scary.

Conclusion

So to conclude, we reviewed some of the controversies and I'd like to say, so what did we learn or what we have learned from the data available at this point is that the key is to recognize those patients with risk factors and symptoms early, then have a good timing for the delivery optimally at 34 to 35 weeks in a control setting.

And it's essential to communicate to your team the depth and extension because it significantly depends on the delivery plan, whether they are actually going to do a hysterectomy, see his cesarean hysterectomy, or there is going to be a fertility or uterine sparing surgery.

We have learned that ultrasound is the best overall first modality with sensitivity and specificity. Pretty good. And what that tells us is if you really, if you have a negative ultrasound, there is no role or need for MRI to evaluate for possible appearance of morbid adherent placenta ultrasound and MRI should be used as complementary modalities.

MRI really can tell us better the topography and extent of invasion, but usually sort of the rule of thumb is that it's more accurate after 24 weeks. But of course, as I showed you, there are exceptions and you really have to look at it case by case basis.

Improved results are with experience, more experienced readers and it's important to each time, those of you who will be starting and looking at those cases more and more to each time when you make the diagnosis, try to go back and look at the pathology report and try to see if you were correct and it, if it was the area where you suggested that there could be perhaps an invasion, did it really correlate with a pathology findings?

And what is the standardized protocol in imaging as well as pathology in at your institution? The key is really the collaborative approach of radiology surgeons and pathologists. And to keep in mind that we need to standardize the terminology and pathologic and surgical management, all of this really shows great research opportunities for more perspective studies with detailed evaluation of the depth of abnormal placentation at delivery to better evaluate the accuracy of ultrasound MRI signs not only in screening for morbidly adherent placenta, but also in differentiating between the different degrees in summary.

And then finally, I'd like to show what we currently do at UCSF. We have a multidisciplinary abnormal center service. And so if patient is referred to us, email blast is sent to multidisciplinary team members at that time.

Then dedicated ultrasound and MRI, most of our patients will get both modalities will be obtained and then thereafter there's patient consultation and plan for delivery date and team as and then from plan for surveillance. And as far as imagers, then ultrasound obviously will be following the growth of the baby as well.

And then depending on the severity of process after the first step imaging whether the patient may or may not need a follow-up MRI prior to delivery and most of our severe cases. We also will also will provide intraoperative ultrasound and not more so to evaluate the placenta, but more to guide our clinical team not to cut into the placenta during the cesarean hysterectomy cases.

So here's one of our cases, patient presented at 24 weeks very heterogeneous placenta focal bulging into the lower uterine segment, increased retro placental vascularity and decreased clear space but also noticed on an MRI that it was not only anterior but also right lateral and posterior.

And so this case, this is an intraoperative ultrasound where we demonstrated that you could clearly see the normal myometrium and then we saw no myometrium, retro placent, only the placenta, but that was not sort of the point because we already knew the diagnosis of course prior to the delivery.

But this was more to demonstrate that where is the edge of the placenta and superior to that would be safe to do the delivery incision. And this patient had invasion of the placenta, which was within 0.1 centimeters of the uterine cirr.

And looking at all these imaging and even looking at this intraoperative ultrasound, that would be very very difficult to tell or see that one millimeter of the uterine ci, which is still covering the uterus.

So this was a sort of a brief overview of the controversies regarding placenta accreta to percreta spectrum. Would you wanna call it a morbidly adherent placenta or placental attachment disorders? Really whatever your clinical institution and or your practice is most familiar with.

And hopefully this will give you some idea of our current concepts and areas where further investigation and research is needed. Thank you very much.