Retained Products of Conception - HD

Retained Products of Conception

I'm really glad that I get to give this talk because this is something that drives a lot of people crazy. Not just radiologists, but the gynecologists and obstetricians as well. I get to do how I do it, which might not be how you and your group have decided to do it, but I hope I'm gonna leave you with a few pearls that you can go back to discuss with your referring clinicians.

I have no disclosures pertinent to this presentation.

What I'm going to hopefully answer today is how we assess why there might be pain or bleeding postpartum. A discussion of how you should deal with the obstetrician who says, well, I was in there during that C-section. There's no way there's stu placenta. If there's lots of flow, how to figure out if it's an RPOC or a VM, and hopefully I'll convince you to get rid of that term a VM when you're dealing postpartum. The myometrium is thin in a patient with retained products. How do you tell if it's an accreta or how do you assess if it's an invasive mole?

Scanning Techniques for Retained Products

Frequently we start out with a transabdominal scan. Now if patients have a C-section, they might have a big dressing on their abdomen. And since you're going to probably go to transvaginal anyway, there's no reason to remove that dressing. But we do take images transabdominally just to make sure we're not missing anything large.

You can frequently see heterogeneous contents within the endometrial cavity. The question is, is this blood products or is it retained products?

When you do a vaginal scan, this is a retroflex uterus. You can see there's heterogeneous material here, we turn on color and you can actually see some of the flow going into this placental tissue. Clearly it's placental tissue, you're going to measure it. The measurement it turns out is very important because at least in my institution, if it's less than four centimeters, they might try and do medical therapy, try and make the blood vessels decrease, and hopefully the patient will pass it on her own. If it's four centimeters or greater, they're definitely going to go in and do a DNC.

We look for a mass in the endometrial cavity. If there's flow, we know it's retained products. If there's no flow, then it could be devascularized retained products or blood clot. But when you see something that looks like placenta, it has placental type calcifications, you can say that it's retained products.

Identifying Small Areas of Retained Products

What about when there's something small like this? If you look at the endometrial echo in the mid uterine cavity, and it is within the endometrium itself, that must be retained products. That's not blood clot. Blood clot is going to extend the endometrial cavity. It won't be just on one side like this.

I know, maybe she had a polyp before she got pregnant, but since she's recently been pregnant, it's likely retained products. Here's another patient with a small area with a small bit of blood flow here. Even though it's just a small area here, it can be very confident that it's most likely retained products.

The reason we wanna be very careful about that is that if they decide to go in and do a DNC, you could end up with a complication like this where they've actually ruptured her uterus and so frequently, they'll go in and they'll do this blind DNC and they'll scrape really hard and frequently, they'll end up doing this. We don't want them to do a DNC procedure when it's just a small area of blood products.

Size does matter. If you have this tiny bit of blood flow here and you don't really see much at all, you can just measure this area with abnormal blood flow within the endometrium. Most likely this is a patient who's going to do very well with tincture of time with or without some kind of medical therapy.

Small areas of retained products can be treated with medications. Usually at my institution they use misoprostol. Larger areas like this we're going to measure in three dimensions. Again, that measurement will help them decide how to go after that material.

The other thing you wanna do is look at the endometrial myometrial interface because you expect placenta to extend beyond the endometrial cavity a little bit. Here we can see this is some calcified material within the endometrial cavity extending into the myometrium. But the further it extends into the myometrium, the more likely it is that you're going to suggest that there's placenta accreta.

Here you can see the myometrium is very thin and this would not be a normal placenta, this is an invasive placenta, whether it's accreta or an accreta, we don't really care. But this is a patient who probably will not do well with the DNC because if they try and scrape this and get the whole thing out, you know, they're gonna rupture the uterus. There's no way they can get this otherwise.

Causes of Postpartum Bleeding

Causes of postpartum bleeding when a patient comes in and bleeding postpartum, it really matters how long ago was the delivery? Because you might have fluid and debris as a normal finding postpartum in the first 24 hours, uterine at knee can be a cause of bleeding. I'm gonna discuss more the sub evolution of the placental site. But it's an important thing to keep in your mind as a cause of bleeding end metritis. Usually the patient will have pain and discharge, maybe have a fever and then retain products.

Retained products is abnormal. The patients will typically present with abnormal bleeding, postpartum pain and they may or may not have a fever. Part of the problem with retained products is that it can coexist with endometritis and that's why the fever might be present.

Retained products occurs when there's placental or trophoblastic tissue in the uterus after delivery or miscarriage. It's actually most frequently after a first or second trimester delivery or termination of the pregnancy. If you think about that, it's because normally, the uterus is made to deliver the placenta after delivery in the third trimester. But in the second trimester, the placenta is still very invasive at that point in time and it hasn't let go yet. That's why you'll frequently end up with retained products after a term delivery.

It makes sense that retained products would be more common after a vaginally delivery than after cesarean, but of course you can get retained products after a C-section.

Incidence and Risk Factors

Here's a study looking at 176 women with sonographic findings of retained products. When they looked at the history, 54% had had spontaneous abortions, 20% vaginal delivery, 18% elective terminations, and 6% C-section. You can see 6%, that's a pretty high number for C-sections.

Retained products in a cesarean patient. In my experience, most likely these have an evidence of an invasive placenta. You should definitely think about that because again, they've been in there, they've had the patient open. Why would some of the placental tissue still be there? Most likely because it's abnormally adherent.

You're gonna see this very thin myometrium around the area of placenta. You definitely wanna look for placenta accreta there and there's no reason to do an mr. We can make that diagnosis just fine with ultrasound.

First Trimester Retained Products

What about first trimester retained products? You know, we think about that as a incomplete abortion. For example, some people will use the term incomplete abortion. Some people will say retained products.

Here's a study looking at 104 women who had a medical abortion at six to nine weeks. 55% had sonographic evidence retained products at two weeks post medical treatment and most resolved without any further therapy. The symptoms weren't correlated with sonographic findings.

Basically it takes a while for first trimester miscarriage to resolve. Using retained products in the first trimester situation is different than we use that term after a second or third trimester delivery.

Term Retained Products

Term retained products, it's thought to occur in about 1% of term pregnancies. The main risk factors are failure to progress during delivery. Placenta accreta in an instrument delivery.

Severe Secondary Postpartum Hemorrhage

I also wanna take a minute to talk about severe secondary postpartum hemorrhage. This is when a patient has already delivered and then she presents later with bleeding. 24 hours to six weeks postpartum delivery after 22 weeks. That's the definition.

In this particular study, they looked at a big cohort of women over nine year period and they found the incidence of secondary postpartum hemorrhage of 0.23%, 60 out of 26,000 deliveries, placental retention. Retained products was the cause in 30% of those, this sub evolution of the placental bed, again, I'm gonna get to that in a minute, happened in 13% and endometritis in 10%.

Keep this in mind when people come back with postpartum bleeding.

Subinvolution of the Placental Site

What is sub evolution of the placental site? I mentioned that the adherence to the uterus is different in the second trimester than in the third trimester. What the placenta needs to do is to invade the myometrium. That's how it gets the vascularity to the fetus. That's how it is able to deliver oxygen in other nutrients.

You see hypo coic tortuous vessels along the inner third of the myometrium without any tissue in the endometrial cavity. This is what a lot of people end up calling an A VM because they don't see a mass in the endometrial cavity. An A VM, I'd like you to think of that as something that the patient has congenitally. This is something that's normal, it's physiologic, but it's persistent.

We just need to have another term for it so that people understand that it can resolve on its own.

Pulse wave doppler sonography can show increased peak systolic velocity with a low velocity wave form. The increased areas of vascularity correlate with placental implantation site documented pre-delivery.

Management of Retained Products

Moving on now to the management, we can do expectant management. That's where you might just give onic agents such as the misoprostol that I mentioned before, or methyl orgon, they can do the surgical management with the DNC or vacuum aspiration. Some people are now more frequently using hysteroscopic removal because that can be associated with fewer adhesions post intervention.

We wanna reserve interventional radiology with uterine artery embolization for those cases that are very hypervascular, that we suspect have early draining veins or those who have severe bleeding.

Predictors of Clinical Management

Here's a study by AYA Kamaya in abdominal imaging last year looking at predictors of clinical management of retained products, and looking at expectant versus medical versus surgical management. They found that when they saw high flow and they just graded their flow qualitatively, that surgery was likely and when they saw low or no flow, that expectant or medical management was more likely. This of course makes sense.

One of the questions that we ask when we see retained products, as I mentioned before, is how large is it three dimensions, quantifying size can affect management, does it have flow? If it has flow, would you call it hypervascular or not?

One of the things that's not clear in the literature is whether you should perform peak systolic velocity, whether you should actually quantify the blood flow. I would like to have an argument for saying yes. Now we can't necessarily angle correct, but we can still get a lot of information from looking at that wave form.

Why Retained Products May Be Hypervascular

Why might retained products be hypervascular and mimic an A VM? It's because of the persistence of those vascular changes in the spiral arteries that are induced by the trophoblastic invasion during pregnancy. You get shunting from the development of AV fistulas within the placenta that are caused by necrosis of the Chorionic vii.

Another problem that you can have is that prior DNC can actually lead to some of these AV communications in the myometrium.

Here's a drawing from the NCBI website showing in early pregnancy the spiral arteries by the end of the first trimester showing how they might grow and by the third trimester, how very large these are. It makes sense that if you just lop off the placenta here, that you might have some abnormal bleeding. We need this for the placental circulation.

When to Mention Subinvolution

When should you mention sub evolution of the placental site? If you see this abnormal vascularity in the myometrium and you don't see a mass in the endometrial cavity, it's really important to mention this because this can be treated medically.

What we need to know is that some abnormal flow, what we might think about as abnormal flow in the myometrium is actually a normal postpartum finding.

In this series of 385 patients who had their first week six weeks study after pregnancy, 8.3% had advanced enhanced vascularity by color doppler in another series of 93 patients. They saw 50% of patients had abnormal vascularity at day three, and that went down to 3% at six weeks postpartum.

Very common to see a lot of vascularity in the myometrium in this study, highly vascularized retained products. They found that if a peak systolic velocity was greater than 60, it was associated with blood loss and procedure related complications. But when they actually did the statistical correlation, they couldn't find that.

This is very problematic because this paper has been misquoted to say that highly vascularized retain products doesn't make a difference. They started out with highly vascularized retain products and then they looked at variations in that and didn't see a difference. But if you look at all retained products, you're gonna see more of a spectrum.

Here is a patient you can see great big vessel in the myometrium, lots of blood flow, at least it looks like lots of blood flow. If you don't look at a scale here, you might think that's a lot of blood flow. But then when you actually look at a scale, you've got a peak systolic velocity that's actually pretty low. This is somebody who's going to do well with A DNC.

Just looking at the color qualitatively, I'm afraid, doesn't work that well. Here's another patient. This looks very similar, great big vessel. Here we've got a peak systolic velocity that's very high, greater than 80. In fact, when we look at this particular patient, we've got a peak systolic velocity of 190, which is really huge, but it's only a small vessel here. We're able to qualify that and this was able to be removed hysteroscopically without a problem.

Placenta Accreta and Invasive Trophoblastic Disease

I've got one minute left to talk about placenta accreta, and I already mentioned the thin myometrium. That's when you're going to mention it.

When do you suggest invasive trophoblastic disease or molar pregnancy? Basically, we're not very good at this. It's a patient who has a bizarre appearance to the retained products with a persistently elevated beta HCG. You can see this looks very heterogeneous after A DNC with lots of abnormal blood flow.

Invasive mole is of course the most common type of persistent trophoblastic neoplasia. We usually see this incidentally after A DNC, another case, and one more case, very heterogeneous, very abnormal appearing, and very vascular.

Role of Advanced Imaging

When do you need a CT or mr. Basically never. I'm not showing you any CT or mr. I am showing you one angiography where we had high peak systolic velocity. You can see this early draining vein. These are the patients that might benefit from embolization prior to treatment.

Key Takeaways

Basically in the first half of pregnancy, elevated risk for retained products, but it can also occur after term delivery and C-section. If it looks like placenta, it probably is placenta color. Doppler flow increases the likelihood of retained products, but the absence of flow does not exclude this diagnosis.

High peak systolic velocity is associated with bleeding at the time of DNC. Don't forget to assess with spectral doppler, and please avoid the term a VM, but mention retained products with high peak systolic velocity that might benefit from uterine artery embolization.

Thank you very much.