Pitfalls in Gynecologic Ultrasound - SD

Pitfalls in Gynecologic Ultrasound

Hi, I'm Dr. Barbara Hertzberg. I'm from Duke University Medical Center where I'm a radiologist. I'm a professor of radiology and associate professor of obstetrics and gynecology.

Our presentation today is on pitfalls and gynecologic ultrasound. During the course of everyday practice, my colleagues and I have all too frequently encountered cases in which our feeling after initial scanning is, I've got it, I've got it. I know exactly what's going on here, only to learn much to our dismay that I got it wrong.

It can mean a lot of different things and yet it's precisely these types of cases that tend to be most instructive. So it's my hope that by sharing our misses and near misses with you, we can help prevent you from falling into the same traps.

What we'll do is spend most of our time talking about the pitfalls of specific gynecologic masses and we'll end by talking briefly about pitfalls related to the urinary tract and to endovaginal ultrasound.

The Dermoid

And we'll start by discussing the dermoid. Dermoids are common masses that frequently have very characteristic findings. For example, the finding of bright linear and intermixed punctate echogenicity within a mass that corresponds to hair is very characteristic as we see in these two dermoids.

Additionally, a complex mass that contains a highly echogenic focus that shadows corresponding to a tooth is another characteristic pattern of a dermoid. And finally, identification of a fat fluid level is also specific for a dermoid, however it is the dermoid plug a highly echogenic component of a mass that sometimes takes only a small portion of the mass, but other times can constitute the entire volume of the visualized mass. That typically tips us off to the possibility of a dermoid.

And here are some examples of a dermoid plug at transabdominal ultrasound and endovaginal ultrasound on the same patient. And you can see that the dermoid plug takes up a lot of the mass, but there is also a cystic component of the mass. Although the dermoid plug is what often tips us off to the presence of dermoid.

Unfortunately, it is also the etiology of most of the pitfalls related to over and under diagnosis of the dermoid. One of the main pitfalls, the most common is that a dermoid plug can be mistaken for a loop of bowel and if it's mistaken for a loop of bowel, the fact that there's a dermoid there may not be perceived at all.

Here are some representative examples. This patient was referred with a palpable left adnexal mass, but on the initial transabdominal imaging, no mass was seen because of the history of a palpable left adnexal mass. Additional scanning was performed and with that additional scanning you can see that there is actually an echogenic mass that attenuates sound located in the left adnexa.

And in going back to the initial images, in retrospect, the mass was likely located here but mistaken for bowel shadowing gas. In a similar example, patient referred with a palpable left adnexal mass, no mass seen on initial transabdominal imaging again because of the presence of a palpable mass. Additional scanning was subsequently performed and shows this echogenic rim with dropout of sound consistent with the dermoid and this dermoid had an additional cystic component shown here.

However, when you go back and look at the initial transabdominal scanning on this patient, the dermoid was nowhere to be found because it wasn't perceived specific images of it had not been obtained.

So in my experience, if an experienced examiner says there's a palpable pelvic mass and we do not identify the mass at ultrasound, usually the mass is present and we've missed the mass. And so we need to go back and look for the mass. And one of the most common scenarios in which this happens that there is a mass and we don't see it in ultrasound, is in the presence of a dermoid. With the dermoid having been mistaken for a loop of bowel.

And one thing that should be done is if the imaging had been done with endovaginal ultrasound, transabdominal ultrasound should be performed and vice versa, if the imaging had been done with transabdominal ultrasound, endovaginal ultrasound should be performed because sometimes one of these ultrasound approaches will visualize the mass when the other approach will not.

So here's an example in which transabdominal images of this patient with a palpable right adnexal mass did not visualize any mass. Therefore, endovaginal ultrasound was performed and shows an echogenic mass originating from the right ovary and you can see beak of ovarian tissue coming around the mass showing the mass's intraovarian.

The other thing that should be done when there's a palpable pelvic mass and no masses seen by ultrasound is to reexamine all the echogenic areas that with previously thought to represent bowel to see if one of these areas may perhaps represent an echogenic dermoid. Here's an example of how to do this.

On this image we have both echogenic bowel as well as an echogenic dermoid so that you can see the difference in within them. Here is the bowel. The bowel will elongate if one twists and turns on it because after all it is a continuous structure and the bowel will abruptly shadow, so that you won't see a lot of the leading edge of the bowel as we see here.

And often the shadowing will have a lot of artifact in it, so-called dirty shadowing due to the shadowing being from air. On the other hand, here is the dermoid and note that while there is a gradual attenuation of sound, it's much more gradual than with the loop of bowel. You can see much deeper into the dermoid mass and you don't have the dirty shadowing that we had with the loop of bowel.

Now just as dermoid plugs can be mistaken for bowel, so can bowel be overcalled and mistaken for a dermoid. And this can happen both in the setting of a normal pelvis and normal bowel as well as in the setting of bowel pathology.

Here's an example of a patient who proved to be normal. We had what looked like a complex mass within the ovary with both a cystic component as well as a solid component shown here, which would be a good candidate for a dermoid. However, when additional scanning was done, this area began to peristalse and therefore it could be confidently identified as just representing bowel.

This was normal bowel with the cystic area that had been seen earlier simply being a prominent follicle in a normal ovary. How about abnormal bowel? Well, this was a case in which we felt rather confident that we had the diagnosis. This patient presented with right lower quadrant pain and had a highly echogenic focus in the right adnexal region.

The echogenic focus seemed to be part of a larger mass, which was hypoechoic around the periphery of it. And the echogenic focus looked a lot like a dermoid plug, which is what we thought it was and we thought we had really found the diagnosis. Then when addition to our dermoid plug candidate, we found a highly echogenic focus with posterior shadowing that we thought might represent the calcification or the tooth within the dermoid.

However, this proved not to be the case. The patient went to the operating room and turned out to have appendicitis. Now how could this almost perfect example of a dermoid actually proved to be appendicitis? While the echogenic structure looked like it was a dermoid plug in the setting of appendicitis, the mesentery and the omentum and the tissues around the inflamed appendix become very inflamed as well and can be echogenic.

And then explaining what looked like it could be a calcification or a tooth in a dermoid, that echogenic focus corresponds to an appendicolith. Finally, a uterine mass can also be perceived as a dermoid, particularly if the uterine mass is echogenic. And this can happen in the setting of a variety of fatty uterine masses such as lipomas, myolipomas or as in this example here, a lipoleiomyoma.

Now in this particular case in which there's a highly echogenic mass in the uterus, one would not mistake the mass for a dermoid because it's clearly within the uterus, but just like fibroids can be exophytic and pedunculated, so can these fatty uterine masses.

So in this example of an echogenic mass that was thought to be located in the cul-de-sac, the mass's seen here on longitudinal image and here on transverse image and was thought to represent a dermoid but turned out at surgery to be an exophytic lipoma.

Now perhaps when one goes back you can see that there was kind of an interface with the uterus that might have retrospectively suggested the possibility this mass could have been arising from the uterus. But nevertheless that was not perceived at the time of the study when the diagnosis was not known.

Uterine Fibroids

With that, we'll shift focus now and talk more about uterine fibroids. Uterine fibroids are extremely common. They typically are hypoechoic, well-defined uterine masses as we see here, but not uncommonly. Fibroids can be exophytic as we see with this posterior fibroid and they can have areas of necrosis of calcification or be pedunculated.

And it's these latter findings that lead to many of the pitfalls in diagnosis of fibroids. So because fibroids can be exophytic, they can stick out into the region where one expects the adnexa to be and simulate adnexal pathology. Both of these examples are examples of how this can happen.

We have an exophytic fibroid here as well as an exophytic fibroid immediately adjacent to the uterus here. Both of which on initial scanning were thought to possibly represent adnexal masses. A pedunculated fibroid can mimic an extrauterine mass.

Here we have a big solid mass superior to the uterus, which it's not clear if it's originating from the uterus or not, but with further scanning a bridge of tissue that was very vascular consistent with a vascular pedicle could be seen and this was a pedunculated fibroid.

So because fibroids are so very common and often misinterpreted as representing other pelvic pathology, if one sees a solid pelvic mass, one should first think of a fibroid even if the mass appears to be adnexal. And then if one can find both ovaries, that makes a fibroid even more likely since the ovaries would've been one of the other main organs of origin for a solid pelvic mass.

Now we can misinterpret fibroids as other pathology not only because of them being exophytic or pedunculated but because of necrosis. This was an interesting example of a patient in the second trimester of pregnancy. You can see the fetal head here who had a huge complex cystic mass with solid areas of tissue within it and there was concern that she might have a very complicated ovarian mass.

However, fortunately it turned out that there had been a prior study done on the patient during the first trimester of pregnancy. You can see the embryonic crown rump length here and at that time the mass had an entirely different appearance. It was completely solid in appearance and had some areas of shadowing from it, and this mass was simply due to a fibroid that had infarcted and degenerated and become very necrotic.

Peripheral calcification is a not uncommon pattern of calcification of fibroids and when it's seen it has the potential to be mistaken for a fetal head. So here we have a rounded rim calcified structure that on first glance was thought to possibly represent a fetal head, but in the setting of a live pregnancy this is usually quite easy to resolve with further scanning, the normal appearing fetal head is seen and it's clear that this is a fibroid.

Where this can be potentially problematic though is in the patient who's had a recent miscarriage or an abortion and is referred to rule out retained products because as in this case the initial impression can be, oh my god, they left the fetal head. However, this is simply a rim calcified fibroid which is much, much more common than a retained fetal head following a miscarriage or an abortion.

In fact, until recently I thought the latter virtually never was seen. And then we saw this case, this is a patient who'd had an abortion and was referred to rule out retained products and you can see echogenic material in the uterus here as well as a rim calcified structure in the cervix.

On further assessment of the rim calcified structure, you can actually see that it has orbits as well. And in fact in this case they had left the fetal head, and the patient delivered the fetal head as well as additional products of conception shortly thereafter in the emergency room.

Other processes that can be mistaken for fibroids, not uncommonly include a retroflex uterus. The retroflex uterus is shown here. The posterior extension of the retroflex uterus looks like it could be a hypoechoic fibroid because its orientation is such that it makes it somewhat tricky to show the endometrial stripe, which is located parallel to the ultrasound beam.

But if one simply adjusts the transducer laterally and angles in trying to show the endometrial stripe, you can see that the stripe is continuous and this is simply a retroflex uterus. This is not uncommon. Here's another example.

We see the uterus in transverse and longitudinal projection here and then we see a hypoechoic structure posterior to it, which it's not at all clear on these initial images that this would be a fibroid and was initially thought to that this would be a retroflex uterus. And this was initially thought to represent a fibroid.

Now this pitfall only occurs at transabdominal ultrasound, because of how the, the endometrial stripe is oriented again relative to the ultrasound beam. And here we can see the endometrial stripe coming down into what was initially thought to be a fibroid and isn't, this is a retroflex uterus.

This can be confirmed with endovaginal ultrasound which will show in a retroflexed or a retroverted uterus that the uterus points to the right side of the image. An anteverted positioned uterus would point to the left side of the image.

Uterine Orientation

With that, I want to talk a little bit about uterine orientation. This is because usually if the uterus appears to be retroflexed or retro positioned at transabdominal ultrasound, it would be expected typically to also appear to be retroflexed or retro positioned at endovaginal ultrasound.

This usually but not always holds true though one way in which this can happen, that on one technique, one approach, it's the uterus is ante positioned and on the other approach it's retro positioned is due to different degrees of filling of the bladder.

Here you can see with this patient's bladder very full, the uterus is ever so slightly ante positioned on a different study performed the same year though the bladder was less full. We can see the bladder here and now you can see that the uterus is actually retroflexed and at endovaginal ultrasound on this patient, when the bladder was totally empty, again the uterus was retroflexed.

So the different degrees of bladder distension, if the uterus is relatively flexible, can cause the uterus to look either ante positioned on one study and retro positioned on the other study.

And it's not just degrees of bladder distension that can do this on an endovaginal ultrasound. The uterus can look both retroflexed as it does here and anteflexed as it does here during the course of a single examination. And this is thought to be due to transducer pressure in this particular patient.

The uterus was flopping into both positions multiple different times depending on how the transducer was oriented and presumably on how the pressure was affecting its orientation. But this is relatively uncommon In most cases, the uterus will stay one way either retro positioned or ante positioned throughout the study.

Another process that can be mistaken for a fibroid is shown here and includes uterine fusion variance. Here we have the uterus and the endometrial stripe. And off to the left side on this endovaginal image, we have a rounded solid structure that looks like it could be a fibroid.

However, with further imaging you can see there are endometrial stripes in both of these studies. Both of these structures because this is not a fibroid on the left but rather the patient has a didelphys uterus.

Now interestingly, once that was realized on the transverse scan planes and an attempt was made to show both uterus at endovaginal ultrasound, it turned out that the uterus on the right was ante positioned and the uterus on the left was retro positioned.

So because fibroids can mimic so many other things and be mimicked by so many other things, it's good to have useful to have some clues that can help one make positive diagnosis of a fibroid. And one of these clues is to see sharp shadows at regular intervals like we see here.

Sometimes shadows from fibroids are due to calcifications, but this particular pattern is not due to calcifications because as you can see these are not coming from echogenic lead points. Calcifications would have echogenic lead points.

In fact these are, this is another example of this shadowing pattern from a fibroid and the shadowing is thought to be due to refraction or phase cancellation at transition zones between different materials within the fibroid.

Now this shadowing pattern, the recurrent shadowing pattern is very typical of fibroids but it's not completely specific and probably the most common exception is to see this shadowing pattern in the setting of adenomyosis.

This is a patient who has the shadowing pattern but does not have a focal mass. Rather the pattern is diffuse, the abnormality in the uterus is diffuse and when you don't see the shadows coming from a focal mass, consider the possibility of adenomyosis.

Hemorrhagic Cysts

Next gynecologic mass we'll talk about is a hemorrhagic cyst, which is also a great mimicker. The typical appearance of a hemorrhagic cyst depends on how big the cyst is and how long it has been between the incident of hemorrhage and the time of imaging. And that's because the appearance of blood evolves with time.

Common appearances include an ovarian cystic lesion filled with low level echoes and lots of thin strands and or septations. Oftentimes the clot within the hemorrhagic ovarian cyst will be retracting from the cyst wall and the hemorrhagic cyst should have increased through transmission.

Here are some typical examples. Here is an example in which you have innumerable fine strands and septa within a hemorrhagic ovarian cyst. And here is an example of clot retracting from the cyst wall, giving you a concave margin with the fluid in the rest of the cyst.

Another common pattern would to be have a straight margin when this clot retracts from the cyst wall, one of the pitfalls is to mistake the blood clot within a hemorrhagic ovarian cyst for solid tissue.

Here is an example of one that was initially mistaken for a neoplastic process because of this solid appearing tissue within the cyst. This was also seen at endovaginal ultrasound. This is an old case. In more recent years this pattern of retracting clot has become more widely known and this mistake wouldn't be made because this is really characteristic for retracted clot.

Fortunately, this patient did not go to the or a follow-up ultrasound was performed and here you can see the hemorrhagic ovarian cyst is entirely gone and now there's a normal appearing right ovary with normal follicles six weeks later.

So as a general rule, if one sees an adnexal mass in a woman of menstrual age, I recommend one asks oneself the question, is a hemorrhagic cyst a significant possibility? If a hemorrhagic ovarian cyst is a significant possibility based on the ultrasound appearance of the mass and if the patient is stable, another step should be performed and that is to perform doppler to be sure there's no blood flow within the tissue within the cystic mass and if there's also no blood flow then a repeat ultrasound should be performed in approximately six weeks to assess if the hemorrhagic ovarian cyst resolves.

Here is an example of this. Here is a cystic lesion in the left adnexa with a lot of echoes, a lot of strands. You can see that at color doppler evaluation there is flow at the periphery of the cyst but not within the material within the cyst.

And sure enough, as a result we waited and re-scanned the patient six weeks later and you can see that the ovary looks normal in appearance. Six weeks later with normal appearing follicles the cyst has resolved.

One other potential problem though is to see flow that is at the periphery of the cyst and partial volume making it look like it's actually within the cyst. Hemorrhagic cysts and corpus luteums often have a rim of flow around the periphery.

And here you can see this rim of flow at the periphery has been projected into the region, the structure making it look like there's actually blood flow within it. However, here is the peripheral rim of blood flow and it's not just at the periphery here it is a spherical rim all the way around the lesion.

And so as you come out of the lesion you can show blood flow within it and that is shown here where on the cine clip you can see rim flow and then you can see flow that could be projected into the cyst.

So it's very important to have a good 3D feeling for where the flow is coming from. Another hemorrhagic cyst pitfall occurs when the cyst is imaged soon after the episode of bleeding because in this stage oftentimes the material within the hemorrhagic cyst is echogenic, the blood may be echogenic and echogenic ovarian lesion can be mistaken for a dermoid since dermoids often have that dermoid plug that is echogenic.

The example on the left was done many years ago. It was thought that this echogenic lesion which is coming from the ovary, you can see peripheral ovarian tissue here was a dermoid. The patient had surgery unfortunately and the diagnosis turned out to be a hemorrhagic ovarian cyst.

A more recent example of this is shown here highly echogenic mass originating from within the ovary which has follicles here. And this patient did not have surgery but had six week follow up ultrasound and the cyst had resolved because it was a hemorrhagic ovarian cyst.

Now there is a clue on each of the images that one might not be dealing with the dermoid and it's something to look for when a an echogenic mass is seen and that is the increase through transmission. You can see increased through transmission behind both of these masses.

That would not be typical of a dermoid plug. A dermoid plug would attenuate the sound. Yes, it is true that the cystic component of a dermoid could have increased through transmission, but that through transmission shouldn't be right posterior to the echogenic mass.

So if you have an echogenic mass, you're thinking dermoid but you see increased through transmission, you should take a step back and ask yourself the question, could this be a hemorrhagic ovarian cyst? And if the answer is yes to that question, a six week follow-up ultrasound should be performed.

Multicystic Masses

Another gynecologic mass that can cause some confusion is to see a multicystic mass. Here's an example of a big multicystic mass, with multiple septations within it. Usually these masses will be cystic ovarian neoplasms and so as expected this particular mass was a mucinous cyst adenocarcinoma.

However, multicystic adnexal masses can be simulated by other pelvic pathology in particular by dilated fallopian tubes that are tortuous as well as by vascular structures.

So here we have what looks to be a multicystic ovarian mass seen both on transabdominal ultrasound on this image and at endovaginal ultrasound here. However, when one looks at this at real time evaluation you can see that the components of the mass are tubular and connect up.

And this was not a multicystic ovarian mass but rather was a dilated hydrosalpinx. Vascular etiologies can also simulate cystic masses in the pelvis. It looks like there's two large cystic structures within this pelvis, but color doppler shows that these are simply large pelvic varices.

This next case was another interesting example of the phenomenon of a vascular mass or a vascular structure simulating a multicystic ovarian mass. This lesion here was thought initially to be a lesion in the ovary and you can see it's already being measured.

However, when you look in different scan planes in addition to the cystic component, you see this elongated unusually appearing structure that looks almost like a fetal spine at gray scale ultrasound but this patient's not pregnant so this can't be the fetal spine.

When once puts color on the cystic component, it fills completely with color doppler indicating its vascular. And then when one scans the structure that looked like a linear fetal spine, you can see it's actually a vascular structure with blood flow within it.

And then when you sample from the interface between the cystic area and this vascular structure, you can see that you get to and fro flow just like you might see with a in the neck of a pseudoaneurysm elsewhere in the body. For example, in the groin s/p cardiac catheterization and in fact this is a pseudoaneurysm.

The linear structure is a bypass graft and this is a pseudoaneurysm originating from the bypass graft. Fortunately color doppler had been performed.

More commonly though is to image some adnexal blood vessels that are slightly prominent in cross section making them look like follicles. And so for a while it was thought at gray scale that this might be the ovary, but it turns out that this was the ovary here nicely shown by using color doppler where we see the blood vessels here and we see the ovary here.

So it's important to put color doppler on any abnormal cystic structure that you don't expect to see anywhere in the body. The one time somebody forgets to do this is by Murphy's law gonna be the one time that it turns out to be a vascular structure.

Urinary Tract Pitfalls

Now we'll move on and talk about the urinary tract at transabdominal ultrasound often done with a full bladder I was taught when I was a resident. Rule number one is to identify the bladder and that is shown here.

I thought that seemed pretty self obvious. Of course you identify the bladder, it's always the cystic structure that is in the superficial aspect of the scan plane anterior to the uterus. However it turns out it's actually really important to be sure that that cystic structure is the bladder because other things can sit there.

So notice that the bladder's typical shape, unless it's extremely over distended, is not completely round rather it's often somewhat teardrop shaped or as in this case somewhat pear shaped. And this is because although subtle the uterus will typically have an impression on the posterior wall of the bladder, not the other way around.

The bladder is more impressible than the uterus itself. And you can see that subtle posterior impression on the bladder at the level of the yellow arrow. Now this is important because some ovarian neoplasms are predominantly cystic and so you may not see any material within these ovarian neoplasms.

They may look just like rounded fluid filled structures and moreover the ovary is mobile and it can interpose itself between the anterior portion of the uterus and the abdominal wall. And so this was initially thought to be the bladder.

However, if you look carefully, the uterus is not impressing on the posterior wall of this structure. Rather it seems like the structure is pushing on the uterus. Now fortunately before this was permanently assumed to be the bladder, the bladder started to fill.

And so at that point in time it became very clear to the person doing the scan that the structure we were seeing was not the bladder what was actually a cystic mass located anterior to the uterus. And this proved to be a large serous cystadenoma.

In a similar example, we have a structure that was initially thought to be the bladder here, no posterior impression of the uterus on the bladder. And at a different time in the study though the patient's bladder actually filled and now you can see the bladder here you can see the expected posterior indentation of the uterus on the bladder.

And where did the mass go? The mass went up here, the bladder pushed it out of the pelvis and you can just see the leading edge of this mass on the transabdominal image with the bladder full.

So when the question comes up of is this really the bladder or not, it's important to either fill the bladder or empty the bladder to be sure you have definitive identification of the bladder in this patient. And a vaginal ultrasound was also performed and although no internal material was seen at transabdominal ultrasound, multiple septations were seen at endovaginal ultrasound.

And this, this mass also proved to be a serous cystadenoma, which seems to be the most common mass to do this simulation of the bladder. Other masses I've seen this with have been very large corpus luteal cysts as well as dermoids that are very uncomplicated in appearance.

Pitfalls also arise from the ureter. When we see a tubular structure in the pelvis and we're doing a gynecologic ultrasound, often the first things we think about are a hydrosalpinx or a dilated blood vessel. But another possibility is a dilated ureter.

This particular structure here, which was seen in the left pelvis, was initially thought to be a left hydrosalpinx. However, with further imaging at real-time evaluation you can see that the structure is actually peristalsing peristalsis is not typical of a hydrosalpinx and would bring up the possibility of either a dilated distal ureter or a loop of bowel.

And so by following the structure, one can decide whether or not it's ureter or a bowel. The ureter is going to rise out of the pelvis, eventually go towards the kidney. Bowel will have a more tortuous appearance if you scan it long enough.

And sure enough, when one scanned up in the flanks, there's pelvicaliectasis on in this left kidney. The patient has both a dilated upper collecting system as well as a dilated distal ureter, but the right kidney has no pelvicaliectasis.

So clues to ureter versus hydrosalpinx include peristalsis of the ureter, and a hydrosalpinx often has partial septations due to mucosal folds. Here is an example of the partial septations in one patient and these can be all the way around the periphery of a hydrosalpinx giving you a so-called cog wheel appearance as we see here.

Endovaginal Ultrasound Pitfalls

We will finish by talking about pitfalls that are specific to endovaginal ultrasound. Now clearly if you could only do one ultrasound approach, one would want to do endovaginal ultrasound. The detail it provides allows us to be so much more confident and so much more specific with our diagnoses.

But unfortunately endovaginal ultrasound is not without its limitations. One of the limitations is actually an easy one to get over, so long as one understands it. And that's that image orientation is altered when you compare it with transabdominal ultrasound.

So while a fluid fluid level is going to be seen horizontally at transabdominal ultrasound as we see with the material layering out in this, multiloculated endometrioma at, and this is a transabdominal image at endovaginal ultrasound, you can see that the fluid, fluid level will be either at a more vertical or a more diagonal orientation, sometimes causing people to not perceive the presence of the fluid fluid level.

But more important as a pitfall is that endovaginal ultrasound only provides a limited field of view and as a result it's possible to miss pathology high in the pelvis because it's beyond the field of view of the endovaginal probe.

It's also possible to incomplete image a large mass. And if you don't image the margins of mass, it's possible to not even perceive the mass exists. Here are some examples.

Here we have an endovaginal image of the uterus and no mass is seen on this image and no mass was seen during the entire endovaginal scan. However, the transabdominal ultrasound shows a very large mass superior to the uterus with the uterus being here and the urinary bladder being here.

In fact, this mass is so large that it measures 12.7 centimeters and yet it could not be imaged at all by endovaginal ultrasound 'cause it was beyond the field of view.

Here's another example of a mass that was only seen at transabdominal ultrasound and not endovaginal ultrasound. A relatively normal appearance of the uterus at endovaginal ultrasound, but a transabdominal ultrasound. There's a huge mass located immediately superior to the uterus.

And this mass can be best imaged by scanning through the abdominal wall 'cause it extends all the way up to the umbilicus where you can see that it is a solid mass and it has shadows and it's characteristic of a large fundal fibroid. But this fundal fibroid would've been totally missed by endovaginal ultrasound alone.

How about in completely imaging the margins of a large mass? This patient was scanned first at endovaginal ultrasound and the initial impression of the person doing the scan was things weren't working 'cause they could not see anything.

Well, when transabdominal ultrasound was performed, it became clear why specific structures could not be seen. That's because this patient has a large dermoid and the dermoid and endovaginal ultrasound was much larger than the field of view, so you couldn't see its margins and it also was attenuating the sound and as a result the dermoid could not be perceived.

So earlier in the lecture we saw an example of a dermoid that could only be seen at endovaginal ultrasound. And now we've come full circle and now we see an example of a dermoid that can only be seen at transabdominal ultrasound.

Finally, here's another example of incompletely imaging, a large structure. Here's a normal looking endovaginal ultrasound of the uterus with a mass seen posterior to it. Because this, the leading edge of this mass was seen, the field of view was markedly increased, the depth was markedly increased and it was actually possible to see the entirety of this mass, which really wasn't a mass at all, but rather a pelvic kidney.

And so with that, I'd like to thank you for your attention today.