[Music] hello my name is Dr Mary fredes I'm the assistant director of ultrasound at Brigman Women's Hospital in Boston Massachusetts and I'm going to be speaking today on mistakes to avoid in the second and third trimester particularly looking at fetal anatomy and measurements so we're going to begin by looking at measurements of the fetus and it's important when you are measuring a fetus in the second and third trimester to know the rules and there are rules to follow for measurements of the head measurements of the abdomen and measurements of the femur once you know the rules you have to follow the rules remember that in the previ able fetus so 20 22 23 weeks a small error in measurements is likely not to be clinically significant when we get to the fetuses are who are at the extremes of measurements those fetuses that measure less than the tenth percentile when we're concerned about iugr or fetuses that are over the 90th percentile and we're worried about macrosoma that's where the errors are going to become more clinically important make sure as always with ultrasound that the image is optimized use the correct plane and the correct end points for measuring first discussing the bio the BPD make sure that the head is symmetrically is symmetric on your uh image and what I mean by that is making sure that the third ventricle and the thalami are right in the middle of the image and you can typically see the fox going down the middle of the head the calvarium should be smooth and symmetric the posterior fossa and orbits should not be on the image the cursors are placed outer to Outer excuse me the outer to inner or Leading Edge to Leading Edge when looking at the ofd it should be the largest possible measurement along the base of the skull with the cavum septum paldum identified anteriorly on the image the calvarium again should be smooth and symmetric no posterior Fuca on the image no orbits on the image the cursors in this instance go middle to middle and let's look at some pictures so for this patient we can see the BPD is measured here from Leading Edge to Leading Edge and the phami are in the middle but here is a little bit of posterior fossa on the image and the calvarium is not intact around the side here and and this is gives us an ofd that's a little bit too small when the head is or the probe is angled just a little bit we get a more oval appearance to the Head the phalam is still in the middle the faul right down the center Leading Edge to Leading Edge middle to middle and the of has increased significantly measuring the abdominal diameter this should be performed at the lever level of the liver the liver is the largest intraabdominal organ in the fetus and it gives us the best representation of the fetal weight the image is taken at the level of the stomach bubble and the inter hepatic umbilical vein and these measurements go skin Edge to skin Edge when errors get made with abdominal measurements it's often because you can't see the skin Edge there's a placenta in the way oligohydramnios is presenting you from preventing you from seeing the uh true edge of the skin or there are fetal Parts there's an elbow there's a knee something's in the way or the sometimes what happens is because of compression from the ultrasound probe the abdomen itself is compressed and becomes too oblique when the measurements are too big it's typically because the measurement has been taken in an oblique plane rather than a true axial plane uh if the fetus is prone that often leads to measurements that are too big what happens in the prone fetus is that the spine obscures the landmarks and you're typically not at the correct level when the abdominal measurements are too small that's usually because the entire abdominal wall is not included either the rib is mistaken for the skin and the cursor is placed on the rib or the uh imager doesn't realize that there's more dependent fat on the fetal downside When anybody lies on their side the fat or the subcutaneous tissue heads down towards the ground and so the Leading Edge or the anterior surface is going to be thinner and the downside is going to be thicker so don't forget to look for more subcutaneous fat on the dependent side of the fetus when you're struggling to get an accurate abdominal measurement because sometimes it can be quite difficult in a late term fetus remember that a round image is best it's important to always keep the abdominal d diameter measurements within 10 mm of each other and this will give you a pretty good estimate even if you can't see the other internal landmarks so let's look at a few examples in this instance we have a prone fetus the fetal spine is at the top of the image and that's a pretty good cursor but this one is a little bit more difficult to say where the Ed true edge of the fetus is same thing over here I'm not exactly sure where the edge is because there's an arm in the way that's blocking the edge of the cutaneous subcutaneous tissue and this cursor down here Lord knows where it's supposed to be because the sh the spine has completely shadowed out this side of the fetus and you just can't be accurate here's a better image of the same fetus and all that's happened is that the probe has been moved just a little bit medially on the mom's um anterior abdominal wall and now we can see the skin surface to fluid skin surface very clearly skin surface skin surface and we can see that our measurements are very close to each other so I know that I have a true um circular diameter when measuring the femur it's important to keep the long axis of the bone or the aifi portion of the bone parallel to the transducer and remember that we're only measuring the diaphysis and the metaphysis we are not including the epiphysis on the femur measurement the measurement should happen at the junction of the cartilage and the bone not at the longest bright white spot in the distal femur that is termed the distal femoral point which is not a true an atomic structure here's an example of a fetal measurement that is that should not be performed this image is set with a depth of approximately 20 cm but only 5 or 6 cm would be necessary to have an accurate look at this femur and you can't see the distal landmark and the proximal landmarks clearly enough to know that your accur that your measurements are accurate so here's a real case that came into our department uh about a month ago and this is a patient who's 41 weeks pregnant and these are the measurements that were submitted so looking first at the abdominal diameter we see we've got the stomach here we've got the inter hppa umbilical vein but there's also a kidney on this image you can see the subcutaneous fat and the Leading Edge and the cursor is here anteriorly and the cursor here posteriorly those look pretty good but this is the diameter that's throwing us off you really can't see where the edge is posteriorly behind the spine and again the anterior Mark is somewhere in this black not um not an accurate location and notice these measurements are 113 millim to 138 millim this is way over the 10 mm cut off and tells me that this is a very oblique measurement and probably not accurate looking at the femur length we don't have the sharp crisp ends at each side that would help us know that it's an accurate measurement and this is the distal end and here's the distal femoral Point heading down and a better spot to put or more accurate spot to put the cursor would be right here and this end again you don't have the sharp end and it's difficult to know where exactly on this curve is the correct spot for the femur here's the BPD measurements that were submitted or the and the head measurements so we have Leading Edge to Leading Edge here the fals and the uh thalami the third ventricle are seen right in the middle so that's a pretty good BPD measurement but notice how round this head is and how short the ofd is and there's a little bit of posterior fossa on here and the plane of the center of the head would be in this direction not across here so for many many reasons this ofd is suspect so the uh imager actually um went on to take this ofd and this is a little bit better we can see that it's along the plane of the fauls it's more elongated we got the measurement up to 124 it's a little bit unclear whether this is the true um anterior uh skull margin but the rest of these measurements are certainly uh very accurate but instead of um using either one of these these were averaged to have a measurement in the middle of 115 uh which is not the best way to do it if you have a measurement that's technically poor that measurement should not be included as an average that measurement should be discarded and stick with the better measurement so here's the second set of measurements that I performed going back in the room and again we have very similar ofd of 95 got the fo running right down the center of the head and a more accurate ofd again coming up with 116 which is happens to be the average of both of these but a more accurate measurement and more reliable looking at the femur in this in this fetus here's the proximal end of the femur and you can see the end of the of the aifi portion of the bone and here's the cartilagenous epiphysis and the isum and this is starting to look like a a neonatal hip ultrasound you can see the image that shows that this hip is normally located in the um um glenoid uh the measurement should be marked right at this end and then at the far end of the femur here's that distal femoral point and the epiphysis with a little bit of ossification in the center and this is where the cursor belongs at this end of the femur and this gives us a more accurate femur measurement when these landmarks are used of 74 mm once again here's the incorrect abdominal diameter and and here's another attempt at a better abdominal diameter here we see stomach inter hypa umbilical vein there's no longer a kidney on the image and we can see Sharp echogenic skin to amniotic fluid margin here skin margin here skin margin and skin margin so when we take these measurements that were performed on September 24th these are the initial measurements at 40 weeks and the fetal weight came out uh 9 lb 10 o or almost 4,400 gram in the 96th percentile and at our institution patients whose weights are above 5,000 grams are sent directly to cesarian section for macrosomia and fetuses whose weights are at 4,500 grams will go go directly to C-section if they are gestational diabetics so this patient is is flirting with the um uh possibility of a primary cesarian section without even a trial of Labor because of the size of this Fe is with the more accurate measurements we see that the weight is actually or or possibly 8B and 5 O which is in the 74th percentile not the 96th percentile okay well what's the answer 9B and 10 ooun or 8 PB and 5 O the patient delivered on October 3rd which was 9 days later and we do understand that fetuses gain approximately a half a pound a week so that the true weight of this fetus approximately 9 days later was 8 lb and 11 o a little bit more than a half a pound larger than we had estimated with the accurate measurements reminding us all that the correct measurement technique is critical moving into the second portion of the talk discussing fetal Anatomy we're going to start with looking at mistakes to avoid when Imaging the fetal head one thing that it's important to avoid is describing normal V normal anatomic variance as pathology and here I'm showing you an example of the case C ver the Cav ver is a posterior extension of the cavum septum paldum it's seen in the midline between the lateral ventricles and it can be seen here underneath the Corpus colossum on the sagittal view when The cavum Verge extends posteriorly it's termed the cavum Vellum interpositum and here we see it earlier on in the midline at 19 weeks and on the sagittal image at the posterior po aspect of the Corpus colossum a little tiny cavum Vellum interpositum a normal variant does not need to be even included in the ultrasound report remember that everything cystic in the brain is not a normal variant in this case we have an irregular fluid collection that's right in the midline but has a curved shape to it and possibly some um extensions out of this shape and don't forget to turn on the color Doppler in this instance because we see that this is a large vein of galin aneurysm another cystic thing in the brain is this round structure here it is not in the midline it's off center on one side it's posteriorly and related to the tentorium seen underneath the temporal occipital lobe uh region here and this is an arachnoid cyst it's important when looking at the fetal head to spend some time looking at the three the lateral ventricles and not to overall ventricular megal the plane of Imaging to measure a lateral ventricle must be level any off axis measurement will increase the size of the ventricle it's important to mark this to put the calipers exactly where the edge of the lateral ventricle is just on the inside of the ventricular lining and be careful not to measure the medial surface of the brain rather than the medial wall of The ventricle and remember we can assume that the ventricles are symmetric unless you visualize a symmetry always use the smallest technically accurate measurement any measurement that you take of the lateral ventricle that is um that is artificially increased is due to um measuring this ventricle obliquely so that the true measurement the smallest measurement you get is the true measurement it's impossible to measure a dilated ventricle as smaller than it truly is but it is possible to take a normal siiz ventricle and make it larger the other thing that you can look at that might help you is the presence of a dangling choid the choid should typically completely fill the lateral ventricle if there is more than 3 mm of space between the medial wall of The ventricle and the chid plexus this suggests ventricular megal and this is particularly useful early in pregnancy but should be monitored rather than diagnosed as abnormal as abnormal here's an example of how to correctly measure the lateral ventricles this is the D ventricle and we see a choid here and then the calipers sit in the atrium of the lateral ventricle along the medial edge here and the lateral edge here an example of the dangling choid where the choid is separated from the medial wall of the lateral ventricle and we can measure this distance from here to here and if you see as much as 3 mm it suggests that there is underlying ventricular megaline and again this is useful early in gation where the 10 mm cut off might be a little bit too big well why does it matter here's an example of a fetus uh where we were measuring both right and lateral ventricles and clearly there's hydrophilus there's no question that these ventricles are dilated but if you notice on this up ventricle the measurement is 33 mm but here's the fox and the presence of the Fox on the back third of the head tells me that we're oblique through the head the fox should be running right down the middle so we have artificially increased the the size of this lateral ventricle here's the same fetus in the down ventricle and the we've also artificially increased the size of the ventricle to 36 mm because we've crossed the midline and this is at least part of the third ventricle and possibly part of the up ventricle that's being measured as well more accurate measurements for this fetus the fox is right down in the midline and we're back in the atrium and we have a measurement of 24 mm and on the downside again here's the dangling Cor the medial aspect of the ventricle and the lateral aspect of the ventricle 25 mm why is this important well this fetus is being monitored for progression of the hydrophilus because of the presence of a lumbosacral meninga myos seal seen here on the sagittal View and seen on the clip and the transverse view with the open posterior elements and the patient obstetrician is using the size of the ventricle to determine whether this fetus is stable or whether there needs to be an intervention because of progressive ventricular megali a few words about chid plexus cyst these occur in less than 1% of fetuses and are associated with triome 18 but as we know it's Cory plexis cysts are often a transient normal finding and when we see a corid plexus cyst it probably is more often normal statistically than associated with triome 18 chid plexus cysts are discreet round anaco structures they should measure over 2 mm and they should be completely within the choid in addition you ought to be able to turn on a chide plexus cyst and see it in every plane of Imaging when cysts are overcalled mistakenly it's typically because the it's not a true cyst the cyst the lesion is not round in three planes and it more likely is something that we call a spongy chid so here are two different patients with chid plexus cysts this is much earlier in uh uh gestation and there's the round black discrete structure completely within the echogenic chid plexus cyst in this fetus with Tricom 18 here's a different fetus the choid plexus cyst is much larger indeed it almost replaces the entire choid in this fetus uh is had normal chromosomes compare those discret black circles to these two fetuses who have a more smudgy irregular IL defined sort of Blackness throughout the choid plexus but no discrete well-defined sphere and either one and these have been termed the spongy choid but a spongy choid is a normal choid it does not need to be put into the report and this head and this head are both normal dandy walker variants occur when there's absence or hypoplasia of the cerebella vermis remember that vermian development is incomplete until at least 18 weeks and when mistakes are made with the diagnosis of Dand Walker variant it's often because the fetus is too young the cerebella vermis has not completely formed and what needs to be done is a follow-up exam in two to three weeks and give that vermis a chance to show up another reason why dandy walker variant can be overcalled is if the images are too oblique or obtained in a semicoronal plane if the posterior fossa is imaged in a coronal plane you can take a picture underneath the vermis and make uh a suggest question of a dandy walker variant so if there's a a question of a dandy walker variant it's important to confirm that you're in an axial plane and then to go on a search for the fourth ventricle and the vermis here's an example of a patient who was felt to have a dandy walker variant here's the posterior fossa here and the cerebellar hemisphere here and then the fourth ventricle which appears to open posteriorly into the CNA Magna but if you notice the calvarium in this instance is incomplete it stops right about here and it we don't pick it up till the other side and that's our clue that this image was taken in a coronal fashion and if the probe was tipped so that the calvarium is intact along the back of the posterior fossa we see as we do on this image here that there is indeed a vermis and a distinct fourth ventricle just in a different spot than was being imaged on the first image here's an example of a patient with the true dandy walker variant the fourth ventricle here is wide open into the CNA Magna and the cerebella hemispheres are flattened and distorted particularly on the superior aspect of this patient with the true Dand Walker variant Mega cyna Magna is often overcalled as pathology when the sister a Magna appears prominent it's important to look at the underlying anatomy of the of the posterior fossa and identify a well-formed cerebellum vermis and fourth ventricle again remember these need to be in the axial plane there are normal septi that run through the back of the CNA Magna and those can be identified and should not be mistaken for a cyst and again when the CNA Magna appears large do a careful search of the brain for other malformations if it's an isolated finding the likelihood that there is that there will be a good outcome in the fetus here's a mega a Magna here a large uh amount of fluid in the posterior fosa a Magna region notice the little crossing septations here and here the measurement is 11 mm but we have a well-formed cerebellum and a midline vermis moving on to mistakes that can occur in the face remember that when you're Imaging the face we need two different images I need an image of the nose and lips looking at The Superficial um soft tissue of the lips and outlines of the nostrils and don't forget to image the orbits there has to be two orbits in every fetus to call the face a normal face face here's a really cute picture of a fetus the parents were delighted it's you know I show it multiple times doesn't it look great you can see the eyes and the cheek and it's it's an adorable picture is it normal well you can't call the face normal because you do not see the soft tissues of the nose and lips here's the image of the nose and lips you can see the lower lip here and the upper lip and there's a cleft indeed coming from the right nostril down into the uh upper portion of the mouth so make make sure that to call a face normal that soft tissue plane of the upper lip is seen in completion here's another patient who was um brought to my attention because of the possibility of a Clift lip and here's the upper lip right here the rest of the face would be here and there is a cleft or a vague cleft right in the midline sort of obliquely there but if we scan a little bit more posteriorly we can see that actually the lip is completely intact when I have the nose on the image and this is just a prominent filtrum or that CFT in the soft tissue in the upper lip and it can be confirmed if possible with 3D imaging there's an image of the fetal face and we can see that the upper lip is completely intact what do I mean by orbits I I want to see two bony orbits here and here they should be symmetrical in the head it's not enough to just see the top orbit both of them need to be identified here's a here's an image of the orbit in a patient this is why we're looking at the orbits because in this instance the two orbits and the nose there's a big soft tissue Mass here protruding from the anterior aspect of the nose between the two orbits and here it is seen on the more sagittal plane and you can see that the tissue here is identical in um echotexture to the tissue of the brain and this is an extra cerebral Goma another structure that can be identified on fetal ultrasound in the region of the orbits is this structure right here a little round AN aoic spherical shaped structure with through transmission possibly identified right in the region of the orbits and on this uh axial image of the lower portion of the orbits here and here we can see the little tiny black circle and this is a dacr cyal this is blocked a blocked lacrimal duct and the uh tear back up into a little bubble of fluid it has no clinical consequence and will disappear after the baby is born should not be considered to be pathology here's another patient again looking for the orbits this is the axial view of the head and this is the region of the orbits but we do not have the well-defined Bony structure of the orbits on either side and the nose is very flattened and on this profile view of the fetus you can see the chin and the lips and notice that the nose is completely absent in this fetus and here's the 3D image you can see a prominent forehead and just collapsed soft tissue areas where the orbits should be and no visible nose and indeed this child was delivered at term with no nose and no uh orbits a few words about mistakes that can occur in the kidneys the kidneys in particular can be very challenging on the 18 week survey and a typical mistake that happens is that the adrenal glands are identified and labeled as kidneys rather than the kidneys themselves and your clue that you could be looking at the adrenal glands is if the stomach is on the image because the stomach is typically higher than the level of the kidneys another clue adrenal glands are very prominent and very hypo aoic and they're easy to see the kidneys are ISO aoic they're very difficult to see they can be quite subtle at 18 weeks if you're lucky there'll be a midline uh black slit or a little bit of fluid in the renal pelvis that will help you confirm that you're looking at kidneys so here's an example of a patient shown to show you at 18 weeks this is reported as kidneys but we're the level of the stomach and here's the hypo aoic on the left hypo aoic area on the right these are the adrenal glands and this image taken much lower down with no stomach on the image is the kidneys here's a kidney here and a kidney here and indeed they're very subtle they're hard to see at 18 weeks here's a clip going from the pelvis up through the abdomen starting at the bottom down by the bladder and again the kidneys here and the adrenal above here's a patient who was seen at 18 and 1 12 weeks with a normal uh kidneys reported and this is the image that came out labeled kidneys and here's the stomach here and we can see a probable kidney on the right here but there's nothing convincing on the left there's a little hypo aoic structure here but this is too high to be to be in the region where a left kidney should be because we have the stomach right there and indeed when this patient returned at 30 weeks again here's the right kidney aorta IVC stomach bubble and a little hypoc coic area here but no definite kidney scene in the left renal fossa sagittal images of each kidney were performed here's the right kidney 32 mm right where it belongs under the diaphragm but on the left kidney we see the lying down adrenal sign where the adrenal is elongated and stretched along the spine because there is no kidney in the left renal fossa okay so there's no kidney in the left renal faasa we don't stop there we need to go looking for it because sometimes it's not missing it's just in a different spot and down in the pelvis we can see posterior to the bladder here's the left kidney and this fetus has a left pelvic kidney which was missed at the 18we scan a few um comments about mistakes to avoid in imaging the heart uh one of the pitfalls that's commonly occurs on the four chamber view is the possibility of looking at a ventricular sepal defect remember that the top of the ventricular septum is very very thin and you can get Dropout which is artifactual in that spot so if there's a question of a vssd you want to make sure that you change your angle and come in from the side and from the uh rather than from the Apex to see the top of the septum also remember that for ventricular septile defect evaluation color is imperative so what do I mean by Dropout on this IM IM of the four chamber we can see the interventricular septum here and it gets very very thin and there's a suggestion that there's a big hole here between the right lateral ventricle and the left lateral ventricle could this be a vssd well when we turn the image just a little bit Slide the probe a little bit more medially so that you're coming in perpendicular to the interventricular septum you can see that that septum is intact all the way up to the root of the aorta let me just say this is right atrium and right ventricle and there's an EOG enic stripe running through the right atrium but if we change the angle here that echogenic stripe is gone and what we're Imaging here is maybe the um coronary sinus another image of the heart we see what looks like a beautiful four chamber view but remember when you're looking at a four chamber a static image is not enough it looks like we have a beautiful interventricular septum here but on the clip I think you can appreciate that the interventricular septum stops and there is uh a vssd running right over the top of the septum another what looks like a beautiful four chamber view we can see the tricuspid valve and the mitro valve but if you look here on the very top of the Apex it looks like there's a black structure here on the end and this is where color is helpful because with color Imaging we can see that there's a small ventricular sepal defect in a membranous portion of the septum in a very unusual location but the color makes it very easy to see that ventricular sepal defect yet again another four chamber view looks beautiful interventricular septum here good motion of the valves the color image though again shows us the interventricular the ventricular sepal defect and once we know it's there we can angle the probe to see the vssd right here when looking at the heart remember that uh a paracardial affusion is normal if there's a par pericardial fluid is normal if there's less than 2 millimet it's not defined as a paracardial affusion until it's larger than 2 millimet and be careful not to mistake the hypo aoic myocardium as paracardial fluid so what do I mean by that well here's the uh possible paracardial effusion seen here but this is actually just the edge of The myocardium you can see some echogenic inner Edge and then the hypo aoic myocardium here when in doubt ident try to identify whether this possible fluid goes past the level of the valves if it crosses the level of the valves it's much more likely to be fluid as seen in this patient where you see The myocardium here and the paracardial fluid going all the way around the level of the mitro valve when Imaging the heart remember that a four chamber view only is not a enough to tell the Fe to uh report a normal heart it's important that the aorta and pulmonary artery or the left and right ventricular outflow tracks are included in your exam and technique is extremely important with these outflow tracks the aorta must be imaged in the aial plane you must identify that the interventricular septum is contiguous with the wall of the aorta and there must be a right ventricle on the image here's a patient where we see a normal four chamber View and a normal four chamber is not enough because when we move to the outflow tract view of the left ventricle we can see that the left ventricular outflow tract which comes out here is actually arising from both lateral ventricles there's a vssd and an overriding aorta and this instance of tetrology of f again seen here would have been missed if we stopped on the four chamber view alone one thing I do want to clarify is that the pl plane of Imaging for the aorta is key on this image which is taken coronally and I know it's coronal because or uh in the sagittal plane because I can see the diaphragm here and the liver and I can see the lungs and I can see the ribs so I've Got A sagittal image this is the lower portion of the heart or the inferior aspect of the heart this is the anterior wall of the heart along the sternum and so that makes this the superior wall of the aorta or the anterior wall of the aorta and the posterior wall of the aorta and then this is the entire left ventricle the issue is that the aorta is nor the the superior and uh inferior walls of the aorta are normal even when there's an overriding aorta it's the medial wall of the aorta that we care about and you can't see the medial wall of the aorta when you take an image in this plane so the medial wall of the aorta is in here somewhere so the better technique for taking an image of the aorta is to stick on the four chamber view stay with the axial plane and follow the interventricular septum up so you see that medial wall of the ABD of the ascending aorta and I you can know that you do that if you keep the right ventricle and the left ventricle on the image at the same time so you follow the asending aorta out and this tells you right this this continuity between the interventricular septum and the medial wall of the aorta excludes with confidence an overriding aorta and a tetrology of fow here's another patient we see a four chamber view looks beautiful but when we look at the image of the aorta we can see now when we follow with both right and left ventricles on the image to see the a ending aorta that there's an overriding aorta here and a ventricular sepal defect and we're then able to identify the overriding aorta in the tetrology of Pho last case that I'm going to show is an example of pseudo aites Pudo aites is uh mistakenly or aites is mistakenly identified when the hypoa rim along the abdominal wall is mistakenly thought to represent aites if that is the only place where you see the aites you should think to yourself maybe it's not real start looking other places particularly easy to see aites in the fetal pelvis down by the bladder so here's an example of pseudo aites we have a transverse view of the abdomen here and there's this hypo aoic Rim seene along the edge of the anterior abdominal wall but notice that this is uh the musculature that extends from the edge of the rib and is not interparent Neally and when we go down to the pelvis we can see that there's absolutely no fluid down near the bladder or around the kidneys and there was no atis in this fetus that brings me to the end of my slides and I thank you so much for your attention