Fetal MRI of Bilateral Renal Agenesis

Today we have an exciting lineup of expert speakers who are world renowned in their respective fields. And I will share my screen. Uh, so our speakers today, we have 7 of them. So it will be, uh, Kara, uh, Stuart, Usha, Mel will be, uh, be joining us by recorded video as she could not join us live today. Um, Bob, Ellen, and, uh, Claudio. Uh, Uh, and they will be speaking to us about their, um, respective expertise. Um, so, I am, uh, I am Sammy Taba. I am the, um, the director of, uh, fetal diagnosis and therapy at the University of Cincinnati, um, and one of the maternal fetal medicine physicians, um, at Cincinnati Children's Hospital Medical Center. And I have my co-moderator with me today, Doctor Hubley, who will introduce herself. Uh, and, uh, we'll be introducing our first speaker as well. I am Munira Habble, a maternal fetal medicine specialist at Cincinnati Children's Fetal Care Center. I'm the director of the Tri-Health Fetal Care Center and the chairman of the Perinatal Research Institute at Good Samaritan Hospital. Today it's An honor for me to present Dr. Usha Nagaraj. She is the first speaker. She's an assistant professor of radiology at the University of Cincinnati College of Medicine. She is a pediatric and neuroradiologist at Cincinnati Children's Hospital with a special interest in fetal imaging. She has published many papers on prenatal imaging. Uh, of a wider spectrum of anomalies, and she had just recently, a few days ago, uh, won the Investigator Young Award at the ISPD, which is the International Society of Prenatal Diagnosis. Today she's going to review prenatal imaging considerations related to congenital anomalies of the kidney and urinary tract. Please welcome with me Doctor Oshana Garaj. Wow, Doctor Hubley, thank you so much for that extremely generous, uh, introduction. Um, uh, and thank you, Doctor Linn, for the invitation to speak this morning. So this is just a brief overview of the value of fetal MRI in the setting of bilateral renal agenesis. Um, my only disclosure not related to the content of this talk is I'm an author with royalties for Elsevier. So, the value of fetal MRI um in the context of bilateral renal agenesis, I think, um, can be summarized in these three points. I think uh the first thing we can do on fetal MRI is help to confirm the diagnosis of bilateral renal agenesis. The second thing that we can do to help in um prenatal counseling is to calculate the lung volumes on these patients. And then finally, fetal MRI can be of assistance in identifying additional anomalies which can also help in the prenatal counseling. So to confirm the diagnosis, when the patient is referred for fetal MRI, um, it is after a 2nd trimester ultrasound, and the findings on the 2nd trimester ultrasound, which are worrisome for bilateral renal agenesis, can be primarily summarized by these 3 findings. Anhydrammias or the absence of any measurable um amniotic fluid pockets around the fetus. We have an example here of a fetus with anhydrammius. Absence of a fluid-filled urinary bladder, um, is also a sign that is worrisome for bilateral, uh, renal agenesis, and here's an example of that. Um, here are the pelvic bones here in the fetus. And then finally, sonographic absence of the fetal kidneys. And then, and this can be a challenging um diagnosis to make on fetal ultrasound, particularly in the setting of anhydramus. Um, but, uh, sometimes we are able to see um these uh dark structures in the renal fossa, triangular structures. These are the adrenal glands. And um when we have bilateral renal agenesis or, or renal agenesis in general, the adrenal glands tend to be elongated in the craniocaudal dimension. So here's the right adrenal gland and the, oh sorry, left adrenal gland in this patient on either side of the spine. Um, the other, uh, sign, uh, on fetal ultrasound that can help us and then, um, Uh, identifying absence of the kidneys is absence of the renal arteries. This is the aorta. When we use color Doppler, we should be able to easily see the renal arteries coming off the abdominal aorta on either side, and this is part of our routine, um, fetal ultrasound protocol. So MRI once um uh the patient is referred uh for uh Diagnosis can be helpful in confirming the suspected diagnosis of bilateral renal agenesis. And fetal MRI does have multiple technical advantages over fetal ultrasound. Um, for one, it is not as limited by anhydramnio. So, uh, fetal ultrasound, um, high-quality images are very dependent on, uh, establishing a good acoustic window by the amniotic fluid, um, and MRI is less dependent on that. Um, certainly, the surface structures of the fetus, um, can be distorted or obscured in the absence of amniotic fluid on fetal MRI, but in general, it is less limited, um, by absence of amniotic fluid than ultrasound. Maternal body habitus, as many who practice sinology know, can be extremely limiting, um, in the practice of uh fetal ultrasound, and fetal MRI is less limited by maternal, um, obesity. Um, of course, uh, Morbid obesity can still potentially pose some technical challenges even on fetal MRI, uh, but we are, are less limited. And fetal positioning, um, while that can be quite limiting on fetal ultrasound, particularly in the third trimester, it's definitely not as limiting on fetal MRI. We can pretty much image the fetus in any position very well, cephalic breach or transverse presentation. We can even activate and deactivate certain aspects of the abdominal imaging coil to improve the regional signal um characteristics in our field of view. So on fetal MRI, the findings that we look for are, um, well, the same findings that we look for on fetal ultrasound. Um, we again can see anhydramnio. So here's a sagittal, um, uh, BTFE or Fiesta image through the uh uterus. We have the, um, uterus here and here is our fetus and um cephalic presentation and here is the cervix and we can see that there is no amniotic fluid around this fetus. We can also look for absence of a fluid-filled urinary bladder. In a normal exam, we should see um a fluid-filled bladder at least at some point in the exam, um, but here we do not, so that is worrisome for renal agenesis. And then absence of the fetal kidneys, so I think MRI can really help us increase our confidence that we do not see um any good candidates for normal renal tissue. So here's an axial T2 weighted image to the fetal abdomen and these dark triangles here are the uh fetal adrenal glands. Like our um ultrasound, this is a coronal image through the fetus. Oops, my apologies. This is the chest. This is this dark linear structure. Here is the aorta. Um, we can also look for elongated renal glands. So, uh, this is a little challenging to see on this image, but, um, These dark triangles here and uh the other one is hard to see, can also help us. Uh, for our renal protocol, we routinely do diffusion-weighted imaging. And the reason we do diffusion-weighted imaging is because the normal kidneys should light up like light bulbs on the diffusion, um, relative to the other structures in the abdomen. So here's an axial image, um, diffusion. imaging of the fetal abdomen in a normal fetus and we can see these two bright balls um which represent the kidneys. Um, here is a diffusion weighted imaging from the patient with suspected, uh, renal agenesis, and we do not see those two bright balls in the area of the Uh, expected kidneys, this dark area, uh, um, anteriorly is the liver. So this can also help us increase our confidence that, uh, we are dealing with a patient with, um, bilateral renal agenesis. Um, fetal MRI, um, can also be helpful in calculating lung volumes, and this is something we routinely do in patients with, uh, uh, suspected bilateral renal agenesis. There are multiple methods by which lung volumes can be acquired. We, uh, have, um, Oh, my apologies. Uh, we, uh, use a coronal T2 weighted images, um, of the chest and, um, we acquire the images with no gap, um. And then we send them to our uh 3D lab where they manually trace the lung volumes on each side and then the area um is uh calculated for each lung and that's um multiplied by the slice thickness and the number of slices to obtain our estimated lung volumes. And when we report lung volumes in these patients, uh, we report them in relation to the, um, available normative data, um, the ripen data, um, published, uh, In 2001, and then the more recent um uh Meyers data from um Uh, 2018. Um, I am so sorry. Let me just get this. Um, Melvin, hello? Hi, Mindy, I am so sorry. I'm in the middle of a live concert. Can you kindly call the fellow? He's at 654-557. Yeah, Christian Carlson. Thank you. My apologies. Um, And I think my, my hope is that the value of lung volumes in this patient population may be better um described by my other colleagues in this session. And then finally, I'll just finish by um uh describing how fetal MRI can be valuable in identifying additional anomalies in these patients, which can be very challenging to see on fetal ultrasound alone. And I'll just end with just a couple of examples of this. So this was a 22 week 4-day gestational age fetus who was um Referred for a fetal MRI, um, for suspected bilateral renal agenesis. This is a coronal image of the uterus and this is a sagittal image through the uterus, um, and we can see anhydramnios and the fetus is in, um, cephalic position. This is an axial and coronal T2 weighted image through the fetus. Um, this is the spine and on the coronal image, these are the lungs. On the axial image, we can see at the level of the adrenal glands, no candidates for normal fetal renal tissue. So, uh, again, increasing our confidence that this is indeed bilateral renal agenesis. Um, on the spine, we do notice there is focal right apex curvature of the spine. And this does raise the suspicion for underlying segmentation anomalies. When we look at this patient further, this is a sagittal fiesta image of the spine. We can see that there's elongation of the spinal cord and it attaches to the end of the fecal sac, which is abnormal. So this cord is probably tethered secondary to a closed spinal dystrophism. We see a similar finding on our axial Two weighted image. This is the um neural plaquehode here within the um sacral spinal canal. And then this black circle here, um, where the urinary bladder should be um is consistent with meconium signal. Meconium is relatively T2 hypo intense. And we can see that again here. And when we look at this vaginal image, we can see that there's definitely a dilated meconium-filled structure in the pelvis. And this is worrisome for a dilated sigmoid colon in the setting of coexisting anorectal malformation. We can confirm the presence of intrinsic T1 hyperintense meconium signal in the dilated sigmoid colon. So when, so we have spinal anomalies and suspected anorectal malformation, we can bring up the possibility of the Bobactral sequence. And I will finish with this case. Uh, this is a 24 week 3 day gestational age fetus who was referred to us for suspected renal agenesis. And again, we have sagittal and coronal fiesta images through the uterus and we can all see the anhydramus. This fetus is in breech position. And when I first looked, I thought, what is this bright structure here? Is that a kidney? No, it's definitely above the liver. So when we look more closely at the lungs, this is coronal and axial T2 weighted images of the lungs. We see these bright T2 hyperintense um masses within the lung parenchyma bilaterally. And these, um, most likely reflect um congenital pulmonary airway malformations or CAAs. Looking further at this patient, so this is our sagittal T1 weighted image. This is the liver. We have this dilated T1 hyperintense bowel loop in the um pelvis, which again is worrisome for a dilated um uh distal colon, uh worrisome for coexisting anorectal malformation. We see that um that it has corresponding T2 hypo intense signal on the T2 weighted images. And this is a sagittal T2 weighted image of the same patient. The conus doesn't appear low, but I, I do feel like it is blunted and I don't see any normal candidate for the sacrum. Um, and I think the final nail in the coffin for this patient was when, um, finishing the survey to look at the extremities, um, the, there was only a single thickened lower extremity identified. We can see it anterior to the fetus here and anterior to the fetal abdomen here. This is the gallbladder, this is the spine. Um, so, uh, the constellation of findings are compatible with, um, serenomyelia, sometimes referred to as the group one caudalagegenesis spectrum as the most severe end of the spectrum. Um, so hopefully I have, uh, Uh, Demonstrated the value of fetal MRI and the evaluation of bilateral renal agenesis, and I'm happy to take any questions. Thank you so much for your time this morning. Thank you, Doctor Nagaraj. Uh, there is a question that is posted by Doctor Stephanie Riddle about how frequently MRI can change the diagnosis of, uh, um, uh, how frequently MRI modify the diagnosis from ultrasound, especially if bilateral renal agenesis was the referring diagnosis. Well, I, I, I'm not sure I know the exact answer to that, but I will say, um, all of the patients that have been referred for suspected bilateral renal agenesis that I have interpreted, um, the MRI has confirmed that suspicion. Um, I think MRI has added additional information that was not seen on the ultrasound, um, like that, um, Sien Amelia case was a good example of that. Another question is, Dr. Nagaraj. There are recent studies from animal models about using MRI to assess the function of renal disease. Do you see any future for such modality? I, I honestly am not um familiar with those studies but um feel free to uh send me uh uh email with the literature. Certainly always interested in if uh applying new sequences to our current protocols, particularly if they're easy to implement and fast. Our fetal MRIs are quite long as it is.