All right, thank you for the introduction and thanks for having me. My title today is There's a Problem with Your Plumbing, Fetal Imaging of Urinary Tract Obstruction. And I have to admit, I was not the person that was clever enough to come up with this catchy title. To be honest with you, I knew nothing about household plumbing until I was preparing for this lecture. And I decided I should do a little bit of background reading. And it turns out that household plumbing is actually quite complicated. So today, we're going to keep things simple. And we're going to talk about a few plumbing concepts that can also be applied to the fetus. So congenital urinary tract anomalies are among the most commonly identified abnormalities on prenatal ultrasound, representing about 20% of congenital fetal anomalies. They can be lethal, and they may be isolated or associated with syndromes. Now, fetal MRI is great for assessing these because it's not limited by amniotic fluid volume, maternal body habitus, or fetal position like ultrasound sometimes is. It has a wider anatomic coverage than ultrasound. We can use fetal MRI to assess for additional anomalies. And it has the added value of assessing the lungs in the fetus that may have oligohydramnios. So a few pitfalls and things to know about the fetal kidneys. They're considered echogenic if the renal cortex is brighter than that of the liver or spleen. But that rule only applies after 32 weeks gestation. This thin rim of T2 hyper-intense signal around the fetal kidneys is normal perirenal fat and should not be mistaken as ascites. Normal pelvic distension in the kidneys, as you can see, measured on the ultrasound below. Normal in the second trimester should be an AP pelvis diameter of less than 4 millimeters. And in the third trimester, an AP pelvis diameter of less than 7 millimeters. And of course, there are reference charts for normal kidney sizes for age. The normal fetal bladder should be seen by 12 weeks. It voids regularly, every 55 to 155 minutes. But there should always be a small post-void residual. And it's important to identify the umbilical arteries on either side of the bladder to confirm that what you're looking at is actually the bladder and not a cystic pelvic mass. And that's shown on ultrasound as well as MRI. You should always identify the gender because it helps you narrow your differential diagnosis. And although this is not GU, you should always check the rectum. So normal meconium production begins at about 13 weeks gestational age. And you should see T1 hyper-intense meconium signal all the way to the rectum by 20 weeks gestational age. And that should extend below the bladder base by about a centimeter. So on our first two images, you see the normal meconium extending below the level of the bladder. And on our last image, you can see an abnormal patient. That's 24 weeks gestation. So they should have meconium all the way to the rectum. They don't. This patient had an anorectal malformation. OK, so let's go through some practice cases. OK, so plumbing problem number one. What if you're missing some parts? So our first fetus is a 26 and 1 half week gestation fetus with anhydramnios. And the mother has a history of a single kidney but is otherwise healthy. So when we look on our ultrasound images, we see that there's no amniotic fluid. We see the umbilical arteries on the middle image but no bladder between them. And then when we look for the kidneys, we don't see the kidneys and we don't see the renal vessels. We use MR to further assess. And the first image shows anhydramnios. The second image shows the umbilical arteries but no bladder. When we look higher up, we don't see the kidneys. And then just like a leaky pipe might affect the drywall or ruin your hardwood floors, abnormalities of the fetal kidneys can lead to negative downstream effects. And in this fetus, because of the anhydramnios, we see small hypoplastic lungs with abnormal signal. So this was a case of bilateral renal agenesis, which you can see in one out of every 4,000 births, three times more common in males. And without intervention, it's lethal, although there have been some recent successes with amnioinfusions. And interestingly, the fetus of a parent with a solitary kidney has a 1% chance of bilateral renal agenesis. Now unilateral renal agenesis is much more common with a favorable prognosis. It can sometimes be associated with syndromes and can be the result of a complete involution of multicystic dysplastic kidneys sometimes. OK, so plumbing problem number two, what if you have the parts but they don't work? So our next fetus has some type of renal abnormality. And when we look on our axial images, we see the right kidney looks relatively normal, maybe a tiny bit of pelvic distension. But when you look at the left kidney on the images, you see that the left kidney is comprised of multiple non-communicating cysts and really no normal renal parenchyma. Now we check. There's normal amniotic fluid. The lungs look normally expanded with normal signal. So this was an example of unilateral multicystic dysplastic kidney, which is a common cause of end-stage renal disease and renal failure in the neonate. It results from early ureteral or pelvoinfundibular atresia. And on imaging, just like our patient, you'll see multiple cysts of varying sizes but no normal renal parenchyma. Most of these involute by 10 years of age. And if you have multicystic dysplastic kidney in one kidney, you need to check the other kidney because it can be associated with contralateral renal anomalies in 30% to 40% of cases, such as reflux or UPJ obstruction. OK, so what if you have a major blockage? Well, urinary tract dilation is common, seen in 1% to 5% of fetuses. And just like household plumbing, you can have different levels of blockage, the UPJ, the UVJ, or the bladder outlet. Urinary tract dilation can be transient. And although a little bit controversial, it's generally agreed upon that milder prenatal cases of urinary tract dilation are more likely to spontaneously resolve, whereas more severe cases are more likely to have postnatal pathology. So let's look at our first patient that has urinary tract dilation, and it's a male fetus. So on ultrasound, we see dilation of the renal pelvis and thinning of the renal parenchyma. And on these coronal MR images from posterior to anterior, we see dilation of the renal pelvis. But we also note that the dilated renal pelvis is out of proportion to the renal calyces. We check there's normal amniotic fluid. The lungs look normally expanded with normal signal. And this is a case of a UPJ obstruction, which is the second most common cause of prenatal urinary tract dilation after transient urinary tract dilation. Happens much more commonly in males than females, and is usually caused by some type of aberrant collagen or fibrous band at the UPJ. Sometimes could be caused by a kink in the ureter or valves or aberrant vessels. On imaging, we'll see dilation of the renal pelvis out of proportion to the renal calyces. And interestingly, there's poor correlation between prenatal pelvic dilation and postnatal function. UPJ obstruction is also often associated with other urological malformations, 15% to 20%. So pay attention to that other kidney. OK, now our next patient is a 24-week fetus, female gender with urinary tract dilation. So on these axial images, we see that there's upper pole urinary tract dilation. The lower pole, there's only mild urinary tract dilation. And when we follow the yellow arrow down, we see that there's a ureter that seems to be going more inferiorly than normal, suspicious for an ectopic ureter. We see that this is a female patient. When we look on our coronal images, we can see that the upper pole in green is dilated much more than the lower pole, with also significant parenchymal thinning of the upper pole. Now when we follow that upper pole ureter down with the yellow arrows, especially on the last image, which is a sagittal oblique image, we can see that that ureter inserts inferior to the bladder. So there's an ectopic upper pole ureter. So this is a case of an ectopic ureter in a duplicated collecting system. Duplicated collecting system is common. It's the most common congenital ureter abnormality, often bilateral. And both ectopic ureter and duplicated collecting system are much more common in females than males. If you have an ectopic ureter in females, it can insert at the lower portion of the urinary bladder, the urethra, vestibule, or the vagina. In the males, it may insert in the seminal vesicles, vas deferens, or ejaculatory ducts. And ectopic ureters can be associated with ureterocele. So a discussion of a duplicated collecting system would not be complete without touching on the Weigert-Meyer rule. So that occurs in completely duplicated collecting systems. And the upper pole ureter often has an ectopic insertion inferior and medially to where it's supposed to insert. It may terminate in a ureterocele. And it may be obstructed. The lower pole ureter inserts in the normal position. But because of the sort of pressure from the ureterocele or ectopic ureter adjacent to it, it often has reflux. OK. So our next obstruction case is a 21-week gestational age male fetus with a dilated bladder. So on ultrasound, we see this dilated bladder. We confirm it's the bladder because we can see the umbilical arteries on either side of it. And when we look at our second picture, we can see that the bladder has a keyhole configuration. We do fetal MR to further assess this. And right off the bat, we see the dilated bladder. We can see it's a male fetus. We see that there's cystic dysplasia of the kidneys. There's lack of amniotic fluid. And there's a significantly dilated posterior urethra. Oh, also, we notice the lungs on other sequences are small and hypoplastic. You can kind of get a sense of that on the middle image. So this is an example of posterior urethral valves, which is the most common cause of bladder outlet obstruction in the male fetus. We'll see an enlarged bladder with a thickened wall and a dilated posterior urethra. And there's frequent but variable renal dilation. So that brings us to a little discussion on fetal megacystis, which can be either from obstructive causes or non-obstructive causes. In obstructive causes, there's an actual blockage. So you'll often see a thickened bladder wall. And examples of those are posterior urethral valves, urethral atresia, and ulcerative colitis. And then there's obstructive causes of fetal megacystis, which can be from obstructive causes, urethral atresia, and megalourethra, and obstructing ureterocele. In non-obstructive causes of fetal megacystis, it's typically related to some type of smooth muscle dysfunction. So examples of those include prune belly syndrome, megacystis microcolon intestinal hypoparastosis syndrome, or the ACTA2 gene mutation. Now, these can sometimes be difficult to distinguish but there are some imaging findings that may help you narrow your differential. So in posterior urethral valves, you may see the keyhole sign, like we saw with our patient, and hydramnios and bladder wall thickening. And this would be a male patient. In prune belly syndrome, you may see an irregular anterior abdominal wall, ureter dilation disproportionate to renal dilation, and a male fetus. In megacystis microcolon intestinal hypoparastosis syndrome, you may see a microcolon, small bowel dilation, polyhydramnios, and a female patient. So let's look at a few companion cases. So our first companion case is an example of prune belly syndrome. This is also known as triad syndrome. The triad includes deficient anterior abdominal wall musculature, urinary tract dilation, and undescended testes in a male fetus. So on our images, we see that the abdominal contour on the sagittal image is quite distended from the absence of the abdominal wall musculature. We see that there's normal amniotic fluid, and we can see that the ureters are quite dilated and tortuous, perhaps a little out of proportion to that of the collecting system. This is another companion case of the ACTA2 gene mutation. So this is also known as the multisystemic smooth muscle dysfunction syndrome, and this is a smooth muscle myopathy that affects arteries, bowel, bladder, iris. And this is something you wanna consider in your differential in cases of megacystis that have atypical features of bladder outlet obstruction. So no bladder wall thickening, normal amniotic fluid, perhaps female gender. And this is an important thing to know about because this gene mutation is not routinely included on kidney disease panels on amniocentesis. So you need to suggest it in your differential diagnosis so that the maternal fetal medicine doc knows to order it. So on our patient, we see a dilated bladder, but no real wall thickening. We see normal amniotic fluid, and this patient does not have any hydronephrosis. Our last companion case is a case of megacystis microcolon intestinal hypoparastosis syndrome, which is also a smooth muscle disorder which leads to abnormal bowel and bladder motility and intestinal pseudo obstruction. So you may see a dilated bladder, dilated small bowel, microcolon, possible hydronephrosis. Now this is interesting because the amniotic fluid is normal or even increased. And this is most common in female gender and it has a very high morbidity and mortality. So in our patient, we see some mild urinary tract dilation. We see a dilated bladder, but there's normal amniotic fluid. And we also can see on our sagittal T1 image, there's only minimal meconium and a small distal colon. Okay, so we've talked about a lot of different plumbing problems. And another problem that many of us are familiar with is if there's a leak. So let's look at our first fetus. That's a 22 week fetus with a left renal cyst. So on ultrasound, we see this cystic structure in the upper aspect of the left renal fossa. When we look a little bit more inferiorly, we can see the left kidney with urinary tract dilation. And on this sagittal image, we see the urinary tract dilation. And then kind of at the upper part of the kidney, we see this avoid cystic structure. Now when we look on MRI, on our axial images, we see the cystic structure, upper aspect left renal fossa. And when we scroll down, we see a renal collecting system that's dilated out of proportion to the calyces and the configuration of the UPJ obstruction. When we look on our sagittal images, we see a very well demarcated fluid collection along the upper pole of the kidney. So this is an example of a urinoma in a patient with a left UPJ obstruction. So a urinoma is encapsulated, extravasated urine that may occur as a result of obstruction, typically at the upper pole. And interestingly, there's often a sharply demarcated line separating the encapsulated fluid from the remaining unharmed portion of the cortex. Now this is a different patient I've included in the figure, and you can see this patient also has a very well demarcated configuration between the fluid collection and the rest of the kidney. And generally, these are associated with good outcomes. Here's another companion leak case, and this is a 29-week male fetus. And on the transverse ultrasound images, we see bilateral urinary tract dilation. We see a dilated bladder with a thickened wall and a keyhole configuration. And then you can see that the green arrows point to a significant amount of ascites. So we did MR to further assess this. And again, we see the urinary tract dilation, the dilated bladder, and significant ascites throughout the fetal abdomen and pelvis, a dilated posterior urethra, and hydramnios, and then small hypoplastic lungs with abnormal signal. So this is a case of urinary ascites in the setting of posterior urethral valves. And urinary ascites can be related to rupture of the chaliceal fornices, transidation across the intact upper urinary tracts, or bladder perforation. And again, urinary ascites is generally associated with good outcomes. So in summary, congenital urinary tract anomalies are common. Urinary tract obstruction can occur at the level of the UPJ, UVJ, or bladder outlet. Contralateral renal anomalies are common. Gender can help us narrow the differential diagnosis. And then pay attention to findings that may result from urinary tract obstruction, such as cystic dysplasia, oligohydramnios, or hypoplastic lungs. Now we're going to do some audience response questions. Question number one. All of the following are true regarding the fetal bladder except, should be seen in all fetuses by 12 weeks gestation, should void regularly, should completely empty when voiding, or can use umbilical arteries on either side of the bladder to differentiate it from other cystic structures in the pelvis. So the fetal bladder should not completely empty when voiding. It should void every 55 to 155 minutes, but there should always be a small post-void residual in the bladder, so it is always abnormal if you do not see the bladder after 12 weeks gestation. Good job. Okay, next audience response question. Which of the following diagnoses is more common in males? Megasystis, micro colon intestinal hypoparastalsis syndrome, ectopic ureter, prune belly, or duplicated collecting system? Prune belly syndrome is the diagnosis that's more common in males. The others are more common in females. Great, thank you for your attention and here's how to reach me if you need me. Good afternoon, everyone. I'll be talking to you today about the appropriate postnatal follow-up for antenatally detected renal and bladder abnormalities. I'd like to review with you the postnatal imaging evaluation of the most common renal and bladder disorders detected antenatally, with an emphasis on ultrasound and nuclear scintigraphy. Most neonates who are referred for postnatal urinary tract imaging are asymptomatic and the examination is prompted by an abnormal antenatal sonogram. We need to confirm the prenatal findings and also assess for progression. Antenatal urinary tract abnormalities are most often either transient pelvic halocele dilation or secondary to ureteropelvic junction obstruction, vesicle ureteral reflux, ureterovesicle junction obstruction or primary mega ureter, multi-cystic dysplastic kidney, posterior urethral valves, duplex kidney with either an ectopic ureter or ureterous seal, or rarely another abnormality such as prune belly syndrome, genetic renal cystic disease or genital abnormalities. Postnatal imaging of the urinary tract consists of both morphological and functional imaging studies. We perform an ultrasound to get morphological information and functional imaging is usually performed after two weeks of age with mercaptoacetyltriglycine or MAG3 scanning. And we wait a couple of weeks because renal function is not fully developed at birth. And we use these studies, the MAG3 studies to evaluate perfusion, differential renal function and excretion. Less often we may perform dimercaptosuccinic acid or DMSA scans to assess renal cortical function and to detect scarring. A VCUG is performed when this ultrasound study shows bilateral urinary tract dilation, signs of urethral obstruction or when dilating reflux is suspected. And from time to time, contrast enhanced voiding urosonography can also be very helpful in particular situations we have found. Magnetic resonance urography or MRU provides both morphological and functional information to evaluate patients with complex anatomy and for pre-surgical planning and the final speaker will be discussing this. So I won't mention any more about it now. So urinary tract dilation is identified in about one to 2% of fetuses on antenatal imaging. And it is associated with a very wide range of possible postnatal outcomes. And the relative absence of evidence-based information correlating the severity of antenatal dilation to postnatal urological abnormalities has unfortunately in the past resulted in significant variation in postnatal clinical management. So there has been a perceived need for a long time for a unified system with widely accepted terminology for diagnosis and management of antenatal and postnatal urinary tract dilation. And the so-called urinary tract dilation or UTD classification system was devised in 2014 and it was designed to correlate with the risks of postnatal uropathy. And it's based on a set of sonographic features that can be applied both pre and postnatally. And those features include the AP renal pelvic diameter, the presence or absence of chaliceal dilation. It's hard to differentiate central and peripheral chaliceal dilation on prenatal sonography but it's easier to do so. And it is done on postnatal sonograms. An assessment of renal parenchymal thickness and the appearance of the parenchyma, the detection of any ureteral or bladder abnormalities and on the prenatal scans to look for the presence or absence of oligohydramnios. So here is a schematic diagram of the antenatal UTD classification. The UTD A1 category is low risk. And this is where the AP renal pelvic diameter is fairly small. So you can see the allowances for a slightly greater dilation in the later stages of gestation. There's either central or no chaliceal dilation. Whereas the higher risk category which is classified as A2-3 has more chaliceal dilation and any one of these additional findings. So abnormal parenchymal thickness or appearance, abnormalities of the ureter or bladder and unexplained oligohydramnios. Particularly when it's suspected to result from a GU cause. The postnatal UTD classification has three categories. Low risk or UTDP-1, intermediate risk or UTDP-2 and the high risk category UTDP-3. And as you can see again, the abnormalities for each category increase in severity. So central chaliceal dilation is a low risk. Once you start to get to peripheral dilation and or ureteral abnormalities, you move up in category to the intermediate risk. And then the most severe risk is generally associated with peripheral dilation and or parenchymal thickness and appearance abnormalities, abnormalities of the ureter and bladder. And these categories are then used in the ideal situation to guide postnatal management. So the low risk patients generally have less aggressive management and treatment. So follow up over a longer period of time, maybe a VCUG or an antibiotics will be obtained and a functional imaging is not generally recommended. As you go up in category to P2 and P3, the recommendations also become more specific. VCUG recommended, for example, in the P3 category antibiotics. And again, functional scanning can be performed depending on the individual situation of the patient. So let's look at some examples of a UTD-A1 here. This was a 21 week old male fetus who had bilateral mild dilation of the pelvis and the palaces on prenatal sonogram. And here we see the same patient's prenatal MRI showing the mild dilation and a normal appearing bladder. When this patient was born, the kidneys were scanned. And again, you can see there's mild dilation of the collecting system on the right, slightly more pronounced on the left. And this patient had a normal VCUG. And within a year, the left side of dilation had completely resolved and the right side of dilation had diminished. There was just a little bit left in that upper whole region. And so this was an example of UTD-P1 on the right, P2 on the left. And this was a case of transient palvocaliceal dilation. Here's another patient, UTD now A2-3, a 32 week, six day old male fetus who had moderate dilation of the pelvis and calyces and some mild parenchymal thinning. Here's the bladder on this prenatal sonogram. Here we have a prenatal MRI. You can see that it's dilated kidney and the collecting system with some thinning of the parenchyma. Here we have the normal side for comparison with thicker parenchyma, normal bladder. At birth, here's this abnormal looking kidney, very distended renal pelvis, central and peripheral calyces, normal bladder, and a normal VCUG. This patient did go on to have a functional study. And we can see that here on the left side, the uptake of the radio tracer is very diminished. There's no spontaneous drainage from a collecting system. Prior to Lasix administration, here we see after Lasix is given, there's very poor excretion on this left side. You see this almost flat excretion curve, whereas the normal right kidney shows very prompt excretion. And this was a case of a UPJ obstruction, UTD P3. Here's another patient now, again, UTD A2-3, a 35 week male fetus with marked now bilateral dilation of the collecting systems on each side and ureters with a distended smooth wall bladder. Here's the bladder, here's the left kidney, pronounced dilation of the collecting system, thinning of the parenchyma, here's the right kidney, a little thinning on that side too, somewhat less pronounced than on the left side, and we see dilated ureters here on each side. After birth, we see this right kidney again with thinning of the parenchyma, significant collecting system dilation, and the right ureter transfers to the bladder with a catheter in the lumen, here's the right ureter, here's the left ureter, the left kidney also dilated but with a greater amount of preserved parenchyma, very dilated ureter. VCUG was performed and you can see there's reflux on each side. Here on the right we have very dilated ureter, very distended calyces, the ureteral insertion site appears normal, and we're also seeing reflux on the left but there's a lot of dilution of the contrast material, the insertion site appears normal, here's a drainage image, there's not great drainage on either side but again a very dilute appearance of the contrast on that left side and a normal urethra. A MAG-3 study was done, here we are pre and post LASIKs, and since these are done from the back we see that there's only function in that left-sided kidney, the one with the dilute contrast, and we're not seeing any function on the right side at all. Prior to contrast administration we're not seeing any spontaneous drainage prior to LASIKs administration but after we do see that there is some drainage, and this patient had UTDP-3 with severe right-sided reflux and very impaired, really absent function, and on the left side a combined problem, reflux as we can see but also obstruction which explains the dilute appearance of the contrast material on that left side. Let's go on to the next case, here is a patient who had a cystic right kidney and a left kidney showing mild pelvic halocele dilation. So here's a bladder, here's a cystic right kidney, lots of cysts that don't appear to be communicating with each other, and here's the left kidney which is more normal in appearance but does have a mildly dilated collecting system and a normal appearing bladder. Postnatally we see that the renal fossa on the right is empty, we see these cysts down here in the pelvis near the bladder, this is an abnormal cystic kidney, ectopically located and here's the left kidney which again shows mild dilation of the renal pelvis and central calyces. Here's a VCUG that was negative but interestingly a contrast enhanced ultrasound which was performed at the same time shows that there's mild to moderate reflux on this side. We see the bladder and on the sagittal view we have a dilated ureter and the collecting system which is mildly distended as well. And here we have a DMSA functional study of the kidneys and we can see that there's only a function in that left kidney, the multi-cystic dysplastic kidney has no function. And so this was a right MCDK, a left UTDP2 patient with grade 3 vesicle ureteral reflux shown only on contrast enhanced imaging, ultrasound imaging. This patient is a 33 week old male fetus who had moderate to severe dilation of both renal collecting systems and ureters. Here we see the right side and the dilated left side and a dilated bladder as you can see here it's got a rather unusual sort of keyhole shaped appearance and posterior urethra and the other finding was that there was decreased amniotic fluid. We can see that there really isn't much in the way of amniotic fluid and that's also worn out here on the prenatal MRI. You see very abnormal kidneys with a tremendously dilated calyces and here we can appreciate the thick wall of that bladder and the dilation of the posterior urethra. On these axial views we see the dilated ureters as well, postnatally very abnormal looking kidneys on each side. So this is on the right side we see the very echogenic parenchyma, there's some peripheral cystic changes as well here on the other side, similar appearance, very echogenic parenchyma with loss of normal corticomedullary differentiation. Dilated ureters going all the way down to this very abnormal thick wall bladder. We have a catheter in the lumen and on the VCG we have the classic findings of posterior urethral valves with a very distended posterior urethra with the valves at this area and then an abrupt change in the caliber of the urethra, only a very small trickle of contrast getting through and on the drainage film again we see the very distorted hypertrophied bladder wall. So this was a patient with UTD-P3 posterior urethral valves. I'd like to show you another case, postnatal imaging of a patient with a duplex kidney and an ectopic ureter. This was a male infant who had a prenatal diagnosis of an obstructed upper pole of the duplex kidney but it was difficult to see where that ureter actually terminated prenatally. Here we see on sagittal view we have a duplex kidney with a dilated upper pole collecting system and ureter extending all the way down to the bladder but not inserting into the bladder but actually extending inferiorly and again we can't really see where it's terminating and here again contrast enhanced ultrasound can help us. We have the bladder, a transverse view filled with contrast, a very dilated ectopic ureter that we see here on transperineal imaging inserting into the neck of the bladder and where it joins the urethra. This dark indentation is the ectopic ureter. There's no reflux so it's not filled with contrast. Here's a companion image from the VCUG. Although we don't see reflux we again do get that impression that notching that sort of notch like area where that dilated ectopic ureter is inserting ectopically. Here's another example of a patient with UTD-A2-3, a 34-week, 6-day-old female fetus who has a duplex left kidney with severe dilation of the upper pole. This is the upper pole and moderate dilation of the lower pole of that kidney and with dilated ureter seen prenatally and this cystic structure in the bladder thought to be a ureter seal prenatally and also seen on this sagittal MRI image as well. Postnatal images again show the duplex kidney with abnormal collecting system and dilated ureters. Here's a dilated ureter from the upper pole, dilated ureter from the lower pole and this complex cystic structure within the bladder which is the ureter seal. Here we see it on a sagittal view with the dilated upper pole ureter which terminates within the bladder in this ureter seal. On VCUG, we see the bladder and the filling defect related to the ureter seal as well as a very dilated lower pole ureter which is refluxing as well. So we've got upper and lower pole abnormalities in this patient and here we have images from a DMSA scan where we have certainly very diminished uptake of radiotracer by the lower pole and you can see by the way it's oriented, this is the lower pole so there was no function in that upper pole where the ectopic ureter seal is located. We just have some function here in the lower pole where there's the reflux occurring and then a normal appearing right kidney. So this was a patient with UTD-P3, a duplex kidney with upper pole topic ureter seal and lower pole vesicle ureteral reflux. And finally, a case of a patient with abnormal kidneys detected prenatally. This was a 34-week, one-day-old female fetus with very enlarged echogenic kidneys, loss of normal corticomedullary differentiation but no abnormal dilation of the venal pelvis or of the ureters. Here on the right, a few very subtle cysts are seen peripherally and the patient had a normal appearing bladder. At birth, you can see that the kidneys here is the right kidney has multiple cysts, again very abnormal architecture and there's a similar appearance on the left side as well with multiple cysts, normal bladder. The liver also has a very coarsened appearance and although we don't have a genetic diagnosis at this point in time because a biopsy has not been done, this patient is presumed to have autosomal recessive polycystic kidney disease. So in summary, I've reviewed with you the postnatal imaging evaluation of the most common antenatally detected renal and bladder abnormalities. The majority of these disorders manifest with urinary tract dilation and most of them will be very well characterized just with ultrasound, voiding cystourethrography, and renal scintigraphy. So I thank you very much for your attention. Thank you for the privilege of sharing with you my passion in MRI urography. So my talk is largely broken up into two sections. First portion we'll discuss about the MRU protocol, specifically about patient preparation and the scan itself. We'll review the MRI sequences. The second portion we'll discuss about how to approach and interpret the information that we extract from the study. We'll review the functional parameters and specific clinical scenarios where the functional parametric changes take place and we can try to make sense of the information that we have. Some of the common indications for performing an MRU urography include neonatal hydronephrosis as well as congenital renal anomalies such as the duplex system and the ectopic ureters. And really the key question that we want to answer with MRU urography is whether or not the hydronephrosis that we observe is simply a patchwork system versus a presence of an active obstruction with increased intrarenal pressure. And this question is critically important for urologists because they have to understand whether or not to intervene or not. So overview of the MRU urography. As you can see it is divided largely into three parts. First is the patient preparation followed by the scan and post-processing and data extraction. In the patient preparation section we'll focus on the diet and hydration. In the scan itself I will review the sequences as well as some of the important key points regarding IV furosemide and IV contrast administration. And then post-processing we'll go over some of the parameters and how they change. Regarding diet at our institution we do not allow any solid foods starting six hours prior to imaging but we do allow clear liquids until one hour prior to imaging. And hydration is important so we do actually encourage patients to take liquids. Once the IV access is established we start a hydration protocol at 20 mils per kilogram for over approximately 30 minutes and then we send the patient over to the MRI scanner. Once the patient is on the table we will initiate moderate sedation and in our institution patients who are younger than nine years old will have moderate sedation but patients who are older than nine year old will not undergo sedation. We also do not perform feed and wrap at our institution. Once the patient is sufficiently sedated or comfortable on the MRI table we then place a Foley catheter and the Foley bag is placed next to the patient below the level of the bladder and checked for adequate drainage. You can perform an MRUgram in either 1.5 or 3 Tesla scanner. IV ferrosamide in contrast administration is done at specific times and to minimize motion especially during the dynamic phase we ask our sedation team to increase sedation several minutes prior to the dynamic phase imaging. So the table on the right is our actual MRUs protocol and sequences and the estimated time for each sequence. As you can see that the whole study takes about 40 minutes and if you could just take a note of when we give ferrosamide increased sedation and IV contrast administration and we try to perform these sequences very consistently and consistency is important. Regarding IV ferrosamide our dose is one milligram per kilogram with maximum of 20 milligrams. We give this at about 15 minutes prior to dynamic imaging and the reason is because the pharmacologic effect takes anywhere from five to 30 minutes and maximum pharmacological effect takes between 15 to 18 minutes. So we want to maximize the fluid and Lasix challenge so-called at the time when we acquired a dynamic phase imaging. Regarding IV Gatavis our dose is 0.1 milliliters per kilogram with maximum of 10 milliliters and we inject the gadolinium after a third dynamic phase has been initiated and the rate of contrast injection is actually weight class based. So we have four weight classes and the injection rate increases as the patient weight increases and we also have a slight differences in the injection rate depending on whether or not you use a 1.5 degree tesla magnet. We have an example here of a normal renal signal intensity curve. So as I mentioned in the previous slide we have a couple of baseline measurements at before time point zero and then inject the contrast and then you can see that the there's a brisk enhancement of the aorta which is the red curve followed soon after by the renal perfusion which is a phase one and phase two is actual glomerular filtration and interstitial phase and followed by phase three where the contrast is now beginning to percolate into the collecting systems. Before we move on to the review of the functional parameters I would like to review with you the concept of compensated and decompensated kidney. For compensated kidney it is generally accepted that the rate of renal drainage equals or exceeds the urine production. Therefore the intrarenal pressure does not rise and there is normal renal transit time and function. However on the decompensated kidney the rate of urine production exceeds the rate of renal drainage so the intrarenal pressure rises that's lead this leads to prolonged renal transit time and compromised kidney function. So next several slides a little busy I apologize but do follow with me. So we'll start with the review of functional parameters. The calyce to transit time is the time for contrast to pass from the renal cortex to the dependent portion of the calyces. Traditionally it has been reported as either symmetrical rapid or delayed compared to the contralateral kidney but more recently we have been reporting more actual quantitative time time values. Mean transit time is the average time for the contrast to pass from the glomerulus into collecting ducts. And in general less than 60 less than 60 seconds is considered normal renal transit time is the time for contrast to reach the up the ureter below the lower pole of the kidneys and as you can see the time points on the on the right that's what we go by. But I want to mention to you that the renal transit time will vary highly depending on how patchy or dilated the renal collecting system is. So this value is the least reliable value when you're assessing the MRU time to peak is the time for a kidney to reach the path maximum parenchymal enhancement. Value metric differential renal function is the volume of the enhancing tissue of a kidney divided by the total volume of the enhancing tissue of both the left and right kidneys. Pat left and right kidneys have a total volume of the enhancing tissue of both the left and right kidneys. Patelic slope also known as patelec number is the estimate of the glomerular contrast filtration using a two compartment patelec compartment kinetic model and patelec differential renal function is the patelec number of that kidney relative to the sum of both the left and right patelec number values unit patelec which is also the estimated unit GFR is the patelec number divided by the functional enhancing renal volume of that particular kidney. Unit patelec differential renal function conceptually similar to the patelec differential renal function but with unit patelec values is the unit patelec value of each kidney relative to the sum of both unit patelec. And an asymmetry index is a comparison of the unit patelec values for each kidney and it tells us any functional derangements there is between the kidneys and the formula for the asymmetry index is as you see there it's unit GFR of the left kidney minus the unit GFR of the right kidney divided by the sum of the unit GFRs of both the right and left kidneys and this value is statistically significant if the value exceeds approximately 0.12. Let's review the pattern of disease. So on the far left on the screen you see the various physiological states and then the functional parameters that we observe and see let's see how they change. So for the compensated kidney which is you know example with that of that would be in hydronephrosis, hydronephrodic kidney without any evidence of decompensation. Hydronephrodic kidney without any evidence of decompensation or obstruction. You'll see that compared to the contralateral kidney we'll see that the chelosterone transit time and mean transit time is fairly symmetrical or it may be even more rapid. Renal transit time will be variable depending on how patchy the collecting system is. The volumetric differential renal function is stable or it's not affected basically you know the volumetric differential renal function is derived from actual estimation of the functioning renal tissue and it's not really affected by the physiological state. That's why it's stable. The patella differential renal function changes would be pretty symmetrical to that of the contralateral kidney and the difference between the volumetric differential renal function and patella differential renal function is narrow. And then unit patella or the estimated GFR is fairly symmetrical compared to the contralateral kidney. Contrasting this with the decompensated kidney so this would be a you know hydronephrodic kidney with evidence of active obstruction. You'll see that the chelosterone transit time and mean transit times are both prolonged. Renal transit time will also be prolonged or delayed. Volumetric differential renal function is unaffected. Patella differential renal function is decreased. Difference between volumetric differential renal function and patella differential renal function becomes wider and unit patella value or the estimated unit GFR of the affected kidney is decreased. Moving on to post-pyloplasty kidney and this is compared to pre-pyloplasty values. In a post-pyloplasty kidney you'll notice that the chelosterone transit time and mean transit time values are fairly symmetrical or rapid. The renal transit time will be variable. Volumetric differential renal function is unchanged again. Compared to the pre-pyloplasty kidney the patella differential renal function actually improves and the difference between volumetric differential renal function and patella differential renal function is narrow and correspondingly the unit patella or the GFR of the post-pyloplasty should improve. In case for hyperfiltration, the transit times, mean transit time and chelosterone transit times are rapid, renal transit time again variable, volumetric differential renal function is unaffected, patella differential renal function is increased and the difference between the volumetric differential renal function and patella differential renal function is actually widened. The reason is because the affected kidney's unit function, the function of the affected kidney is actually paradoxically increased and you'll see an example of that and unit patella values increased as well. And then lastly the concentration defect, similar pattern of changes in the functional parameters with the compensated and hyperfiltration and oftentimes the concentration defects is superimposed on a compensated kidney as well but I just made it listed here because these are the changes that you would see in a concentration defect. Okay so we have our first case which is a 10-month-old with left-sided hydronephrosis. The image on the left shows you the mid reconstruction of our MRU showing left-sided hydronephrosis. The graph in the middle is the renal signal intensity curve and I have listed the functional parameters of the left kidney on the table on the right. So what is your diagnosis? A compensated hydronephrosis, B decompensated hydronephrosis, C hyperfiltration, D concentration defect. The answer is compensated hydronephrosis. Let's go over the reasons why. So here I have also listed the functional parameters of the right kidney which is the normal reference standard in analyzing the left kidney. You notice that the mean transit time and KLSU transit times are more rapid compared to the right kidney. The volumetric differential renal function and patella differential function and the difference between the two are narrow. The unit GFR of the left kidney is similar to that of the right kidney and the GFR, the slight differences in the GFR is not statistically significant. So this is a case of yes, there is hydronephrosis in the left kidney but there is no evidence of pressure rise with fluid and LASIK challenge. So this is an example of a compensated hydronephrosis. Case number two, 16-year-old with left-sided hydronephrosis, similar layout of the question. What is your diagnosis? A compensated, B decompensated, C hyperfiltration, D concentration defect. So the answer is decompensated hydronephrosis. Let's go over the reason why. I have provided the functional parameters of the right kidney which we will use as our internal standard control. Compared to the right kidney, the left kidney has markedly prolonged mean transit time and delayed KLSU transit time. You notice that volumetric differential renal function may be as they are but notice the drop in patella differential renal function in the left kidney and the patella GFR or the unit GFR of the left kidney is also compromised as well. And that difference in GFR is also statistically significant. So this is a pretty typical pattern of functional parameters, the changes in functional parameters that we see in a decompensated hydronephrosis. So this would be, you know, a kidney that would have actively rising pressure as a result of fluid and LASIK challenge. And for these kidneys, urologists would actually have to go in and surgically intervene to basically decompress it. Case number three, 16-year-old with right-sided hydronephrosis, similar question format, what's your diagnosis? A, compensated, B, decompensated, C, hyperfiltration, D, concentration defect. Hyperfiltration. And let's go over the reasons why. So again, in this patient with right-sided hydronephrosis with UPJ morphology, I have the functional parameters of both the right and left kidneys and you can see that in the right kidney, the transit times, which are the mean transit time and channel transit times are shorter or rapid compared to the left. The volumetric differential renal function is whatever the value that we get with estimation but you'll notice the increase in PADLAC differential renal function and the unit PADLAC, the estimated GFR in the right kidney. This is an anomaly that we observe sometimes and this particular pattern of change in the affected kidney is consistent with hyperfiltration. Okay, last question, case number four, seven-month-old with right-sided hydronephrosis, what's your diagnosis? Okay, the answer is concentration defect. Let's go over the reason why. So very similar to the previous case, right? But the only difference that we see here is that the PADLAC differential renal function and the unit GFR in the affected right kidney is low. So it's not exactly hyperfiltration but we still see the rapid transit times in the affected kidney. So this pattern of change is consistent with concentration defect. So in summary, I reviewed with you the patient preparation and imaging of the MY urography. We also reviewed the concept of decompensated and compensated hydronephrosis and reviewed the functional parameters that we extrapolate and evaluate with MR urography and how those functional parameters change with some examples of clinical scenarios that we commonly encounter. Thank you very much.

fetal imaging

urinary tract obstructions

fetal MRI

congenital anomalies

prenatal ultrasound

kidney development

UTD classification

MRI urography

hydronephrosis