The Fetal Genitourinary Tract - SD

Introduction

I am Beverly Coleman, professor of radiology at the University of Pennsylvania and Philadelphia.

And today we're going to discuss the fetal genital urinary tract.

Today's presentation is on the fetal genital urinary tract and we are going to cover what's normal, which I think is really important before we go on to discuss three other subtopics, renal developmental variants, urinary tract obstruction, and finally cystic renal disease.

Normal Fetal Urinary Tract

What We Know About the Normal Fetal Urinary Tract

What do we know about the normal fetal urinary tract?

The kidneys with the resolution we have available now can be visualized as early as 12 to 13 weeks on vaginal scans and 14 to 16 weeks on abdominal scans.

The kidneys exponentially increase in size with gestational age and there are grams now available for renal length.

There's a constant ratio between the renal and the abdominal circumference that's around 27 to 30%.

As the kidneys grow, there's increased conspicuity by the third trimester, so it's possible to display excellent cortico medullary differentiation and see the renal cortex, sinus and perinephric fat color Doppler can be used to evaluate the renal vasculature in utero.

Here's a slide that demonstrates normal fetal kidneys at various gestational ages.

Notice that early on using an eight megahertz transvaginal scan.

We can see that at 14 weeks.

Here is the appearance of the fetal kidneys that blends in with the normal texture of the abdominal structures on a scan at 20 weeks using a 12 megahertz transducer.

Notice that we can now see the renal pelvis and the renal capsule begin to be differentiated and by the time we get to 30 weeks using a 12 megahertz transducer, there's excellent cortical medullary differentiation where we can see the numerous pyramids and the kidneys obviously have grown exponentially in length.

This is a ciné clip at about 27 weeks showing the normal expected differentiation between the renal cortex peripherally and the medullary pyramid centrally, as well as the different architecture which is slightly brighter in the region of the renal sinus.

The Bladder

Similar to the kidneys, the bladder evolves over time.

It can be visualized earlier than the kidneys at about 10 to 12 weeks transvaginally and 14 to 16 weeks transabdominally.

By introduction into the second trimester, the vast majority of the bladder should be seen with either of these techniques.

What we know about the bladder is it fills and empties every 25 to 30 minutes, so you should be able to see the bladder cycle at least once during a normal obstetrical ultrasound examination.

Also similar to the kidneys, the bladder changes in volume over time with the maximum volume of up to 36 milliliters.

At term color Doppler can be used to display the umbilical arteries that lie on either side of the bladder.

And here's two examples of how the bladder can vary during a sonographic examination.

Different patients color doppler showing umbilical arteries and a collapsed bladder just after voiding in utero, whereas this is a very well distended bladder where we can actually see the adjacent umbilical arteries in gray scale.

Normal Adrenals and Fetal Gender

Now let's move on to the normal adrenals and fetal gender.

The adrenal glands are very small and are, as you know, in position they can be visualized much later clearly in the second and third trimester.

They also increase in size with gestational age and again, there are now nomograms to let us evaluate whether the adrenals are too large or too small.

Fetal gender is also important when evaluating the urinary tract and it's important to know that early on in the first trimester, the male female gender can really not be assessed.

After about 25 weeks, the testicles descend into the scrotal sac and should be clearly visualized in the third trimester.

The uterus and ovaries are rarely seen.

Here's an example of normal fetal adrenal glands and it shows our resolution over time with improved ultrasound equipment.

This is about 2003 and the adrenal glands of these vague sort of like hypoechoic areas on either side of the kidneys.

And then here is a more beautiful adrenal gland with a typical hypoechoic cortex and echogenic middle or medullary region in 2007.

And then finally by 2012 we can see the typical ice cream sandwich appearance of the adrenals with again the hypoechoic periphery and the more echogenic center.

Here's an example again, of the normal appearance of the genitalia.

By the time we get into the second trimester, we would like to be able to see the scrotal region as well as the penile shaft, which has a nice arrow appearance.

And in females this is at 28 weeks, we can see the region of the labia and the echogenic central line denoting female gender.

Why is gender assessment important If we are dealing with the urinary tract?

Well, there's certain structural abnormalities that involve the urinary tract that are more common in certain genders.

There's also family histories of X linked disorders.

There are syndromes that can be associated with genital anomalies and gender assignment, particularly in evaluating a urinary tract abnormality is important in multiple gestations and it can be used to exclude maternal cell contamination after an amniocentesis procedure.

Fetal Urine Production

What do we know about fetal urine production?

Well, we realize that it begins very early in embryonic life, but it's not detectable by the sonographer at that early gestational age.

Fetal urine production varies with gestational age from just a few milliliters per hour to up to 28 milliliters per hour at term.

After the first trimester ends and we are well into the second trimester, the vast majority of amniotic fluid actually is from the urinary tract and about a third still remains from pleural fluid from the lungs, early in gestation before the kidneys start to function.

The amniotic fluid is actually an ultrafiltrate of maternal plasma.

And then as the pregnancy advances the fluid more resembles fetal plasma.

By the time we get into the second trimester, again fetal urine production predominates in the 20 week range and here we can see how the volume increases from about 500 milliliters of amniotic fluid volume at 20 weeks, up to 1200 milliliters at 32 and 1800 at term.

There are multiple ways as you know, to evaluate amniotic fluid volume.

Subjective assessment is very reliable in experienced hands.

There's a semi quantitative method of evaluating amniotic fluid volume, looking at all four quadrants and then the fastest method is the deepest vertical pocket where you basically take a diameter vertical from front to back of the largest pocket of fluid.

At our institution, we basically report both the amniotic fluid volume as an index because we wanna see the overall appearance of the fluid in all quadrants.

And out of that we give a measurement for the deepest vertical pocket.

Clearly, amniotic fluid volume represents a very delicate balance between the production of fluid by the organs you see listed here and the removal of fluid again by the organs and structures that you see here.

And amniotic fluid volume is critical to the pulmonary development of the lungs during gestation in evaluating the abnormal urinary tract, which we are going to proceed to now, I think it is critical to use a systematic approach and we wanna ask ourselves a number of questions.

Are the kidneys clearly normal?

And if so, we should assess the number size location in the overall echo texture and intrarenal anatomy.

If the kidneys are not normal, are we dealing with unilateral or bilateral disease?

If we think there is disease, is it obstruction?

And if so, where is it and how bad is it if it's not obstruction, are there renal cysts?

Where and how significant are those?

Can we actually see the ureters in the bladder?

Well, are the adrenals in the genitalia normal?

And then overall and most important is, is there enough amniotic fluid volume so that the lungs will develop normally.

GU Abnormalities: Renal Developmental Variants

Now we are going to move into our various categories to talk about GU abnormalities and we'll start with renal developmental variants.

When we use this term, I'm actually referring to conditions such as absence of one kidney kidneys in the abnormal location and kidneys with various fusion anomalies.

And we'll start with renal agenesis.

As all of you know, this can be a unilateral or bilateral condition.

It's critical to distinguish between the two because unilateral renal agenesis has an excellent prognosis, whereas bilateral renal agenesis is basically fatal.

There is obvious differences in these two entities with normal fluid development because of the one normal kidney in a unilateral case in virtually no fluid in the bilateral case.

And all of you have seen examples of these.

So let's go on to see some cases this today.

Here's a solitary kidney on the right side that has excellent cortico medullary differentiation.

We can see the measurements of this kidney look at the cortex.

Notice the normal or general scan the kidney is normal in size and echo texture.

Color doppler demonstrates patency of the main renal artery and vein to that kidney and there is an abnormal flattened or lying down adrenal gland on the contralateral side showing that there's no kidney in the normal renal fossa on the left.

Another case of unilateral renal agenesis and a set of twins, a flattened hypoechoic adrenal gland on the contralateral right side and a normal kidney.

On the left side.

Here again we can see the left renal artery going to the kidney that is spared on the left, an absence of a renal artery on the right.

Bilateral renal agenesis as I previously mentioned, is a lethal condition.

Again, more common in males than females with a two and a half to one ratio.

Because there are no kidneys, basically the key finding is that the amniotic fluid is down and we cannot find a normal bladder.

Occasionally you can be fooled because the adrenals may appear prominent and simulate the kidneys.

There's less than expected fetal movement.

There's mal development of the lungs and oftentimes because of the lack of amniotic fluid, there's abnormal face that have been referred to as the potter's face.

Here's an example of bilateral flattened adrenal glands and this is musculature, but notice we have the ice cream sandwich appearance here and color doppler shows absence of the renal arteries bilaterally.

Here's another case that we evaluating with the vaginal approach and I urge you to use that if the fetus is in a breech position.

Here we can see that the adrenal glands are flattened bilaterally with the hypoechoic cortex in the echogenic center.

Here we see looping using the vaginal approach and the total lack of amniotic fluid volume.

This is an example of bilateral renal agenesis and a set of twins where one twin has the VACTERL complex.

Notice that there is a lower extremity abnormality.

Musculoskeletal anomalies are common, including limb abnormalities.

And here we see fusion of the left foot that actually had approximately eight toes in the setting of a normal and separate right foot here is the lying down of flattened adrenal gland, absence of the bladder with the two umbilical arteries adjacent to each other and notice that there are musculoskeletal abnormalities with a fused vertebrae involving the ribs.

This was a case of dichorionic diamniotic twins and therefore a cord cautery was performed of the abnormal twin and the parents went on to deliver a normal singleton.

Renal Ectopia

Renal ectopia basically refers to the condition of the kidney not being observed in its normal retroperitoneal position in the flank.

In a number of cases when we don't see the kidney in the normal flank, there's gonna be unilateral renal agenesis about 50% of the time.

However, it is important if the kidney is not visualized in its normal position to go and look in other areas because 37% of the time the kidney will be in a pelvic location.

There may be renal ectopia because of fused deformities such as horseshoe kidney and crossed fused renal ectopia and therefore it's important to look low in the pelvis for the kidney.

What does the pelvic kidney look like?

Basically, again, the renal fossa is empty, there's a flattened adrenal gland the same as if the kidney were absent.

And then the problem with looking at it in the pelvis is that it can be hypoechoic and similar in architecture to the bowel and be missed and therefore it's important to turn on color doppler to look for the renal artery going to the pelvis.

'cause often that can be used to help you localize exactly where the kidney is.

These pelvic kidneys can be normal in size.

Sometimes they can be malrotated and difficult to visualize.

Here we see one case where it was a referral for unilateral renal agenesis.

Note that there's a left kidney in the normal renal fossa.

On the right side we see the liver and no kidney Here is a malrotated pelvic kidney low and in a unusual configuration on the right here's the normal left kidney in the normal renal fossa and color Doppler shows a high takeoff of the left renal artery compared to a lower takeoff just above the bifurcation of the right renal artery going to the pelvic kidney.

Here's another case where there is absence of the right umbilical artery and here we see a two vessel cord with the left and no.

Right here we can see the renal artery extending again low just above the bifurcation.

Going to what appears like a dysplastic pelvic kidney that is actually easier to localize because there are numerous renal cysts adjacent to the bladder.

And here we can see that dysplastic kidney measured on this static image and notice that the adrenal glands are shown here with a sort of flattened appearance.

And the reason is because there was unilateral left renal agenesis so no kidney on this side and a dysplastic right pelvic kidney which basically is the same as having neither functioning kidney.

So this condition is not compatible with life.

Horseshoe Kidney

A horseshoe kidney deformity basically refers to communication of the lower poles by a renal isthmus that's usually anterior to the aorta and inferior vena cava.

It can be missed if it's just a fibrous connection, but if there's a significant amount of renal tissue, you can actually see the communication and as the fetus breathes and moves that the two kidneys actually move as one.

Oftentimes these kidneys are malrotated with the lower poles angling toward the midline and this condition can be associated with various aneuploidies like trisomy 21, turner syndrome.

Myelomeningocele cases actually can be associated with horseshoe kidney.

So let's look at an example of that.

Here we can see at 17 weeks the lower pole tends to be down and curved toward the midline.

More here is the contralateral right kidney, again the kidneys are down, here's the bladder and the lower pole is curved more medially.

And if we have a coronal view, here's the bladder and here we can see the communication to the two lower poles.

This is the isthmus of the horseshoe kidney deformity on this image and if you look in real time in this case we can see that there is a communication across.

But interestingly the right moiety of the horseshoe kidney is dysplastic and easier to visualize because of these numerous scattered cysts and the kidney communicates with the contralateral more normal echo texture of the left renal moiety color Doppler shows that there is a vessel going to each of the kidneys and here is a dysplastic right kidney.

Here is the left kidney with the isthmus coming across communicating between the dysplastic right kidney and the more normal echo texture of the left renal moiety.

And this is a patient who could survive because there's normal amniotic fluid volume On this image there was a normal filled bladder, so the left renal moiety is functioning at least at this time.

Crossed Fused Renal Ectopia

Cross fused renal ectopia refers to an ectopic kidney that's low in the pelvis, however it's in the opposite flank.

Most often this occurs when the left kidney is low and fused to the contralateral right kidney.

Approximately 95% of the time the kidneys can appear large and bilobed.

The renal arteries again are often a tip off.

Usually one is slightly more inferior and again these can be associated with neuromuscular or musculoskeletal abnormalities.

Here's an example of crossed fused renal ectopia.

And on this ciné clip we can see that there are two renal pelvis here and here.

This is a renal moiety.

Here's a contralateral renal moiety and we can see the bladder here.

This kidney has crossed over and fused with the lower pole of that kidney color.

Doppler shows the renal vessels going to the two different moieties and clearly separate from the bifurcation of the aorta that we see lower down.

This is a view showing the fused moiety and color doppler showing the two renal vessels going to the different moieties and notice that the adrenal glands again have a flattened lying down appearance because the kidney on the left side that has crossed to the right is not in its normal retroperitoneal location.

Another example of crossed fused renal ectopia.

The kidney has a appearance of more renal tissue than is expected all on one side.

And here we can see this large area of renal tissue again where the left side has crossed and fused with the lower pole of the right renal moiety.

This is an unusual case of a pancake kidney where both renal moieties are sort of thick.

The kidneys are down and notice that the upper poles in the lower poles are almost at the same levels.

The renal hilar appear to be kissing each other and this is what we would call an old fashioned pancake kidney and you can actually measure kidney one and kidney two and notice that they're about at the same level and very, very similar in overall echo texture.

Urinary Tract Obstruction

Let's move on to urinary tract obstruction.

And under this category we are gonna discuss mild renal pelvis dilatation because I talked about that yesterday.

UPJ obstruction UVJ pathology and finally end up with lower urinary tract obstruction.

Mild Renal Pelvis Dilatation

Just a brief mention of mild renal pelvis dilatation.

Again the concern for this condition is that it can be a marker for trisomy 21 and other aneuploid conditions.

We usually evaluate the renal pelvis again by taking AP measurement on the axial transverse view we use the numbers greater than four millimeters in the second trimester and greater than seven millimeters in the third trimester to refer to mild renal pelvis dilatation.

The vast majority of these patients will actually resolve in utero again as we discussed yesterday.

And if the renal pelvic diameter persists and stays large or progresses in utero, then these patients can be evaluated after birth.

Most often this can be a bilateral symmetric condition.

If it's unilateral, generally there's mild dilatation of the right more commonly than the left.

Only 3% of normal fetuses will have mild pelvis dilatation and again this condition can be progressive in utero.

And the most important thing in dealing with mild renal pelvis dilatation is to distinguish those patients who need further workup from those who do not.

And again, here's an example of very minimal dilatation of the renal pelvis in the left, nothing on the right but here's the appearance of the left renal pelvis compared to the right without evidence of ectasia and normal cortical medullary differentiation.

So these are basically normal kidneys of no real concern.

An extrarenal pelvis can occur as a variant of normal.

This is an interesting case where it actually occurred in a pelvic kidney we can see that the kidney is very low and actually the extrarenal pelvis which is full, helps us identify this pelvic kidney.

With the lower pole adjacent to the bladder, we can see an extra renal pelvis in kidneys in their normal location.

And basically it just refers to the renal pelvis outside the region of the renal cortex and in the region of the renal hilar, this patient had normal gender and a fluid filled bladder.

So no real concern there.

Significant Dilatation of the Fetal Urinary Tract

So what do we do when we think about significant dilatation of the fetal urinary tract?

A grade zero if you look at the fetal urology grading system is basically normal.

One is considered very mild dilatation of the pelvis possibly with visualization of the infundibulum with no ectasia.

When you start to get a few mildly dilated calyces that goes on to two, all of the calyces are three and frank overall ectasia with pressure and mass effect on the developing renal cortex is the most severe grade or grade four hydronephrosis if you will.

So criteria for significant hydronephrosis, again we wanna emphasize mild renal pelvic dilatation can change, it can be transient during the examination it can be a physiologic change or it could be an abnormality in the second trimester.

Mild is considered less than seven and greater than four and moderate is seven to 10 and severe is greater than a centimeter.

So anytime the renal pelvis is larger than a centimeter, we want to begin to be concerned in the third trimester.

Those numbers increase as you can see here, greater than 1.5 centimeters is considered severe.

Anytime the pelvis gets greater than a centimeter something is going on, even if it's a variant of normal or very mild ureteral pelvic junction obstruction.

And the importance is to determine which patients should be followed and monitored to see if there's possible progression to significant renal disease in utero.

So let's start with some common anatomic entities and we'll go with ureteral pelvic junction obstruction first.

Ureteropelvic Junction (UPJ) Obstruction

This UPJ area is the most common site for prenatal obstruction.

It has been estimated to occur in about one in every 2000 live births.

So obviously if you evaluate a lot of obstetrical cases you're gonna see UPJ obstruction.

The tip off is if the pelvis is dilated without a dilated ureter or bladder, it can be mild at seven millimeters, again moderate at seven to 15 and severe, greater than 15 millimeters or 1.5 centimeters.

And there are various causes as you can see here.

One of the main concerns with UPJ is is often associated with a contralateral renal abnormality reported in as many as one fourth of cases.

And the significance is what is that extrarenal anomaly?

Are there other structures that can be involved outside of the urinary tract?

And in addition, what is the significance of the contralateral renal anomaly?

Obviously if we have a UPJ obstruction and renal agenesis, all of the renal function is going to come through that one kidney that has a UPJ obstruction and that can be of concern if it is a unilateral abnormality.

Generally all the time the amniotic fluid volume will be normal.

Occasionally you can get what we call paradoxical polyhydramnios and it's been reported in up to a third of the cases.

If there is oligohydramnios or anhydramnios, again that puts the fetus at significant risk Because of the question of whether there is going to be developing pulmonary hypoplasia, 10% of UPJs can be bilateral and again that is compatible with life as long as they're not severe obstructions.

Here's a case of mild bilateral UPJ obstruction.

One extrarenal pelvis turned out to be nine millimeters, the other turned out to be 10 millimeters.

There were umbilical cord cysts that evolved during pregnancy again of no concern.

And this kid went on to a normal delivery and had postnatal ultrasound examination that showed bilateral mild UPJ obstruction.

Here's a unilateral UPJ obstruction at about 19 weeks of gestational age.

Here's the dilated renal pelvis.

We can see that there's mild dilatation of the upper pole and the lower pole calyx.

Here's the renal pelvis that's seven millimeters and notice that the contralateral kidney is totally normal.

Here's color doppler showing the renal vessels.

Here's the dilated pelvis of the UPJ obstruction and normal male genitalia.

The obstruction can become so severe that you actually get what we call blown out UPJ obstruction in the cyst that the weakest part of the urinary tract obstructs.

And then there's a leak and this is not the pelvis but a very large urinoma.

Here is the collecting system and the kidney deviated by this very large urinoma.

This is the renal pelvis and the dilated collecting system.

Notice the ballooned calyces.

Here's the stomach that is compressed and displaced by this large urinoma, which is a collection of localized urine due to rupture usually of an infundibulum, with adjacent fluid collection near the kidney but outside of the confines of the cortex.

Ureterovesical Junction (UVJ) Pathology

Let's move on now to ureterovesical pathology.

This is probably most commonly going to be related to duplication of the collecting system.

We can also see an ectopic ureter sometimes with a single collecting system stenosis at the UVJ or a condition called congenital megaureter.

So let's start looking at examples of what's most common obviously.

And that's gonna be the duplicated collecting system.

All of you have probably seen cases of this where you actually see a kidney that has more than one renal pelvis and as you know the size is going to be asymmetric 'cause in unilateral cases oftentimes the duplicated system is going to be larger more than 95% of the time.

The upper pole moiety just for review is the one that tends to obstruct the lower pole collecting system tends to reflux And the bladder can be scanned multiple times to try to check for ureteral jets because this condition is more common in females, you wanna always look for the genitalia.

Here's an example of a kidney that looks quite prominent and the issue is, is this a duplicated collecting system And we can see what looks like a renal pelvis and what is the area that we see up here.

It looks like another part of the collecting system.

And notice the long appearance of the kidney.

And here we can see that there's duplication with two renal arteries, one coming off normally on the left and another coming off lower just above the bifurcation.

And here's that right kidney that has a smaller length overall compared to the left kidney which is actually duplicated.

Here's another case of duplication and we can see the renal pelvis are extra renal in this case.

Both of them are dilated in the six to seven millimeter range here in the region of the bladder.

You should never see linear or rounded echogenic structures within the bladder.

These are ureteral jets that we can see here.

And here is a view of the right kidney and the left kidney.

With the dilated renal pelvis.

These were ectopic ureters in a case of ectopic ureters with solitary renal pelvis.

And here's the region of the ureters.

Here's a duplication with severe upper pole obstruction and lower pole reflux.

And if you notice there is ectasia with thinning of the cortex in both of the lower pole region and the upper pole region.

Notice the tortuous and dilated ureters that we can see here.

And here we can see ureteral jets within the bladder area.

Again, you should never see echogenic webs or linear areas within the region of the bladder.

And this is a case where we have severe upper pole obstruction and lower pole reflux with ureteral jets again seen bilaterally.

Here's a unilateral duplication where reflux interestingly is more severe than obstruction 'cause in the typical case it's the other way around where the upper pole is more often dilated than the lower pole.

And here we can see a markedly dilated lower pole.

This is the upper pole near the region of the diaphragm.

Here's the stomach, here's the pelvis for the upper pole compared to the pelvis for the lower pole.

This is a view measuring the kidney which is over four centimeters in length which would be the size for a term kidney.

And here we can see the duplicated renal arteries.

Going to this kidney of unilateral duplication where the main issue is reflux rather than obstruction.

Again, this can be monitored during fetal life and evaluated afterwards.

Here's an example of bilateral duplications, again ureteral jets.

At the bladder base we can see that there's two linear echogenic areas and here a more typical appearance of a greater degree of dilatation in the upper pole compared to the lower pole.

So this is a case where there is more dilatation from the obstruction of the ectopic ureter as opposed to the more normal orthotopic ureter.

Here's one kidney on one side and the contralateral kidney on the other side where the lower pelvis is a little bit bigger.

Bilateral duplications.

There was an excellent study even though it's old that looked at postnatal outcome of a lot of kidneys that suggested diagnosis of hydronephrosis after 20 weeks in utero they graded the kidneys using the urologic society grading and the findings were as you would expect, the lesser degree of obstruction, the least dilated the kidney.

The more likely this could be managed medically and very conservatively as opposed to the greater degree of dilatation and obstruction, the more likely surgery would be needed to handle the genital urinary abnormality.

Here's another study where they looked at the AP diameter of the renal pelvis and correlated that with the degree of dilatation that was observed postnatally and with the need for postnatal corrective surgery and whether there was actual renal compromise.

And again, as you would expect, the greater the degree of dilatation, this is seven to nine to greater than 10 millimeters compared to a lesser degree of dilatation, the more likely there would be to have renal compromise after birth and the need for corrective surgery after birth and after up to 50 to 60% of cases where the kidneys were more than nine to 10 millimeters dilated in utero.

Here's an example of a case of congenital megaureter and we can see that there is dilatation of a big tubular structure but notice that the tubular structure is outside the kidney.

The renal pelvis are not absolutely huge.

There's well-preserved renal cortex, there's cortico medullary differentiation.

The kidney is somewhat echogenic but the vast degree of dilatation is related to this markedly dilated ureter.

This is actually the ureter, this is the lower pole of the kidney.

The structure underneath was the bladder and we know that this is a bladder 'cause we can see its cycle and change over time.

So here's an example of a congenital megaureter, A significant anomaly which would again have to be evaluated after birth.

And here we can see another case where we observe that there's voiding in utero marked dilated ureter that we can see here.

Here's the renal pelvis and color doppler is showing a normal kidney with flow on the contralateral side flow to the affected right kidney.

And here again is the normal kidney and we need actually one normal kidney for survival.

Notice the appearance of the normal left kidney in congenital megaureter.

Lower Urinary Tract Obstruction (LUTO)

Let's move on now to lower urinary tract obstruction, which will be our final category under the obstruction category.

The imaging features of this would be a dilated bladder, kidneys and ureters 'cause the obstruction is going to be somewhere down, near the lower urinary tract.

The degree of dilatation does not necessarily correlate with the dysplasia and the most important thing is to find out if there has been terminal damage to the kidneys such that they're not functioning very well.

There's a lot of terms that can be used.

We used to call this almost all the time posterior urethral valves, but now generally we use the designation LUTO to refer to some type of obstruction lower down.

Here's an example of the typical keyhole appearance where we have a dilated thick wall bladder and a dilated posterior urethra.

Here's a view of the posterior urethra adjacent to the rectal sigmoid colon.

Notice that the bladder in the urethra a much more dilated than the renal pelvis in this case.

Here is another case of an absolutely huge bladder.

You generally, again as I noted, should not show debris or any kind of solid material in the bladder.

3D rendering showing the bladder is extending to the level of the gallbladder.

Here's the fluid debris level where the bladder is much more dilated than the contralateral renal pelvis that we can see here.

And we can actually estimate the bladder volume greater than 80 milliliters, so clearly not normal in utero.

Obstructive cystic dysplasia we can actually characterize obstruction in utero based on potter's, designation.

Type four is GU tract obstruction where we can have either unilateral bilateral disease.

The kidneys may be larger small and the worst prognosis is if we go on to cystic renal dysplasia in lower urinary tract outlet obstruction.

That is a definite risk because both kidneys are at risk because of the lower level of obstruction.

Here we see a markedly dilated keyhole. Here's the bladder.

Here are dilated ureters on either side.

Again, the bladder notice that the kidneys are already echogenic.

The renal pelvis are not nearly as dilated because the kidneys can actually stop making urine.

And here on this view we can see that renal cysts have already started to develop within the kidneys.

You can actually have dysplasia of the kidneys that can be segmental.

Here we can see renal cysts scattered around the region of the upper pole of the left kidney at 20 weeks.

As long as the lower pole appears normal and stays normal and the contralateral kidney is okay, this kid can have a reasonable outcome.

What do we use for criteria to make a diagnosis of renal dysplasia?

Overall, echogenicity is not as specific.

So the most sensitive and specific finding is renal cyst.

If you see renal cortical cysts, there's a hundred percent specificity and a hundred percent predictive value for the finding of renal dysplasia, which is less specific if you have overall renal echogenicity as it's increased without cysts or clearly less specific than just dilatation per se.

When can we see hyperechoic kidneys or echogenic?

It can be obstructive renal dysplasia, hereditary disease and even non hereditary diseases.

And we can have examples with ischemia or infection.

We can see echogenic kidneys in various syndromes such as beckwith wiedemann and also in chromosomal abnormalities in various conditions.

And even echogenic kidneys can be seen as a normal variant.

Here's a patient with normal sized echogenic kidneys.

Obviously normal amniotic fluid volume and some articles have been written about the significance of this and whether this can be a variant of normal and some of these patients, will not terminate and elect to be followed and we have had some cases where the kidneys went on to have a normal outcome even though they appeared echogenic.

The most important thing is similar to when we are evaluating echogenic bowel to look at the kidneys with various transducers to see if the overall increased echogenicity holds up regardless of the resolution of the transducer used.

Here's an example of lower urinary tract obstruction in twins where the male was affected.

Notice that the kidneys are overall echogenic and they are echogenic bilaterally with a lobulated urinoma outside the left kidney.

Here we can see the increased echogenicity and cortical thinning of this kidney.

And because this was an IVF pregnancy and this, pregnancy, is at risk, the outcome for this kid is going to be limited compared to the other twin.

We can make management decisions about how we would like to handle this case.

With the outcome of possibly a normal contralateral twin.

He has lower urinary tract obstruction at 21 weeks.

When you have blowout of lower urinary tract obstruction, you can actually have gross urinary ascites, which is what we see in this case.

The kidneys are plastered against the retroperitoneal wall and notice that they maintain their cortico medullary differentiation.

They're not brightly echogenic and urinary ascites can actually be a good thing.

This is massive urinary ascites where there's less pressure on the collecting system.

Notice the degree of splaying of the ribs because of the gross urinary ascites.

And again, these patients can be tested to see if the kidneys are going to function.

Normally what we do is a fetal urinary biochemistry, tap the bladder three times to see if the kidneys are going to fall in the normal range.

And we can test entities such as sodium chloride, osmolality and the other entities that you see here to see if the kidneys are actually functioning.

Normally when we get abnormal values we can counsel the parents that the kidneys are not going to do well because they're not functioning well in utero.

When we talk about whether the dysplasia is related to the distended bladder, notice that a, dilated bladder is not always cause for total loss of renal function because the bladder can be distended from various entities.

And here you can see that we have listed the more common posterior urethral valves all the way down to other syndromes that are not even necessarily obstructive, in etiology.

Here's an example of a patient who, has GU anomalies associated with non-immune hydrops.

And so this patient is going to get a poor prognosis because you can see the heart is beating slowly.

There's urinary ascites, there's overall cardiomegaly, the kidneys are already appearing echogenic and even though we don't see cystic renal dysplasia at this point, this isn't going to be a case where we are concerned.

Whereas megacystis in this case we can see a markedly dilated penile urethra.

This is a male fetus.

We are looking at the genitalia but we can again be concerned because there are tiny little cortical cysts that we can see in these kidneys that are very echogenic.

And so there is a degree of obstruction even though it's not, posterior urethral valves in a male, the kidneys are already being adversely affected.

This is a case of a female fetus.

So lower urinary tract outlet obstruction is not going to be in the differential diagnosis based on posterior urethral valves.

This is a case of megacystis microcolon intestinal hypoperistalsis syndrome.

We can see the huge bladder, the dilated collecting system in tortuous ureters and the collapsed hypoperistalsis bowel in this female patient that almost looks like lower urinary tract outlet obstruction but is a totally different entity.

Cystic Renal Disease

When we talk about classifying cystic renal dysplasia, potter described four different types and here we can see autosomal recessive disease type number one multicystic dysplastic kidney two dominant disease three and obstruction comes in under the fourth category.

So let's look at some examples of this.

One of the most common is gonna be multicystic dysplastic kidney a Potter type two.

All of you have seen examples of these cases where the kidneys are enlarged with various cysts.

Male to female ratio is two to one and in unilateral cases, which is 80% of the time, you go on to a normal outcome.

Here's a unilateral case of multicystic dysplastic kidney, totally normal contralateral kidney, likely a good outcome 'cause we only need one kidney for survival.

In multicystic dysplastic kidney, there's random distribution of the cysts that can be variable in size.

There's no communication between the cysts.

You lose a normal renal form contour where is generally in hydronephrosis, the calyces line up in a row, they communicate with the pelvis and the contour is preserved.

What we usually do with multicystic dysplastic kidney, particularly if the contralateral kidney is normal, we will follow these patients over time and make sure that the amniotic fluid volume stays normal and deal with it after the fact.

If it's a bilateral case that is not compatible with survival.

And here we can see bilateral enlarged kidneys, multicystic dysplastic kidney disease the same as having no kidneys and that is a lethal condition.

Similarly, autosomal recessive polycystic kidney disease is lethal.

Large echogenic kidneys bilaterally greater than two standard deviations above the mean.

These kidneys don't function and so the bladder is absent.

Here we can see markedly enlarged echogenic kidneys.

We now have the resolution sometimes to be able to actually see some of these tiny little cysts.

As you know, this condition is not compatible with life.

Oftentimes the kidneys can be so enlarged that they enlarge the entire abdomen.

We wanna differentiate clearly between autosomal recessive and dominant disease because dominant disease is generally normal amniotic fluid volume and normal renal function at birth compared to the lethal autosomal recessive disease.

Here is another case of autosomal recessive polycystic kidney disease where we can actually resolve some of the tiny little cysts.

But notice that this does not have the appearance of multicystic dysplastic kidney bilaterally.

This case was actually referred to us as bilateral renal agenesis.

And so if you have trouble, finding the kidneys in echogenic, conditions like this, you can always, sometimes resort to using a vaginal probe.

Here we can see that there's virtually no amniotic fluid and this case is not compatible with life.

And here we use the vaginal scan using an eight megahertz and you can see that these are enlarged kidneys are more visible.

Here's a liver up here.

The kidneys are almost going to the level of the heart.

Autosomal dominant polycystic kidney disease is much rarer, often can be totally missed in utero.

Here we see enlarged echogenic kidneys, but not nearly as large as the recessive kidneys.

Using a nine megahertz we can actually resolve a couple of the small cortical cysts in utero.

So important to make that differentiation because this is compatible with life and with survival.

Conclusion

I'd like to end in conclusion to describe what I believe is, the whole point of this, talk, which is that it's really critical.

Examine the entire GU tract using a systematic approach.

We need to try to make as a specific diagnosis as possible look carefully for associated abnormalities because that helps in the counseling of the patients and we wanna be able to give as much information as possible so that the appropriate management can be, used in every single pregnancy case with the GU abnormality.

Thank you for your attention.