Fetal Genitourinary System - HD

Introduction

My name is Sarah Durphy.

I am a assistant professor of radiology at Harvard Medical School and an attending radiologist at Brigham and Women's Hospital in Boston, Massachusetts.

And I will be speaking on fetal genital urinary abnormalities.

I have no financial disclosures.

Overview of Genitourinary Abnormalities

Genital urinary abnormalities comprise about 20% of all congenital structural anomalies and about the majority of these congenital anomalies in the GU tract can be detected prenatally in approximately 80 to 85% of cases.

It's important to make the diagnosis prenatally because this will permit antenatal counseling as, as well as permit prompt postnatal evaluation and treatment, thereby avoiding therapeutic delays that may result in loss of renal function.

Potentially these anomalies may be isolated or can be seen with other abnormalities, particularly chromosomal abnormalities can be seen in 12% of these fetuses.

And unlike other abnormalities, genital urinary abnormalities may in fact lead to other deformities which we'll discuss shortly.

A-U-A-I-U-M guidelines state that all second and third trimester ultrasounds should include images of the kidneys or the renal fossa.

And we can start to see the kidneys on prenatal ultrasound at about nine weeks gestation transvaginally, and 12 to 13 weeks gestation transabdominally.

And it's not until the around 20th week gestation that you begin to see the nice cortico medullary differentiation that we can see here in this kidney of a fetus of about 20 weeks gestation.

Evaluation of Fetal Kidneys

When we evaluate the fetal kidneys, we need to assess for the presence of two kidneys and the location in the renal fossa and sometimes this view here with color doppler, a coronal view of the aorta can nicely show you the renal arteries on both sides, which can confirm the presence of a kidney on either side of the fetus, which sometimes the kidneys may be somewhat difficult to assess since they are only slightly echogenic.

And their margins can be somewhat ill defined.

We can look at the size of the fetal kidneys echogenicity, and also look for cysts or hydronephrosis.

We don't normally see the fetal ureters because the caliber of the ureter is usually less than about a millimeter, but as the ureters dilate to two to three millimeters, as you can see here with fluid within the ureter, we start to be able to see the mildly dilated ureter.

A UM guidelines also state we should be able to see the bladder within the pelvis and certainly even during the first look examination at the end of the first trimester, we can see fluid within the bladder within the pelvis.

The umbilical arteries will splay around the bladder in some cases and we can confirm that this is actually the bladder and not a pelvic cyst perhaps because the bladder will fill and empty over time.

Changing size.

Now it's important to understand that the amniotic fluid is virtually all generated from amniotic fluid by about 18 weeks gestation.

So a normal amount of amniotic fluid confirms that at least one of the kidneys is functioning properly and there's a patent conduit from the kidney to the bladder and then out into the amniotic fluid and an overall good prognosis for the fetus.

However, if the amniotic flu is diminished and there is severe prolonged oligo ramoses, which can occur if the kidneys are not functioning properly or if there is severe obstruction bilaterally, this in turn can lead to other abnormalities within the fetus, including pulmonary hypoplasia, which is important because this can be lethal as well as facial abnormalities including lowed ears or a flattened nose and limb positional abnormalities including club feet and other, positional abnormalities.

Renal Position Abnormalities

Now, when we look at the fetal kidneys, let's first talk about whether the kidneys are present and if they're present in the proper location.

So what do we think about when we can't see the kidney in the expected location of the renal fossa?

Well, about half the time, this is due to the fact that the kidney developed normally, but is in a location that is not within the renal fossa, and this is renal opia.

The most common cause of renal ectopia is a pelvic kidney, but horseshoe kidney or cross fused utopia can also be seen with renal ectopia half of the time.

However, when we don't see a kidney within the renal fossa, this is because the kidney failed to develop it all and this can be unilateral or bilateral.

Now sometimes it's hard to tell whether the kidney is present or absent within the renal fossa.

And there is a sign the lying down adrenal sign, which was described way back in 1992 to confirm the absence of a kidney within the renal fossa.

The normal adrenal is, has an inverted y shape and when there is no kidney in the renal fossa, this adrenal gland can stretch out into the renal fossa, which is unoccupied and look like a long linear hypoechoic structure sort of adjacent to the spine within the renal fossa.

And this is the lying down adrenal sign and it implies that there is no kidney within the renal fossa.

Pelvic Kidney

Now when we talk about renal ectopia, again, the most common cause is a pelvic kidney and this occurs when the, kidney develops normally, but never, ascends normally into the renal fossa during development and what you'll see and a transverse view here in the abdomen, we have a normal left kidney with a little bit of fluid within the renal pelvis and there is no kidney identified in the right renal fossa.

And this of course could be confirmed in a para sagittal view with the lying down adrenal sign.

But instead we looked in the pelvis and you can see it's a little bit tough to see this sort of transverse, positioned kidney sitting above the fetal bladder low down within the fetal pelvis.

This is a pelvic kidney.

Now pelvic kidneys can be hard to see that mildly echogenic kidney can be obscured by adjacent bowel within the fetus.

And in this particular case prenatally, a normal left kidney was seen and there was nothing in the right renal fossa and no pelvic kidney or other kidney could be identified on the right and this was thought to be unilateral renal agenesis.

However, the baby was born and was brought down for a renal ultrasound and you can see nicely in the right upper quadrant a nice line down adrenal sign, which looks so pretty because this has taken postnatally.

And when we searched even more, we looked down in the pelvis and you can see in the right lower quadrant a pelvic kidney which was not able to be identified prenatally.

Crossed Renal Ectopia

Now, cross renal opia is a rare cause of renal opia and this occurs when, one kidney ascends normally and the second kidney on the other side instead of ascending normally crosses over to the contralateral side and ascends, beneath the normally position kidney.

And the upper upper pole of that malpositioned kidney fuses with the lower pole of the normally positioned kidney.

And so what you have is one enlarged bi lobe kidney representing the two kidneys attached together.

Here's the normally positioned kidney and then the second crossed, fused kidney below it with nothing on the other side.

And here we have another case of cross renal utopia.

This case was not picked up at 18 weeks gestation.

There was, thought to be normal kidneys, it was difficult to say, but there was a two vessel cord and two vessel cords can often be seen in the presence of genital abnormalities.

The patient was brought back at 26 weeks for a growth scan and when you look in the right renal fossa, there's the line down adrenal sign.

There is no right kidney within the renal fossa, but instead if you look on the left, you see an extra large kidney with this bi lobe appearance representing the cross fused renal ectopia on the other side on the left side in this case.

Horseshoe Kidney

Now horseshoe kidney occurs when both kidneys ascend but only ascend partially and the lower poles of both kidneys sort of rotate medially and ause across the midline anterior to the aorta and the fetal spine.

And these horseshoe kidneys can be associated with other abnormalities including a duplex collecting system and reflux.

And in this particular case you can see the horseshoe kidney here were lower in the abdomen than the normally positioned kidneys because we have here a picture, image of the bladder.

In this same cross section you can see the kidney crossing anterior to the aorta and the spine behind.

And in this particular case, again seen with a two vessel cord seen associated with genital urinary anomalies often and in this particular case A VSD.

Renal Agenesis

Now sometimes it's not that the kidney failed to ascend properly, but in fact never developed.

And this is renal agenesis.

And when this is unilateral, the patient, the fetus will, can have a normal life expectancy after birth.

But you will see just like in pelvic kidney, you'll see an absent renal, an empty renal fossa like we see here, nothing here on the left, a normal right kidney on the other sign.

You can confirm this with a lying down adrenal sign for in the empty renal fossa and sometimes the contralateral kidney will be large as it compensates for the, absence of the other kidney.

And we can see here a normal kidney on one side on the other side, the line at down adrenal sign, no kidney was seen in the pelvis, this was unilateral renal agenesis.

Bilateral Renal Agenesis

Now what happens if the kidneys don't develop on either side and you have bilateral renal agenesis?

Well, this is a lethal abnormality.

Unfortunately, you're not going to be seeing the kidneys in the renal fossa.

When we look here in this particular case, we see these little hypo coic areas adjacent to the spine, which actually are the somewhat bunched up adrenal glands, not the kidneys.

Because there's no, urine being formed because there's no kidneys, you won't be able to see a bladder.

And there will be severe, severe oligohydramnios because no, fetal urination is occurring.

And so it's very difficult in these cases to make the diagnosis of absent kidneys because you don't have that nice acoustic window of the amniotic fluid which normally surrounds the fetus.

We can see here, images of the fetal pelvis and you're not able to see the bladder within the pelvis as the umbilical arteries swing around, in the, around the area where the the bladder should be.

Here's another case of bilateral renal agenesis.

Was, die, die twins and the one twin was normal.

And here with the posterior placenta, we have the second twin at 14 weeks and you can see the amount of amniotic fluid is markedly decreased.

Bilateral renal agenesis was suspected.

We did this coronal aortic view and we couldn't see any renal arteries on either side.

There was no fluid, visualized in the urinary bladder.

Bilateral renal agenesis was suspected and the patient was brought back two weeks, later and you could see again no kidneys visualized within the renal fossa.

No fluid within the bladder, very, very little, amniotic fluid at this point in a spine abnormality, in this lethal abnormality for this fetus.

Increased Echogenicity of Kidneys

Now moving on to echogenicity within the kidneys, there are many, many causes of increased echogenic kidneys.

Some of these are inherited diseases, some are acquired.

And you can see in the list I've broken them down into kidneys which are echogenic and increased in size and those that are echogenic and normal size.

And when we talk about increased, size echogenic kidneys, some of the things we would consider would be inherited polycystic kidney disease, some genetic syndromes, which some of which I'll showed you, some acquired things like a CMV infection, renal vein thrombosis, as well as chromosomal abnormalities in the normal echogenic sized echogenic kidneys include normal kidneys as well as obstructive cystic dysplasia.

Enlarged Echogenic Kidneys

Now here's an example of enlarged echogenic kidneys.

Here we have a transverse view of the fetal abdomen with these large kidneys sort of coming way in front of the fetal spine.

And this was seen in association with holo pro cephalic in a fetus with trisomy 13.

And here is a kidney.

It's very remarkable how large and echogenic these kidneys are.

You can see in this, fetal abdomen how big these kidneys are measuring over five centimeters.

That's larger than a kidney would be, in a full term baby at birth.

And when you did a profile view of the fetus, you can see that here's the upper lip and the lower lip and there's this large tongue which is sticking out, and could never, retract into the mouth.

And this is because this tongue is enlarged and this is a fetus with macroglossia associated with these large echogenic kidneys in the, fetus with Beckwith weedman syndrome.

Renal vein thrombosis is not common, but you can see en large echogenic kidneys.

This is often seen with coagulation disorders leading to renal vein thrombosis.

It can be seen with sepsis or possibly maternal diabetes and you can see these kidneys, and these characteristically have these more linear echogenicity within the kidney, but they can be acutely more swollen in a more acute situation.

Renal Cystic Diseases

Moving on to renal cystic disease, again, these are a group of inherited and acquired, in developmental disorders including multicystic, dysplastic kidney, the inherited polycystic kidney disease, as well as renal cysts and renal dysplasia.

And the most common, seen cystic disease of the fetus would be multicystic dysplastic kidney.

And this is in fact the most common abdominal mass that is seen within an neonate.

And this, actually develops very early in gestation before 10 weeks and it occurs when there is complete obstruction or atresia at the renal pelvis very early on.

And this complete obstruction leads to, severe dysplastic changes within the fetal kidney, which results in a replacement of the normal normal renal parenchyma with these multiple non-com commuting, communicating cysts, ovarian sizes and shapes.

And fortunately, the kidney, the other kidney is normal, will generate urine in, there will be a normal amount of amniotic fluid in some cases, particularly, UPJ and can be seen in the contralateral kidney.

So you need to look, when you see multicystic dysplastic kidney, you need to look at the other kidney for contralateral abnormalities.

Multicystic Dysplastic Kidney

And here's an example of a multicystic dysplastic kidney.

You can see these cysts of multiple shapes and sizes filling the renal fossa.

There is no no normal renal parenchyma, within this kidney.

This is a non-functioning kidney.

And here's another case.

We can see sort of the, downside, a multicystic dysplastic kidney.

None of these, cysts communicate with each other.

This is not hydronephrosis, but on the upside in the contralateral kidney, there's hydronephrosis here, there's dilatation of the ureter as well.

In a patient with multicystic dysplastic kidney on the left as well as a UVJ obstruction on the right, it would be very important in this particular case to, look carefully at the amniotic fluid volume to make sure that enough urine is being generated and filling the amniotic cavity.

Autosomal Recessive Polycystic Kidney Disease

Now, autosomal recessive polycystic, kidney disease, in this inherited disorder there is cystic dilatation of the renal tubules as well as hepatic fibrosis.

And the degree of, renal involvement is often inversely proportionate to the degree of liver involvement.

And, depending on how, much involvement there is within the kidneys will determine what the prognosis is for the, fetus or neonate.

And, the earlier that you see, manifestations of autosomal recessive polycystic, kidney disease, it's usually the kidneys that are involved first.

So when we're seeing the manifestations within the in utero within the fetus, it's usually because there is, the kidneys are involved and this unfortunately has a poor prognosis for the fetus.

And what does this look like on ultrasound?

While there is cystic dilatation of the tubules, we actually do not see these cysts, prenatally.

What we do see are these very, very large echogenic kidneys and the echogenicity are the interfaces between these tiny little cysts within the tubules and you can see how large the cysts are in this abdomen, basically filling the entire abdominal cavity.

These, kidneys here measure over eight centimeters if you can believe, almost the size of a, an adult, kidney.

Because these kidneys are not functioning well, they are, completely replaced by these, dilatation of the tubules.

You may, not see any fluid within the bladder and these, fetuses will have severe oligohydramnios and will have pulmonary hypoplasia unfortunately at birth.

And here's a case where it didn't look quite so bad.

At the time of the survey, these kidneys are not particularly enlarged, but they're extremely echogenic and already you can see that the, amount of amniotic fluid is decreased.

There's oligo hydrus, but at birth in the, nicu, we went up to scan this fetus who is having difficulty, breathing.

And here are these kidneys.

These kidneys are massive.

These were 12 centimeters each, the size of a, an adult kidney.

On both sides you can see this is what the, autosomal recessive, polycystic kidneys, disease would look at birth.

And this, neonate did not survive

Autosomal Dominant Polycystic Kidney Disease

autosomal dominant polycystic renal disease.

We usually think of this as a disease of young adulthood and the patients present with cysts, hypertension, and sometimes renal failure.

But occasionally, you can see manifestations of this disease prenatally, on, fetal, prenatal ultrasound and like autosomal recessive polycystic renal disease.

These patients, these fetuses will have enlarged echogenic kidneys, but there isn't as much, damage to the kidneys.

In that these kidneys are able to, to produce urine resulting in, normal amniotic fluid and fluid within the bladder.

You can see here we have these large echogenic kidneys in this, fetus that had autosomal dominant polycystic kidney disease.

There is a little bit of fluid, and urine within the bladder in this particular case.

And this fetus had a mother and a grandfather both with autosomal dominant polycystic kidney disease.

Meckel-Gruber Syndrome

Mecal gruber syndrome is another inherited syndrome, which is autosomal recessive, which results in enlarged echogenic kidneys and cystic, kidneys.

You can see these large, again cystic kidneys filling the entire abdomen of this fetus.

And when you see this, not only are we going to think of, polycystic kidney disease, but these syndromes which can be associated with other anomalies including encephalocele, polydactyly and cardiac abnormalities.

And you can see here these echogenic kidneys not quite as large as the last case with polydactyly within the hand, six fingers as well as six toes.

And another case with this one had much larger cystic kidneys filling the abdomen.

Here's the fetal abdomen, and in this particular case you can see a defect within the posterior skull and encephalocele posterior encephalocele, scooting out the back of the fetal head.

The images as you can see are not as, easy to see things as they are, sometimes, and this is because of the oligo hio, present in this case because of the, renal disease.

Renal Cysts and Dysplasia

Now what about renal cysts?

These occasionally can be seen, these are look like cysts, in adults as well as a unilateral round or oval, och fluid-filled lesion.

They're usually seen within the periphery of the kidney and the region of the, renal cortex.

And when you see a renal cyst, it could be an isolated renal system, which there is usually a good prognosis, they often will regress on their own, but you need to think of two other, possibilities on your differential, including, hydronephrosis of the upper pity and a duplex, renal collecting system or as an early sign of, renal dysplasia.

Now renal dysplasia is an important, diagnosis to know about and to think about.

And this occurs when there is, longstanding renal obstruction in the back.

Pressure of this obstruction, leads to dysplasia of the surrounding parenchyma and when you get dysplasia within the surrounding parenchyma, this manifests on ultrasound is increased echogenicity over the cortex as well as multiple peripheral cortical cysts.

And once you get these changes of renal cystic dysplasia from an underlying obstruction, this has a poor prognostic sign for function of this kidney.

Usually the kidney will no longer function and this is irreversible and you may or may not see the underlying hydronephrosis because if there is poor absent renal function, there is no longer urine being generating to dissent.

The, the collecting s system proximal to the obstruction, you can see here a case of bilateral renal cystic dysplasia.

Here is the transverse view of the abdomen with these cystic structures within the renal fossa representing bilateral renal cystic dysplasia from longstanding, obstruction.

Early on you can see the severe, severe, oligohydramnios, in association with this bilateral renal cystic dysplasia and lethal prognosis.

Hydronephrosis

Now, now we'll begin to talk about hydronephrosis or dilatation.

This is a common abnormality that we will see frequently if we're doing a fetal ultrasound.

And if you're going to look for hydronephrosis, you need to measure the renal pelvis in a transverse view of the fetal abdomen.

You're going to measure, the, the renal pelvis for an AP diameter, the right and the left side.

You're gonna report this measurement.

This is gonna be important, but we're also gonna look in a sagittal plane looking through the kidney for, areas where the CAEs might be dilated as well.

We're gonna look at the cortex two to make sure that there aren't any changes of renal cystic dysplasia, including increased echogenicity like we see here, or maybe some cysts that might be associated with that.

Are there the ureters dilated, is the bladder involved?

Is it degree of amniotic fluid, normal or compromised due to the obstruction?

And because there is an association, with Trisomy 21 and mild, dilatation of the renal pelvis, you might want to be sure that there were no other findings on the scan to suggest trisomy 21.

Now there was a consensus, conference.

I, urge you to look at this, reference in the Journal of Pediatric Urology from 2014, a consensus panel which included some radiologists as well as the Society of fetal urology, which has, drafted, nomenclature and guidelines as to when to call possible hydronephrosis or hydronephrosis prenatally as well as postnatally.

And, there are criteria broken down into the second and third trimester.

You can see in the second trimester, four to six millimeters, AP diameter of the renal pelvis is considered possible hydronephrosis, but if it's greater than or equal to seven millimeters, it's considered abnormal.

In the third trimester, you get a little bit more leeway.

Seven to 9.9 millimeters would be, possibly hydronephrosis and greater than 10 would be considered abnormal.

Certainly if you see ectasis, abnormal renal parenchyma, dilated ureters or an abnormal bladder, regardless of the measurement, this would be considered to be abnormal.

Causes of Antenatal Hydronephrosis

Now what are the cause of antenatal, hydronephrosis?

Sometimes in, many cases this will be transient.

So if you follow this prenatally and also postnatally a lot of, hydronephrosis that we see prenatally will resolve.

The most common cause of antenatal hydronephrosis from a, pathologic standpoint would be UUPJ obstruction and then down the line with reflux, mega ureter UVJ obstruction, valves, as well as, the duplicated, renal collecting system.

Ureteropelvic Junction (UPJ) Obstruction

Now, uretal pelvic junction obstruction is the most common cause of neonatal hydro nephrosis, and this occurs when there's abnormal musculature within the proximal ureter, which leads to abnormal, bolus formation and propulsion of urine, from the renal pelvis down into the ureter, like, most, genital urinary abnormalities more commonly seen in, males than females.

And it's not a mechanical obstruction, but a functional obstruction, it's usually unilateral, but you can see contralateral renal anomalies in 25% of cases.

Now here we can see UPJ obstruction, we have this dilatation in the renal pelvis, there was no dilatation of the ureter, the bladder was fine, but in this particular case we see the dilatation, but the kidney is small and echogenic.

And when you look at the renal cortex, you already see little renal cysts of renal cystic dysplasia.

From this longstanding obstruction in this kidney would be, poorly functioning.

And in response, the other kidney has enlarged is, hypertrophied, to take on the responsibility and the function of two kidneys instead of one.

Vesicoureteral Reflux

Now reflux, can be seen on prenatal ultrasound as well.

And you can see this is hydronephrosis and hydro ureter and it's, interesting to watch because it's a, as you look at the, collecting system over time you'll see the, renal pelvis and the ureters get bigger and smaller as the retrograde flow of urine from the bladder up into the ureters and renal pelvis.

Go sort of back and forth.

This, reflux usually occurs, when there's an abnormal, relationship between the distal ureter extending tunneling through the bladder wall to the UVJ.

Primary Megaureter

Primary mega ureter occurs when there is an AP peristaltic segment within the distal ureter.

So again, this is a functional obstruction, not a mechanical obstruction, to flow of urine from the kidneys into the bladder.

Also seen more commonly in males than females.

And on ultrasound you can see, hydronephrosis dilatation of the, renal, pelvic cae system and also dilatation of the ureter.

So without this intermittent, waxing and waning of the hydro necrosis, primary mega ureter is indistinguishable from reflux.

And importantly, if these are followed, particularly if the dilatation is not severe, the majority of these, neonates after birth will this will over time spontaneously resolve.

Renal Duplication

Now, renal duplication occurs when there are two ureteric buds, which meet the meric blasts edema to form two renal collecting systems in one kidney.

And, the, upper pole, collecting system will often insert ectopically into the, bladder leading to things like a urease seal.

But you'll see hydro, you may see hydronephrosis with a duplicated collecting system, which will be different, differentially affecting the upper and lower poles because the upper pole will obstruct and the lower pole will reflux.

We can see other cases with less degree of dilatation, here in this right kidney with two, collecting systems with differential dilatation.

And another case with the, separation here between the upper and the lower pities.

Which when you look down in the bladder, you can see this almost yolk sac appearance of the ureter seal, within the bladder, which can be seen in about half of cases of, renal duplication.

Prognosis and Follow-up for Hydronephrosis

Now what do we tell parents when we see dilatation of the renal collecting system prenatally?

Are they going to worry what's gonna happen to the baby once the baby is born?

And it turns out, if you look at the degree of hydronephrosis, you can break it down into mild, moderate, or severe hydronephrosis.

The presence of postnatal pathology goes up with the degree of prenatal, hydronephrosis.

So you can tell parents, whose, fetus has mild hydronephrosis that that the chance of there being postnatal pathology is about 11.9%, but if they have severe prenatal hydronephrosis, the chance of there being postnatal pathology is much higher, close to 90%.

Okay, so how are we gonna follow these fetuses?

Once we have detected, prenatal possible hydronephrosis or hydronephrosis?

And the recommendations from the consensus panel, when the degree of hydronephrosis is mild would be to consider a third trimester ultrasound follow up and certainly, postnatal evaluation.

But when the degree of hydronephrosis is moderate or severe, you're going to recommend follow up in four to six weeks to take a look at how the, degree of dilatation is doing.

If there is any oligohydramnios, suspected posterior urethral valves or suspected, renal cystic dysplasia, these are the kind of areas where you might wanna consider some sort of intervention.

And the reason why we wanna follow these patients prenatally, because even if you have moderate hydro necrosis as seen here at 26 weeks, you come back at 35 weeks, the degree of hydro necrosis may progress.

And what about if you only have mild ectasis?

You're in the possible hydronephrosis category even in that particular category, if you follow these patients, even those the hydronephrosis may progress in utero in 28 to 37% of cases.

Now what happens if you follow these over time, postnatally?

And in this study, they looked at mild, moderate, severe hydronephrosis in about, in, in many, many, neonates.

And, and within the first three months or so, what was seen prenatally was often replicated postnatally.

So even in the mild cases and 80% of time if you scan the, the child at about three months of age, you're going to see the abnormality postnatally on ultrasound.

But if you follow over time, and this follow up was done at about two to three years, after birth, the degree, of, of persistence of the abnormality dropped off precipitously in the mild category and even, down to 25% in the moderate category.

But most of the, patients who had had severe hydronephrosis prenatally still had, hydronephrosis at two to three years.

And over half of these, neonates in children required surgery.

And you can break this down, in another paper based on degree of hydronephrosis, just to show you that, when the degree of dilatation is small, five to nine millimeters, the chances that the child will be normal, stable or improved is very high.

But when the degree of hydronephrosis is severe, the likelihood of surgery, is in increases, tremendously.

And in this particular study there were several children who died.

This was related to other abnormalities, not their renal pathology.

Fetal Bladder Abnormalities

Now moving on to the fetal bladder, the abnormalities that we see on prenatal ultrasound involve the absence of the fetal bladder.

In which case we're thinking of things like bladder, extraphy or no renal function.

Absent renal function, no urine is being generated to extend the bladder with fluid or urine.

And we'll look at cases where their, fetal bladder is dilated, which case, we are thinking about posterior urethral valves, p prune, belly syndrome, urethral atresia or reflux.

Posterior Urethral Valves

Now posterior urethral valves is probably the most common severe, genital urinary abnormality seen exclusively in males when there is a membrane within the posterior urethra.

So everything behind that membrane dilates due to the obstruction from this membrane.

So you'll have a dilated posterior urethra, you'll have a dilated bladder, dilated ureters, dilated, renal, collecting system and hydro necrosis.

And you're going to have oligohydramnios as the amount of amniotic as the amount of amniotic fluid is diminished from the lack of, fetal urination.

And here you can see this very large bladder in a small fetus with oligohydramnios surrounding.

Now here are some examples of posterior urethral valves.

You can see this marked dilatation of the, renal pelvis bilaterally, the dilated ureters, very, very large bladder.

And here the bladder you can see with this keyhole appearance with the, dilatation of the posterior urethra.

As you follow this, you can see that the, kidneys have a very echogenic, appearance of the cortex.

So you would worry about some early signs of, renal cystic dysplasia.

And in this particular case, now you can see, at a, at a different time that there is a ton of ascites here and this is due to bladder rupture from the, tremendous amount of pressure from the, obstruction.

Now what are the prognostic indicators for posterior urethral valves?

Certainly if there's oligohydramnios, the prognosis will be worse.

And if the diagnosis is made earlier, the prognosis is worse.

If you begin to see signs of renal cystic dysplasia, that is a poor prognostic sign as well as associated abnormalities or perinephric, oma.

Prune Belly Syndrome

Now prune belly also occurs in males and this is due to absent abdominal musculature and abnormal smooth muscle.

And because of this, the bladder will dilate it.

You'll see hydro terone necrosis just like in posterior urethral valves, but unlike posterior urethral valves, there'll be a normal amount of amniotic fluid.

There'll be no urine ascites because this is a functional abnormality, not a mechanical obstruction.

And as opposed to posterior urethral valves, you can look for fluid in the penile urethra.

Here you can see fluid traveling all the way down the penis, to the MEUs and you would never see this in valves.

And this can be a very valuable, finding to distinguish prune belly syndrome from posterior urethral valves.

Here you can see a markedly markedly dilated bladder, very big hydro nephrosis in the kidneys bilaterally, but notice the normal amount of amniotic fluid in the fetus with p prune belly syndrome.

Bladder Exstrophy

Now bladder extrophy occurs when the bladder is averted through a defect with the anterior abdominal wall.

It's almost like an em falle but lower down.

But because the bladder is averted and the mucosa is exposed to the amniotic fluid cavity, there is no bladder.

You shouldn't be able to see a bladder within the pelvis, but instead you see a soft tissue mass on the surface of the lower anterior abdominal wall representing that, inverted ted bladder.

And the amount of amniotic fluid should be normal and the kidneys will be normal as well.

And you can see here, here is that mass, this is the bladder that, the bladder extra free.

There's no bladder within the pelvis just to show you a normal umbilical cord insertion because it does look some like in, falle.

And here's sort of the picture.

You can see what we're, we were after the, baby was born.

You can see what we were looking at.

Here's the normal umbilical cord insertion and this bladder extraphy.

This is the bladder mucosa that you'll actually are actually seeing, which is exposed, to the, amniotic fluid cavity and then air after birth.

Ovarian Cysts

Now one last, comment I'd like to make is about ovarian cyst.

These are cysts that can be seen only in female fetuses, which can be, developed due to maternal or placental hormone stimulation.

And you'll see these cys separate from the bladder.

They don't, get bigger and smaller over time like the bladder would representing ovarian cyst and like ovarian cyst in adults.

These may undergo torsion or hemorrhage.

We could see a cyst here.

There was a little bit of echogenic material layer independently within this fetus, from an ovarian cyst.

And two weeks later, and ultrasound, you could see there was ascites and a normal ovary here and what had happened.

This cyst had actually ruptured leading to ascites, and the cyst was no longer seen and that, is entirely possible prenatally.

Conclusion

Now, I've done with my talk we've had an, an overview of certain findings we can see within the kidneys, including abnormalities of location, abnormalities of obstruction, dilatation.

We've looked a little bit at dilated ureters and dilated and absent bladder.

And always remember when you're thinking of the genital urinary system, you need to assess the amniotic fluid volume because that will certainly have implications for prognosis for the fetus after birth.

Thank you.