Center for Fetal Diagnosis and Treatment

Lower Urinary Tract Obstruction (LUTO)

Overview

In the fetus, obstruction to urine flow
Fetus with posterior urethral valves obstructive uropathy.
View larger image »may result in severe kidney damage (renal dysplasia) and underdevelopment of the lungs (pulmonary hypoplasia), which are life-threatening conditions.

We have found that bypassing the obstruction can prevent the detrimental effects on fetal lung and kidney development. We have also documented the natural history of the human disease and have developed tests of fetal renal function that may allow us to provide prenatal treatment to those few fetuses who will benefit.

Evaluation

A high-resolution ultrasound is performed to document the presence of a lower
Ultrasound showing characteristic "keyhole" bladder.
View larger image »urinary tract obstruction (LUTO), also known as obstructive uropathy. We have found that three serial bladder taps performed over the course of three to four days have been most predictive of identifying underlying renal injury.

Urine obtained at the initial bladder drainage represents old urine from within the fetal bladder. Urine from the second drainage represents urine that has collected in the bladder from the upper collecting systems, and the third urine specimen, most recently produced by the fetal kidneys, is usually the most reliable for analysis.

The bladder should be drained as completely as possible
Fetal MRI showing 22-week fetus with posterior urethral valves.
View larger image »with each of the successive bladder taps performed on consecutive days at 24- to 48-hour intervals. Urine should be sent for electrolyte and protein analysis.

A fetal echocardiogram should also be performed to rule out congenital heart defects that occur in increased frequency in these cases. An ultrafast fetal MRI can be useful in evaluating the kidneys, collecting system and bladder in complex cases.

Treatment options

Double pigtail catheter shunt.
View larger image »
Fetus with catheter in place to decompress bladder and restore amniotic fluid.
View larger image » If the serial fetal bladder drainages for urinary electrolytes and protein components come back favorable and if there is a recent history of decreased to no amniotic fluid (oligohydramnios, anhydramnios) and no chromosomal abnormalities in a male fetus, the family may be offered fetal intervention with a vesicoamniotic shunt placement or fetal cystoscopy to further evaluate the source of fetal urinary tract obstruction.

Infant outcomes

There is very little information about the long-term outcomes of boys retreated prenatally for lower urinary tract obstruction. In a recent review of cases that underwent prenatal bladder shunting at our Center, survival was 95 percent.

Childhood outcomes have been favorable in a recent study of 18 boys who are now older than 5 years of age with 45 percent having acceptable renal function, and 22 percent having mild to moderate renal impairment. Thirty-three percent have developed renal failure but have done well after renal transplant. In addition, bladder function was better than expected with 61 percent achieving the ability to control and empty their bladders, while the rest require use of a catheter to completely drain their bladders.

Future trends

Because of the technical limitations of shunt therapy with up to 40 to 50 percent of cases experiencing displacement or obstruction, we are presently developing techniques to perform evaluation of the inside of the fetal bladder and proximal urethra (in-utero microcystourethroscopy) to identify the source of the obstruction and surgically destroy it prenatally. This approach holds promise as a more definitive surgical treatment that would eliminate the need for temporizing shunts with their inherent physical limitations, and it would allow more normal bladder and urinary tract development during fetal life.

Pregnancy outcomes

Natural history studies in pregnancies with early urinary tract obstruction and oligohydramnios suggest the chances of survival to be less than 5 percent, with expectations for severe renal impairment.

In carefully selected cases that meet criteria for possible renal salvage, survivals from a respiratory basis have been 95 percent, but renal outcomes have remained variable depending on severity and early age of obstruction in pregnancy. Families must understand that fetal bladder shunting is only a temporary measure, and more detailed evaluation and surgical therapy will be necessary after birth. Also, there are physical limitations of the indwelling shunts after placement with obstruction or physical displacement from the bladder occurring in 40 to 50 percent of cases, requiring replacement and the risks associated with repeat procedures.

Fetal Lower Urinary Tract Obstruction Case

A 25-year-old G2 P1 was referred for evaluation of a fetal lower urinary tract obstruction. Initial ultrasound evaluation at 20 weeks gestation revealed a male fetus with a significantly enlarged bladder, severely decreased amniotic fluid volume (oligohydramnios) and bilateral hydronephrosis. The sonographic appearance of the fetal bladder was that of a “keyhole sign,” indicating a proximal urethral obstruction such as posterior urethral valves or urethral atresia. No other anomalies were visualized. The fetal echocardiogram was normal.

The family was counseled regarding the natural history of bladder outlet obstruction, the associated poor prognosis if left untreated and potential interventions for carefully selected candidates who demonstrate salvageable renal function.

The family chose to proceed with an evaluation to assess renal function and to discern if indeed there was a fetal lower urinary tract obstruction. Three ultrasound guided bladder drainages were performed at intervals two days apart. Chorionic villous sampling was also performed to rule out a fetal chromosomal anomaly that occurs in 6 to 8 percent of such cases. Results revealed normal male chromosomes (46, XY). The urine electrolytes and proteins revealed a borderline pattern. However, underlying functional renal asymmetry was suspected based on the sonographic appearance of the kidneys. One kidney was suspected to be damaged as indicated by its echogenic appearance and the presence of several cysts within the renal tissue. The other kidney, however, demonstrated minimal increased echogenicity, had no visible cortical cysts and was presumed to be less damaged. To learn more, an ultrasound-guided needle aspiration was performed to assess function in the more normal-appearing kidney. Urine from this kidney showed only a mild degree of damage with potential for salvage with intervention.

After further consultation about the risks and benefits of intervention, the family decided to pursue vesicoamniotic shunt placement. At 21 weeks gestation, an amnioinfusion was performed to restore amniotic fluid volume to normal, and a vesicoamniotic shunt catheter was placed into the fetal bladder without complication. Follow-up ultrasounds revealed restored amniotic fluid volume and a properly placed and functioning bladder shunt. The rest of the pregnancy was uncomplicated.

Delivery occurred vaginally at 36 weeks following spontaneous onset of labor. The baby had a vesicostomy placed after delivery, followed by correction of the outlet obstruction, which proved to be posterior urethral valves. One kidney was damaged with minimal function, while the other continues to function normally. The child is now thriving, happy and 5 years old.

Frequently asked questions

How common are lower urinary tract obstructions (LUTO)?

Urinary tract abnormalities as a group are seen in approximately 1 in 100 pregnancies. However, the more significant lower urinary tract obstruction occurs in approximately 1 in 500 pregnancies.

What causes these anomalies?

LUTOs are typically isolated developmental anomalies. In some cases, however, they can be part of a chromosomal or genetic condition, such as Down syndrome or megacystic-microcolon syndrome.

I have had one baby with a lower urinary tract obstruction. What is my risk of having a second child with this condition?

Isolated lower urinary tract anomalies are usually not associated with an increased risk of recurrence. However, if the obstruction is related to underlying chromosomal or genetic conditions, the risk of recurrence equals the risk of recurrence of the underlying condition.

How can I find out if my baby will benefit from prenatal intervention?

To determine whether or not any given fetus is a candidate for prenatal therapy, a thorough evaluation is necessary. This includes a level II sonogram, a fetal echocardiogram, an ultrafast fetal MRI and a serial renal electrolyte profile.

This is important because urinary tract obstructions come in all forms, shapes and sizes. The prognosis for each individual case depends upon the underlying cause of the obstruction, along with its location, severity and age of onset.

Amniotic fluid is an important prognostic indicator because a critical phase in lung development occurs around 18 to 20 weeks of gestation. Low or absent amniotic fluid during this time period can result in pulmonary hypoplasia. The sonographic appearance of the renal tissue is another important prognostic indicator. Urine electrolyte levels also provide information regarding the extent of underlying renal damage. For the greatest potential benefit, it is important to intervene before irreparable damage occurs.

I am interested in finding out if my baby is a candidate for prenatal treatment, but I do not live near Philadelphia. Can some of the required testing be performed at a local medical center?

Yes, it may be possible to have some of the above-mentioned tests performed at a local medical center specializing in high-risk pregnancy. Films and videos can then be forwarded to our center for review. We welcome all inquiries.

If you are not sure how to proceed, please contact our office at 1-800-INUTERO (1-800-468-8376) and we can help you to make the necessary arrangements.

Why do I need multiple fetal bladder taps?

Multiple fetal bladder taps performed 23 to 48 hours apart are necessary to assess the remaining renal function over time in a decompressed state. We know that the first urine aspirated from the fetal bladder has been there for some time and is not typically predictive of underlying renal function. The second tap represents urine from the ureters. The third tap is fresh urine and is the most predictive of underlying renal function. In some cases, however, a fourth or fifth tap is needed to determine renal status.

How can I get more information about my particular situation?

We welcome all inquiries from families and healthcare professionals. If you would like to discuss your particular case, please do not hesitate to contact us by phone or e-mail.