Management of very young fetuses with LUTO

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I congratulate Capone and colleagues on their efforts to draft new guidelines for the management of fetal lower urinary tract obstruction (LUTO), which were published in Nature Reviews Urology (Capone, V. et al. Definition, diagnosis and management of fetal lower urinary tract obstruction: consensus of the ERKNet CAKUT-Obstructive Uropathy Work Group. Nat. Rev. Urol. 19, 295–303 (2022))1.

In this manuscript, the authors make some observations based on previous studies: a bladder diameter ≥15 mm in the first trimester of pregnancy suggests severe LUTO with little chance of spontaneous resolution2; the presence of anhydramnios early in the second trimester of pregnancy results in a fetal mortality rate close to 100%, and untreated fetal LUTO with an early onset (first or early second trimester of pregnancy) can lead to death in up to 80% of fetuses1,2,3,4; and a small window of opportunity for improved renal outcomes and survival exists (<6 weeks), as renal function gets lost progressively in fetuses with severe LUTO5.

Abnormal dilation of the lower urinary tract or of developmentally related anatomical structures from severe urinary outflow obstructions have a prominent position and unmistakable appearance (an anechoic sphere) in the lower abdomen of the fetus and, therefore, can easily be detected in fetuses in the first and early second trimesters of pregnancy. However, the new guidelines1 about LUTO management primarily focus on mid-gestation fetuses and provide no recommendations about how to best handle this early-gestation subgroup of fetuses with LUTO. Thus, the staging system that the authors propose as well as some of the European Reference Network for Rare Kidney Diseases (ERKNet) recommendations for prenatal definition, diagnosis and management of LUTO1,6 do not fit the needs of the youngest and most severely affected fetuses.

The purpose of this Correspondence is, therefore, to raise awareness about the availability of intervention methods alternative to the use of double pigtail catheters, such as trimmed 6F-single pigtail catheters or stent shunts, which enable clinicians to perform vesico-amniotic shunt insertion in first and early second trimester fetuses with LUTO with improved safety and efficacy7,8.

Moreover, I propose a new management algorithm to deal with young fetuses with LUTO, who might most benefit from this procedure, developed and tested at the German Center for Fetal Surgery & Minimally-Invasive Therapy (DZFT - Mannheim, Germany)7. The proposed management technique is also less invasive for mothers and fetuses than previous strategies, as repeated punctures for karyotyping and serial collection of fetal urine before the actual shunt insertion are avoided.

The algorithm includes the following steps: treatment of fetuses with isolated severe LUTO within days from the first diagnosis (from as early as 12 weeks of gestation onward); karyotyping performed from amniotic fluid collected at the time of shunt insertion; avoidance of any treatment delays not waiting for oligohydramnios to occur; implementation of weekly follow-up monitoring over the remainder weeks of gestation; and re-intervention within days in the presence of shunt dislodgement, shunt malfunction or signs of additional severe bilateral upper urinary tract obstructions or urinary ascites7.

Using this algorithm, 19 of 28 fetuses (68%) survived to postnatal discharge from hospital after a mean number of interventions of 1.6 per fetus (range 1–4)7. Overall, 15 of the 19 surviving fetuses (79%) had normal renal function, and pulmonary hypoplasia was present in only 2 fetuses (11%)7. These results reflect some of the best renal and pulmonary outcomes ever described following vesico-amniotic shunt insertion in a cohort of fetuses with LUTO.

Results from early vesico-amniotic shunt insertions in first or early second trimester fetuses with severe LUTO performed in our centre and by other groups9,10 showed similarly encouraging outcomes. Considering the life-saving potential of this approach, I believe that this information needs to accompany the novel management guidelines for fetal LUTO1.

After more than three decades of therapeutic stagnation in this corner of prenatal medicine, good evidence supports the idea that results from future studies will confirm that vesico-amniotic shunting before the completion of 16 weeks of gestation improves postnatal conditions of fetuses with LUTO. However, further follow-up studies are clearly needed to assess whether and for how long the improved renal and pulmonary outcomes observed in young fetuses with LUTO might persist.

There is a reply to this letter by Capone, V., Persico, N. & Montini, G. Nat. Rev. Urol. https://doi.org/10.1038/s41585-022-00637-7 (2022).

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Correspondence to Thomas Kohl.

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Kohl, T. Management of very young fetuses with LUTO. Nat Rev Urol (2022). https://doi.org/10.1038/s41585-022-00636-8

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