Evaluation of the fetal urine sample through vesicocentesis: an approach to diagnostic and therapeutic application

1. Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rio Grande do Sul, Brazil
2. Hospital Materno-Infantil Presidente Vargas (HMIPV), Rio Grande do Sul, Brazil
3. Complexo Hospitalar Santa Casa de Porto Alegre (CHSCPA), Rio Grande do Sul, Brazil

Corresponding author

Rafael Fabiano Machado Rosa
UFCSPA
Rua Sarmento Leite, 245, sala 403; Centro
CEP 90050-170; Porto Alegre-RS, Brasil
Phone: +55 (51) 3303-8771
e-mail: rfmrosa@gmail.com

CASE REPORT

V. G. was a 21-year-old pregnant woman for the first time referred for the high-risk prenatal care due to an alteration in obstetrical ultrasound. There was an image suggestive of megabladder. The 20-week ultrasonography (USG) examination showed absence of the amniotic fluid (anhydramnios) and an enlarged bladder with narrowing of the urethra in the proximal region, suggestive of lower urinary tract obstruction (LUTO). At 21 weeks of gestation the fetal bladder was punctured for relief of obstruction, and biochemical and karyotype analysis of the material was performed. The volume of fetal urine removed was 282 ml. There were no complications during or after the procedure. The karyotype was normal (46,XY). The biochemical analysis showed the following results: potassium: 3 mEq/l (reference value: < 3 mEq/l); sodium: 109 mEq/l (reference value: < 100 mEq/l), and chlorides: 93 mEq/l (reference value: < 90 mEq/l), indicative of renal damage. Second-trimester ultrasound showed absence of amniotic fluid; increased echogenicity of the renal parenchyma, and distended bladder with “keyhole signal” (Figure 1). Fetal echocardiography was normal. The 25-week ultrasound also showed severe ascites, pericardial effusion, fetal bladder walls thickening, and the right kidney with diminished dimensions (Figure 2). The infant was born through vaginal delivery, at 27 weeks of pregnancy, weighing 1,960 grams and Apgar scores of 1 at first and fifth minutes. The infant had a significant abdominal distention and upper and lower limb deformities (Figure 3). He presented respiratory distress and evolved to death about 2 hours after birth.

Figure 1 − 22-week ultrasound scan showing distended bladder (A) and the keyhole sign (B), suggestive of the LUTO (see white arrows)
LUTO: lower urinary tract obstruction.

Figure 2 − 25-weeks ultrasound scan images showing severe ascites (A) and pericardial effusion (B) (see white arrows)

Figure 3 − Postnatal physical aspect of the infant showing significant distension of the abdomen and upper and lower limb abnormalities

LUTO comprises a heterogeneous group of pathologies associated with early-onset severe oligohydramnios. Chromosomal abnormalities associated with LUTO include Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18)^(1-3). Posterior urethral valve (PUV) is considered one of the most common causes of LUTO. PUV can be defined as the presence of membranes that obstruct the urethral lumen, leading to urinary retention and renal damage. It presents an incidence of 1 for every 5,000 to 8,000 live male births. The severity and degree of obstruction caused by PUV depends on the relation between the membrane and the urethra. Prenatal diagnosis of PUV is based on maternal ultrasound, with evidence, for example, of the “keyhole signal”⁽⁴⁾. Oligohydramnios when associated with LUTO has an estimated mortality rate of 95%. This occurs due to pulmonary hypoplasia caused by the fetal compression secondary to the oligohydramnios. The mortality rate in cases of PUV is directly related to pulmonary insufficiency in 45% of the cases⁽¹⁾.

Fetal urine analysis is an important part of the follow-up after the procedure, as the rate of renal insufficiency among survivors is estimated to be 50%-66%⁽¹⁾. Vesicocentesis is usually performed between the 16^th and 32^nd gestational weeks using an 18-22G needle guided by USG. The technique is indicated in cases of intense oligohydramnios (impossibility of amniocentesis) or difficulty in access the placenta (impossibility of placental biopsy)⁽⁵⁾. Decreased solute reabsorption, protein catabolism, increased loss of substances in fetal urinary output and the degree of urine hypertonicity have been associated with the extent of the damage. Usually, hypotonic fetal urine becomes concentrated, and elevated levels of sodium, chloride, potassium, phosphate and osmolality have been associated with renal failure and worse outcome. Elevated levels of β2-microglobulin suggest tubular dysfunction, and is the most sensitive and specific predictor of outcome⁽⁶⁾. Ruano et al. (2015)⁽⁷⁾ found that fetuses with severe forms of LUTO and poor renal function do not produce adequate urine output to fill the bladder within two days after the relief puncture.

Fetal urine can also be used to study chromosomes using the karyotype technique⁽⁵⁾. The cell pellet from fetal urine can be cultured and analyzed in a similar way to the technique for amniocytes. The technique includes preparation of the biological material (~ 15-20 ml of fetal urine) for culture, washing cells with the culture medium, incubation and collection of cells to obtain metaphase chromosomes and analysis of the chromosomes. The results should be obtained in 20 days, on average, and the culture performed in 10 to 14 days⁽⁸⁾. Vesicocentesis should be performed several times a week to maintain decompression for treatment purposes, but it presents risks of infection, abortion, rupture of membranes and premature delivery⁽⁵⁾. Therefore, the performance of fetal bladder puncture in these cases has diagnostic and therapeutic function. This procedure can improve the survival through lung development preservation⁽³⁾.

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