Amniotic fluid index and fetal bladder outlet obstruction. Do we really need more?

Department of Nephrology and Urology, Bambino Gesu' Children's Hospital, Rome, Italy.
The Journal of Urology (Impact Factor: 4.47). 11/2005; 174(4 Pt 2):1657-60. DOI: 10.1097/01.ju.0000179538.85893.cb
Source: PubMed


With the constant advances in technology and expertise of prenatal diagnosis, necessity of early counseling in cases of bilateral obstructive uropathy has become of paramount importance. To better evaluate fetal renal function new biochemical (serum and urine) fetal markers have been introduced in the literature. However, they are only available at select centers and always requiring an invasive approach. Furthermore, paucity of normal controls sometimes makes interpretation of results difficult. Owing to this growing interest towards biochemical evaluation of fetal renal function, assessment of amniotic fluid, which is mostly expression of fetal urination, has progressively fallen into disrepute, and studies comparing the amount of amniotic fluid with renal function are scant.
In a 3-year period 28 cases of bilateral obstructive uropathy were seen prenatally at the Artemisia Medical Center. All cases were initially reviewed at 17 to 20 weeks of gestation when a distended fetal bladder with thickened wall and enlarged kidneys were visualized. At the same time ultrasonographic assessment of amniotic fluid was performed by calculating the amniotic fluid index. An amniotic fluid index less than the 25th percentile was considered below average and an index less below the 5th percentile was considered oligohydramnios, whereas an index between 50th and 75th percentiles was considered normal. All cases were subsequently evaluated for renal function up to age 1 year. Impaired renal function was defined as a serum creatinine greater than 1.2 mg/dl before age 1 year.
Of the 28 cases 18 had an index of oligohydramnios (group 1) and 10 had a normal index (group 2). No significant variations were observed in amniotic fluid index at repeated consultations throughout pregnancy. Two cases in group 1 and 1 case in group 2 were lost to followup while in the other group 1 cases intrauterine death occurred. Bilateral obstructive uropathy was confirmed in all instances after birth as valves in 18 cases and urethral atresia in 3. Of the 12 surviving group 1 cases there were 3 neonatal deaths from severe lung hypoplasia, and in the remaining 9 cases mean serum creatinine at each evaluation before age 1 year was 1.3 +/- 0.2 mg/dl. All patients in group 2 survived with a mean serum creatinine at each evaluation of 0.6 +/- 0.1 mg/dl (p <0.05).
Despite widespread use of prenatal biochemistry, evaluation of amniotic fluid by the amniotic fluid index remains a reproducible and inexpensive method to predict renal function in cases of bilateral obstructive uropathy of any origin. It retains its validity not only in severe, but also in milder reductions. Conversely, intact amniotic fluid mostly invariably predicts normal renal function at long-term evaluation. For a better understanding of the disease such information is to be promptly conveyed to the prospective parents at each prenatal consultation.

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    • "If management with vesicocentesis is performed, urine should undergo karyotype and biochemical studies, including osmolality, beta-2 microglobulin and electrolytes, to evaluate renal function. Some investigators have suggested however that amniotic fluid indices are of greater importance than urinary biochemistries in selecting cases that would benefit from intervention [21]. "
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    ABSTRACT: Fetal megacystis, an abnormally enlarged bladder identified at any gestational age, may be transient and resolve spontaneously or may be an early manifestation of bladder outlet obstruction. Anterior urethral valves are the most common cause of the rare condition of congenital obstruction of the anterior urethra. Herein is reported the prenatal observation and postnatal management of a case of megacystis with anterior urethral valves. The etiology is reviewed and strategies recommended for patients with these rare entities.
    Full-text · Article · Oct 2010 · Journal of pediatric urology
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    • "oligohydramnios (AFI < 25th percentile) to be predictive of chronic renal failure or death in patients with PUV [41]. Oligohydramnios , dilated posterior urethra (keyhole sign), ANH, thick-walled bladder, and increased renal echogenicity are worrisome signs for severe bladder outlet obstruction that warrant counseling and possible fetal intervention such as early delivery or vesicoamniotic shunting [44e46]. "
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    ABSTRACT: The evaluation and management of fetuses/children with antenatal hydronephrosis (ANH) poses a significant dilemma for the practitioner. Which patients require evaluation, intervention or observation? Though the literature is quite extensive, it is plagued with bias and conflicting data, creating much confusion as to the optimal care of patients with ANH. In this article, we summarized the literature and proposed recommendations for the evaluation and management of ANH. © 2010 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
    Full-text · Article · Jun 2010 · Journal of pediatric urology
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    ABSTRACT: Prognosis of fetuses with renal oligohydramnios (ROH) is often still regarded as poor. Neonatal complications and the long-term follow-up of fetuses with ROH in two pediatric centres are described. Method. 23 fetuses (16 males, 7 females) were included as patients. Primary diseases included congenital anomalies of the kidney and urinary tract (n = 16), autosomal recessive polycystic kidney disease (n = 4) and renal tubular dysgenesis (n = 3). The analysis includes retrospective chart review. Seven children died (30%), the majority (n = 4, 17%) within the neonatal period due to pulmonary hypoplasia and renal insufficiency. Fourteen patients (61%) required postnatal mechanical ventilation for a median of 4 (range 1-60) days; 11 infants had an associated pneumothorax. All 16 surviving children have chronic kidney disease (CKD) at a current median age of 5.7 years (range 0.5-14.5), managed conservatively in eight patients [median glomerular filtration rate 51 (range 20-78) ml/min/1.73 m(2)]. Eight patients reached end-stage renal disease at a median age of 0.3 years (range 2 days to 8.3 years), including one patient with pre-emptive kidney transplantation. Five of the patients requiring dialysis underwent successful renal transplantation at a median age of 3.5 years (range 2.5-4). Growth was impaired in seven children requiring growth hormone treatment. Cognitive and motor development was normal in 12 (75%) of the 16 patients and showed a delay in four children, including two with associated syndromal features. ROH is not always associated with a poor prognosis and long-term outcome in survivors is encouraging. The high incidence of neonatal complications and long-term morbidity due to CKD requires a multidisciplinary management of these children.
    Full-text · Article · Mar 2007 · Nephrology Dialysis Transplantation
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