Serum beta 2-microglobulin in fetuses with urinary tract anomalies

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

Adequate prediction of fetal exposure of drugs excreted by the kidney requires the incorporation of time-varying renal function parameters into a pharmacokinetic model. Published data on measurements of fetal urinary production rate (FUPR) and creatinine at various gestational ages were collected and integrated for prediction of the fetal glomerular filtration rate (GFR). The predicted GFR values were then compared to neonatal values recorded at birth. Collected data for FUPR across different gestational ages using both 3D (N = 517) and 2D (N = 845) ultrasound methods showed that 2D techniques yield significantly lower estimates of FUPR than 3D (p < 0.0001). A power law function was shown to best capture the change in FUPR with fetal age (FA) for both 2D ( F U P R 2 D ( m L min ) = 0 . 000169     FA 2 . 19 ); and 3D ( F U P R 3 D   ( m L min ) =   3 . 21 × 1 0 - 7   FA 4 . 21 ) data. The predicted FUPR based on the observed 3D data was shown to be strongly linearly related (R ² = 0.95) to measured values of amniotic creatinine concentration (N = 664). The FUPR_3D data together with creatinine levels in the fetal urine and serum resulted in median predicted fetal GFR values of 0.47, 1.2, 2.5, and 4.9 ml/min at 23, 28, 33, and 38 weeks of fetal age (50% CV), respectively. These values are in good agreement with neonatal values observed immediately at birth. The derived FUPR and creatinine functions can be utilized to assess fetal renal maturation and predict fetal renal clearance.

Evaluation and fetal intervention in severe fetal hydronephrosis

PURPOSE OF REVIEW

Fetal hydronephrosis secondary to congenital anomalies of the kidney and urinary tract (CAKUT) can adversely affect neonates in the postnatal period with long-term consequences. A prenatal diagnosis of CAKUT can have an early fetal intervention to minimize these consequences. This review aims to provide an overview of the possible fetal intervention with severe hydronephrosis.

RECENT FINDINGS

Clinical course and outcomes of CAKUT are predicted based on biochemical markers and radiological findings. In spite of advancements and accurately diagnosing the severity of hydronephrosis, there are many controversies surround on selection of cases with antenatal hydronephrosis (ANH) that will benefit from fetal intervention. Despite better diagnosis and techniques fetal intervention is limited to mainly lower urinary tract obstruction patients to improve amniotic fluid volume and assist in lung development.

SUMMARY

ANH can potentially detect the severity of congenital renal anomalies but unable to recognize a specific disease. A multidisciplinary approach is required to diagnose and properly stage cases of severe CAKUT and potential surgical intervention can be considered.

Selection of candidates for foetal intervention in congenital lower urinary tract obstruction

PURPOSE OF REVIEW

Congenital lower urinary tract obstruction (LUTO) is a rare group of conditions characterized by high perinatal morbidity and mortality if associated with oligohydramnios or anhydramnios in early pregnancy. Although foetal intervention has the potential to improve perinatal survival in a select group of foetuses with LUTO, the actual selection of those candidates most likely to benefit from intervention remains challenging.

RECENT FINDINGS

Foetuses with LUTO who are potential candidates for prenatal intervention should undergo detailed multidisciplinary evaluation to ensure proper assessment and counselling. Using a combination of multiple ultrasound-based renal parameters, including measurement of foetal bladder volumes before and after vesicocentesis and kidney size and morphology, combined with repeated foetal urine biochemistry may allow for better selection than any single test.

SUMMARY

Foetal intervention should be offered to women carrying a foetus with LUTO only after appropriate evaluation and counselling. A combined approach utilizing ultrasound and biochemical measurements of foetal renal function appears best. Research focusing on the development of more accurate markers is needed.

Fetal lower urinary tract obstruction: What should we tell the prospective parents?

Fetal lower urinary tract obstruction (LUTO), which often results in marked perinatal morbidity and mortality, is caused by a heterogeneous group of anatomical defects that lead to blockage of the urethra. The classic prenatal presentation of LUTO includes megacystis with hydronephrosis. While mild forms of the disease can be associated with favorable outcomes, more severe disease commonly leads to dysplastic changes in the fetal kidneys, and ultimately oligohydramnios, which can result in secondary pulmonary hypoplasia and renal failure at birth. The aim of this review is to provide practitioners with a general overview of the diagnosis and treatment of LUTO based on disease severity, along with some points to consider when counseling prospective parents of fetuses with this condition.

Current status of percutaneous umbilical cord blood sampling in Japan

AIM

The aim of the survey is to investigate current practice and complications of percutaneous umbilical cord blood sampling (PUBS) in Japan.

METHODS

In this retrospective survey, data including perioperative information, indications, details of the procedure and procedure-related complications were collected for patients who underwent PUBS between 2012 and 2016 in Japanese perinatal care centers.

RESULTS

One hundred and fifty-three patients underwent PUBS and a total of 223 procedures were analyzed in this study. Fetal anemia was the most common indication for PUBS, representing greater than 70% of all cases. Anemia specific to monochorionic twins, such as acute feto-fetal hemorrhage subsequent to single intrauterine fetal death (IUFD) and twin anemia-polycythemia sequence, were the leading causes of suspected fetal anemia. Maternal anesthetics were given during the procedure in 70% of cases. The PTC needle (Hakko, Japan) was most commonly used in the procedure. The most frequent complication was bleeding from the umbilical cord puncture site; however, it did not require immediate delivery during or after the procedure in any case. IUFD occurred in 11 (4.9%) procedures, 7 of which appeared to be related to the underlying fetal disease. The overall completion rate of the procedure was 97%.

CONCLUSION

Percutaneous umbilical cord blood sampling was most commonly performed for the evaluation of fetal anemia, usually due to complications of monochorionic twins, followed by the measurement of fetal thyroid function. The safety and the completion rate of the procedure in Japan appear satisfactory.

Comparison of biochemical analysis of fetal serum and fetal urine in the prediction of postnatal renal outcome in lower urinary tract obstruction

OBJECTIVES

To compare the prognostic value of fetal serum biochemistry and fetal urine biochemistry in predicting renal outcome in lower urinary tract obstruction (LUTO).

METHODS

We retrospectively studied renal outcome following a prenatal diagnosis of LUTO in cases for which both fetal blood and fetal urine were sampled. We classified the renal outcome as either "favorable," when postnatal renal function was normal, or "adverse," in the case of postnatal chronic renal failure or when renal histological lesions were present at autopsy in the case of termination of pregnancy. A prognostic model was constructed for urine and serum separately. β2-Microglobulin was the only remaining independent predictor in fetal urine. β2-Microglobulin in serum and urine were compared by using receiver operating characteristic curves.

RESULTS

In the 50 cases included, the rate of adverse outcome was 34 of 50(68%): autopsy confirmed severity of renal disease in all 27 cases who underwent termination of pregnancy, and among the 23 live born children, 7 developed renal failure. Fetal serum and urine markers were all significantly associated with renal outcome (P < .01). The receiver operating characteristic curves for fetal serum and fetal urinary β2-microglobulin were similar (area under the curve = 0.908 versus 0.909, P = .96).

CONCLUSION

Fetal serum biochemistry and fetal urine biochemistry are of similar prognostic value in predicting postnatal renal outcome in fetuses with LUTO.

Sequential fetal serum β2-microglobulin to predict postnatal renal function in bilateral or low urinary tract obstruction

OBJECTIVE

Fetal serum β2-microglobulin has been shown to predict postnatal renal outcome in cases of fetal obstructive uropathy. We assessed the value of serial measurements of fetal serum β2-microglobulin in the prediction of postnatal renal outcome.

METHODS

We retrospectively studied renal outcome in 42 fetuses with bilateral or low urinary tract obstruction that had fetal blood sampling on at least two occasions to assay serum levels of β2-microglobulin. Amniotic fluid volume at the time of each sampling was recorded. We classified renal outcome as either favorable (when postnatal renal function was normal) or adverse (when postnatal chronic renal failure occurred or when renal dysplasia at autopsy was noted). A β2-microglobulin cut-off of 5 mg/L and amniotic fluid index of 5 cm were used to predict postnatal renal outcome.

RESULTS

Renal outcome was adverse in 28 cases and favorable in 14. In 12 (28.6%) cases, fetal serum β2-microglobulin concentration differed between the first and last measurement. Prediction of postnatal renal outcome was correct in 11 of these cases based on the last β2-microglobulin measurement. The sensitivity of β2-microglobulin in predicting renal outcome was significantly higher (P = 0.005) when using the last rather than the first measurement (96.4% vs 64.3%), with similar specificity for both measurements (85.7% vs 78.6%, non-significant). The sensitivity of amniotic fluid volume was also significantly higher (P = 0.005) when using the last rather than the first measurement (75.0% vs 35.7%), with similar specificity for both measurements (64.3% vs 71.4%, non-significant).

CONCLUSION

Sequential measurement of serum β2-microglobulin, performed for adverse ultrasound findings, such as renal parenchymal abnormality or decreasing amniotic fluid volume, predicts postnatal renal outcome more accurately than does a single assay. This may be due to possible worsening of renal injury with increasing duration of urinary tract obstruction. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Computing the Z Score and Centiles for Cross-sectional Analysis: A Practical Approach

Although Z scores have been reported in the literature, one of the problems for the nonstatistician is understanding the systematic approach used to compute the predicted mean and standard deviation, components of the Z score equation, which may vary as the independent variable changes over time (eg, gestational age). This review focuses on a step-by-step analysis using linear, quadratic, and fractional polynomials to compute the mean and standard deviation as a function of a continuous independent variable. Once the mean and standard deviation are computed, the Z score and centile can be derived and Z score calculators created that enable investigators to implement the results in the laboratory and/or clinical setting.

Fetal lower urinary tract obstruction: proposal for standardized multidisciplinary prenatal management based on disease severity

OBJECTIVE

To present a single center experience of a standardized prenatal multidisciplinary management protocol for fetal lower urinary tract obstruction (LUTO) and to propose a classification of fetal LUTO based on disease severity.

METHODS

This was a retrospective cohort study of 25 consecutive fetal patients with prenatal diagnosis of primary LUTO. Fetal intervention was offered after evaluation by a multidisciplinary team. Analyses were conducted using Bayesian methodology to determine predictors of survival at 6 months postpartum. Odds ratios (ORs) with 95% credibility intervals are reported.

RESULTS

Fifteen (60.0%) of the 25 patients referred for assessment survived to postnatal evaluation. Fetal vesicoamniotic shunt was placed in 14 (56.0%) patients with 12 survivors. Multivariable analysis suggested that fetal intervention (OR, 6.97 (0.88-70.16), Pr(OR > 1) = 96.7%), anhydramnios (OR, 0.12 (0.04-0.35), Pr(OR < 1) = 99.9%), favorable fetal urine analysis (OR, 3.98 (0.63-25.15), Pr(OR > 1) = 92.7%) and absence of renal cortical cysts (OR, 3.9 (0.66-24.2), Pr(OR > 1) = 93.3%) were predictors of survival.

CONCLUSIONS

Fetal intervention and fetal renal function were independently associated with postnatal survival of fetuses with LUTO. A classification based on the severity of disease is proposed. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Reference values of fetal serum β2-microglobulin in the Chinese: evaluation of its clinical usefulness

Background: The level of β2-microglobulin was generally used to evaluate the renal function in adults. Elevated levels of β2-microglobulin were also applied to assess the perinatal situations in neonates and fetuses. The aim of our study was to establish and determine the reference values of fetal serum β2-microglobulin in the Chinese and to assess its clinical benefits in abnormal fetuses.

Methods: Data from 308 normal cord blood samples were obtained to calculate the normal reference values of fetal serum β2-microglobulin. According to the equations we obtained, we analyzed the level of β2-microglobulin in four case groups: renal malformation, hydrops, cytomegalovirus (CMV) infection and rubella virus (RV) infection.

Results: In the normal group, the concentration of β2-microglobulin decreased with the gestational age, with a mean value of 4.35±0.59 mg/L. The upper limit of β2-microglobulin was calculated as 7.55–0.074×gestational age in weeks. The levels of β2-microglobulin were significantly higher in the four case groups than the normal group. For the four groups, the sensitivity is 72.7%, 69.6%, 86.7% and 100%, respectively.

Conclusions: Fetal serum β2-microglobulin may be used as a predictor to evaluate the situations of fetal diseases.

Fetal blood sampling

OBJECTIVE

We sought to review indications, technical aspects, risks, and recommendations for fetal blood sampling (FBS).

METHODS

A systematic review was performed using MEDLINE, PubMed, EMBASE, and Cochrane Library using the terms "fetal blood sampling," "percutaneous umbilical blood sampling," and "cordocentesis." The search was restricted to English-language articles published from 1966 through July 2012. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries also were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Evidence reports and guidelines published by organizations or institutions such as the National Institutes of Health, Agency for Health Research and Quality, American Congress of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Grade (Grading of Recommendations Assessment, Development, and Evaluation) methodology was employed for defining strength of recommendations and rating quality of evidence. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence.

RESULTS AND RECOMMENDATIONS

Ultrasound-guided FBS is the only procedure that provides direct access to the fetal circulation. When invasive testing is planned for suspected severe fetal anemia or thrombocytopenia, we recommend FBS as the procedure of choice, with availability of immediate transfusion if confirmed. We recommend against the use of FBS for indications in which other less invasive, and therefore lower risk, alternatives are available. The overall success rate of FBS is high, and blood samples can be obtained in >98% of patients. We suggest that counseling for FBS include discussion about the potential risk of FBS that may include, but may not be limited to: bleeding from puncture site (20-30%); fetal bradycardia (5-10%); pregnancy loss (≥1.3%, depending on indication, gestational age, and placental penetration); and vertical transmission of hepatitis or human immunodeficiency virus. We recommend that FBS be performed by experienced operators at centers with expertise in invasive fetal procedures when feasible.

Fetal obstructive uropathy complicated by urinary ascites: outcome and prognostic value of fetal serum β-2-microglobulin

OBJECTIVES

To determine whether the prognostic value of fetal serum β-2-microglobulin is altered and whether the occurrence of fetal urinary ascites prevents kidney damage in cases of fetal obstructive uropathy with urinary ascites.

METHODS

This was a retrospective study of cases of fetal bilateral obstructive uropathy that occurred between 2006 and 2010, for which both fetal serum and ascites samples were sent to our laboratory for analysis. β-2-microglobulin was assayed in both fetal serum and the corresponding ascites. Renal outcome was analyzed. Histological features of the kidney in cases of termination of pregnancy and renal function of liveborn infants were recorded.

RESULTS

Fourteen cases with analysis of fetal serum and fetal ascites in a context of urinary obstruction were included. Renal outcome was unfavorable in eight cases (57%) and favorable in six (43%). When fetal serum β-2-microglobulin was < 5 mg/L, renal outcome was favorable in all cases (4/4). When fetal serum β-2-microglobulin was ≥ 5 mg/L, 8/10 cases (80%) had an unfavorable renal outcome (sensitivity, 100%; specificity, 66%).

CONCLUSION

Fetal serum β-2-microglobulin reliably predicts postnatal renal outcome in obstructive uropathy complicated by urinary ascites. Moreover, urine extravasation does not seem to protect fetal renal function.

Congenital urinary tract obstruction: defining markers of developmental kidney injury

Congenital urinary tract obstruction (diagnosed antenatally by ultrasound screening) is one of the main causes of end-stage kidney disease in children. The extent of kidney injury in early gestation and the resultant abnormality in kidney development determine fetal outcome and postnatal renal function. Unfortunately, the current approach to diagnostic evaluation of the severity of injury has inherently poor diagnostic and prognostic value because it is based on the assessment of fetal tubular function from fetal urine samples rather than on estimates of the dysplastic changes in the injured developing kidney. To improve the outcome in children with congenital urinary tract obstruction, new biomarkers reflecting these structural changes are needed. Genomic and proteomic techniques that have emerged in the past decade can help identify the key genes and proteins from biological fluids, including amniotic fluid, that might reflect the extent of injury to the developing kidney.

[Impact of fetal urinary ascites on serum beta2 microglobuline in obstructive uropathies: a case report]

We report a posterior urethral valves case diagnosed at 33 week's gestation on a fetus presenting with anamnios and urinary ascites. In this fetus, the serum beta2 microglobuline rate was high, suggesting a very poor renal prognosis. At 1-year-old, the creatinine rate is nearly normal. In case of urinary ascites, the serum beta2 microglobuline rate could be improved in relation with the transperitoneal reabsorption of this protein.

Congenital urinary tract obstruction

Congenital urinary tract obstruction is a heterogenous condition with a varying natural history. Accurate diagnosis within the late-first and second trimesters allows for counselling of the parents and planning of multi-disciplinary care for the pregnancy and newborn. Antenatal investigations to predict postnatal renal function are of varying accuracy. However, some factors have been shown to be predictive of poor outcome in terms of renal function at birth and infancy. There is the possibility of in-utero intervention in these fetuses.

Syndrome d’insuffisance rénale fœtale

Some anomalies of the kidney and urinary tract evolving in utero may compromise the renal function in the newborn. Early therapeutic options do exist, especially in obstructive nephropathies. The decision depends on a correct evaluation of the foetal enal function and prognosis, which is based on a range of methods: ultrasound echography, biochemical analysis of foetal urine, and, more recently, foetal serum markers such a beta-2 micro globulin. These methods are reviewed.

Invasive assessment of fetal renal abnormalities: urinalysis, fetal blood sampling and biopsy

There are a number of potential biochemical markers that may have some role in predicting renal function postnatally. These include urinary sodium, calcium and beta2-microglobulin. The latter may also be measured in fetal serum. However, the accuracy of these parameters at a point in time is far from perfect as urinary tract obstruction is a progressive disease which may be best defined by repeated observations throughout pregnancy.

Fetal serum concentrations of cystatin C and beta2-microglobulin as predictors of postnatal kidney function

OBJECTIVES

Cystatin C and beta(2)-microglobulin are established serum markers of renal function in children and adults. In contrast to creatinine, diaplacental exchange is minimal. The aim of the study was to establish reference values in fetal serum and to test their efficiency in predicting postnatal kidney function.

STUDY DESIGN

This was a prospective noninterventional study measuring cystatin C and beta(2)-microglobulin by particle-enhanced immunoturbidimetry in excess serum from 129 cordocenteses performed in 84 fetuses. Reference intervals (mean +/- 1.96 SD) were calculated in a subgroup of 54 fetuses without evidence of kidney disease, and these reference values were evaluated in 75 sera from 55 fetuses.

RESULTS

Mean cystatin C was 1.66 +/- 0.202 mg/L (upper limit 2.06), and mean beta(2)-microglobulin was 4.25 +/- 0.734 mg/L. Unlike cystatin C, beta(2)-microglobulin decreased significantly with gestational age so that the upper reference limit was 7.19-0.052 x gestational age in weeks. beta(2)-Microglobulin had higher sensitivity (90.0% vs 63.6%) and cystatin C a higher specificity (91.8% vs. 85.5%) for the prediction of impaired renal function; diagnostic efficiency was equal (87.6% vs. 86.1%). Fetuses with impaired renal function at birth or who were aborted for renal malformations had higher cystatin C concentrations than those in a control group. beta(2)-Microglobulin was increased only in fetuses who were aborted.

CONCLUSION

Fetal serum cystatin C and beta(2)-microglobulin concentrations may be useful predictors of postnatal kidney function.

Prenatal evaluation of fetal renal function based on serum beta(2)-microglobulin assessment

The relationship between fetal renal function (FRF) and fetal serum beta(2)-microglobulin (B2MG) was investigated by comparing its value in 112 unaffected fetuses with that of 23 fetuses presenting with urinary tract malformations (UTM). Fetal serum level of B2MG was totally unrelated to gestational age; its value increased in cases of severe impairment of FRF but was similar to controls in all mild uropathies (p<0.05). Evaluating serum B2MG could be beneficial in fetuses with severe renal damage, but is of no use in unilateral UTM since only the global FRF is tested and not the function of each single kidney.

Fetal serum beta2-microglobulin predicts postnatal renal function in bilateral uropathies

BACKGROUND

Predicting postnatal renal function is crucial for the prenatal evaluation of fetal bilateral uropathies. Prenatal ultrasound can identify intrauterine terminal renal failure, but is not sensitive enough to identify those infants who would survive with an impaired renal function. Because it reflects fetal glomerular filtration, fetal serum beta2-microglobulin is a potential predictor of postnatal renal function.

METHODS

Fetal serum beta2-microglobulin (beta2m) was assayed in 61 cases of bilateral or low obstructive uropathy, 74 controls, and 17 cases of bilateral renal agenesis, and was correlated with renal function.

RESULTS

Fetal serum beta2m was 3.2 mg/L (range 1.5 to 4.7) in controls (N = 74), 9.5 mg/L (range 6.7 to 11.3) in bilateral renal agenesis (N = 17), 7 mg/L (5.1 to 10.6) in uropathy in which terminal renal failure resulted in termination of pregnancy (N = 26), and 3.7 mg/L (range 2.3 to 11.2) in live births with uropathy (N = 35). In the latter subgroup, fetal serum beta2m was significantly and positively correlated (r2 = 0.91) with postnatal serum creatinine. All survivors with a postnatal serum creatinine < or =50 micromol/L ha a fetal serum beta2m lower than 5 mg/L. Four of 6 survivors with a postnatal serum creatinine> 50 micromol/L had a fetal serum beta2m greater than 5 mg/L.

CONCLUSION

Fetal serum beta2-microglobulin is a marker for renal function and predicts postnatal serum creatinine in bilateral or low fetal obstructive uropathy.

Prenatal diagnosis. Therapeutic implications

Prenatal diagnosis of structural anomalies provides the opportunity to influence the postnatal outcome. The greatest value of antenatal screening is, in fact, the awareness of the urogenital abnormalities, such as presumed UPJ obstruction, so that appropriate investigation and treatment can be offered immediately after birth and before permanent damage occurs owing to obstruction or infection. Crombleholme and coworkers reported that prenatal consultation impacted favorably on outcomes by preventing early termination of pregnancy owing to misconceptions about the existing condition. It also permitted delivery of complex cases in a tertiary care setting, thereby preventing a delay in postnatal management. A systematic approach to the infant in the prenatal and postnatal periods is important. The natural history of prenatally detected hydronephrosis continues to be defined, and there is no ideal test to predict the outcome of UPJ obstruction. Several investigators are evaluating various markers in urine that may help to identify fetuses who require early postnatal intervention. More complete understanding regarding the natural history of unilateral pediatric UPJ obstruction and its response to surgery will not be available until several randomized, prospective clinical studies are completed. The collaborative effort of obstetricians, neonatologists, geneticists, radiologists, and pediatric urologists should provide answers to many questions surrounding prenatally diagnosed UPJ obstruction.