A single-center study to evaluate the efficacy of a fetal urine peptide signature predicting postnatal renal outcome in fetuses with posterior urethral valves

BACKGROUND

Posterior urethral valves (PUVs) account for 17% of pediatric renal failure. The management of pregnancies involving fetuses with PUV is hampered by the fact that current clinical parameters obtained from fetal ultrasound and/or fetal urine biochemistry are insufficient to predict postnatal renal function. We previously have developed a fetal urine peptide signature (12PUV) that predicted with high precision postnatal renal failure at 2 years of age in fetuses with PUV. Here, we evaluated the accuracy of this signature to predict postnatal renal outcome in fetuses with PUV in an independent single-center study.

METHODS

Thirty-three women carrying fetuses with suspected PUV were included. Twenty-five fetuses received vesicoamniotic shunts during pregnancy. PUV was confirmed postnatally in 23 patients. Of those 23 fetuses, 2 were lost in follow-up. Four and 3 patients died in the pre- and perinatal periods, respectively. Follow-up renal function at 6 months of age was obtained for the remaining 14 patients. The primary outcome was early renal failure, defined by an eGFR < 60 mL/min/1.73 m² before 6 months of age or pre- or perinatal death.

RESULTS

The peptide signature predicted postnatal renal outcome in postnatally confirmed PUV fetuses with an AUC of 0.94 (95%CI 0.74-1.0) and an accuracy of 90% (95%CI 78-100). The signature predicted postnatal renal outcome for the suspected PUV cases with an AUC of 0.89 (95%CI 0.72-0.97) and an accuracy of 84% (95%CI 71-97).

CONCLUSIONS

This single-center study confirms the predictive power of the previously identified 12PUV fetal urinary peptide signature.

Longitudinal serum and urine steroid metabolite profiling in a 46,XY infant with prenatally identified POR deficiency

Although POR deficiency (PORD) is assumed to be accompanied by excessive placental androgen accumulation and enhanced adrenal and testicular androgen production via the backdoor pathway as well as compromised testicular androgen production via the frontdoor pathway, there is no direct evidence for the flux of excessive placental androgens into the fetal circulation and for the production of dihydrotestosterone (DHT) via the backdoor pathway. We examined longitudinal serum and urine steroid metabolite profiles in a 46,XY infant with PORD who was prenatally identified because of the progressive fetal masculinization and maternal virilization from the mid-gestation and the presence of fetal radio-humeral synostosis and was confirmed to have compound heterozygous mutations of POR (p.Q201X and p.R457H). The results showed (1) markedly and inappropriately elevated serum androstenedione and testosterone (T) values at birth, (2) a markedly increased serum DHT value with a normal DHT/T ratio at birth, (3) transient elevation of serum T and DHT values accompanied by a normal DHT/T ratio and concomitant elevations of intermediate steroid metabolites on both the frontdoor and backdoor pathways at 30 days of age, and (4) persistent PORD-compatible urine steroid profiles. Although the data obtained from a single infantile patient are too premature to be generalized, they imply: (1) the transfer of excessive placental androgens into the fetal as well as the maternal circulations from the mid-gestation, (2) lack of a clinically discernible amount of DHT production via the adrenal backdoor pathway around birth, and (3) the activation of both the frontdoor and backdoor pathways in the testis around the mini-puberty, with no production of a clinically discernible amount of DHT via the testicular backdoor pathway.

Fetal urine biochemistry at 13-23 weeks of gestation in lower urinary tract obstruction: criteria for in-utero treatment

OBJECTIVES

To assess the value of fetal urine biochemistry before 23 weeks of gestation in cases of lower urinary tract obstruction (LUTO) to refine prognosis and to select potential candidates for in-utero intervention.

METHODS

This was a retrospective study including 72 cases of LUTO with fetal urine sampled before 23 weeks and assayed for total protein, β-2-microglobulin, sodium, chloride, calcium, phosphorus, glucose and gamma-glutamyl transpeptidase (GGTP). Two groups were defined according to renal outcome: 1) bilateral renal dysplasia on histological examination or renal failure at birth; 2) normal postnatal renal function or histologically normal appearance of the kidneys. Correlations between fetal urinary biochemical markers and postnatal renal function were studied.

RESULTS

LUTO was isolated in 56/72 (77.8%) cases and was associated with other malformations in 16/72 (22.2%) cases. High GGTP levels (236 IU/L vs 5 IU/L; P < 0.0001) were observed in fetal urine in the five cases of urodigestive fistula. A significant difference between outcome groups was observed for β-2-microglobulin (P = 0.0017), sodium (P = 0.0008), chloride (P = 0.0028) and calcium (P = 0.0092) but not for protein, glucose or phosphorus. Sensitivity and specificity in defining a poor renal prognosis were 80.6% and 89% for β-2-microglobulin, 61.3% and 100% for sodium and 64.5% and 100% for calcium, respectively.

CONCLUSIONS

Fetal urinalysis before 23 weeks of gestation allowed distinction between three groups: 1) fetuses with normal urine biochemistry for which fetal therapy should be discussed; 2) fetuses with abnormal urine biochemistry for which prognosis for renal outcome is poor and for which the benefit of fetal therapy is likely to be compromised; 3) fetuses with urodigestive fistula.

Isolated hyperechoic fetal colon before 36 weeks' gestation reveals cystinuria

OBJECTIVES

To determine whether there is an association between the fetal ultrasound finding of hyperechoic colon and the gestational age at which it presents and cystinuria.

METHODS

A prospective national survey was performed in France including all observations of isolated fetal hyperechoic colon detected at routine second- and third-trimester ultrasound over a 2-year period. Collected images were reviewed by experts. Colon was defined as being hyperechoic when its echogenicity was at least equal to that of the iliac bone. It was diagnosed when large tubular echogenic portions of the colon, without a focal mass and without posterior acoustic shadows, were observed at the periphery of the abdomen. Urinary amino acid analysis was performed after birth in the cases identified to test for cystinuria.

RESULTS

Nineteen fetuses with ultrasound findings of hyperechoic colon were included, and the mothers of 16 of these agreed to participate in the study. In eight of nine cases of hyperechoic colon observed before 36 weeks' gestation cystinuria was confirmed at birth. In the seven remaining cases, observed after 36 weeks, none was found to have cystinuria and all had normal images at previous routine ultrasound scans at 22 and 33 weeks. When present, no difference in the sonographic appearance of hyperechoic colon was noted between the two groups. In the cystinuria-affected cases, the length of the hyperechoic mass appeared to increase with gestational age.

CONCLUSIONS

In our experience, the presence of a hyperechoic colon at routine ultrasound scan before 36 weeks' gestation should prompt screening for cystinuria at birth, while later observation (> 36 weeks) of this finding does not appear to be related to any disease.

Urindiagnostik in der Schwangerschaft

Schwangerenvorsorge umfasst neben präventiven Maßnahmen auch das Screening bzw. die rechtzeitige Erkennung und Therapie von Schwangerschaftskomplikationen. In den jeweiligen Vorsorgerichtlinien sind neben der allgemeinen körperlichen und der vaginalen Untersuchung, dem Ultraschall und gegebenenfalls hämatologischen Untersuchungen auch die Untersuchung des Urins der Schwangeren vorgesehen. Derzeit wird routinemäßig der Urin der Schwangeren hinsichtlich Infektionszeichen, Glukosurie und Proteinurie untersucht. Während die Bestimmung der Glukosurie für die Detektion eines Gestationsdiabetes keinen Nutzen hat und als Screeningmethode nicht mehr empfohlen wird, kann durch die Untersuchung des Urins auf Bakterien und Infektionszeichen sowie eine frühzeitige Therapie eine Risikominimierung für maternale und neonatale Komplikationen erzielt werden. Den größten Stellenwert in der Urindiagnostik hat die Detektion und die Quantifizierung einer Proteinurie bei Patientinnen mit Hochdruckerkrankungen zur Diagnostik einer Präeklampsie, sowie zur Planung des geburtshilflichen Managements. Hierbei gilt nach wie vor die Quantifizierung der Eiweißausscheidung im 24-Stunden-Sammelurin als Methode der Wahl.

SURUSS in perspective

BACKGROUND

Until the publication of the Serum Urine and Ultrasound Screening Study (SURUSS) report, it was difficult to compare the different antenatal screening tests for Down's Syndrome because of variations in study designs. We here present the main results from SURUSS, updated to take account of recent information on nuchal translucency in Down's Syndrome pregnancies, and discuss their implications.

METHODS

SURUSS was a prospective study of 47,053 singleton pregnancies (including 101 pregnancies with Down's Syndrome) conducted in 25 maternity units. Nuchal translucency measurements were taken. Serum and urine samples collected between 9 and 13 weeks, and again between 14 and 20 weeks of pregnancy were stored. Samples from each affected pregnancy and five matched controls were tested for currently used or suggested biochemical Down's Syndrome screening markers. Pregnancies were followed up to determine the presence or absence of Down's Syndrome. For an 85% Down's Syndrome detection rate, the false-positive rate for the Integrated test (nuchal translucency and pregnancy associated plasma protein-A [PAPP-A] at 11 completed weeks of pregnancy, and alpha-fetoprotein, unconjugated oestriol [uE3], free beta or total human chorionic gonadotrophin (hCG) and inhibin-A in the early second trimester) was 0.9%, the Serum integrated test (without nuchal translucency) 2.7%, the Combined test (nuchal translucency with free beta-hCG and PAPP-A at 11 weeks) 4.3%, the Quadruple test (alpha-fetoprotein, uE3, free beta or total hCG and inhibin-A) 6.2%, and nuchal translucency at 11 weeks, 15.2%. All tests included maternal age. Using the Integrated test at an 85% detection rate, there would be six diagnostic procedure-related unaffected fetal losses following amniocentesis per 100,000 women screened compared with 35 using the Combined test or 45 with the Quadruple test.

CONCLUSIONS

The Integrated test offers the most effective and safe method of screening for women who attend in the first trimester. The next best test is the Serum integrated test. The Quadruple test is the best test for women who first attend in the second trimester. There is no justification for retaining the Double (alpha-fetoprotein and hCG) or Triple (alpha-fetoprotein, uE3, and hCG) tests, or nuchal translucency alone (with or without maternal age) in antenatal screening for Down's Syndrome.

Amniotic fluid: not just fetal urine anymore

Amniotic fluid (AF) is a complex substance essential to fetal well-being. This article reviews recent discoveries and the current understanding of the origin and circulation of AF and its nutritive, protective, and diagnostic functions. Future directions for AF research are also discussed.

Prenatal diagnosis of megacystis-microcolon-intestinal hypoperistalsis syndrome: contribution of amniotic fluid digestive enzyme assay and fetal urinalysis

OBJECTIVES

Megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is a usually lethal disease during the first year of life. There is no specific ultrasound prenatal diagnosis and no identified genetic locus. The value of amniotic fluid digestive enzyme assay and fetal urine biochemistry in the prediction of MMIHS was analysed.

METHODS

Retrospective study of 14 MMIHS cases. Amniotic fluid digestive enzymes and fetal urine biochemistry were compared in MMIHS and megabladder (63 and 264 cases respectively).

RESULTS

Abnormal amniotic fluid digestive enzyme profile (vomiting of bile or digestive secretion leakage) was observed in 8/10 MMIHS cases. These profiles were observed in 7/63 controls; 80% sensitivity (95%CI = 55%-100%); 89% specificity (95%CI = 81%-96%). Fetal urinalysis was normal in 12/12 MMIHS cases except high calcium (>0.6 mmol/l). This profile was observed in 33/264 megabladder control cases; 100% sensitivity; 98.7% specificity (95%CI = 83.5%-91.5%).

CONCLUSION

For the first time, we propose a prenatal diagnosis of MMIHS based on amniotic fluid digestive enzyme assay and on fetal urinalysis.

Diagnosis and outcome of fetal lower urinary tract obstruction in the northern region of England

OBJECTIVE

We reviewed the prenatal and postnatal management of fetal lower urinary tract obstruction (LUTO) in a large geographically defined population.

METHODS

The records of 113 cases of LUTO seen over a 14-year period were examined. The predictive accuracy of prenatal findings for chronic renal failure (CRF) and a comparison of prenatal-suspected and non-suspected cases were made.

RESULTS

The incidence of LUTO was 2.2 in 10 000 births. During the study period, prenatal detection improved from 33 to 62%. Sensitivity of prenatal ultrasound detection of renal dysplasia and fetal urinary sodium, calcium, and beta2-microglobulin for CRF or renal dysplasia on autopsy were 59, 33, 66, and 63% respectively. Compared to undetected cases, those detected prenatally had higher mortality and a higher rate of CRF at 24 months (17% vs 57%, p < 0.01).

CONCLUSION

Our observations confirm the poor prognosis associated with fetal LUTO. The value of serial fetal urine biochemistry, other prenatal predictors of postnatal renal function, and the benefits of vesicoamniotic shunting require larger series and longer follow-up.

The utility of fetal urine biochemistry in the management of lower urinary tract obstructions. A report of 3 cases

The aim of this study is to implement the use of biochemical parameters in the analysis of fetal urine to assist with decision making for surgical intervention for fetal obstructive uropathy. Three patients were selected over a 6 month period following ultrasound diagnosis of megabladder and oligohydramnios. Amniocentesis and cystocentesis were performed for karyotyping and biochemical urinary electrolyte evaluation, respectively. Fetal urine biochemistry assisted in decision making with regard to patient and fetal well being. In each of the cases the parameter cutoffs were diagnostic of fetal condition. While the long term benefits of fetal intervention for obstructive uropathy are still debated, we feel that the use of urine biochemical criterIa provide the best current method to select the subjects to be submitted to vesicoamniotic shunt centres.

Evidence of fetal C-reactive protein urinary excretion in early gestation

BACKGROUND

C-reactive protein has been measured in amniotic fluid in the second and third trimesters of gestation, and its elevated concentration has been found to be associated with adverse pregnancy outcome. It remains unexplained whether amniotic fluid C-reactive protein is of fetal origin.

CASE

We report the measurement of C-reactive protein in fetal urine obtained by transabdominal vescicocentesis in a fetus at 15 weeks' gestation affected by obstructive uropathy. Using an enzyme-linked immunosorbent assay, C-reactive protein was detected at a concentration of 234 ng/mL.

CONCLUSION

The fetal kidneys excrete C-reactive protein as early as 15 weeks' gestation.

Perinatal outcome in fetuses with megacystis in the first half of pregnancy

OBJECTIVE

To present the outcome of a consecutive series of 19 fetuses referred to our center for megacystis in the first half of the pregnancy.

STUDY DESIGN

Retrospective analysis.

METHODS

19 cases of early fetal megacystis were reviewed. Inclusion criteria were the visualization of an enlarged bladder with a maximum longitudinal diameter >10 mm and a gestational age of no more than 19 weeks.

RESULTS

The median gestational age at diagnosis was 16 weeks (range 12-19 weeks). The median maximum longitudinal diameter of the fetal bladder at the time of diagnosis was 21 mm (range 11-35 mm). The fetal megacystis was associated with another extra renal anomaly in six cases (30%). There was no fetus with abnormal karyotype. Termination of pregnancy was performed in 11 cases because of the severity of the renal disease. One spontaneous intrauterine death occurred. A vesicoamniotic shunt was inserted in three cases, two of which died in utero. The surviving fetus that was shunted died in the neonatal period from acute renal failure. In the remaining four fetuses, resolution of the megacystis occurred spontaneously (n = 2) or following serial single-needle aspiration (n = 2). One of these had renal insufficiency requiring kidney transplantation.

CONCLUSION

The outcome of fetuses with early obstructive uropathy is poor, with or without in utero therapy. Pathophysiology, clinical presentation and outcome of fetuses with early uropathy may differ from those previously described in the latter part of pregnancy.

In utero therapy for lower urinary tract obstruction

Lower urinary tract obstruction has a significant impact on neonatal and child health. Pulmonary hyperplasia and renal impairment could be direct or indirect consequences of this condition leading to significant morbidity and mortality. Evaluation of fetuses with suspected lower urinary tract obstruction is performed not only to confirm the diagnosis but also to assess renal prognosis. Ultrasound examination and urinary analysis aid in the evaluation of these fetuses. The decision to perform fetal intervention in these cases is a difficult one. Vesico-amniotic fetal shunting, open fetal surgery and more recently endoscopic fetal surgery for this condition are available as possible modalities of fetal intervention. Case selection for fetal intervention is extremely important in order to both avoid unnecessary intervention in those unlikely to survive, and also to avoid procedure related complications in fetuses likely to do well without intervention. Vesico-amniotic shunting has the advantage of bypassing the obstruction, however it is often associated with complications. Open fetal surgery is not usually recommended because of the complications and high fetal loss rate. Endoscopic surgery to visualise and treat the cause of lower urinary tract obstruction has been tried. Fetal endoscopic surgery is in its infancy and endoscopic procedures are limited to a few groups. This current review addresses evaluation, case selection and therapeutic options for lower urinary tract obstruction in utero. It also discusses the limited data against which the efficacy of the various options can be assessed. The current state of fetal intervention is detailed in the present review.

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.

National Institute of Child Health and Development Conference summary: amniotic fluid biology--basic and clinical aspects

This report summarizes the National Institute of Child Health and Development sponsored conference on amniotic fluid (AF) biology, held 28-29 September 1999, in Detroit, Michigan. National and international investigators with expertise in AF biology addressed the regulation of AF volume and composition as well as the clinical aspects of interpreting fetal health and well-being from AF indices. A major purpose of the meeting was to consider future directions and opportunities for basic and clinical research which focus on understanding the physiology and pathophysiology and providing therapeutic interventions for abnormalities of AF volume. To achieve this, the workshop participants addressed the current state of knowledge, recent scientific advances and priorities for major questions for which answers must be sought. The fact that it is not known whether AF volume is regulated or what volume-regulatory mechanisms might be involved is a major problem that needs addressing. In the later half of gestation, potential AF volume-regulatory pathways include the two major inflows into the amniotic compartment, i.e. fetal urine and lung liquid, and the two major outflows, i.e. fetal swallowing and intramembranous absorption. If AF volume is regulated, then this must occur through regulation of intramembranous flow, because the other three flows are regulated by the fetus to meet fetal needs. Regulation of AF composition is similarly unknown. In clinical practice, a variety of ultrasonographic indices of AF volume are used, but the relationships of these indices to AF volume have not been determined, nor have their dependency on fetal size, shape or position within the uterus. Further, although aberrations in AF volume both above and below normal are associated with increased fetal and neonatal morbidity and mortality, the predictive utility of the various AF indices remains low and there is little consensus on which is best utilized under conditions of oligohydramnios, normal AF volumes, or polyhydramnios. Further, various clinical AF therapies remain largely experimental and their optimization and utilization need exploration. This report is a condensation of the views presented by the conference participants.

[Prenatal diagnois of uropathies. Ten case reports]

Obstructive uropathies are a frequent cause of child renal failure. The prenatal diagnosis of such abnomalities should lead to appropriate management.

OBJECTIVE

To evaluate the interest of ultrasonographic prenatal diagnosis of urinary tract malformations.

PATIENTS AND METHODS

Retrospective study of 10 cases of urinary tract malformations diagnosed in utero. The mean age of the patients was 34.9 years and the mean gestational age at the prenatal diagnosis was 28.2 weeks of amenorrhea. The abnormalities diagnosed were: 2 cases of ureteropelvic junction obstruction, 3 cases of posterior urethral valves and 5 cases of mild hydronephrosis. The fetal karyotype, realised in 8 cases, was normal. In one case the urinary abnormalities was part of a multiple malformation syndrome and led to the termination of the pregnancy. 7 cases had a post-natal follow-up: 5 had a surgical management and two new borns had transient pyelectasies. The prediction of postnatal renal function is made by ultrasonographic appearance of the kidney and the amniotic fluid. Although the analysis of fetal urine for the assessment of renal function leads to conflicting results, it seems that sodium and beta-2 microglobulin urinary rates provide useful informations.

Relationship between graded degrees of anemia and amniotic fluid volume in the ovine fetus

OBJECTIVE

Severe fetal anemia is associated with polyhydramnios in both human and ovine fetuses. This study examined the relationship between varying degrees of anemia and amniotic fluid volume in fetal sheep.

STUDY DESIGN

Eleven long-term catheterized ovine fetuses at 126 +/- 1 days' gestation (mean +/- SE) were subjected to hemorrhage of 20 to 80 mL daily for 9 consecutive days to produce varying degrees of fetal anemia. Five additional animals served as time control animals. Statistical analysis was by least squares regression and 3-factor analysis of variance.

RESULTS

Amniotic fluid volume was 793 +/- 147 mL and did not change with time in the control fetuses. In the fetuses that were subjected to hemorrhage the amniotic fluid volume changed little through the hematocrit range of 40% to 25%. As fetal hematocrit fell below approximately 25%, amniotic fluid volume began to increase. With greater degrees of anemia the amniotic fluid volume increased as an exponential function of hematocrit and approached 2000 mL excess fluid as hematocrit dropped to <15%. According to bivariate regression the increase in amniotic fluid volume was related to fetal hematocrit, PaO(2), and urinary flow rate as well as to plasma and amniotic fluid lactate concentrations. According to multivariate regression only fetal PO(2) and urinary flow rate were significantly related to the increase in amniotic fluid volume.

CONCLUSIONS

Although mild anemia was not associated with increased amniotic fluid volume, moderate to severe fetal anemia was associated with an exponential rise in amniotic fluid volume. This rise may have been mediated by a hypoxemia-induced diuresis, by a diuresis related to a lactate-induced osmotic accumulation of fetal fluid, or by both mechanisms.

Second-trimester maternal urine human chorionic gonadotrophin beta-core fragment concentrations in Asian pregnancies with fetal chromosomal abnormalities

The aim of this study was to investigate the second trimester concentrations of maternal urine human chorionic gonadotrophin beta-core fragment (HCGbetacf) in Asian pregnanci2es with fetal chromosomal abnormalities. HCGbetacf concentrations were analysed from 34 urine samples in chromosomally abnormal pregnancies, including 28 cases of Down's syndrome, one case of trisomy 18, and five cases of other chromosomal abnormalities (one mosaic deletion and four translocations), and in a cohort of 268 normal pregnancies receiving second trimester amniocentesis. Results were normalized to urine creatinine (Cr) concentration and converted to the multiple of the median (MOM) concentration for the appropriate gestation. The median HCGbetacf MOM concentrations of Down's syndrome pregnancies (12.89) was significantly higher than that of normal pregnancies (1. 06) (P < 0.00001). Wide variations of HCGbetacf concentrations were observed in other chromosomally abnormal pregnancies. There were 18 of 28 (64%) Down's syndrome cases but one of five (20%) other chromosomally abnormal cases with HCGbetacf concentrations above the 95th centile of the control values (8.22 MOM cut-off). These findings suggest that HCGbetacf could be a potential marker in urine screening for fetal Down's syndrome in Asians.

Hydronephrosis in pregnancy: simultaneous depiction of fetal and maternal hydronephrosis by magnetic resonance urography

Magnetic resonance urographic (MRU) techniques possess image quality and diagnostic capability that are improving with increasingly sophisticated imaging sequences and shorter scanning times. We describe the application of a fast breath-hold MR sequence (HASTE) in the assessment of ureteric obstruction in pregnancy. In the patient presented, HASTE MRU was successful in depicting ureteral anatomy and demonstrated dilation of both ureters below the level of the pelvic brim. This observation suggested distal ureteral obstruction rather than simple hydronephrosis of pregnancy. As a result, bilateral nephrostomies were performed and neonatal prematurity was avoided. Interestingly, in this patient, HASTE MR imaging also showed evidence of concurrent fetal hydronephrosis.

Urinary screening tests for fetal Down syndrome: II. Hyperglycosylated hCG

Hyperglycosylated hCG is a form of hCG with more complex oligosaccharide side chains. A specific immunoassay was developed to measure hyperglycosylated hCG. Levels were measured in urine samples from 1157 women between 11 to 22 weeks of gestation, undergoing genetic analysis because of advanced maternal age. Values were normalized to urine creatinine concentration and plotted against gestational age, median values were determined and multiples of the control median (MoM) calculated. The median MoM and log standard deviation (log SD) of the 1134 control samples was 1.0 and 0.47, and of the 23 Down syndrome cases was 7.8 and 0.48, respectively. This indicated a 7.8-fold increase in hyperglycosylated hCG levels in Down syndrome cases. In the accompanying article, a stability problem was found with beta-core fragment measurements in frozen urine samples. In anticipation of similar problems, nine urine samples were tested for hyperglycosylated hCG fresh and after storage in the freezer. No clear difference was found in hyperglycosylated hCG values. In addition, no trend was found in hyperglycosylated hCG MoM values or in Down syndrome detection rates in urine samples stored for one, two or three years in the freezer. Samples were split into five equal groups according to creatinine concentration. A trend was observed, hyperglycosylated hCG MoM values decreasing with advancing creatinine concentration (1.77, 1.08, 1.01, 0.73 and 0.60 at 0.25, 0.50, 0.79, 1.11 and 1.73 mg/ml, respectively). An error was noted. This was corrected with a regression equation. After correction, the median MoM and log SD of the control samples was 1.0 and 0.44, and of Down syndrome samples was 7.3 and 0.42, respectively. Correction of this error, while reducing the elevation of Down syndrome cases, tightened the spread of samples. Samples were ranked and centiles determined. 18 of 23 Down syndrome cases (78 per cent) exceeded the 95th centile of the control population. ROC analysis indicated 79 per cent detection at 5 per cent false-positive rate. Urine samples were collected during two periods of gestation, an early period (11th to 14th completed week) and the period when chemical screening is normally performed (15th to 21st week). ROC analysis indicated 80 per cent and 78 per cent detection rates, respectively, at 5 per cent false-positive rate, in the two gestational periods. Hyperglycosylated hCG values were modelled with beta-core fragment values, total oestriol values and maternal age. ROC analysis indicated 97 per cent detection rate at 5 per cent false-positive rate. This detection rate and this level of Down syndrome and control patient discrimination surpasses that of any other serum, urine or ultrasound screening protocol. Hyperglycosylated hCG should be considered as a new screening test for aneuploid pregnancies, with the potential of detecting almost all cases of Down syndrome. Evaluation is needed by other centres in order to bring hyperglycosylated hCG into clinical practice.

Fetal uropathy

Our understanding of the causes, mechanisms, and prenatal management of fetal obstructive uropathy has increased significantly. Improved methods of prenatal evaluation have allowed the better selection of fetuses for invasive therapy, and studies indicate better survival and renal outcomes in carefully selected cases. New biological markers in fetal urine may provide a better understanding of the pathological processes of renal damage, additional prognostic markers, and lead to non-surgical approaches to preventing renal damage.

Urinary screening tests for fetal Down syndrome: I. Fresh beta-core fragment

Variable results have been reported using urine beta-core fragment as a marker for fetal Down syndrome. Initial studies by Cuckle et al. (1994) and Canick et al. (1995) indicated that beta-core fragment was an outstanding marker, detecting >80 per cent of Down syndrome cases. Since these reports, widely varying results have been published, indicating between 20 per cent and 66 per cent detection of cases at 5 per cent false-positive rate. The wide variation in the reported data has led to a loss of enthusiasm for this marker as a useful test for Down syndrome screening. Here we report the results of a three-year prospective study in which urine samples were collected daily from women undergoing fetal karyotype analysis for advanced maternal age. Samples were tested within one week of collection and then frozen. We also investigated the likely causes of the variability observed in beta-core fragment data. We collected 1157 urine samples over 955 days. Beta-core fragment levels were measured. A regression line was calculated for the weekly medians of the 1134 control samples and multiples of the control median (MoM) were determined. The median MoM for the controls was 1.0 and the logarithmic standard deviation (log SD) was 0.41. The median MoM for the 23 Down syndrome cases was 5.44 and the log SD was 0.45. Over the study period, 65 per cent of Down syndrome cases exceeded the 95th centile of the control group. The median MoM of control samples and the proportion of Down syndrome cases detected by the test was relatively constant during the study period. The unaffected cases were divided into three equal divisions, corresponding to approximately the first, second and third year of sample collection. No trend was found in the median control MoM values in three sample collection periods (r2=0.04). A similar number of cases exceeded the 95th centile of control samples in the three sample collection periods, 63 per cent, 66 per cent and 66 per cent. Consistent results were indicated during the three years of sample testing. Levels of total oestriol were determined in urine samples and MoM statistics derived. The median oestriol level in Down syndrome cases was 0.59 MoM. Only 12 per cent of cases had MoM levels below the fifth centile. Gaussian models were prepared combining biochemical data and maternal age distribution. While beta-core fragment by itself detected 65 per cent of Down syndrome cases, beta-core fragment modelled with maternal age detected 66 per cent, and modelled with age and total oestriol levels detected 82 per cent of cases at 5 per cent false-positive rate. At the completion of the study, we thawed and reassayed 20 random urine samples (10 control and 10 Down syndrome) collected at different times during the study period. While the control samples (74-1700 ng/ml) had slightly increased values when reassayed (mean value 137 per cent of original prospective value), the Down syndrome samples (360-20,500 ng/ml) all had decreased values when reassayed (mean=53 per cent, t-test, controls versus cases, p = 0.0003). The Down syndrome samples were decreased to between 93 per cent and 12 per cent of the original value. A relationship was identified between the magnitude of the original beta-core fragment value and the change in immunoreactivity when reassayed (r2=0.998). The higher the initial beta-core fragment value the greater the loss of immunoreactivity. We considered the possibility that the beta-core fragment molecules aggregate upon storage in the freezer. We repeated the assay of the 20 samples after treatment with a high salt buffer. Down syndrome samples recovered half of the lost beta-core fragment immunoreactivity (mean increase in beta-core fragment levels 56 per cent, t-test, controls versus cases, p=0.004). We infer that aggregation of beta-core fragment upon storage interferes with beta-core fragment measurements. This may be the cause of the poor beta-core fragment screening performance reported using sto

Urinary compound W in pregnant women is a potential marker for fetal thyroid function

OBJECTIVE

Previously we reported 3,3'-diiodothyronine sulfate-like material (compound W) in maternal serum, and studies suggest that compound W is derived from thyroid hormones of fetal origin. In this study we characterized gestational changes of urinary compound W concentrations to correlate with changes in serum concentrations.

STUDY DESIGN

Urinary samples were collected from 94 women at various gestational ages ranging from 3 to 40 weeks. Urinary compound W was first identified biochemically. The concentrations of compound W (adjusted for creatinine levels) were assessed by a 3,3'-diiodothyronine sulfate radioimmunoassay in ethanol extracts of urine samples.

RESULTS

Compound W increased to 88 +/- 1.4 pmol (of 3,3'-diiodothyronine sulfate equivalent)/mmol creatinine in urinary samples obtained from 26 women in the first trimester of pregnancy compared with 40 +/- 6.9 pmol/mmol creatinine in 10 nonpregnant women. Excretion of compound W increased further during the second and third trimesters: 171 +/- 17 (n = 18) and 434 +/- 26 (n = 50) respectively. In contrast, urinary 3,3',5-triiodothyronine sulfate concentrations measured by radioimmunoassay were similar during pregnancy to values in nonpregnant women.

CONCLUSIONS

Urinary compound W concentrations increase with the progression of normal pregnancy and correlate with the increase in serum levels. Random spot urine compound W concentrations, adjusted for creatinine levels, may be used in place of serum levels in conditions in which obtaining serum samples may be technically difficult, especially during population screening.

Combining beta-core fragment and total oestriol measurements to test for Down syndrome pregnancies

Recent articles by Cuckle et al., Canick et al., and Isozaki et al. have evaluated urine beta-core fragment as a screening test for Down syndrome in second-trimester pregnancies. They found over four-fold elevation of beta-core fragment levels in Down syndrome pregnancies, and between 62 and 88 per cent detection of this trisomy at a 5 per cent false-positive rate. Urine beta-core fragment may be a superior screening test for Down syndrome pregnancies. In the present study, urinary total oestriol has been evaluated as a marker to use in combination with beta-core fragment in screening for Down syndrome pregnancies. The two markers were evaluated separately in relation to the urine creatinine concentration. To amplify screening performance, we evaluated the ratio of beta-core fragment to total oestriol levels (creatinine-independent). beta-core fragment and total oestriol levels were determined (normalized to creatinine, ng/mg creatinine) in urine samples from 480 unaffected and 12 Down syndrome pregnancies, collected consecutively at a single prenatal diagnosis centre. The median beta-core fragment level in Down syndrome cases was 4.5 MOM. Fifty-eight per cent of Down syndrome cases had beta-core fragment levels exceeding the 95th centile of unaffected pregnancies. The median total oestriol level in Down syndrome cases was 0.33 MOM. Forty-two per cent of Down syndrome cases had total oestriol levels exceeding the 95th centile of unaffected pregnancies. We investigated the ratio of the two determinants (beta-core fragment, ng/ml divided by total oestriol, ng/ml) in our sample set. The median beta-core fragment:total oestriol ratio in Down syndrome cases was 13 MOM. Seventy-five per cent of Down syndrome cases had a ratio exceeding the 95th and the 99.5th centile of unaffected pregnancies. Total oestriol complements beta-core fragment in urine screening for Down syndrome pregnancies. A test measuring the ratio of the two urine determinants may be a significant improvement over current serum methods for detecting Down syndrome.

Screening for Down syndrome using urine hCG free beta-subunit in the second trimester of pregnancy

Human chorionic gonadotropin (hCG) free beta-subunit levels were determined in 709 control and 13 Down syndrome urine samples from the second trimester of pregnancy. Results were normalized to urine creatinine concentration and converted to multiples of the unaffected pregnancy medium (MOM). The concentration of free beta-subunit in Down syndrome cases was 3.9 MOM. Seven of 13 Down syndrome pregnancies (54 per cent) had free beta-subunit levels at or above the 95th centile of unaffected pregnancies. Urine free beta-subunit may potentially be useful as a screening test for Down syndrome.

Levels of urinary beta-core fragment, total oestriol, and the ratio of the two in second-trimester screening for Down syndrome

Levels of beta-core fragment and total oestriol in second-trimester maternal urine samples were measured in 32 Down syndrome pregnancies and 206 control pregnancies. Beta-core fragment and total oestriol values were corrected for the urinary creatinine level and expressed as multiples of the control medians (MOM). In addition, the ratio of the beta-core fragment level to the total oestriol level, without creatinine correction, was calculated, and expressed as MOM values. The median beta-core fragment, total oestriol, and ratio levels in Down syndrome cases were 5.42, 0.64, and 9.32 MOM, respectively. In the Down syndrome pregnancies, 66 per cent of the beta-core fragment levels were above the 95th centile of control levels, while 22 per cent of the total oestriol levels were below the fifth centile of control levels. In combination with maternal age, measurement of beta-core fragment and total oestriol levels in Down syndrome pregnancy resulted in an 80 per cent detection rate at a 5 per cent false-positive rate. Use of the ratio resulted in a univariate detection rate of 72 per cent. In combination with maternal age, the ratio resulted in a detection rate of 81 per cent at a 5 per cent false-positive rate. Based on this unmatched study, the measurement of a ratio of beta-core fragment to total oestriol levels, without the need for creatinine correction, may be useful in screening for fetal Down syndrome in second-trimester urine.

Second-trimester maternal urinary gonadotrophin peptide screening for fetal Down syndrome in Asian women

Maternal urinary gonadotrophin peptide (UGP) was recently found to be elevated in second-trimester Down syndrome pregnancies. There is controversy about its screening efficacy. Data in the Asian population are scanty. We measured the UGP levels in 29 Down syndrome pregnancies and 297 controls and expressed them as a ratio of the urine creatinine concentration. Median UGP MOM was elevated to 3.44 (95 per cent confidence interval 1.99-5.13) in cases, compared with controls. UGP values were widely scattered in cases and controls with extensive overlap such that only 35 per cent of Down syndrome cases were expected to be detected at a 5 per cent false-positive rate. The data of the present study and previous reports show that there is a wide variability of gestation-specific UGP median values. UGP alone does not appear to be an effective screening marker for fetal Down syndrome.

Successful treatment of fetal megavesica in the first half of pregnancy

OBJECTIVE

Our goal was to assess fetal kidney function in fetuses with megavesica diagnosed during the first half of pregnancy before treatment.

STUDY DESIGN

In a prospective interventional study 9 fetuses with megavesica diagnosed during the first half of pregnancy underwent vesicocentesis. Fetal urine biochemical markers (urine electrolytes, osmolarity, and beta 2-microglobulins) were determined after diagnostic vesicocentesis of the fetal megavesica.

RESULTS

Surprisingly, in four fetuses who underwent sampling at 13 to 18 postmenstrual weeks, vesicocentesis proved both diagnostic and therapeutic. Pregnancy proceeded with normal amniotic fluid volume, a normal-sized urinary bladder with normal dynamics, and normal postnatal renal function. A fifth fetus had trisomy 18. In three of the remaining four fetuses in whom sampling was performed at 16 to 20 postmenstrual weeks, biochemical markers indicated a poor prognosis. In the remaining fetus marginal results of biochemical studies prompted intrauterine treatment, but death from respiratory problems ensued after premature delivery at 31 weeks.

CONCLUSIONS

Fetal megavesica in the first half of pregnancy is an indication for an immediate diagnostic vesicocentesis. This is the first report emphasizing early diagnosis of fetal megavesica with subsequent fetal vesicocentesis and demonstrating that this minimally invasive procedure can be life-saving if performed in early pregnancy.

Effects of prolonged hypoxemia on fetal renal function and amniotic fluid volume in sheep

OBJECTIVE

Our purpose was to determine the effects of prolonged hypoxemia on fetal renal function and amniotic fluid volume and composition.

STUDY DESIGN

Twelve pregnant ewes underwent surgery at 115 +/- 2 days after mating (term approximately 147 days) for the implantation of fetal vascular, bladder, and amniotic sac catheters. At 125 +/- 1 days seven fetuses were studied during 6 days of hypoxemia and five control fetuses were studied over six days of normoxemia. Index values of fetal renal function and amniotic fluid volume were measured.

RESULTS

During hypoxemia fetal SaO2 and PaO2 were reduced from 60.9% +/- 1.6% and 21.9 +/- 0.6 mm Hg to 29.6% +/- 3.8% and 14.9 +/- 0.8 mm Hg, respectively. Fetal hypoxemia was associated with a transient acidemia (arterial pH 7.29 +/- 0.02) at 4 hours. There were no sustained alterations in fetal urine production (9.5 +/- 0.8 ml/hr/kg) or glomerular filtration rate (1.3 +/- 0.1 ml/min/kg) during hypoxemia. In control fetuses the amniotic fluid volume increased over 7 days, from 717 +/- 169 ml to 1031 +/- 147 ml, whereas in the hypoxemic fetuses it did not change (741 +/- 68 ml) over the same period.

CONCLUSION

During prolonged fetal hypoxemia in the absence of acidemia, fetal urine production is maintained, whereas the normal gestational increase in amniotic fluid volume is prevented, raising the possibility that intramembranous reabsorption of amniotic fluid is increased by hypoxemia.

Use of urinary beta-2-microglobulin to predict severe renal damage in fetal obstructive uropathy

PURPOSE

Establish a clinically relevant threshold for urinary beta 2-microglobulin (beta 2m) to predict the presence of several renal damage in fetuses with obstructive uropathies.

METHODS

Retrospective review was conducted of urinary beta 2m levels, clinical outcomes, and pathological findings in 36 fetuses evaluated for presumed obstructive uropathy. Patients were divided into those free of renal injury (group 1, n = 13) and those with clinical or pathological evidence of severe irreversible renal injury (group 2, n = 23).

RESULTS

Including all patients, a threshold beta 2m value of > 6 was able to predict the presence of severe renal damage with a 83% sensitivity and 71% specificity. beta 2m levels tended to decrease with increasing gestational age among those patients without renal injury (group 1), while beta 2m levels increased among those with severe renal damage (group 2). There was no difference in mean beta 2m levels in those < 20 weeks (p = 0.065) while there was a high degree of difference in those > 20 weeks of gestation (p < 0.001). In those > 20 weeks, a threshold of > 10 predicted the presence of severe renal damage with 100% sensitivity and specificity.

CONCLUSIONS

Urinary beta 2m, especially in the fetus > 20 weeks, may be a clinically useful marker to detect the presence of severe renal damage due to obstructive uropathy and thus be an important adjuvant in the proper selection of fetuses for antenatal intervention.

Development of human renal function: reference intervals for 10 biochemical markers in fetal urine

Evaluation of fetal renal function by analysis of fetal urine sampled in utero may improve perinatal care after a prenatal diagnosis of bilateral obstructive uropathy. We provide reference intervals for 10 fetal urinary compounds and examine their variation with gestational age. Forty-one fetuses with bilateral obstructive uropathy (urine sampled between 20 and 38 weeks of gestational age) had normal, healthy values for serum creatinine (< or = 50 mumol/L) at ages 1-2 years. These cases were thus assumed to represent a reasonable approximation to healthy values. Sodium and beta 2-microglobulin concentrations significantly decreased with gestational age; calcium, ammonia, and creatinine significantly increased; glucose, phosphorus, chloride, urea, and total protein concentrations did not vary. Our results provide reference values for prenatal evaluation of fetal renal function and suggest that glomerular filtration of macromolecules and tubular reabsorption of glucose and phosphorus are mature by 20 weeks of gestation, whereas tubular reabsorption of sodium and beta 2-microglobulin increases progressively during the second half of gestation.

Shortcomings in predicting postnatal renal function using prenatal urine biochemistry in fetuses with congenital hydronephrosis

Ten fetuses with hydronephrosis underwent one to seven urine sampling procedures at 23 to 36 weeks' gestation to evaluate renal function. Postnatally, the infants' renal function was assessed by a combination of serum creatinine measurement, ultrasonography and renal scintigraphy. Six infants had pyelo-ureteric junction obstruction, two had megabladder with megaureter, and two had vesico-ureteric reflux. All infants had normal serum creatinine levels at the time of postnatal follow-up, but five of the seven with unilateral involvement had moderate or severe renal damage. Abnormal urinary electrolyte concentrations were found antenatally in only two of them. For the three infants with bilateral hydronephrosis, postnatal evaluation showed moderately or severely damaged kidneys despite prenatal evidence of normal biochemical indexes. Fetal urine electrolyte measurement may be accurate in the diagnosis of renal dysplasia, but its sensitivity is poor in predicting moderate renal dysfunction.

In utero fetal urine analysis and renal histology correlate with the outcome in fetal obstructive uropathies

We evaluated 8 second-trimester fetuses who had undergone termination because of obstructive uropathies and correlated the renal histopathology with fetal urine biochemical prognostic parameters. Prenatal evaluation included serial vesicocentesis, karyotyping, and sonography. According to the urinary biochemical parameters, 3 fetuses were classified to be in the good prognostic category, 2 in the borderline prognostic category, and 3 in the poor prognostic category. The kidneys were evaluated both grossly and microscopically for hydronephrosis, pelvicaliceal dilatation, cystic changes and fibrosis. Fetuses in the poor prognostic category had severely damaged renal architecture, microcysts, macrocysts, and extensive fibrosis. Fetuses in the good prognostic category had minimal histopathologic changes with preservation of the architecture. Fetuses in the borderline category showed a moderate degree of renal damage but with focally preserved architecture. We conclude (1) that there is a direct correlation between elevation in urinary electrolytes and proteins and extent of underlying renal histopathological damage and (2) that appropriate detailed prenatal evaluation of the renal function can identify fetuses who could potentially benefit from in utero therapy.

Fetal urinary insulin-like growth factor I and binding protein 3 in bilateral obstructive uropathies

Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 mumol/l at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat < or = mumol/l. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18,159 +/- 9083 pg/ml; 2657 +/- 669 ng/ml) and 2 (1574 +/- 847 pg/ml; 176 +/- 50 ng/ml) in comparison with group 3 (35 +/- 6 pg/ml; 21 +/- 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (> 50 mumol/l). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment.

Measurement of fetal urine production in mild infantile polycystic kidney disease--a case report

It is generally recognized that the sonographic findings of infantile polycystic kidney disease (IPKD) are bilaterally enlarged kidneys, oligohydramnios, an absent fetal bladder, and the typical kidney texture. Since there is a broad spectrum of renal compromise with IPKD, in utero diagnosis is thought to be limited to the severe forms. This paper reports a mild case of IPKD, where the in utero diagnosis was established by measuring fetal urine production and amniotic fluid volume serially during pregnancy, and by ultrasonographic examination of fetal kidneys.

Urinary beta-core human chorionic gonadotrophin: a new approach to Down's syndrome screening

Human chorionic gonadotrophin (hCG) is the most discriminatory maternal serum marker of Down's syndrome. We have carried out a study to establish whether urinary beta-core-hCG, a major metabolic product of hCG, might be an even better marker. Urine samples were available from seven singleton pregnancies with Down's syndrome, and one each of Edwards' syndrome, triploidy, and twins discordant for Down's syndrome. beta-Core-hCG levels were corrected for creatinine and expressed as multiples of the normal gestation-specific median (MOM) level derived from 67 singleton controls. There was a highly statistically significant elevation in level among the singleton Down's syndrome cases (P < 0.0005; Wilcoxon rank sum test). All had levels exceeding 2 MOM with a median of 6.11 MOM (95 per cent confidence interval 3.7-10.0). The levels were extremely low in Edwards' syndrome (0.08 MOM) and triploidy (0.02 MOM), but the twin pregnancy discordant for Down's syndrome did not have a raised beta-core-hCG level (0.64 MOM). The findings are sufficiently encouraging to investigate the possibility of urinalysis as a routine modality in the prenatal screening for Down's syndrome and other common serious aneuploidies.

Fetal urinary biochemistry predicts postnatal renal function in children with bilateral obstructive uropathies

OBJECTIVE

To investigate the ability of fetal urinalysis to predict in utero the renal function of children with bilateral uropathy who survive to the second year of life.

METHODS

This was a prospective cohort study of 100 consecutive patients with prenatal diagnosis of bilateral uropathy who underwent fetal urine sampling. Fetal urinary concentrations of sodium, chloride, calcium, phosphorus, ammonium, urea, creatinine, glucose, proteins, and beta 2 microglobulin were measured. Prenatal findings were matched with renal function of survivors at 1-2 years. The single end point was serum creatinine, which was considered abnormal when greater than 50 mumol/L (0.56 mg/dL) during the second year of life.

RESULTS

Elevated serum creatinine was found in 17 of 42 children with isolated uropathy who survived more than 1 year. For prediction of elevated serum creatinine during the second year of life, the fetal urinary concentration of beta 2 microglobulin was both specific (0.83) and sensitive (0.80); sodium, chloride, and urea levels were sensitive (0.70 or greater) but lacked specificity (less than 0.65); and fetal urinary glucose, phosphorus, calcium, ammonium, and total proteins were specific (0.70 or greater) but lacked sensitivity (0.65 or less).

CONCLUSIONS

Our results provide a new approach to prenatal management of congenital obstructive uropathies by identifying those fetuses at risk for survival with suboptimal renal function. These fetuses might benefit from intrauterine therapy. In contrast, no attempt at prenatal uro-amniotic shunting should be made when a spontaneously good outcome is predicted by fetal urinalysis.

Fetal urine analysis for the assessment of renal function in obstructive uropathy

OBJECTIVES

The assessment of fetal renal function plays a key role in the evaluation of posterior urethral valve obstruction cases. The aim of our study was to determine the value of several urinary compounds, including beta 2-microglobulin, N-acetyl-beta-D-glucosaminidase, and microalbumin in the assessment of prenatal renal function in cases of posterior urethral valve and their potential role in the selection of such cases for in utero shunting.

STUDY DESIGN

A range of urinary compounds was measured, including beta 2-microglobulin, N-acetyl-beta-D-glucosaminidase, and microalbumin in 25 cases of posterior urethral valve obstruction. These cases were divided into four groups based on outcome. The Mann-Whitney test and analysis of covariance were used.

RESULTS

Sodium, calcium, and beta 2-microglobulin were the best predictors for fetal survival. beta 2-Microglobulin values > 13 mg/L were almost invariably associated with fatal outcome.

CONCLUSION

The estimation of beta 2-microglobulin may help in counseling parents and in selecting cases for in utero shunting.

The response of the fetal kidney to obstruction

In a fetal ovine model the renal effects of different anatomic levels of fetal urinary obstruction were studied. Parameters of prenatal renal growth and differentiation were characterized and correlated with the patterns of renal response to in utero obstruction. Complete ureteral or urethral obstruction was produced in the sheep fetus at 55 to 60 days of gestation. Animals were delivered and sacrificed at near term (140 days), and the kidneys were removed and prepared for analysis. Parameters examined included weight, histology, glomerular number and total surface area, as well as urinary sodium, creatinine, osmolarity and N-acetyl glucosaminidase. Three patterns of response were identified, producing hydronephrotic, cystic or dysgenetic kidneys. Hydronephrotic kidneys were usually the result of bladder outlet obstruction or ureteral obstruction with spontaneous urinary decompression. These kidneys were large (20.7 gm. versus normal 10.8 gm., p less than 0.0001), with thinning of cortical parenchyma that was structurally intact. Glomerular number and surface area were normal. Cystic kidneys were large (14.2 gm., p less than 0.05) with grossly visible cysts and an effaced medulla. Cortical structure was distorted by cysts but basic elements were intact. Glomerular number and surface area were not reduced. Dysgenetic kidneys were small (3.9 gm., p less than 0.0001) with markedly abnormal cortical structure and little recognizable medulla. Histological elements similar to fetal structures were present, including cuboidal/columnar tubular epithelium and peritubular mesenchymal collars. Glomerular number and surface area were significantly less than normal (p less than 0.001). The kidneys contralateral to unilaterally obstructed kidneys were significantly larger than normal (16.2 gm., p less than 0.0001), with normal histology, glomerular number and surface area, indicating in utero contralateral renal hypertrophy. Urinary sodium was variably affected in the hydronephrotic kidneys and was identical to plasma in the dysgenetic kidneys. These results indicate the technical feasibility of in utero models of urinary obstruction. Renal growth and patterns of differentiation were markedly affected by in utero obstruction. They should be a major focus in the investigation of congenital obstructive uropathy, since normal processes of renal growth and differentiation form the basis for postnatal function.

Evaluation of renal function

Renal function can now be evaluated in utero and after birth. Most of the methods used to investigate suspected renal dysfunction or disease are not presently applicable to the fetus; however, prenatal and postnatal evaluation of renal function has assumed a greater importance as the consequences of birth before term become more apparent.

Fetal urine biochemistry in the assessment of obstructive uropathy

In 60 fetuses with obstructive uropathy, sodium, total calcium, urea, and creatinine were measured in samples obtained by "urodochocentesis" or pyelocentesis at 16 to 36 weeks' gestation. The patients were retrospectively assigned into two groups on the basis of outcome. Group 1 (n = 20) included infants who either had normal postnatal renal function or absence of prenatal renal dysplasia. Group 2 included infants who either had histologic evidence of renal dysplasia or subsequently developed renal failure. In group 1 the urinary sodium decreased and creatinine increased with gestation, demonstrating maturation in fetal renal function. In group 2 the urinary sodium and calcium were higher and the urinary urea and creatinine were lower than in group 1. The best predictor of outcome was the combination of either high calcium or high sodium with a positive predictive value of 91.3% and negative predictive value of 77.7%. In the antenatal evaluation of obstructive uropathy, fetal urinary biochemistry provides useful information for more accurate counseling of the parents and a rational basis for selecting patients who may benefit from intrauterine therapeutic interventions.

Fetal urine biochemistry: an index of renal maturation and dysfunction

OBJECTIVE

To construct a reference range for fetal urinary sodium, potassium, urea, creatinine, calcium and phosphate with gestation and to assess to what extent these biochemical indices are modified in fetuses with lower urinary tract obstruction.

DESIGN

Prospective descriptive study.

SETTING

Royal Postgraduate Medical School London.

SUBJECTS

24 women between 17 and 35 weeks gestation with an ultrasound diagnosis of fetal lower urinary tract obstruction, with or without renal dysplasia and a control group of 26 women between 16 and 33 weeks gestation with normal amniotic fluid volume and fetal anatomy.

INTERVENTIONS

Fetal urine samples (1-100 ml) were aspirated from the control fetuses either before termination of pregnancy (n = 9) or at the time of intrauterine transfusion for Rh alloimmunization (n = 17). The fetuses with obstructive uropathy had urine samples aspirated on one occasion (n = 14) or serially (n = 10).

MAIN OUTCOME MEASURES

Relation between urine biochemistry and renal damage ascertained clinically or at postmortem.

RESULTS

In the control group, urinary sodium and phosphate decreased and creatinine increased significantly with gestational age, consistent with increasing fetal glomerular filtration rate and progressive maturation of tubular function. Urinary sodium and calcium were significantly higher in fetuses with renal dysplasia compared with those with lower urinary tract obstruction but normal renal histology or normal clinical outcome. Serial urinary samples from fetuses with obstructive uropathy showed more pronounced deviation from the normal with increasing gestation in all fetuses with renal dysplasia. The highest sensitivity in the detection of renal dysplasia was shown by urinary calcium (100%) whereas urinary sodium showed the best specificity (80%).

CONCLUSION

Renal damage is the direct effect of urinary obstruction, rather than an association so that treatment should start as soon as possible. Urinary biochemistry may be helpful in the management of these patients.

Evaluation of fetal renal function: unreliability of fetal urinary electrolytes

In the fetus with bilateral hydronephrosis it has been reported that a normal volume of amniotic fluid, absence of renal cortical cysts, urinary sodium less than 100 mEq./l., chloride less than 90 mEq./l. and osmolarity less than 210 mOsm. are prognostic factors indicative of good renal function, whereas oligohydramnios, cortical cysts and higher urinary levels of sodium, chloride or osmolarity suggest irreversible renal dysplasia. We report 5 cases in which the fetal urinary electrolytes were not predictive of ultimate renal function. In 3 instances fetal urinary electrolytes and osmolarity were abnormally elevated but the infants survived without ventilatory support. In 2 of these 3 patients the volume of amniotic fluid was normal. Diagnoses included posterior urethral valves, prune belly variant and bilateral ureteropelvic junction obstruction. In 2 cases with oligohydramnios fetal urinary electrolytes were suggestive of satisfactory renal function but the infants died of pulmonary hypoplasia and had bilateral renal dysplasia, prune belly syndrome and urethral atresia. Presently, the volume of amniotic fluid remains the most important prognostic sign in the fetus with bilateral hydronephrosis. Further work is necessary to identify other factors that may be more reliable as prognostic indexes of fetal renal function.

Cocaine in the cradle: a hidden epidemic

Intrauterine exposure to cocaine is reaching epidemic proportions and is affecting the lives of an increasing number of infants and children. The toxic effects are manifested as microcephaly, growth retardation, brain infarcts, congenital malformations, and withdrawal symptoms lasting for several weeks. Preliminary long-term follow-up studies reveal worrisome psychologic alterations that may profoundly affect the personality of exposed individuals.

Fetal intervention in obstructive uropathy: prognostic indicators and efficacy of intervention

Management of the fetus with bilateral hydronephrosis is controversial; ability to predict outcome and efficacy of prenatal intervention are unknown. We studied 40 fetuses referred for ultrasonography, examination of fetal urine, and possible therapy. We retrospectively assigned fetuses to a good prognosis group if fetal urine was hypotonic (sodium less than 100 mEq/L, chloride less than 90 mEq/L, osmolarity less than 210 mOsm/L) and there was no ultrasonographic evidence of dysplasia; we assigned fetuses to a poor prognosis group if even one criterion was abnormal. Survival was greater in the good prognosis group than in the poor prognosis group (81% vs 12.5%; 87% vs 30%, excluding abortions) (p less than 0.005). We then attempted to assess the efficacy of prenatal urinary decompression by comparing outcome within the good and poor prognosis groups. Survival with intervention was greater in both the good prognosis group and the poor prognosis group (89% vs 70% and 30% vs 0%). In 6 of the 8 survivors in the good prognosis group, severe oligohydramnios was reversed by decompression. We conclude the fetal urine electrolyte levels and ultrasonographic appear helpful in predicting residual fetal renal function and neonatal outcome and that prenatal decompression may prevent the development of fatal pulmonary hypoplasia.