SDS-PAGE as an additional test to determine fetal kidney function prior to intrauterine diversion of urinary tract obstruction

The analysis of urine obtained from fetuses with hydronephrosis, seen on ultrasound, can give a misleading assessment of residual renal function. Additional parameters for assessment of fetal renal function would be helpful. We have used SDS-polyacrylamide gel electrophoresis to separate urinary proteins from a fetus with obstructive uropathy and severe oligohydramnios, already present at 18 weeks of gestation. The dilated urinary bladder of the fetus was successfully shunted in utero with a double pigtail catheter which worked for 17 weeks, and a boy without renal or pulmonary insufficiency was born at 36 weeks. In this case the prenatal protein analysis by electrophoresis was a better indicator of the ultimate good pregnancy outcome than the evaluation of urinary electrolytes and osmolarity alone. We therefore suggest the addition of this test to the profile of renal function studies performed on fetal urine.

Urine production and bladder function in fetuses with open spina bifida

Hourly fetal urine production rate (HFUPR) and bladder filling and voiding were determined by real-time ultrasonography in 13 fetuses with open spina bifida (OSB) and compared with those of 101 normal fetuses from uncomplicated pregnancies at 16-40 weeks gestation. In normal pregnancy, the fetal bladder volume increases linearly with time and then decreases rapidly with micturition. The mean cycle length does not change significantly with gestation but both the mean bladder volume and HFUPR increase. In fetuses with OSB, ultrasonographic examination has demonstrated deviations from normal in both bladder filling and bladder emptying.

The nonpredictive value of fetal urinary electrolytes: preliminary report of outcomes and correlations with pathologic diagnosis

Fetal urine was sampled 12 times in nine fetuses with sonographically diagnosed urinary tract obstruction to assess renal function. By previously proposed criteria, four fetuses were predicted to have poor renal function. Two of these fetuses were found to have renal dysplasia on autopsy after elective termination. The other two died in the neonatal period but only one of these had histologic evidence of renal dysplasia. Five fetuses were predicted to have good renal function. Three of these developed renal failure after birth, one was found to have renal dysplasia on autopsy after elective termination, and one is alive and well. We conclude that fetal urine electrolytes are not necessarily an accurate predictor of neonatal renal function.

Fetal urinary electrolytes in bladder outlet obstruction

Ultrasound findings and urinary electrolytes in the fetus were correlated with fetal outcome and postmortem findings in 8 cases of fetal bladder outlet obstructions. One of the two fetuses, suggesting normal renal function according to urinary electrolytes, displayed renal dysplasia at birth. Six fetuses were predicted to have poor renal function, 5 of these were found to have renal dysplasia at autopsy. The interpretation of fetal urinary electrolytes as a prognostic indication for the presence or absence of renal dysplasia needs to be clarified.

Measurement of the fetal urine production rate using real-time ultrasound in fetuses with bilateral hydronephrosis

The fetal urine production rate (FUPR) in 147 normal fetuses after 27 weeks of gestation and 5 with bilateral hydronephrosis was measured using real-time ultrasound. Later, the correlation between FUPR and renal function was evaluated postnatally. In the normal fetuses, FUPR (mean +/- 2 SD) increased gradually from 1.9 +/- 1.6 at 27-28 weeks of gestation to 7.5 +/- 4.5 ml/10 min at 37-38 weeks of gestation. In the 5 cases with bilateral hydronephrosis, FUPR was within normal ranges and increased with advances in gestation. Intrauterine intervention was not performed in any of the cases, and, at present, renal insufficiency is nil.

Protein analysis in amniotic fluid and fetal urine for the assessment of fetal renal function and dysfunction

Micromolecular proteins (molecular weight less than 68 kD) in amniotic fluid are assumed to be derived largely from fetal urinary excretion and therefore may reflect fetal kidney function and maturation. Microprotein concentrations in amniotic fluid, neonatal urine and urine of fetuses with bilateral urinary tract dilation were analyzed using microgradient gel electrophoresis to separate proteins according to their molecular size. Alpha-1-microglobulin and beta 2-microglobulin were assayed as singular micromolecular marker proteins. Microproteins in amniotic fluid decreased progressively with advancing gestation during the 3rd trimester. Micromolecular protein concentrations in the first postnatal urine of healthy infants born prematurely or at term were similar to those in amniotic fluid of corresponding fetal age and yielded an identical developmental pattern. A strong correlation existed between the microprotein concentrations in amniotic fluid and fetal urine. It is concluded that fetal urinary production is the main determinant for the microprotein content of amniotic fluid and that a major fetal pathway exists for the intrauterine metabolism of these proteins. The 3rd trimester decrease in amniotic fluid seems to be dependent on the increasing reabsorption capacity of proximal tubular cells representing morphological and functional kidney maturation. The exact diagnostic value of microprotein analysis for the assessment of disturbed fetal kidney function has still to be defined by further investigation.

Continuous ovine fetal hemorrhage: sensitivity of plasma and urine arginine vasopressin response

Intravascular hemorrhage of the ovine fetus is a potent stimulus for arginine vasopressin (AVP) secretion. However, the method (acute, continuous) and rate of blood withdrawal may influence the fetal response. To determine the hemorrhage threshold for AVP secretion in response to slow continuous hemorrhage, five chronically catheterized ovine fetuses were continuously hemorrhaged (0.6% blood vol/min) to 24-30% blood volume withdrawal. Immediately after hemorrhage fetal blood was reinfused at an equivalent rate. In addition to AVP measurements by radioimmunoassay, fetal urinary responses were monitored as an index of fetal AVP secretion. Significant increases in plasma AVP occurred during hemorrhage (1.0 +/- 0.1 to 8.0 +/- 2.0 pg/ml). The fetal plasma AVP-hemorrhage threshold, as defined by regression analysis, occurred at withdrawal of 13.0% blood volume. Fetal urine volume significantly decreased from a mean basal rate of 0.59 +/- 0.03 to 0.21 +/- 0.06 ml/min at the completion of hemorrhage. Urinary sodium, potassium, and osmolar excretion also significantly decreased at the completion of hemorrhage. Urinary AVP excretion, urine osmolality, sodium, and potassium concentrations did not change significantly during the hemorrhage period but increased significantly during the reinfusion period; the delay a result of renal and catheter dead space. Reinfusion of blood resulted in a return of plasma AVP to basal levels. These results define a threshold for AVP secretion and demonstrate significant urinary effects in response to slow continuous hemorrhage.

Isovolemic hypotension in ovine fetus: plasma arginine vasopressin response and urinary effects

Chronically prepared third trimester fetal lambs were administered intravenous infusions of nitropruside. Mean basal systolic and diastolic blood pressure (59.8 and 42.4 mmHg, respectively) decreased significantly during the infusion (49.2 and 36.8 mmHg, respectively) and increased significantly during the recovery period (66.4 and 48.5 mmHg, respectively). Fetal plasma arginine vasopressin (AVP) significantly increased from a mean basal level of 1.25 +/- 0.09 to 6.81 +/- 0.39 pg/ml during the hypotensive period. Urinary AVP basal levels of 1.21 +/- 0.13 pg/ml increased to 3.18 +/- 0.66 pg/ml during the hypotensive period and 5.87 +/- 0.82 pg/ml during the recovery period (P less than 0.05). The fetal urinary response to nitroprusside appeared biphasic. The hypotensive phase was marked by decreases in both free water and osmolar clearances. During the recovery phase free water clearance remained decreased, while osmolar clearance returned to basal levels. Thus AVP secretion represents an important mechanism for ovine fetal modulation of solute and water excretion in response to utero hypotensive stress.

Amniotic fluid glucose values in normal and abnormal pregnancies

Glucose values were determined in 102 urine samples of newborn infants and in 2295 amniotic fluid (AF) samples of women between the 14th and 42nd week of pregnancy. One thousand, six hundred fifty-five of the AF samples derived from normal pregnancies, 50 from pregnancies with fetal malformations, 115 from cases of hydramnios, 246 from pregnant women with an abnormal oral glucose tolerance test, and 230 from insulin-dependent diabetics. Mean AF glucose concentration rises slightly between the 14th and 17th week of pregnancy, decreasing from 46 to about 16 mg% at the end of pregnancy. In cases of fetal malformations, 68% of the glucose levels was below the tenth percentile of normal values. Hydramnios showed no deviation from normal values. In patients with abnormal glucose tolerance, AF glucose increased by a total of 42% and by 67% in fetal hyperinsulinism. Insulin-dependent diabetics had glucose values elevated by a total of 77% and by 106% in fetal hyperinsulinism. The AF glucose profile reflects the level of maternal blood glucose that is transported to the fetus and excreted in the fetal urine as a major source of glucose in AF.

An assay for urinary estriol-16 alpha-glucuronide based on antibody-enhanced chemiluminescence

An immunoassay for estriol-16 alpha-glucuronide in pregnancy urine is described that utilizes antibody-enhanced chemiluminescence. The steroid glucuronide was covalently conjugated with the chemiluminescent marker aminobutyl-ethyl-isoluminol. The light yield of this conjugate upon oxidation was augmented by specific antibody, and this effect was inhibited by addition of the homologous steroid glucuronide (10-100 pg) in a dose-dependent manner. The assay does not require separation of bound and free ligand and proved satisfactory with respect to sensitivity, precision and accuracy. Assay results obtained by radioimmunoassay and chemiluminescence immunoassay were in good agreement (r = 0.98; n = 25).

Diagnosis of neural crest tumors by reversed-phase high-performance liquid chromatographic determination of urinary catecholamine metabolites

Aberrations in the metabolic pathways of catecholamines in patients with neural crest tumors result in characteristic urinary excretion patterns of their catabolites. Tumors such as pheochromocytoma, neuroblastoma and ganglioneuroma usually defy clinical diagnosis because of their rarity, small size, intraabdominal position and clinical symptoms similar to those of essential hypertension. Quantitative determination of catecholamine metabolites such as vanillylmandelic acid (VMA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) offers possibilities for reliable confirmation of diagnosis. However, previous techniques for the assessment of catabolite levels suffered from inadequate sensitivity, reproducibility or specificity, which seriously diminished their usefulness as biochemical determinants in the prognosis of these life-threatening tumors. Reported in this paper is the analysis of urinary levels of VMA and MHPG using reversed-phase high-performance liquid chromatography with electrochemical and sectrophotometric detection. We present the excretion patterns showing these metabolites in 15 control subjects, 15 patients with pheochromocytoma and 5 patients with neuroblastoma.

Relationship between fetal urine production and amniotic fluid volume in normal pregnancy and pregnancy complicated by diabetes

The hourly fetal urine production rate (HFUPR) was calculated from ultrasonic measurements of fetal bladder volume. A normal HFUPR reference curve, constructed from measurements in 189 normal pregnancies between 24 and 42 weeks gestation, showed a rapid increase of HFUPR from 3-3 to 24-4 ml up to 40 weeks followed by a slight decline. The amniotic fluid volume was estimated by the p-aminohippuric acid method within 12 hours of HFUPR measurements. In 67 normal pregnancies, there was no relationship between HFUPR and amniotic fluid volume measured between 36 and 41 weeks gestation. In 12 patients with fetal growth retardation, a relationship was found between reduced fetal urinary output and low amniotic fluid volume between 36 and 38 weeks gestation. In the 16 diabetic patients studied between 28 and 40 weeks gestation, there was no relationship between HFUPR (within or below normal range) and the high amniotic fluid volume (above 1500 ml in 13 patients). The implication of these findings are discussed.

Fetal proteinuria in diagnosis of congenital nephrosis detected by raised alpha-fetoprotein in maternal serum

High concentrations of alpha-fetoprotein (alpha-FP) were found at 14, 19, and 21 weeks gestation in the serum of a woman with a history of unexplained fetal death in her previous pregnancies. The alpha-FP concentration of the liquor also was high at 21 weeks and the pregnancy was terminated. Though the fetus was macroscopically normal, measurement of albumin, alpha-FP, IgG, and alpha2-macroglobulin in the fetal urine showed a selective proteinuria, and congenital nephrosis was diagnosed after examination of the fetal kidneys by electron microscopy. Possibly some fetuses reported to be "false-positive for neural tube defect" may have had renal lesions of this nature. Examination of fetal urine may be the simplest initial diagnostic procedure in any future case.

Growth hormone response in fetal alcohol syndrome

In the fetal alcohol syndrome (FAS) there is severe physical growth retardation both prenatally and postnatally. Secretion of growth hormone (GH) after insulin-induced hypoglycaemia and arginine infusion was analysed in 5 cases of FAS to find out whether changes in GH secretion might account for the abnormal growth pattern. Results showed a normal or slight hyper-response of GH up to 150 ng/ml, and normal somatomedin activity in those blood samples with high GH level. It was concluded that the growth retardation in FAS is not caused by GH or somatomedin deficiencies.

Low oestriol excretion: incidence, significance and treatment in an obstetric population

In a series of 6,361 consecutive patients, low oestroil excretion late in pregnancy was detected in 871 cases (13-6%) and was associated with significantly increased incidences of still birth (P less than 0-001), neonatal death (P less than 0-001) and intrauterine growth retardation (P less than 0-001). Persistently low oestriol excretion occurred in approximately 3% of patients and two-thirds of these were suitable for conservative treatment with intravenous infusion of dextrose (25%) and fructose (20%) (2 1. of each in 48 hours). In 97 of 147 patients (65%), low oestriol excretion was favourably affected by this regimen, with significantly improved perinatal results (P less than 0-001).

Alpha-fetoprotein in antenatal diagnosis of congenital nephrosis

Alpha-fetoprotein (A.F.P,) levels were found to ge significantly raised in maternal serum and amniotic-fluid samples form the 16th and 18th weeks of gestation in a woman with an apparently normal fetus but with histological evidence of congenital nephrosis of the Finnish type. Increased concentrations of A.F.P. in early pregnancy with a living fetus are therefore not specific for neural-tube defects; More likely they result from the fetal circulation. Extended investigations, including kidney morphology, should be done in cases of apparent false-positive A.F.P. tests.