The early prenatal sonographic diagnosis of renal agenesis: techniques and possible pitfalls

Fetal Therapy for Renal Anhydramnios

The most severe forms of congenital anomalies of the kidney and urinary tract present in fetal life with early pregnancy renal anhydramnios and are considered lethal due to pulmonary hypoplasia without fetal therapy. Due to the high rate of additional structural anomalies, genetic abnormalities, and associated syndromes, detailed anatomic survey and genetic testing are imperative when stratifying which pregnancies are appropriate for fetal intervention. Restoring amniotic fluid around the fetus is the principal goal of prenatal treatment. The ongoing multi-center Renal Anhydramnios Fetal Therapy (RAFT) trial is assessing the safety and efficacy of serial amnioinfusions to prevent pulmonary hypoplasia so that the underlying renal disease can be addressed.

A new sonographic marker in the diagnosis of prenatal bilateral renal agenesis, segmental anterior deviation of the aorta

Objectives

Bilateral renal agenesis is a rare congenital anomaly that is associated with high neonatal mortality. Bilateral renal agenesis is most often present with anhydramniosis in the mid-trimester.

Case presentation

We report a case of bilateral renal agenesis diagnosed prenatally. We presented the ultrasound and pathology images of this fetus with a new sonographic sign, segmental anterior deviation in the abdominal aorta.

Conclusions

To our knowledge, this is the first reported case of a fetus with a segmental aortic anterior deviation.

Prenatal diagnosis of congenital anomalies of genito-urinary system on fetal magnetic resonance imaging

Background

The aim of this study is to elucidate the spectrum of commonly encountered anomalies affecting fetal genito-urinary system (GUS) on fetal MRI and examine its utility in providing better morphological information resulting in improved diagnostic accuracy and in detecting additional malformations. The study also aims to highlight the promising role of fetal MRI in the detection and characterization of renal fusion anomalies like the horseshoe kidney or developmental abnormalities such as renal agenesis/ectopia.

Results

The mean age of study participants was 29 years ± 3 years. The gestation age of pregnant mothers ranged from 18 weeks and 1 day to 39 weeks and 0 day. Amniotic fluid was reduced or absent in 41% (N = 13) and normal in 59% (N = 18) of participating mothers. Overall, urinary obstruction was the commonest anomaly encountered (29%) followed by the multicystic dysplastic kidney (MCDK) (22%). Bilateral renal disease was seen in all mothers having features of anhydramnios {B/L MCDK (N = 3), autosomal recessive polycystic kidney disease (ARPKD) (N = 2), posterior urethral valves (PUV) (N = 2), B/L renal agenesis (N = 3), and megacystis (N = 1)}. Fusion anomalies (horseshoe kidney) and rotation anomaly (malrotation) were detected in one case each. Additional extrarenal findings were seen on fetal MRI in 35% (N = 11) cases.

Conclusions

Fetal MRI improves diagnostic accuracy in anomalies affecting the fetal kidney and genito-urinary systems by better morphological delineation. It has the ability to detect additional extra-renal malformations and perform a more accurate assessment of associated pulmonary hypoplasia. The diffusion-weighted sequence is particularly useful in confirming the diagnosis of renal agenesis/ectopia.

Study of Lethal Congenital Malformations at a Tertiary-Care Referral Centre in North India

Lethal congenital malformations (LCMs) are fatal birth defects that are an important cause of fetal/neonatal death. There is a lack of informative data about these malformations in India, a country that shares the maximum burden of neonatal mortality due to congenital birth defects. Therefore, we conducted a retrospective analysis to know the prevalence of LCMs in late pregnancy, to find out associated factor/variables and to evaluate fetal/neonatal outcome of such anomalies; at a tertiary-care referral centre in North India. All deliveries with LCMs after 24 weeks of gestation were included in the study. Data about antepartum history (maternal age, parity, education, socioeconomic status, consanguineous marriage, folic acid intake, any chronic medical disorder, availability of anomaly scan, unplanned pregnancy); intrapartum events (gestational age at delivery, mode of delivery); postpartum events (weight of the baby, gender of the baby); newborn evaluation; and details of hospital stay were recorded from medical record sheet over the duration of one year. We found that anencephaly, severe meningomyelocele, multicystic dysplastic kidneys and non-immune hydrops with major cardiac defects were more prevalent among all LCMs. On the evaluation of the various studied variables, maximum babies with LCMs were born to mothers who were between 20 and 35 years of age, those who were illiterate, belonged to middle/lower socio-economic class, multigravida, and those who had no detailed anomaly scan. We feel that there is an urgent need to formulate a universally accepted definition of LCMs, to identify preventable risk factors and to formulate management strategy for both mother and liveborn baby with LCMs, in order to minimize the hidden burden of these defects in stillbirth/ perinatal/ neonatal mortality statistics.

Fetal Kidneys Ultrasound Appearance in the First Trimester - Clinical Significance and Limits of Counseling

OBJECTIVE

The objective of this study was to determine the visualizing rate of fetal kidneys at various gestational ages in late first trimester (FT) and to establish the clinical significance of their two-dimensional ultrasound (2DUS) appearance in the FT.

METHODS

In a prospective cross-sectional study, 1456 women from an unselected population underwent a detailed assessment of fetal anatomy at 11+0 -13+4 weeks of gestation with the use of transabdominal sonography. Information on the ultrasound findings, antenatal course and perinatal outcome was obtained in 1331 cases.

RESULTS

44 cases in which a congenital kidney disease was detected by ultrasound in the prenatal period were identified. The renal pathology was suspected in the FT in 8 cases, and confirmed by a standard test (postmortem autopsy or second-trimester scan) in 4 cases. The standard detailed second-trimester scan at 18-22 weeks diagnosed another 23 cases but refuted suspicion in 4 FT positive cases. The third trimester added another 17, all confirmed by the postpartum scan. For FT presence or absence of congenital renal anomalies, sensitivity, specificity, +LRs and -LRs of 2DUS were 9.09%, 99.69%, 29.25, and 0.91.

CONCLUSION

FT prenatal kidneys' visualization is critically dependent on the gestational age. FT diagnosis holds uncertainty. An early diagnosis carries a risk of providing a false-positive or a false-negative result, because the differentiation of the renal system is delayed or the diagnosis is not amenable yet to prenatal ultrasound. No FT findings can exclude the mid-trimester follow-up ultrasound scan. Second and third trimester scan are relevant for congenital kidney diseases.

Ultrasound diagnosis of fetal renal abnormalities

Development of the urogenital system in humans is a complex process; consequently, renal anomalies are among the most common congenital anomalies. The fetal urinary tract can be visualised ultrasonically from 11 weeks onwards, allowing recognition of megacystis at 11-14 weeks, which warrants comprehensive risk assessment of possible underlying chromosomal aneuploidy or obstructive uropathy. A mid-trimester anomaly scan enables detection of most renal anomalies with higher sensitivity. Bilateral renal agenesis can be confirmed ultrasonically, with empty renal fossae and absent bladder filling, along with severe oligohydramnios or anhydramnios. Dysplastic kidneys are recognised as they appear large, hyperechoic, and with or without cystic spaces, which occurs within the renal cortex. Presence of dilated ureters without obvious dilatation of the collecting system needs careful examination of the upper urinary tract to exclude duplex kidney system. Sonographically, it is also possible to differentiate between infantile type and adult type of polycystic kidney diseases, which are usually single gene disorders. Upper urinary tract dilatation is one of the most common abnormalities diagnosed prenatally. It is usually caused by transient urine flow impairment at the level of the pelvi-ureteric junction and vesico-ureteric junction, which improves with time in most cases. Fetal lower urinary tract obstruction is mainly caused by posterior urethral valves and urethral atresia. Thick bladder walls and a dilated posterior urethra (keyhole sign) are suggestive of posterior urethral valves. Prenatal ultrasounds cannot be used confidently to assess renal function. Liquor volume and echogenicity of renal parenchyma, however, can be used as a guide to indirectly assess the underlying renal reserve. Renal tract anomalies may be isolated but can also be associated with other congenital anomalies. Therefore, a thorough examination of the other systems is mandatory to exclude possible genetic disorders.

Late-presenting diaphragmatic hernia associated with intrathoracic kidney: tachypnoea as unique clinical sign

Intrathoracic renal ectopia associated with a congenital diaphragmatic hernia represents a very rare congenital malformation. The incidence of intrathoracic renal ectopia with congenital diaphragmatic hernia is reported to be less than 0.25%. The authors report on a 5-month-old female infant with late-presenting congenital diaphragmatic hernia associated with a left-sided intrathoracic ectopic kidney and adrenal gland. While prenatal ultrasound showed no pathology, the postnatal ultrasound assumed a left-sided renal agenesia. After recurrent episodes of tachypnoea, a chest x-ray confirmed the diagnosis of congenital diaphragmatic hernia which was repaired without complications. Intraoperatively, intrathoracic ectopic kidney was diagnosed. The authors discuss embryogenesis, the diagnostic algorithm and therapy as well as follow-up of this rare malformation.

Fetal genitourinary anomalies--a pictorial review with postnatal correlation

An accurate diagnosis of fetal genitourinary abnormality is essential because some genitourinary abnormalities are associated with pulmonary hypoplasia, which ultimately affects the neonatal outcome. Adrenal masses are rare; however, presence of any lesion located at the superior pole of the kidney should raise the possibility of an adrenal mass. Fetal genital anomalies are rare as well and some of the most difficult to diagnose. A combination and pattern of findings allows for specific diagnosis of renal tract abnormalities. This article reviews the imaging appearance of fetal genitourinary abnormalities with perinatal imaging correlation where available.

First trimester ultrasound: current approaches and practical pitfalls

Revolutionary technological improvements and high-frequency transvaginal scanning have enabled the resolution of ultrasound imaging in the first trimester to increase such that detailed early fetal development can now be well visualized. This investment in imaging technology has enabled not only normal embryonic development but also chromosomal abnormalities and structural anomalies to be more easily and accurately diagnosed before the second trimester. This article is intended to help radiologists in the interpretation and clinical application of normal and abnormal first trimester ultrasound findings in early pregnancy. We review the current literature and applications and interpretations of first trimester ultrasound.

Ontogeny of gastric emptying patterns in the human fetus

OBJECTIVE

Fetal swallowing and gastric emptying contribute importantly to amniotic fluid (AF) homeostasis and fetal gastrointestinal development. We speculated that fetal gastric emptying must be functional early in gestation to prevent rapid increases in AF. We sought to determine the human fetal ontogenic pattern of gastric emptying.

STUDY DESIGN

Gastric emptying of eighty normal fetuses at 12-39 weeks was studied. Real-time ultrasound of the fetal stomach was continuously recorded for 1 hour. The gastric area ratio (GAR) was defined as the gastric area divided by the abdominal transverse area. The delta GAR was defined as the change between the maximum and the minimum gastric area ratiox100 (expressed as percent). A change of the fetal gastric area more than the 10th percentile of the delta GAR at 36-39 weeks was used to define gastric emptying.

RESULTS

The 10th, 50th and 90th percentile of delta GAR at 36-39 weeks' was 5.2, 6.5 and 8.7%, respectively. Fetal gastric emptying was detected as early as 12 5/7 weeks of gestation. The proportion of fetuses demonstrating gastric emptying (>10th percentile delta GAR) increased with gestational age: 4/33 (12.1%) 12-23 weeks, 3/9 (33.3%) at 24-27 weeks, 8/11 (72.7%) at 28-31 weeks, 12/14 (85.7%) at 32-35 weeks, and 11/13 (84.6%) at 36-39 weeks.

CONCLUSIONS

Fetal gastric emptying occurs by the beginning of the second trimester, contributing to AF regulation. The increased frequency of gastric emptying in late gestation is likely secondary to increased swallowing, altered fetal behavioral state or endogenous production of gastrointestinal motility factors.

Performing a fetal anatomy scan at the time of first-trimester screening

Over the past decade, prenatal diagnosis has shifted rapidly from the second trimester into the first trimester. Although the nuchal-translucency scan may detect a small proportion of fetal structural malformations, fetal anatomy is not routinely assessed until the fetal anatomical survey is performed in the second trimester between 18 and 22 weeks. The recent development of high-frequency transvaginal ultrasound transducers has led to vastly improved ultrasound resolution and improved visualization of fetal anatomy earlier in gestation. Several pilot studies of a first-trimester anatomic survey have reported detection rates comparable with those achieved in the routine second-trimester anatomic survey. As advanced ultrasound technology becomes more available, there is an urgent need to evaluate the diagnostic ability of a first-trimester anatomic survey and to determine the role of a first-trimester anatomic survey in the current screening paradigm.

Prenatal diagnosis of ectopic intrathoracic kidney in a fetus with a left diaphragmatic hernia

Intrathoracic renal ectopia as a result of a congenital diaphragmatic hernia (CDH) is a rare congenital anomaly. We present a case in which the prenatal diagnosis of an ectopic intrathoracic kidney was made on routine anatomical survey at 28 weeks' gestation. Color doppler sonography imaging revealed the renal artery coursing into the infant's thorax and was consistent with CDH, but fetal MRI suggested an intact diaphragm. However, neonatal evaluation confirmed the diagnosis of intrathoracic kidney with posterior CDH, which was repaired without complication. In contrast to diaphragmatic hernia with liver or bowel herniation, infants with intrathoracic ectopic kidneys generally do well.

First trimester ultrasonography in screening and detection of fetal anomalies

An obstetrical ultrasound examination provides invaluable information regarding the fetus. Until the mid-1980s, ultrasound in the first trimester was limited to localization of the pregnancy, establishing viability, and accurate dating. With the advent of high-resolution ultrasound and transvaginal scanning, a significant amount of information about the fetus can be gained and provided to the patient at a very early stage in gestation. This article provides an overview of the role of first trimester (11-13 + 6 weeks' gestation) ultrasound in screening and diagnosis of fetal anomalies. The first trimester is an ideal time for screening for aneuploidy, primarily due to the advantages that nuchal translucency (NT) measurement provides. NT measurement is also useful in establishing the risk of congenital cardiac disorders and a number of genetic and non-genetic syndromes. Significant NT thickening is associated with an increase in perinatal morbidity and mortality. Potential mechanisms resulting in increased NT are discussed. A number of new ultrasound markers for fetal aneuploidy have been investigated over the past several years, some of which appear to improve the screening efficacy of early ultrasonography. The role of these is reviewed. A number of fetal anomalies can now be consistently diagnosed in the first trimester. Their appearance at this early gestational age is discussed as well. It is clear that, data obtained by first trimester ultrasound are useful in counseling expectant parents and in planning the appropriate follow-up.

Umbilical cord length in urinary tract abnormalities associated with oligohydramnios: evidence regarding developmental pathogenesis

We performed a retrospective review of the length of the umbilical cords of stillborn fetuses with renal agenesis, cystic kidneys, and bladder outlet obstruction and compared the cord length with normative data. Among the 41 cases, 31 had umbilical cord lengths that were shorter than average. However, the remaining 10 cases had an average to increased cord length. Urinary output in those cases might have been sufficient in early pregnancy to allow adequate fetal activity and sufficient umbilical cord lengthening. We suggest that the length of the umbilical cord can have implications relative to the developmental pathogenesis of some congenital urinary tract abnormalities.

Fetal MRI of the urinary system

The assessment of the urinary system is typically performed by ultrasound. Nevertheless, an ultrasound may be inconclusive in fetuses with renal diseases that result in anhydramnios or oligohydramnios. In such cases, and in other cases in which ultrasound is limited, further investigation with MR should be considered. In the following article, we will provide an overview of the most commonly encountered disorders of the urinary system and their appearance on fetal MR imaging. Fetal MR imaging can accurately diagnose a wide variety of urinary tract disorders and must be seen as a valuable complementary tool to ultrasound in the assessment of the urinary system, particularly in cases of inconclusive ultrasound findings.

The clinical significance of an empty renal fossa on prenatal sonography

OBJECTIVE

The purpose of this study was to characterize the significance of an empty renal fossa on prenatal sonography.

METHODS

A hospital database was reviewed retrospectively to find all fetuses with an empty renal fossa diagnosed on prenatal sonography between 1989 and 2003. For each case, prenatal and postnatal data were recorded.

RESULTS

Ninety-three fetuses had an empty renal fossa: 49 on the left, 41 on the right, and 3 unspecified. Forty-four fetuses were male and 29 were female. For 20, the sex was not recorded. The average gestational age at diagnosis was 29.5 weeks. Final diagnoses were made on the basis of prenatal and postnatal imaging. The missing kidney was ectopic in 39 cases (42%): 34 in the pelvis, 4 fused to the contralateral kidney, and 1 in the thorax due to a congenital diaphragmatic hernia. The absent kidney was never located in 44 cases (47%) and presumed to be congenitally absent. Ten kidneys (11%) originally thought absent were normally located, 7 of which were dysplastic, 2 normal, and 1 infiltrated by a tumor. In 39 patients (42%), other anomalies were identified, sometimes involving multiple systems, most commonly genitourinary (29) and cardiovascular (13). Of the 77 cases with the number of umbilical cord vessels recorded, 68 (88%) were normal and 9 (12%) had only 2 vessels.

CONCLUSIONS

If a kidney is not found in the renal fossa, most are either ectopic (42%) or congenitally absent (47%). An empty renal fossa is often (42%) associated with other congenital anomalies.

False diagnosis of renal agenesis on fetal MRI

We report a twin pregnancy in which prenatal ultrasound revealed anhydramnios and bilateral absence of the kidneys in both fetuses. To overcome the difficulties faced in obtaining accurate information on fetal ultrasound in cases with oligohydramnios, an attempt was made to use fetal magnetic resonance imaging (MRI) to confirm the renal status. However, while the fetal MRI showed renal agenesis in both twins, postnatal follow-up revealed that one twin, which survived, had a small unilateral kidney not seen antenatally on fetal ultrasound or MRI. The second twin had bilateral renal agenesis and died of pulmonary hypoplasia. Care should be taken when using fetal MRI to replace fetal ultrasound in cases with poor visibility.

Early detection of fetal structural abnormalities

Most published data on the detection of fetal anomalies at 11-14 weeks are from specialized centres with considerable experience in fetal anomaly scanning. However, there is still limited information on the feasibility and limitations of the screening of these anomalies compared with the now classical mid-gestation screening. This review indicates that overall, the detection rate of fetal anomalies at 11-14 weeks is 44% compared with 74% by the mid-pregnancy scan. Major abnormalities of the fetal head, abdominal wall and urinary tract, and of the umbilical cord and placenta, can be reliably detected at 10-11 weeks of gestation. Detection of other anomalies such as spina bifida, diaphragmatic hernia or heart defects is limited before 13 weeks of gestation. So far it cannot be stated that routine first trimester screening can be used on a large scale to evaluate the fetal spine and heart in the general population. In particular, in screening for congenital heart defects, the ability to perform a full cardiac examination increases from 20% at 11 weeks to 92% at 13 weeks. The early prenatal diagnosis of these anomalies may be improved by screening at 13-14 weeks rather than during the first trimester.

Detection of fetal structural abnormalities with US during early pregnancy

Ultrasonography (US) is performed during early pregnancy for dating, determination of the number of fetuses, assessment of early complications, and increasingly for evaluation of the fetus, including measurement of the thickness of the nuchal translucency (NT). Measurement of NT thickness between 11 and 14 weeks gestation, combined with maternal age and maternal serum biochemistry, can be an effective method of screening for trisomy 21 and other chromosomal abnormalities. Furthermore, an increased NT thickness in the presence of a normal karyotype is associated with an increased frequency of structural defects and genetic syndromes. Therefore, this finding is an indication for a more detailed anatomic survey of the fetus. Besides nuchal abnormalities, a wide range of other congenital anomalies can be diagnosed with US at 11-14 weeks gestation, including defects of the central nervous system, heart, anterior abdominal wall, urinary tract, and skeleton. The anatomic survey can be performed with a standardized protocol by using transabdominal US and, when necessary, transvaginal US. A thorough knowledge of the US features of normal fetal development is necessary to avoid potential diagnostic pitfalls.

MRI of Fetal Genitourinary Anomalies

OBJECTIVE

The objective of our study was to show examples of fetal MRI evaluations of congenital genitourinary anomalies and to review the embryology in relation to the MRI findings.

CONCLUSION

MRI was performed on 35 pregnant women with sonographic findings that suggested that their fetuses had genitourinary anomalies. Oligohydramnios or anhydramnios was identified in 22 of 35 women and did not hinder visualization of anomalies. MRI allowed the amniotic fluid and the presence, location, and morphology of kidneys and bladder to be assessed in all fetuses at any stage of gestation and depicted sufficient anatomic detail for us to evaluate the perineum in 27 of 35 pregnancies. Therefore, we found MRI to be an excellent technique for revealing the anatomy of genitourinary anomalies in the fetus.

Ultrasound diagnosis of structural abnormalities in the first trimester

The advances in ultrasound technology have made it possible to identify fetal structural abnormalities and genetic syndromes in the first trimester. First trimester prenatal diagnosis of fetal central nervous system, renal, gastrointestinal, cardiac, and skeletal abnormalities is reviewed.

The use of first trimester ultrasound in routine practice

Since the introduction of ultrasound scanning in early pregnancy, transabdominal or transvaginal ultrasonography has taken on an important role in routine clinical practice in terms of the care of the fetus and the mother. The use of ultrasound in very early pregnancy makes it possible to confirm the intrauterine living embryo or diagnose the extrauterine pregnancy in which medical treatment with low morbidity is feasible with early detection. Early scanning can provide exact dating with acceptable error, which is one of problems encountered in clinical practice. Chorionicity can be correctly established by early scanning (before 14 weeks of gestation) to manage multiple pregnancies properly. The nuchal translucency, which is a transitory abnormality, can be measured for the early screening of Down's syndrome, trisomy-18, trisomy-13, Turner's and some other aneuploidy at the 11-14 weeks gestation with approximately 80% detection rate. Early diagnosis of some major abnormalities such as anencephaly, megacystis, polycystic kidney, omphalocele is also possible by early scanning. This provides great advantages as the clinical management will be quite different for a case of omphalocele or megacystis. Therefore the early ultrasound scanning has become a routine standard method in the care of the pregnant woman.

Fetuses and infants with congenital urinary system anomalies: correlation between prenatal ultrasound and postmortem findings

OBJECTIVE

Detection of congenital urinary system anomalies is an important part of the prenatal ultrasound examination. The present study compares prenatal ultrasonographic findings and postmortem examinations of fetuses and infants with renal and urinary tract anomalies.

DESIGN

Criteria for inclusion were an ultrasound examination at the National Center for Fetal Medicine (Trondheim, Norway) and autopsy performed during the period 1985-94. Results from the ultrasound examination and autopsy regarding urinary system anomalies were categorized according to the degree of concordance.

RESULTS

Urinary system anomalies were found in 112 (27%) of 408 fetuses with congenital anomalies. The renal and/or urinary tract anomaly was the principal reason for induced abortion or cause of death in 50 cases (45%). In 97 (87%) of the 112 cases there was full agreement between the ultrasound observations and the autopsy findings. In five cases the autopsy revealed minor findings not mentioned in the ultrasound report. The main diagnosis was thus correct in 102 cases (91%). In four cases major autopsy findings had not been found by ultrasound examination; in another four, none of the autopsy findings were suspected by ultrasound, and in two, minor ultrasound findings were not confirmed at autopsy.

CONCLUSIONS

The accordance between ultrasound diagnoses and postmortem examinations proved to be satisfactory. The close co-operation between ultrasonographers and perinatal pathologists is mutually beneficial. In addition to complementing prenatal diagnosis, postmortem examination is of vital importance for the quality control of ultrasonography in fetal diagnosis and plays an important role in genetic counseling.

First trimester malformation screening

First trimester fetal malformation screening still represents a diagnostic challenge in modem obstetrics. Being solely dependent on ultrasound instrumentation, and the skill and experience of the operator, recently improved by introducing high frequency transvaginal approach and digital image processing. This opens a new field of ultrasound in obstetrics called sonoembriology. Until now sonoembriology in routine clinical practice resulted in numerous reports about early detection of rare anomalies and uncommon syndromes. The reported sensitivity of sonoembriology with a respect to a final pregnancy outcome was more than 60% of all malformations in total, while in combination with ultrasound screening in second trimester, increases to in excess of 80%. The commonest anomalies detected by sonoembriology are anomalies of the head and brain, heart, abdominal wall, unbilical cord, urinary tract and skeleton. There is an important role of sonoembriology in the assessment of the nuchal translucency in the screening programme for chromosomal anomalies. This changes the well-known concept "fetus as a patient" to "embryo as a patient" and opens new frontiers in fetal diagnosis and therapy.

Diagnosis of fetal renal anomalies

Urinary tract abnormalities are fairly common in the perinatal period. Ultrasonography is an effective diagnostic tool for identifying fetal urinary tract anomalies and can be helpful in establishing prognosis and guiding treatment decisions. The sonographer is encouraged to characterize and localize the fetal urinary tract abnormality when identified. In doing so, the correct diagnosis can be selected from the differential possibilities, providing vital clinical information needed to develop a care plan for both the pregnant woman and her fetus.

Prenatal failure to visualize kidneys: a spectrum of disease

OBJECTIVES

To better understand the outcomes and management of patients when there is a failure to visualize kidneys on prenatal ultrasound.

METHODS

Nine thousand five hundred twelve prenatal ultrasound studies performed on 4900 patients were reviewed retrospectively for the findings of a failure to visualize kidneys. The prenatal ultrasounds, pregnancy outcomes, and postmortem studies were reviewed for each of the 10 patients identified.

RESULTS

Nine of 10 patients experienced fetal death in the index pregnancy: 7 had therapeutic abortions, 1 had an intrauterine fetal demise, and 1 gave birth to a stillborn infant. One patient gave birth to a live infant with Bartter's syndrome and grossly normal kidneys, as diagnosed by ultrasound. Developmental renal anomalies were identified in only 4 of 10 cases, and only 2 patients had true bilateral renal agenesis. There was 1 case each of bilateral renal medullary cystic dysplasia and bilateral renal hypoplasia. Three cases had no renal anomalies and included 1 case each of Turner's syndrome, chronic abruption, and a cord accident. In 2 cases, postmortem examinations were not performed because of family wishes.

CONCLUSIONS

Prenatal failure to visualize kidneys represents a spectrum of clinical problems not all of which are fatal. Close consultation with an experienced ultrasonographer is essential to provide informed counseling to expectant parents. Pathologic examination should be recommended when there is fetal demise and a suspicion of genitourinary anomalies. Screening of family members of the index patient and genetic counseling may be indicated.

Fetal outcome in nuchal translucency with emphasis on normal fetal karyotype

The aim of this study was to evaluate fetal outcome in fetuses with a nuchal translucency thickness of 3 mm or more, with emphasis on those with a normal karyotype. Between 1991 and 1994, a total of 104 pregnancies with suspected ultrasound abnormalities were referred to our prenatal unit for a fetal anomaly scan before 16 weeks of gestation. Of these 104 pregnancies, 54 were referred because of a nuchal translucency thickness of 3 mm or more. Data on these 54 pregnancies will be presented. Karyotyping was performed in all cases. An abnormal karyotype was found in 26/54 (48 per cent) pregnancies. A normal karyotype was established in the remaining 28 pregnancies. In this subset, five associated structural anomalies were detected at the first anomaly scan (9-15 weeks). Two pregnancies were terminated because of isolated nuchal translucency. In four of the continuing 21 pregnancies, additional structural anomalies were detected only at the second anomaly scan (16-20 weeks). Two of these were terminated because of bilateral renal dysplasia and a combination of exomphalos and ectopia cordis. Finally, 19 pregnancies progressed uneventfully and resulted in spontaneous delivery at a median gestational age of 40 weeks. A statistically significant difference in mean nuchal translucency thickness was found between cases with and without associated structural anomalies. This relationship indicates a more pronounced nuchal translucency thickness to be associated with a higher incidence of additional structural anomalies and, as a result, a poorer fetal outcome.

The significance of early second-trimester sonographic detection of minor fetal renal anomalies

A study of 6350 consecutive transvaginal ultrasound examinations was performed as part of a routine fetal evaluation. Twenty-one cases (0.33 per cent) of early second-trimester sonographic detection of minor renal abnormalities (unilateral renal agenesis, pelvic kidney, and double collecting system) are presented. The sonographic diagnosis was made at 14-18 weeks of pregnancy and confirmed, in all of the 21 fetuses, postnatally or by post-mortem. A high incidence of associated fetal anomalies (24 per cent) and parental renal abnormalities (14 per cent) was demonstrated. Transvaginal sonography was found to be a useful tool for diagnosing these renal anomalies as early as 14 weeks of pregnancy. The likelihood of various associated anomalies and long-term implications on renal function raise questions concerning the prenatal management of such patients.