Fetal renal defects: associated malformations and chromosomal defects

Fetal Urinary Ascites From Bladder Rupture: A Rare Complication of Posterior Urethral Valve

Prenatal ultrasonography (USG) plays a crucial role in diagnosing fetal urinary tract anomalies and distinguishing between lower urinary tract obstructive (LUTO) and neurological causes (seen with spinal dysraphism, myelomeningocele, meningocele, and sacral agenesis) of urinary bladder distension. Fetal urinary ascites, a rare but severe complication, can result from bladder rupture associated with obstructive uropathy such as posterior urethral valves (PUV). This case study presents a rare instance of fetal urinary ascites due to PUV detected during prenatal ultrasonography at 20 weeks of gestation (WOG). By highlighting this uncommon but clinically significant condition, we aim to enhance the understanding and management of similar cases in clinical practice.

When should we offer antenatal sequencing for urinary tract malformations? A systematic review, cohort study and meta-analysis

OBJECTIVE

Determine the incremental yield of prenatal exome sequencing (PES) over chromosome microarray (CMA) and/or karyotype for urinary tract malformations (UTMs).

METHOD

A prospective cohort study encompassing data from the English Genomic Medicine Service North Thames Laboratory Hub for fetuses with bilateral echogenic kidneys (BEKs) was combined with data from a systematic review. MEDLINE, EMBASE, Web of Science, MedRxiv and GreyLit were searched from 01/2010-02/2023 for studies reporting on the yield of PES over CMA or karyotype in fetuses with UTMs. Pooled incremental yield was determined using a random effects model. PROSPERO CRD42023364544.

RESULTS

Fourteen studies (410 cases) were included. The incremental yield for multisystem UTMs, any isolated UTMs, and BEKs was 31% [95% CI, 18%-46%; I2  = 78%], 16% [95% CI, 6%-26%; I2  = 80%] and 51% [95% CI, 27%-75%; I2  = 34%]. The most common clinical diseases and syndromes identified, based on the variant genes detected, were Bardet-Biedl syndrome (BBS genes), dominant and recessive polycystic kidney diseases (PKD1, PKD2 and PKHD1) and renal cysts and diabetes syndrome (HNF1B).

CONCLUSION

There was a notable incremental genetic diagnostic yield when PES was applied to multisystem UTMs and BEKs. There was a modest incremental yield when this technique was used for UTMs other than BEKs.

Microarray analysis in pregnancies with isolated unilateral kidney agenesis

BackgroundThe objective of our study was to examine the risk for submicroscopic chromosomal aberrations among fetuses with apparently isolated solitary kidney.MethodsData acquisition was performed retrospectively by searching Israeli Ministry of Health-computerized database. All cases having chromosomal microarray analysis (CMA), referred because of an indication of isolated unilateral kidney agenesis between January 2013 and September 2016, were included. Rate of clinically significant CMA findings in these pregnancies was compared to pregnancies with normal ultrasound, based on a systematic review encompassing 9,792 cases and local data of 5,541 pregnancies undergoing CMA because of maternal request.ResultsOf the 81 pregnancies with isolated solitary kidney, 2 (2.47%) loss-of-copy number variants compatible with well-described deletion syndromes were reported (16p11.2-16p12.2 and 22q11.21 microdeletion syndromes). In addition, one variant of unknown significance was demonstrated. The relative risk for pathogenic CMA findings among pregnancies with isolated unilateral renal agenesis was not significantly different compared with the control population.ConclusionCMA analysis in pregnancies with unilateral renal agenesis might still be useful, to the same degree as it can be in the general population.

Protein Kinase 2β Is Expressed in Neural Crest-Derived Urinary Pacemaker Cells and Required for Pyeloureteric Contraction

Nonobstructive hydronephrosis, defined as dilatation of the renal pelvis with or without dilatation of the ureter, is the most common antenatal abnormality detected by fetal ultrasound. Yet, the etiology of nonobstructive hydronephrosis is poorly defined. We previously demonstrated that defective development of urinary tract pacemaker cells (utPMCs) expressing hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) and the stem cell marker cKIT causes abnormal ureteric peristalsis and nonobstructive hydronephrosis. However, further investigation of utPMC development and function is limited by lack of knowledge regarding the embryonic derivation, development, and molecular apparatus of these cells. Here, we used lineage tracing in mice to identify cells that give rise to utPMCs. Neural crest cells (NCCs) indelibly labeled with tdTomato expressed HCN3 and cKIT. Furthermore, purified HCN3+ and cKIT+ utPMCs were enriched in Sox10 and Tfap-2α, markers of NCCs. Sequencing of purified RNA from HCN3+ cells revealed enrichment of a small subset of RNAs, including RNA encoding protein kinase 2β (PTK2β), a Ca²⁺-dependent tyrosine kinase that regulates ion channel activity in neurons. Immunofluorescence analysis in situ revealed PTK2β expression in NCCs as early as embryonic day 12.5 and in HCN3+ and cKIT+ utPMCs as early as embryonic day 15.5, with sustained expression in HCN3+ utPMCs until postnatal week 8. Pharmacologic inhibition of PTK2β in murine pyeloureteral tissue explants inhibited contraction frequency. Together, these results demonstrate that utPMCs are derived from NCCs, identify new markers of utPMCs, and demonstrate a functional contribution of PTK2β to utPMC function.

Diagnostic accuracy of midtrimester antenatal ultrasound for multicystic dysplastic kidneys

OBJECTIVES

To establish the diagnostic accuracy of obstetric ultrasound at a tertiary fetal medicine center in the prenatal detection of unilateral and bilateral multicystic dysplastic kidney (MCDK) in fetuses in which this condition was suspected, and to undertake a systematic review of the relevant literature.

METHODS

This was a retrospective observational study of all cases referred to a regional tertiary fetal medicine unit due to suspicion of either unilateral or bilateral MCDK between 1997 and 2015. Diagnosis was confirmed by postnatal ultrasound reports or postmortem examination. The accuracy of prenatal ultrasound in the diagnosis of MCDK was calculated. Using a systematic search strategy we also performed a review of the literature regarding the prenatal diagnosis and diagnostic accuracy of MCDK.

RESULTS

We included 144 women in our analysis; 37 (25.7%) opted for pregnancy termination (TOP) (due to unilateral MCDK with additional abnormalities, suspected bilateral MCDK or severe obstructive uropathy). Complete pre- and postnatal data were available in 126 pregnancies, including 104 livebirths, 19 TOPs with postmortem findings available and three intrauterine fetal deaths. Two infants died shortly after birth (due to known bilateral MCDK or known cranial vault defect). The overall number of cases of MCDK confirmed postnatally was 100; of these, 98 were diagnosed prenatally (true positive), while two were thought to be hydronephrosis prenatally (false negative) and the diagnosis of MCDK was made after birth. In nine cases, the initial antenatal diagnosis of suspected MCDK was revised, either later in pregnancy (n = 2) or postnatally (n = 7) (false positive). Overall, the diagnostic accuracy in our population for the use of antenatal ultrasound to detect MCDK was 91.3%, while that reported in the existing literature was found to range from 53.3% to 100%. MCDK was isolated in the majority (71%) of cases, while in 29% of cases it was found to be associated with other renal and extrarenal fetal abnormalities.

CONCLUSIONS

Antenatal ultrasound had a diagnostic accuracy of about 91% in the prediction of postnatal MCDK and can therefore be used to guide antenatal counseling. However, prenatal or postnatal revision of the diagnosis occurred in about 7% of cases and parents should be counseled appropriately. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal diagnosis of fetal multicystic dysplastic kidney via high-resolution whole-genome array

BACKGROUND

Women with fetal multicystic dysplastic kidneys (MCDK) are commonly referred for genetic counseling, for which identification of the correct etiology is a prerequisite.

METHODS

A total of 72 women with fetal MCDK at Guangzhou Women and Children's Medical Center were examined via invasive prenatal diagnosis from May 2010 to June 2015. Standard karyotyping analysis was provided to all fetuses, and chromosomal microarray with Affymetrix CytoSan HD arrays was offered to cases whose DNA samples were available.

RESULTS

Abnormal karyotypes were detected in 3 of 72 (4.17%) fetuses. Of the 69 (95.8%, 69/72) fetuses with normal karyotypes, 30 (42%, 30/69) underwent chromosome microarray analysis (CMA) testing. The CMA identified pathogenic copy number variations in five fetuses, leading to a pathogenic detection rate of 16.7% (5/30). Well-known microdeletion or microduplication syndromes including renal cysts and diabetes (RCAD) syndrome and Williams-Beuren syndrome (WBS) were identified in three cases. Moreover, four chromosomal imbalanced regions were also identified in our MCDK fetuses: 22q11.1 duplication, 4q35.2 deletion, 22q13.33 duplication and 1p33 duplication. Genes PEX26, ELN, HNF1B, ALG12, FRG1, FRG2 and CYP4A11 were possible candidates for fetal MCDK. The proportions of variants of unknown significance before and after parental analysis were 13.3% (4/30) and 3.3% (1/30), respectively.

CONCLUSIONS

In the present study, the frequency of chromosomal abnormalities in MCDK fetuses was 4.17% and all rearrangements were imbalanced aberrations. CMA was able to increase the pathogenic detection rate to 16.7% in MCDK fetuses with normal karyotype. Critical regions for RCAD syndrome, WBS and copy number variants of 22q11.1 duplication, 4q35.2 deletion, 22q13.33 duplication and 1p33 duplication were associated with fetal MCDK. Genes PEX26, ELN, HNF1B, ALG12, FRG1, FRG2 and CYP4A11 were possible candidates for fetal MCDK.

Laser Ablation of Posterior Urethral Valves by Fetal Cystoscopy

Objective: To report the results of fetal cystoscopic laser ablation of posterior urethral valves (PUV) in a consecutive series in two referral centers. Methods: Twenty pregnant women with a presumptive isolated PUV were treated with fetal cystoscopy under local anesthesia. Identification and fulguration of the PUV by one or several firing-contacts with diode laser were attempted. Perinatal and long-term outcomes were prospectively recorded. Results: The median gestational age at procedure was 18.1 weeks (range 15.0-25.6), and median operation time was 24 min (range 15-40). Access to the urethra was achieved in 19/20 (95%) cases, and postoperative, normalization of bladder size and amniotic fluid was observed in 16/20 (80%). Overall, there were 9 (45%) terminations of pregnancy and 11 women (55%) delivered a liveborn baby at a mean gestational age of 37.3 (29.1-40.2) weeks. No infants developed pulmonary hypoplasia and all were alive at 15-110 months. Eight (40% of all fetuses, 72.7% of newborns) had normal renal function and 3 (27.3%) had renal failure awaiting renal transplantation. Conclusion: Fetoscopic laser ablation for PUV can achieve bladder decompression and amniotic fluid normalization with a single procedure in selected cases with anyhydramnios. There is still a significant risk of progression to renal failure pre or postnatally.

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.

The Society for Fetal Urology consensus statement on the evaluation and management of antenatal hydronephrosis

The evaluation and management of fetuses/children with antenatal hydronephrosis (ANH) poses a significant dilemma for the practitioner. Which patients require evaluation, intervention or observation? Though the literature is quite extensive, it is plagued with bias and conflicting data, creating much confusion as to the optimal care of patients with ANH. In this article, we summarized the literature and proposed recommendations for the evaluation and management of ANH.

Unilateral multicystic dysplastic kidney: a meta-analysis of observational studies on the incidence, associated urinary tract malformations and the contralateral kidney

BACKGROUND

Many papers are published on cohorts with unilateral multicystic dysplastic kidney (MCDK) patients, but show variable results as to the incidence of associated urinary tract abnormalities. The objective of this study was to describe the status of the urinary tract, including contralateral hypertrophy and malformations, in patients with unilateral MCDK based on a meta-analysis of the literature, taking into account the timing of diagnosis (pre- versus postnatal) as a possible source of bias.

METHODS

A systematic review of the scientific literature in English was conducted using PubMed and Embase. A meta-analysis was performed with the studies that were identified using our reproducible search.

RESULTS

Based on analysis of the data in 19 populations, the overall incidence of unilateral MCDK is 1 in 4300 with an increasing trend over the years. A total of 67 cohorts with over 3500 patients with unilateral MCDK were included in the meta-analysis. Fifty-nine percent of patients were male and the MCDKs were significantly more often found on the left side (53.1%). Associated anomalies in the solitary functioning kidney were found in 1 in 3 patients, mainly vesicoureteric reflux (VUR, in 19.7%). In patients with VUR, 40% have severe contralateral VUR, defined as grade III-V. Contralateral hypertrophy, present in 77% of patients after a follow-up of at least 10 years, showed a trend to be less pronounced in patients with VUR. Timing of the diagnosis of MCDK did not essentially influence the results.

CONCLUSIONS

These aggregate results provide insight into the incidence, demographic data and associated anomalies in patients with unilateral MCDK. One in three patients with unilateral MCDK show anomalies in the contralateral, solitary functioning kidney. However, studies into the long-term consequences of these anomalies are scarce.

Upper urinary tract dilatation: prenatal diagnosis, management and outcome

Upper urinary tract dilatation is one of the most common abnormalities detected on prenatal ultrasound scanning. It is commonly due to transient urine flow impairment (UFI) at the level of the pelvi-ureteric and vesico-ureteric junctions, which improves with time in most cases. It is usually in the neonatal period that the diagnosis is confirmed and during the first 18 months of life that the prognosis of the dilatation is defined.

Genetic syndromes and prenatally detected renal anomalies

Renal anomalies are frequently detected on the routine second trimester scan offered to all pregnant women in the UK. These anomalies may be isolated but can also be associated with other congenital anomalies. Many combinations of ultrasound scan findings constitute recognised genetic entities. Knowledge of these conditions is essential for adequate management of the pregnancy and subsequent balanced parental counselling. This short review discusses the common genetic syndromes associated with the renal abnormalities identified on the antenatal ultrasound scan, and also provides an overview of renal symptoms in chromosome imbalances and after teratogenic influences.

Congenital urinary tract obstruction

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

Trisomy 17 in a baboon (Papio hamadryas) with polydactyly, patent foramen ovale and pyelectasis

Trisomy 13 in humans is the third most common autosomal abnormality at birth, after trisomy 21 and trisomy 18. It has a reported incidence of between 1:5,000 and 1:30,000 live births. It is associated with multiple abnormalities, many of which shorten lifespan. We describe here the first reported case of a baboon (Papio hamadryas) with trisomy of chromosome 17, which is homologous to human chromosome 13. The trisomic infant was born to a consanguineous pair of baboons and had morphological characteristics similar to those observed in human trisomy 13, including bilateral polydactyly in the upper limbs, a patent foramen ovale, and pyelectasis. Molecular DNA analysis using human chromosome 13 markers was consistent with the affected infant inheriting two copies of chromosome 17 derived from the same parental chromosome. This trisomy was, therefore, due to either an error in meiosis II or the result of postzygotic nondisjunction. The parental origin, however, could not be determined.

The risk of a major trisomy in fetuses with pyelectasis: the impact of an abnormal maternal serum screen or additional sonographic markers

OBJECTIVE

This study was undertaken to evaluate the contribution of either an abnormal second-trimester maternal serum screen or the presence of additional sonographic markers of aneuploidy to the risk of a major trisomy (13, 18, and 21) in fetuses with pyelectasis.

STUDY DESIGN

A retrospective review of a large amniocentesis database was performed. Specimens obtained after the sonographic detection of fetal pyelectasis were eligible for analysis. Age-matched women who underwent amniocentesis solely for maternal anxiety or advanced maternal age served as controls.

RESULTS

760,495 amniocentesis specimens were analyzed. Fetal pyelectasis was detected in 671 cases. Pyelectasis, with either a single or multiple additional sonographic markers, was associated with an 8-fold and 62-fold increase in the prevalence of major trisomies (odds ratio = 7.7, 95% CI = 1.2-32.6, P = 0.02) and (odds ratio = 61.9, 95% CI = 13.2-144.6, P < .001), respectively. Pyelectasis with an abnormal maternal serum screen, with or without additional sonographic markers, was associated with a 32-fold and a 205-fold increase in major trisomies (odds ratio = 32.2, 95% CI = 5.3-94.8, P < .001) and (odds ratio = 205.8, 95% CI = 37.9-427.6, P < .001), respectively.

CONCLUSION

In fetuses with pyelectasis, the presence of additional sonographic markers or an abnormal maternal serum screen significantly increases the risk of trisomy 13, 18, and 21.

Fetal Pyelectasis

OBJECTIVE

Several studies have noted an increased prevalence of pyelectasis in male fetuses. It is speculated that pyelectasis represents a normal physiologic variant in males, whereas its presence in females indicates an increased risk of chromosomal abnormalities. Thus, we sought to investigate the association between fetal gender and the risk of major trisomies in fetuses with pyelectasis.

METHODS

Retrospective analysis of a Genzyme Genetics amniocentesis database (1995 to 2004) was performed. Specimens obtained after an ultrasonographic finding of pyelectasis were eligible for analysis. The prevalence of major trisomies (trisomy 13, 18, or 21) in male and female fetuses with pyelectasis was compared using binomial distribution.

RESULTS

A total of 760,495 amniocentesis specimens were analyzed. Fetal pyelectasis was reported in 671 cases. A male predominance, with a male-to-female ratio of 2.14:1 (457 compared with 214) was statistically significant (P < .001). A major trisomy was detected in 26 male fetuses (5.7%): 18 cases of trisomy 21, 2 cases of trisomy 18, and 6 cases of trisomy 13. Nine female fetuses had a major trisomy (4.2%): 6 cases of trisomy 21 and 3 cases of trisomy 13. There was no significant difference in the overall prevalence of trisomies between male and female fetuses (P = .14).

CONCLUSION

We concur with previous studies documenting a higher prevalence of pyelectasis in male fetuses. In addition, our results indicate that the prevalence of major trisomies among fetuses with pyelectasis is unlikely to be dependent on fetal gender. Thus, counseling patients with regard to the genetic implications of fetal pyelectasis should be gender independent.

LEVEL OF EVIDENCE

II-2.

Should determination of the karyotype be systematic for all malformations detected by obstetrical ultrasound?

OBJECTIVE

The aim of this study was to determine whether karyotyping should be performed for every fetal malformation detected in low risk populations.

METHODS

A karyotype was obtained from 428 fetuses examined over a 10-year period after fetal malformation was diagnosed using obstetrical ultrasound. These fetuses were separated into two groups, one with isolated malformations and the other with multiple malformations. The association between each type of malformation and the result of karyotype was evaluated.

RESULTS

Forty-eight chromosomal abnormalities were encountered in 428 fetuses (11.2%). The karyotype was abnormal in 32/343 (9.3%) fetuses with isolated malformations and 16/85 (18.8%) fetuses with multiple malformations (p=0.022). The probability of an abnormal karyotype among the group of isolated malformation depended on the anatomical system involved (p<0.001). Our study demonstrated several isolated malformations without chromosomal abnormality (hydronephrosis with high obstruction, unilateral multicystic dysplastic kidney, gastroschisis, intestinal dilatation, meconium peritonitis, cystic adenomatoid malformation, pulmonary sequestration, tumor, vertebral anomaly).

CONCLUSION

Each fetus with multiple malformations needs a chromosomal analysis. Within the group of isolated malformations, our study emphasizes that medical maternal history and the type of malformation need to be taken into account before performing a fetal karyotype.

Isolated fetal pyelectasis and chromosomal abnormalities

OBJECTIVE

The primary objective of this study was to determine if isolated pyelectasis is a risk factor for trisomy 21.

STUDY DESIGN

Twelve thousand, six hundred and seventy-two unselected singleton fetuses were examined by prenatal ultrasound during the second trimester at a single institution. The sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio of pyelectasis (either isolated or in association with other soft markers/structural anomalies) to detect trisomy 21 were calculated.

RESULTS

Pyelectasis (anteroposterior pelvic diameter >/=4 mm) was detected in 2.9% (366/12,672) of the fetuses. Among these, 83.3% (305/366) were isolated, and 16.7% (61/366) were associated with other markers/structural anomalies. The prevalence of trisomy 21 was 0.087% (11/12,672) and, among these fetuses, 2 (18.1%) had pyelectasis, 1 isolated, and 1 associated with other markers/structural anomalies. The presence of isolated pyelectasis had 9.09% sensitivity, 97.6% specificity, 0.33% positive predictive value, and 99.9% negative predictive value to detect fetuses with trisomy 21. The likelihood ratio of trisomy 21 in this group of fetuses was 3.79 (95% CI 0.582-24.616). Among fetuses with pyelectasis and other associated markers/structural anomalies, the sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio for trisomy 21 were 9.09%, 99.5%, 1.64%, 99.9%, and 19.2 (95% CI 2.91-126.44).

CONCLUSION

In the absence of other findings, isolated pyelectasis is not a justification for the performance of an amniocentesis.

Mild renal pyelectasis in the second trimester: determination of cut-off levels for postnatal referral

OBJECTIVE

To establish guidelines for postnatal referral of fetuses presenting with mild pyelectasis in the second trimester of pregnancy.

METHODS

In a retrospective study, 87 fetuses with a renal pelvis anteroposterior (RPAP) diameter of > or = 4 mm and < or = 10 mm before 28 weeks of gestation were included. All patients had a third-trimester scan and fetuses with an RPAP diameter of > or = 10 mm at that stage were referred for postnatal assessment. The family practitioner of all infants with an RPAP of < 10 mm in the third trimester was contacted for follow-up information. The RPAP diameter most predictive of renal pathology was determined with receiver-operating characteristics (ROC) curve analysis for both the first and second scans.

RESULTS

In 36 of 87 infants, 49 abnormal kidneys were diagnosed. Seven infants required surgery on eight renal tracts. The ROC curves of the first scan, second scan and differences between scans resulted in an area under the curve of 0.60, 0.87 and 0.85, respectively. The sensitivities and specificities for a cut-off level of 8, 9 and 10 mm at the second scan were 80%, 71% and 61% and 79%, 90% and 93%, respectively. At a cut-off level of 10 mm, only cases of insignificant minimal dilatation and a case of vesicoureteric reflux (VUR) requiring surgery were not detected.

CONCLUSION

After establishing a diagnosis of mild pyelectasis before 28 weeks, a second scan is mandatory to determine which infants need postnatal evaluation. A cut-off level of 8 mm has a low specificity but includes most cases of pathology. A cut-off level of 10 mm detects most significant pathology; however, VUR may not be detected.

Concomitant anomalies in 100 children with unilateral multicystic kidney

OBJECTIVES

To determine the incidence and type of associated urogenital anomalies in children with a unilateral multicystic kidney and to assess in children with nephrectomy the additional diagnostic value of cystoscopy and, in girls, of colposcopy.

METHODS

This was a follow-up study of 100 fetuses with antenatally detected unilateral multicystic kidneys. After ultrasound confirmation of the diagnosis within a few days after birth voiding cystourethrography and isotope scan were performed in 83 of the surviving children to exclude vesicoureteral reflux and to establish renal function. Eighty-one children underwent nephrectomy and, prior to surgery, all underwent cystoscopy and girls also underwent colposcopy.

RESULTS

Seventy-five children had one or more additional urogenital anomalies: 39 had anomalies of the contralateral kidney, 40 had anomalies of the ipsilateral kidney and 30 had one or more anomalies of the lower urogenital tract. With cystoscopy 54 anomalies of the genitourinary tract were detected in 48 children and with colposcopy three anomalies were detected in 35 girls. Eighty-one children had a nephrectomy or heminephrectomy and 33 of them needed other urological intervention. Thirteen fetuses died (mostly from agenesis of the contralateral kidney) and six infants had no surgery at all.

CONCLUSION

Children with a unilateral multicystic kidney are at considerable risk of having other urogenital anomalies. When cystoscopy and colposcopy are added to routine investigations the rate of detection of anomalies is 75%, twice that reported in the literature.

Congenital renal tract anomalies: outcome and follow-up of 402 cases detected antenatally between 1986 and 2001

OBJECTIVE

To determine the long-term prognosis of antenatally detected renal tract anomalies in order to optimize parental counseling.

METHODS

This was a follow-up study of all renal tract abnormalities detected antenatally in a Level 3 ultrasound department between 1986 and 2001. Follow-up data (median age, 8 years) were retrieved from the records of the Paediatric Urology Department or the attending pediatrician.

RESULTS

A urinary tract anomaly was detected in 408 fetuses. There were four false-positive diagnoses. From two children follow-up data were incomplete, leaving 402 cases for analysis. A chromosomal abnormality was present in 7/81 (8.6%) fetuses that had karyotyping. Termination of pregnancy was performed in 55 (13.7%) cases and a further 66 (16.4%) children died during the perinatal period and up to 1 year of age. In 106/121 (26.4% of all fetuses) deceased children the cause of death was directly related to the renal tract anomaly. In the 281 surviving children a total of 545 renal tract anomalies were diagnosed postnatally, requiring a total of 381 surgical interventions in 156 infants. Outcome in survivors was generally good, with impaired renal function in nine infants and hypertension in three (4% of the survivors).

CONCLUSIONS

Congenital renal tract anomalies are associated with a high mortality rate, especially when they are structural developmental anomalies of the kidneys. Survivors require multiple operations, but the outcome is generally favorable. Ultrasound diagnosis, especially when made early, of non-lethal urinary tract anomalies may prevent additional renal damage by timing of delivery and early postnatal treatment.

Variability in dilatation of the fetal renal pelvis during a bladder filling cycle

OBJECTIVE

To investigate the variation in the dimensions of the fetal renal pelvis in relation to the degree of bladder filling in fetuses with mild pyelectasis.

METHODS

Eighteen third-trimester pregnant women with mild uni- or bilateral fetal pyelectasis, defined as an anteroposterior (A-P) diameter of the renal pelvis between 5 and 10 mm, were recruited for the study. The women were examined for 2-3 h by ultrasound. The A-P and transverse dilatation of the renal pelvis and the bladder dimensions (to calculate fetal bladder volume) were measured at 2-3-min intervals. Postnatally, all infants were investigated by ultrasound at 3-4 months.

RESULTS

In 6/18 fetuses a consistent relationship between the size of the renal pelvis and bladder filling was found, with a mean difference in renal pelvic diameter before and after voiding of 6.7 mm and a largest observed difference of 14.3 mm. In 12/18 fetuses no such relationship was found. Postnatally, five infants were referred to a pediatric urologist. The investigations in these five infants could not confirm the hypothesis that variation in renal pelvic size in relation to bladder size may predict prenatal vesicoureteric reflux (VUR).

CONCLUSIONS

In mild pyelectasis the size of the renal pelvis is highly variable in one-third of cases. The association with bladder volume and micturition suggests evidence of VUR, but this could not be proven. If cut-off values are used to differentiate between normal and abnormal renal pelvic size then not only gestational age but also the degree of bladder filling at the time of measurement should be taken into account. Caution should be expressed when the diagnosis of a possible urological anomaly is based on a single measurement during just one investigation.

Controversial ultrasound findings

This article has reviewed a few of the more controversial findings in the field of obstetric ultrasound. For each one evidence-based strategies for the management of affected pregnancies have been suggested, derived from what the authors believe is the best information available. In some cases, this information is very limited, which can make counseling these patients extremely difficult. Some physicians find using specific likelihood ratios helpful in these complex discussions. An example of the relative likelihood ratios for several markers of trisomy 21 is illustrated in Table 10. Although the management of each of the findings discussed in this article is different, a few generalizations can be made. To begin with, the detection of any abnormal finding on ultrasound should prompt an immediate detailed ultrasound evaluation of the fetus by someone experienced in the diagnosis of fetal anomalies. If there is more than one abnormal finding on ultrasound, if the patient is over the age of 35, or if the multiple marker screen is abnormal, an amniocentesis to rule out aneuploidy should be recommended. Of the six ultrasound findings reviewed here, the authors believe that only echogenic bowel as an isolated finding confers a high enough risk of aneuploidy to recommend an amniocentesis in a low-risk patient. The other findings in isolation in a low-risk patient seem to confer only a modest increased risk of aneuploidy, if any, and this risk is certainly less than the risk of unintended loss from amniocentesis. Wherever possible, modifiers of this risk, such as maternal age, history, and first and second multiple marker screening, should be used to define more clearly the true risk of aneuploidy. As obstetric ultrasound moves forward, particularly into the uncharted waters of clinical use of three- and four-dimensional ultrasound, one can expect a whole new crop of ultrasound findings with uncertain clinical significance. Clinicians are well advised to await well-designed studies to determine the clinical significance of these findings before altering clinical care.

The association between fetal pyelectasis on second trimester ultrasound scan and aneuploidy among 25,586 low risk unselected women

OBJECTIVE

To determine the association of fetal pyelectasis FP found at the time of second trimester detailed ultrasound scan with aneuploidy in an unselected low-risk population.

DESIGN

Retrospective study of ultrasonographic reports, films and hospital notes over an eight-year period from 1991 to 1998.

SETTING

District general hospital obstetric department with 3500 deliveries annually serving a low-risk cosmopolitan population.

MAIN OUTCOME MEASURE

The prevalence of aneuploidy in cases of fetal pyelectasis.

METHODS

The obstetric ultrasound reports and films of 29,591 cases were reviewed to identify those with FP at their detailed anomaly scan between 18 and 24-weeks gestation. The study sample included women whose scan showed the fetal renal pelvis of either kidney to be five millimetres or more in the anteroposterior diameter. Demographic data and other ultrasonographic abnormalities were noted. The genotype and phenotype of the babies were traced from a combination of cytogenetic reports and paediatric notes.

RESULTS

There were 320 cases of FP among the 25,586 low-risk study population available in the studied gestational period (18-24 weeks) giving a prevalence of 1.25 percent. Of these, 301 cases of FP were found in isolation and 19 were found in association with another ultrasonographic marker. None of the 315 cases delivering at the Northwick Park & St. Mark's Hospital had aneuploidy. Pyelectasis was more likely to be bilateral (57%), and more in male fetuses (72%). The mean diameter for the pyelectasis at diagnosis was 6.5 mm (1.4 SD) ranging between 5 and 15 mm. One hundred and thirty seven cases (43%) resulted in spontaneous resolution.

CONCLUSION

The prevalence of FP at the anomaly scan in an unselected low-risk population is not high (1.25%). Our data suggest that the risk of aneuploidy associated with isolated FP in a low-risk, unselected population is so small that it should not be an indication for invasive prenatal karyotyping.

Prenatal diagnosis of apparently isolated unilateral multicystic kidney: implications for counselling and management

Cases where initial prenatal diagnosis was made of isolated unilateral multicystic kidney (UMCK) were reviewed to determine appropriate counselling and management strategies. For the 73 cases, chromosome abnormalities, pregnancy complications and family histories were reviewed. In addition, subsequently diagnosed birth defects, and pediatric medical and surgical outcomes were available for 54 cases. Of those with outcome information available renal/genital-urinary tract abnormalities were diagnosed subsequently in 33% and non-renal abnormalities in 16% of cases. Of the non-renal abnormalities, congenital heart defects were most frequent (7%). One chromosome abnormality, a trisomy 21, was present among 32 cases where karyotypes were known (3%). Amniotic fluid volume abnormalities were present in 11 cases but not predictive of associated anomalies, with the exception of one case where polyhydramnios accompanied multiple malformations consistent with VATER association. A family history of structural renal anomalies was reported in 11 cases (20%). There were 14 cases of partial or complete involution (25%), including two cases of complete prenatal involution of the cystic kidneys. No long-term associated morbidity such as hypertension or malignancy was present in our cohort. Based on our study and corroborating literature, amniocentesis should be offered to women when a seemingly isolated UMCK is detected on routine prenatal ultrasound. Furthermore, a detailed ultrasound with careful assessment of the fetal heart and contralateral kidney is indicated at diagnosis and during the third trimester to assess for further evidence of structural abnormalities, as well as amniotic fluid volume abnormalities. Careful assessment of the newborn is indicated with appropriate speciality referral as required.

The association of aneuploidy and mild fetal pyelectasis in an unselected population: the results of a multicenter study

INTRODUCTION

Mild pyelectasis is a common finding and there is some debate as to its association with aneuploidy. The results of a large, prospective, multicenter study of mild pyelectasis designed to determine the incidence and association with aneuploidy in an unselected population are reported.

METHODS

A large multicenter, prospective observational study of unselected fetuses with mild pyelectasis identified between 16 and 26 weeks' gestation in routine ultrasound departments.

RESULTS

There were 737 fetuses with mild pyelectasis of which 12 had an abnormal karyotype. Pyelectasis was isolated in three fetuses with Down syndrome, but in one the mother was older (36 years).

CONCLUSION

These data confirm the fact that the presence of mild fetal pyelectasis increases the risk for aneuploidy, in particular trisomy 21. However, other risk factors should be considered before embarking on fetal karyotyping, as for most pregnancies complicated by isolated mild pyelectasis, risks of aneuploidy will remain small.

Prenatal diagnosis of del(15)(q26.1) and del(18)(q21.3) due to an unbalanced de novo translocation: ultrasound, molecular cytogenetic and autopsy findings

A case of partial deletion of the distal parts of chromosomes 15 and 18 [(15)(q26.1)(18)(q21.3)] due to a de novo translocation is reported. Cordocentesis and fetal karyotyping was done because of severe oligohydramnios and bilateral absence of kidneys. Renal defects are a frequent finding in fetuses with different chromosomal anomalies; this particular chromosomal rearrangement however has not been reported yet in a fetus with bilateral renal agenesis. FISH was performed for detailed clarification of the chromosomal anomaly. Prenatal karyotyping appears to be important in fetuses with renal agenesis.

Prenatal diagnosis of fetal urinary ascites

We report on a rare in utero appearance of the rupture of the fetal bladder caused by low urinary tract obstruction with subsequent urinary ascites. The findings on prenatal sonography, postnatal X-ray examinations and postnatal surgical treatment are described and the literature is reviewed.

Second trimester markers of aneuploidy

The risks of aneuploidy associated with identification of a sonographic marker in the low risk population is controversial. Prior risk estimates have been derived usually from high risk populations. Screening programmes in the first trimester, second trimester and combined first and second trimester will undoubtedly alter the second trimester scan as a screening tool for aneuploidy. This chapter reviews the current sonographic markers and the difficulties in their application to the general population.

Functional urinary tract obstruction developing in fetuses with isolated gastroschisis

OBJECTIVE

To evaluate the frequency and natural history of urinary tract abnormalities developing in fetuses presenting with initially isolated gastroschisis.

METHODS

Serial ultrasounds were performed prospectively on fetuses identified by our prenatal diagnosis program as having a gastroschisis. When abnormalities in the urinary tract were identified prenatally, newborns were evaluated by a pediatric urologist.

RESULTS

Over a 1-year period four out of 12 fetuses with gastroschisis developed deformations of the urinary tract. In three fetuses the bladder herniated through the abdominal wall defect. Two also had upper tract dilatation. A fourth fetus developed bilateral hydronephrosis with a normally situated bladder. Once the gastroschisis was repaired none of the newborns had evidence of structural obstruction of the urinary tract, however, hydronephrosis with or without reflux persisted for several months.

CONCLUSIONS

Deformations of the fetal urinary tract can develop secondary to gastroschisis. They do not appear to represent separate malformations and evaluation with fetal karyotyping may not be indicated. When hydronephrosis is present ongoing urologic evaluation of the neonate is indicated.

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.

Bilateral renal agenesis and fetal ascites in association with partial trisomy 13 and partial trisomy 16 due to a 3:1 segregation of maternal reciprocal translocation t(13;16)(q12.3; p13.2)

A female fetus with bilateral renal agenesis and fetal ascites was found to have partial trisomy 13 (pter-q12.3) and partial trisomy 16 (p13.2-pter), 47,XX,+der(13)t(13;16)(q12.3; p13.2)mat. The chromosomal aberration was due to a 3:1 segregation with tertiary trisomy transmitted from a maternal reciprocal translocation 13;16. Prenatal ultrasound of a 29-year-old, gravida 2, para 0 woman at 22 gestational weeks showed fetal ascites, severe oligohydramnios and non-visualization of fetal urinary bladder and kidneys. The pregnancy was terminated. At delivery, the proband displayed dysmorphic features of hypertelorism, a prominent glabella, epicanthic fold, a stubby nose with a depressed nasal bridge, anteverted nares, thin lips, micrognathia, low-set ears, a short neck and a distended abdomen. Necropsy confirmed bilateral renal agenesis and ascites. A cytogenetic study performed on fibroblasts obtained from the proband's skin revealed an extra supernumerary chromosome. The mother was later found to have a reciprocal translocation. Fluorescence in situ hybridization for a submicroscopic deletion in chromosome 22q11 in the proband was negative. The parents had no urological anomalies. Our observation further extends the clinical spectrum associated with proximal trisomy 13q and distal trisomy 16p. We suggest prenatal cytogenetic analysis in fetuses with urological anomalies, including renal agenesis, to uncover underlying genetic disorders.

Insights into the pathogenesis and natural history of fetuses with multicystic dysplastic kidney disease

To better delineate the natural history of multicystic displastic kidney disease (MCDKD) and provide insights into the pathogenesis of this condition, we report our experience in 102 prenatally detected cases. MCDKD is most commonly an incidental finding on prenatal ultrasound examination. The abnormality may be unilateral (76 per cent) or bilateral (24 per cent). In unilateral cases, abnormality of the contralateral kidney is common (33 per cent). Associated non-renal abnormalities occur frequently with both unilateral (26 per cent) and bilateral (67 per cent) MCDKD, and increase the risk for an abnormal chromosome study. Males are more likely to be affected than females with a ratio of 2.4:1, but females are twice as likely to have bilateral MCDKD and associated non-renal abnormalities, and four times more likely to have an abnormal chromosome study. We suggest that the option of chromosomal analysis should be discussed with all patients diagnosed with MCDKD in their fetus, if there is bilateral renal involvement or if an associated non-renal abnormality is present. Unilateral MCDKD without associated renal or non-renal abnormalities was not associated with an abnormal chromosome study, and resulted in favourable outcomes. While unilateral MCDKD, lack of associated anomalies, normal chromosome study and adequate amniotic fluid are all reassuring findings, a complete neonatal urologic work-up should be performed in all newborns. We believe the evaluation should include voiding cystourethrography to rule out vesicoureteral reflux. Our findings allow more precise counselling of patients regarding prognosis, and subsequent management of the fetus found to have MCDKD.

Prenatal diagnosis of a de novo trisomy 6q22.2-->6qter and monosomy 1pter-->1p36.3. Case report with a 2-year follow-up and a brief review of other prenatal cases of partial trisomy 6q

We report a de novo trisom 6q22.2-->6qter and monosomy 1pter-->1p36.3 identified in amniocytes by GTG banding and FISH. While ultrasonography demonstrated malformations that did not suggest a specific chromosomal syndrome, a male infant with features consistent with trisomy 6q was born. He was followed up until 23 months, when he died after cardiac surgery. The only two other prenatal cases of trisomy 6q were compared with our patient. A literature review showed that trisomy 6q has not been reported in association with the anomalies seen by ultrasound in this case.

Isolated fetal hydronephrosis: beware the effect of bladder filling

The aim was to assess the role that fetal bladder size has in the determination of fetal hydronephrosis. Forty-three fetuses were evaluated for fetal hydronephrosis in the second trimester of pregnancy. Anteroposterior measurements of the renal pelvis were obtained with a full bladder and again when the bladder emptied in each fetus. Statistical analysis was performed using the Spearman rank order correlation coefficient to assess the relationship between bladder status and renal dilation. The anteroposterior size of the fetal renal pelvis diminished from 6.8 +/- 1.8 mm on a full bladder scan to 4.5 +/- 1.6 mm when the bladder was emptied (P < 0.001). Fifty-three per cent of the fetuses whose renal pelvic measurements were 5 mm or more on a full bladder scan had normal-appearing renal pelvises when their bladders emptied. The status of the fetal bladder should be considered when evaluating fetal hydronephrosis.

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.

Potter's syndrome in the second trimester--prenatal screening and pathological findings in 60 cases of oligohydramnios sequence

Fifty-two second-trimester and eight third-trimester (> 28/40) autopsies with clinical or pathological evidence of oligohydramnios sequence ('Potter's syndrome') were reviewed. Twenty-eight cases had renal anomalies (71 per cent in terminations following prenatal ultrasound), 27 had no renal malformation (35 per cent with chorioamnionitis), and five had external assessments only. In 15 cases, the renal lesion was part of a multiple malformation syndrome. Seven cases had a lesion which either recurred in a sibling in the same family or was a recognized autosomal recessive syndrome. Three cases had an abnormal karyotype, two of which had renal anomalies. Maternal serum alpha-fetoprotein (AFP) did not discriminate between cases with renal malformations and those without. Pulmonary hypoplasia was commoner in third-trimester than in second-trimester cases. External appearance and absent umbilical artery were not reliable predictors of underlying internal anomalies. These findings reflect the shift from postnatal to prenatal diagnosis in modern practice. In this series, mainly second-trimester cases, 50 per cent of cases had no malformations, in a condition which is traditionally associated with renal disease. The high incidence of chorioamnionitis suggests that the mechanism of oligohydramnios is occult amniotic fluid leakage. Prenatal diagnosis of oligohydramnios in the second trimester is dependent on ultrasound scanning and a full post-mortem examination is necessary to identify any underlying fetal cause.

Predictive value of fetal serum beta 2-microglobulin for neonatal renal function

When fetal urinary-tract malformations (UTM) are discovered, management is based on the prediction of postnatal renal function, currently made by fetal urinary biochemistry and sonography. Serum beta 2-microglobulin has been used postnatally to estimate renal function and does not cross the placenta. We investigated the relation between fetal serum beta 2-microglobulin and renal function by comparing 64 unaffected fetuses and 15 fetuses with UTM. A beta 2-microglobulin above a 5.6 mg/L cut-off gave cross-validated sensitivity of 80.0%, specificity of 98.6%, a positive predictive value of 88.9%, and a negative predictive value of 97.1% for our cohort study.

Combining humerus and femur length for improved ultrasonographic identification of pregnancies at increased risk for trisomy 21

OBJECTIVE

Our purpose was to evaluate the value of the combination of femur and humerus length measurements in ultrasonographic screening for trisomy 21.

STUDY DESIGN

Direct necropsy measurements were analyzed on 703 midgestational fetuses (641 normal, 62 with trisomy 21). The (leg+arm length)/foot length ratio was found to be significantly shortened for fetuses with trisomy 21. On the basis of necropsy data 576 midgestational pregnancies were evaluated ultrasonographically for (femur+humerus length)/foot length ratio to identify fetuses at increased risk for trisomy 21.

RESULTS

An ultrasonographic (femur+humerus length)/foot length ratio < or = 1.75 gave a 15.3 odds ratio risk for trisomy 21 in our high-risk population and correctly identified 53% of fetuses with trisomy 21, with a false-positive rate of 7%. In addition, the use of this ratio eliminates the need for gestational age-corrected nomograms and complicated calculations in ultrasonographic screening.

CONCLUSION

The (femur+humerus length)/foot length ratio may be an additional effective ultrasonographic marker for identification of fetuses at increased risk for trisomy 21.

Amniotic fluid erythropoietin levels in normal and Down's syndrome pregnancies

The aim of this study was to measure the levels of erythropoietin in amniotic fluid from normal and trisomy 21 pregnancies at 10 to 20 weeks gestation. Samples of amniotic fluid were collected from 142 women with singleton pregnancies after genetic amniocentesis; 110 had a normal fetal karyotype and 32 had trisomy 21. Erythropoietin was measured using a double antibody radioimmunoassay. Amniotic fluid erythropoietin levels in normal pregnancies increased from 10 weeks (mean 3.2 mU/ml; range < 2.0-6.3 mU/ml) to 20 weeks gestation (mean 7.9 mU/ml; range 2.0-11.5 mU/ml). There was a significant linear correlation between gestational age and erythropoietin levels (r = 0.543; P < 0.0001). For the 32 patients with trisomy 21 pregnancies the median multiple of the median (MoM) was 1.11 (range 0.42-2.1). There was no difference between erythropoietin levels in amniotic fluid from normal and Down's syndrome pregnancies (U = 2352, P = 0.75, 95% CI = -0.11, 0.18); (Mann-Whitney U-test).