Imperforate anus: A relatively common anomaly rarely diagnosed prenatally

Prenatal Ultrasound in the Diagnosis of Anorectal Malformations: Correlating Prenatal Signs With Postnatal Outcomes

OBJECTIVE

This study explored prenatal ultrasound markers in patients with anorectal malformations (ARMs).

METHODS

All patients treated for ARM in our institution from January 2014 to December 2021 with an available expert fetal anomaly scan (eFAS) were reviewed. The eFAS images were assessed to evaluate the fetal anus, specifically by identifying hyperechoic anal mucosa surrounded by hypoechoic anal sphincter, referred to as "target sign" (TS). Furthermore, indirect signs of ARM were assessed and correlated with postnatal clinical symptoms.

RESULTS

Of the 115 patients treated for ARM, 32 mothers underwent eFAS. TS was assessed in 22 fetuses, of which 17 (77.3%) had an absent or abnormal TS. Of the patients with a postnatally confirmed complex type of ARM, 90% had an absent or abnormal TS. One or more indirect signs of ARM were found in 16 out of 32 fetuses (50.0%), comprising echogenic bowel (n = 3), echogenic meconium (n = 2), dilated intestines (n = 7), echo-lucent cavity behind the urinary bladder (n = 4), abnormal external genitalia (n = 6), and polyhydramnios (n = 5).

CONCLUSION

This retrospective cohort study provides valuable insights into the potential role of TS assessment and indirect signs in the prenatal diagnosis of ARM. Future studies should further validate our findings and elicit whether TS assessment should be incorporated into prenatal screening protocols.

Infracoccygeal/transperineal window: new method to prenatally diagnose and classify level of anal atresia

OBJECTIVES

To introduce a two-dimensional sonographic method to assess the fetal anus, and to evaluate the feasibility of this method to diagnose anal atresia prenatally and identify the presence or absence of anoperineal fistula (in males) and anovestibular fistula (in females).

METHODS

This was an observational study of suspected cases of anal atresia referred to a single center in Israel between August 2018 and October 2023. In addition to conventional evaluation of the perineum in the axial plane, fetuses referred to our center for suspected malformation were scanned with a new method termed the 'infracoccygeal/transperineal window'. This window consisted of a midsagittal view of the fetal pelvis, including the distal rectum and the anal canal. Normal anatomy was confirmed when the anal canal was continuous with the rectum and terminated at the expected location on the perineum. In female fetuses, the normal anal canal runs parallel to the vaginal canal and diverges posteriorly, terminating at the perineal skin, distant from the vestibule. In male fetuses, the normal anal canal diverges posteriorly in relation to the corpora cavernosa, terminating at the perineal skin, distant from the scrotum. High anal atresia was identified when a blind-ending rectal pouch was demonstrated in the pelvis without a fistula to the perineum or vestibule. Low anal atresia was determined when a rectal pouch was continuous with an anteriorly deflected fistula. In females, the fistula converges with the vaginal canal, terminating at the vestibule; in males, the fistula deflects anteriorly, terminating at the base of the scrotum. Postnatally, the diagnosis and type of anal atresia were confirmed through physical examination with direct visualization of the fistula, radiographic studies, surgical examination and/or postmortem autopsy.

RESULTS

Of the 16 fetuses diagnosed prenatally with anal atresia, eight were suspected to have low anal atresia and eight were suspected to have high anal atresia. The median gestational age at diagnosis was 23 (range, 14-37) weeks. All cases showed additional structural malformation. Eleven patients opted for termination of pregnancy, of which four had low anal atresia and seven had high anal atresia. Postnatal confirmation was not available in four cases due to curettage-induced mutilation or in-utero degradation following selective termination of the affected twin, leaving 12 cases for analysis, of which seven were diagnosed with low anal atresia and five with high anal atresia. In these 12 cases, all prenatal diagnoses were confirmed as correct, rendering 100% sensitivity and 100% specificity in this high-risk fetal population.

CONCLUSIONS

The infracoccygeal/transperineal window is an effective method to detect and classify the level of anal atresia prenatally. This may improve prediction of postnatal fetal continence and optimize prenatal counseling. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

New ultrasound features in diagnosing fetal anal atresia: a multicenter prospective cohort study

This research aimed to assess the validity of ultrasound scans with new features in detecting fetal anal atresia and verify the effectiveness of these new features. Additionally, we aimed at investigating the perinatal incidence of anal atresia. This multicenter prospective study recruited 94,617 normal gravidas and 84 gravidas with anal atresia fetuses. The gold standard for diagnosing perinatal anal atresia is routine neonatal anus examinations. The incidence calculation was based on the results of the gold standard. The validity of our new approach was evaluated via a diagnostic test involving all 94,701 subjects. The effectiveness of our new features was assessed through an ablation study in a randomly established new dataset, with the ratio of anal atresia to non-anal atresia cases of 1:4. The annual perinatal incidence of anal atresia between 2019 and 2023 ranges from 0.57‰ to 1.29‰. Our new method performed great regarding the Youden index, diagnostic odds ratio (DOR), area under the curve (AUC) of the receiver operating characteristic curve (ROCC), AUC of the precision-recall curve (PRC), F1-score, and Cramer's V. In the ablation study, our new approach surpassed its competitors concerning Youden index, DOR, AUC of the ROCC, and AUC of the PRC. Ultrasound scans show high validity and clinical value in detecting fetal anal atresia. Our new ultrasound features significantly promote the detection of fetal anal atresia.

Population-based surveillance of congenital anomalies over 40 years (1981-2020): Results from the Paris Registry of Congenital Malformations (remaPAR)

INTRODUCTION

Registries of congenital anomalies (CAs) play a key role in the epidemiological surveillance of CAs. The objective was to estimate the prevalence of CAs and proportions of prenatal diagnosis, terminations of pregnancy for fetal anomaly (TOPFA) and infant mortality in the Paris Registry of Congenital Malformations (remaPAR) over 40 years, from 1981 to 2020.

MATERIAL AND METHODS

remaPAR records all births (live births, stillbirths ≥22 weeks of gestation and TOPFA at any gestational age) with CAs detected prenatally until the early neonatal period. We estimated the prevalence of CAs and proportions of prenatal diagnosis, TOPFA and infant mortality, overall and for a selected group of CAs in 3-year intervals.

RESULTS

The prevalence of CAs remained stable during the study period: 2.9 % of total births and 2.1 % of live births. Genetic anomalies were the most frequent subgroup (about 23 %), followed by congenital heart defects (about 22 %) and limb defects (about 20 %). Among non-genetic anomalies, the prevalence per 10,000 births was the highest for hypospadias (about 18 %) and the lowest for bilateral renal agenesis (about 1 %). Prenatal diagnoses increased from about 17 % in the 1980s to approximately 70 % in the most recent period (2018-2020), whereas the proportion of early TOPFA <16 weeks of gestation increased from 0.4 % to 14 %. Infant mortality ranged from 0 % for transverse limb reduction defects to 86 % for hypoplastic left heart syndrome.

CONCLUSION

The overall prevalence of CAs was fairly stable in Paris from 1981 to 2020. Prenatal diagnoses substantially increased, accompanied by much smaller increases in TOPFA.

A practical method for prenatal diagnosis of anal atresia by second trimester ultrasound screening - A retrospective study

OBJECTIVES

The study aimed to demonstrate the performance of anal atresia ultrasound screening in the second trimester and to describe associated experiences in a primary care fetal medicine clinic.

MATERIALS AND METHODS

We retrospectively analyzed the medical records of fetuses who underwent a second-trimester screening at the Taiji clinic between November 2019 and May 2022. Fisher's exact test was conducted to investigate potential risk factors.

RESULTS

There were 28 459 fetuses screened in our clinic during the study period; eventually, 6 cases were diagnosed with anal atresia after birth. The incidence of anal atresia in our sample was 2.11 in 10 000. Based on our findings, potential risk factors significantly associated with anal atresia included: multiple pregnancies (p-value = 0.0185) and in-vitro fertilization (p-value = 0.038). Half of the anal atresia cases were associated with abnormalities affecting other organ systems, most frequently the genitourinary system (66.7%) and cardiovascular system (66.7%), especially persistent left superior vena cava (2 cases).

CONCLUSION

Anal atresia is a malformation that requires extensive care; the clinical management after the prenatal discovery of its signs should include testing for chromosomal abnormalities and close monitoring of the amniotic fluid volume. Therefore, prenatal ultrasound screening for anal atresia in the second trimester is critical, particularly in the cases of multiple and IVF pregnancies, and multiple abnormalities. The fetuses with ultrasound signs of anal atresia should be followed at a later gestational period and referred to a specialized institution for postnatal management planning and parental counseling.

Prevalence and mortality among children with anorectal malformation: A multi-country analysis

PURPOSE

We examined the total prevalence, trends in prevalence, and age-specific mortality among individuals with anorectal malformation (ARM) METHODS: We conducted a retrospective cohort study using data from 24 population- and hospital-based birth defects surveillance programs affiliated with the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) from 18 countries and for births from 1974 to 2014. We estimated pooled and program-specific total prevalence per 10,000 total births. Poisson regression was used to assess time trends in prevalence from 2001 to 2012 when most programs contributed data. We calculated selected age-specific proportions of deaths, stratified by case status RESULTS: The pooled total prevalence of ARM was 3.26 per 10,000 total births (95% Confidence Interval = 3.19, 3.32) for birth years 1974-2014. About 60% of cases were multiple or syndromic. Prevalence of multiple, syndromic, and stillborn cases decreased from 2001 to 2012. The first week mortality proportion was 12.5%, 3.2%, 28.3%, and 18.2% among all, isolated, multiple, and syndromic cases, respectively CONCLUSIONS: ARM is relatively rare, with multiple and syndromic cases showing decreasing prevalence during the study period. Mortality is a concern during the first week of life, and especially among multiple and syndromic cases. Our descriptive epidemiological findings increase our understanding of geographic variation in the prevalence of ARM and can be used to plan needed clinical services. Exploring factors influencing prevalence and mortality among individuals with ARM could inform future studies.

A Spectrum of Ultrasound and MR Imaging of Fetal Gastrointestinal Abnormalities: Part 2 Anorectal Malformation, Liver, and Abdominal Wall Anomalies

Ultrasound (US) and magnetic resonance imaging (MRI) are two modalities for diagnosing fetal gastrointestinal (GI) anomalies. Ultrasound (US) is the modality of choice. MRI can be used as a complementary method. Despite its expanding utilization in central nervous system (CNS) fetal malformation, MRI has not yet been established for evaluation of fetal GI abnormalities. Therefore, more attention should be paid to the clinical implications of MRI investigations following screening by US.

Avoiding the antenatal counselling faux pas: bridging the gap between prenatal prognostication and postnatal outcome of closed spina bifida

PURPOSE

Closed spina bifida (CSB) is rare in prenatal literature, and various lesions are grouped under this broad nosological entity CSB, leading to confusing and misleading prognostic conclusions.

METHODS

This is a retrospective observational cohort study of prenatally detected CSB cases using two-dimensional ultrasound, complemented by three-dimensional ultrasonography and foetal MRI in indicated cases, from October 2014 to October 2021 in a tertiary-level single centre.

RESULTS

The most common upper vertebral level of CSB was lumbar in 66.6% (10/15). The sub-classification of lesions based on prenatal ultrasound showed an agreement in 53% of the cases. Sixty percent had associated abnormalities identified postnatally, the most common being anorectal malformation seen in 33.3%. On postnatal follow-up, 46.6% had bowel incontinence and bladder dysfunction, and 33.3% developed lower limb deformities.

CONCLUSIONS

All CSBs do not have a uniformly favourable prognosis. The prognosis of CSB depends on the pathological type, the presence of associated abnormalities and the management.

Significance of the 'line sign' in the diagnosis of congenital imperforate anus on prenatal ultrasound

Background

The prenatal diagnosis of foetal imperforate anus is difficult. Most previous studies have been case reports. To provide useful information for diagnosing foetal imperforate anus, a retrospective review of diagnostic approaches was conducted. Ultrasonography was performed in 19 cases of foetal imperforate anus from 2016 to 2019 at our prenatal diagnostic centre. The prenatal sonographic features and outcomes of each case were collected and evaluated.

Result

The anal sphincter of a normal foetus shows the ‘target sign’ on cross-sectional observation. Of the 19 cases of imperforate anus, 16 cases were diagnosed by the ultrasound image feature called the ‘line sign’. 1 case with tail degeneration was low type imperforate anus with the irregular ‘target sign’ not a real ‘target sign’. There was two false-negative case, in which the ‘target sign’ was found, but irregular.

Conclusion

In this study, we find that the anus of a foetus with imperforate anus presents a ‘line sign’ on sonographic observation. The absence of the ‘target sign’ and then the presence of the ‘line sign’ can assist in the diagnosis of imperforate anus. The ‘line sign’ can be used as a secondary assessment to determine the type of the malformation following non visualization of the ‘target sign’. The higher the position of the imperforate anus is, the more obvious the ‘line sign’. It is worth noting that the finding of the short ‘line sign’ and irregularr ‘target sign’ can not ignore the low type imperforate anus.

A Fetus with Imperforate Anus Developing Pulmonary Hypoplasia Triggered by Transient Urethral Obstruction

Pulmonary hypoplasia is a rare entity in a fetus with imperforate anus. The fetus was diagnosed with high-type imperforate anus with rectourethral fistula based on the dilated fetal bowel and the presence of bowel calcification at 19 weeks of gestation. As gestation advanced, fetal ultrasonography demonstrated development of pulmonary hypoplasia, progressive bowel dilation, and persistent oligohydramnios from 28 weeks of gestation despite a fluid-filled bladder without hydroureter or hydronephrosis. To prevent further worsening of pulmonary hypoplasia caused by thoracic compression due to bowel dilation and oligohydramnios, a male neonate was delivered by cesarean section at 32 weeks of gestation. The neonate showed respiratory failure requiring full respiratory support. Although a catheter did not pass through the urethra into the bladder at birth, cystourethrography revealed the patency of fistula and stenosed lower urinary tract. Prenatal and postnatal findings strongly suggested that the meconium in the colon might have passed into the urethra in the penis, resulting in the physical blockage of urine outflow to the amniotic space which leads urine flow from the bladder to the colon through the fistula, which resulted in subsequent oligohydramnios and bowel dilation. To the best of our knowledge, this is the first case report of a fetus with imperforate anus developing pulmonary hypoplasia possibly due to urethral obstruction.

Ultrasound screening for fetal anomalies in a single center: diagnostic performances twenty years after the Eurofetus Study

PURPOSE

To establish the accuracy of ultrasound in detecting fetal anomalies looking at the concordance between prenatal and postnatal diagnosis.

MATERIALS AND METHODS

Retrospective analysis of concordance between prenatal and postnatal/autoptic diagnosis of fetuses with congenital abnormalities. Data are from a single center (Policlinico di Modena); all fetuses included were born between 2017 and 2018 and with a follow-up of at least 6 months. We included all deliveries (including perinatal deaths) and termination of pregnancy (TOP) for fetal indication. We calculated sensibility, sensitivity, Positive and Negative Likelihood Ratio, positive and negative predictive value of ultrasound.

RESULTS

During the study period 5920 deliveries, including perinatal deaths, and 28 TOP for fetal indication were registered at our center. The prevalence of congenital malformations was 2.6% (153/5920). At least one ultrasound was performed in our center in 1250 women delivering in our unit. All 28 TOP had the anomaly scan performed in our center. Among the total 1278 women scanned in our unit, there were 128 (10%) suspicious scans. In 5/128 (3.9%) cases we diagnosed a false alarm; in 8/128 (6.2%) cases an evolutive malformation with in-utero regression. The prenatal diagnosis was confirmed in 77 (60.2%) cases at birth and in 28/128 (21.9%) at postmortem analysis while there were 10/128 false positive (7.8%). Among the 153 congenital malformations diagnosed at birth, the anomaly scan was performed in our Prenatal Medicine Unit in 92 (60.1%) fetuses. Among these, there were 15 false negatives (9.8%) while in 77/92 (83.7%) the malformation at birth agreed with the sonographic diagnosis. Sensitivity and specificity of ultrasound were 87.5% (IC95 80.2-92.8%) and 99.1% (IC95 98.4-99.6%) respectively with a Positive Likelihood Ratio and Negative Likelihood Ratio of 101.3 (IC95 54.5-188.5) and 0.13 (IC95 0.08-0.2); Positive Predictive Value and Negative Predictive Value were 91.3% (IC95 85-95.1%) and 98.7(IC95 98-99.2%).

CONCLUSION

Anomaly scan in pregnancy allows the diagnosis of congenital malformations with a sensibility of 87.5% and specificity of 99.1%. The main limitations of this study are its retrospective design and that it was conducted in a single referral center.

Visualization of the fetal anus by prenatal ultrasound for the diagnosis of anorectal malformations: is it feasible?

PURPOSE

The goal of this study was to determine the feasibility of identifying the anal dimple (AD) on routine prenatal ultrasound. Using the presence, absence, appearance, and location of the anal dimple as an indirect sign for possible underlying anorectal malformations (ARM), we hypothesize that evaluation of the anal dimple as part of the fetal anatomic survey may increase the sensitivity in detecting less severe ARMs.

METHODS

In a prospective longitudinal observational study, pregnant women who underwent prenatal ultrasound (US) at the Colorado Fetal Care Center between January 2019 and 2020 were enrolled. The variables recorded included gestational age, singleton versus multiple pregnancy, gender of the fetus, visualization of the AD, and reason for non-visualization of the AD.

RESULTS

A total of 900 ultrasounds were performed, evaluating 1044 fetuses, in 372 different pregnant women. Gestational ages ranged from 16 to 38 weeks. The AD was visualized in 612 fetuses (58.6%) and not seen in 432 (41.4%). The two most common reasons for non-visualization were extremes in gestational age (n = 155; 36%) and fetal position (n = 152; 35.3%). The optimal gestational age range for AD visualization was 28-33 weeks + 6 days, with 78.1% visualization rate.

CONCLUSION

Visualization of the anal dimple by ultrasound is feasible and may aid in the detection of less severe ARMs, ultimately impacting pregnancy management and family counseling. The optimal timing for anal dimple visualization is late second and third trimester.

Can Anorectal Atresia Be Diagnosed in the First Trimester of Pregnancy? A Systematic Literature Review

Anorectal atresia (ARA) is a common congenital anomaly, but prenatal diagnosis is difficult, late, and unspecific. Utilizing a case of a 46 year old primipara with an egg donation In Vitro Fertilization (IVF) pregnancy, diagnosed at the first trimester scan with an anechoic isolated structure, which indicates anal atresia, we performed a systematic literature review in order to evaluate early prenatal ARA diagnosis. A total of 16 cases were reported as first trimester ARA suspicion, and only three had no associated anomalies. The most frequent ultrasound (US) sign was the presence of a cystic, anechoic pelvic structure of mainly tubular shape, or a plain abdominal cyst. In the majority of cases, structures were thin-walled and delimitated from the bladder. The presence of hyperechoic spots signifying enterolithiasis and peristaltic movements were helpful in order to establish the bowel origin of the lesion. Considering the high eventuality that the lesion is transitory, meaning later in pregnancy the fetus looks normal, early detection of such a sign should prompt further structural detailed evaluation, karyotyping, and appropriate pregnancy and postnatal counselling.

The diagnosis of an imperforate anus in female fetuses

Imperforate anus is an anomaly caused by a defect in the development of the hindgut during early pregnancy. It is a relatively common congenital malformation and is more common in males. Although there are cases of a solitary imperforate anus, the condition is more commonly found as a part of a wider spectrum of other congenital anomalies. Although urgent reconstructive anorectal surgery is not necessary, immediate evaluation is important and urgent decompressive surgery may be required. Moreover, as there are often other anomalies that can affect management, prenatal diagnosis can help in optimizing perinatal care and prepare parents through prenatal counseling. In the past, imperforate anus was diagnosed by prenatal ultrasonography based on indirect signs such as bowel dilatation or intraluminal calcified meconium. Currently, it is diagnosed by directly checking the perineum with prenatal ultrasonography. Despite advances in ultrasound technology, accurate prenatal diagnosis is impossible in most cases and imperforate anus is detected after birth. Here, we present two cases of imperforate anus in female fetuses that were not diagnosed prenatally.

Imaging of anorectal malformations in utero

PURPOSE

To document the imaging findings suggestive of anorectal malformation (ARMs) on prenatal US and MRI.

METHODS

Retrospective evaluation of the screening US and prenatal MRI exams of the rectum and ano-perineal region in normal fetuses and in patients with ARMs.

RESULTS

Examples showing the normal rectal and anoperineal anatomy on prenatal US and MRI exams and the imaging findings observed in different types of confirmed ARMS.

CONCLUSIONS

Prenatal diagnosis of ARMs requires both a systematic evaluation of the fetal pelvis and perineum and an appropriate knowledge of its suggestive imaging findings.

Prenatal imaging of anorectal malformations - 10-year experience at a tertiary center in Switzerland

BACKGROUND

Anorectal malformation is a spectrum of congenital defects of the distal bowel, mostly diagnosed at birth.

OBJECTIVE

To describe the prenatal imaging findings of anorectal malformations, explore the causes of the low rates of prenatal diagnosis, compare the accuracy of prenatal ultrasound (US) and magnetic resonnance imaging [MRI] and evaluate the relevance of information obtained at MRI.

MATERIALS AND METHODS

Children treated for anorectal malformation at our hospital and with available prenatal studies were retrospectively identified and included in the study. We reviewed prenatal imaging exams, listed findings suggestive of the diagnosis, and compared results with the final classification.

RESULTS

Fourteen fetuses and neonates - eight with intermediate-high type anorectal malformation and six with cloacae - fulfilled the inclusion criteria. All had associated congenital anomalies. Prenatal exams included 13 US and 8 MRI exams, with 7 children having both exams. Suggestive findings for anorectal malformation were detected in 50% of the cases prenatally and in 85% upon review. They were prospectively detected in 31% and 50% of the cases at US and MRI and retrospectively in 62% and 100% at US and MRI, respectively. MRI was superior to US because it improved the diagnosis, especially in cloacae, and provided relevant additional information that changed management in two cases.

CONCLUSION

The most important signs suggesting anorectal malformation are an absent target sign and anomalous distal bowel wall and rectal fluid. Complementary prenatal MRI improves the diagnosis of anorectal malformation.

Prenatal Dilated Rectum: Do We Need to Worry?

BACKGROUND

Advances in prenatal imaging is increasing detection of abnormally dilated bowel. There is no literature to date defining the criteria for a dilated rectum or its association with postnatal pathology. The aim of this study is to investigate the clinical significance of a prenatally identified dilated rectum.

METHODS

A retrospective review was performed of all cases of "dilated bowel" on prenatal ultrasound between January 2000 and December 2017 at a single institution. We excluded ventral wall defects from review and sought to include only cases of a prominent or dilated rectum. Collected data included prenatal bowel measurements, postnatal diagnoses, need for surgical intervention, and outcomes. Descriptive statistics were applied.

RESULTS

One hundred and ninety-three cases of prenatal "dilated bowel" were identified in which 12 (6.2%) had specifically visualized a prominent or dilated rectum. Nine of these (75.0%) had no rectal or intestinal abnormality on postnatal evaluation and were discharged feeding and defecating normally. The remaining three cases exhibited clinical pathology necessitating additional management: (1) meconium plug, (2) jejunal atresia with cecal perforation, and (3) rectal perforation with retroperitoneal abscess. All three had rectal biopsies with identification of ganglionated submucosa.

CONCLUSIONS

Although a prenatal dilated rectum is a normal variant in the vast majority of cases, it may be associated with a gastrointestinal abnormality requiring surgical intervention. Interestingly, there were no cases of Hirschsprung's disease or anorectal malformations in this cohort. These results, in conjunction with continued efforts to identify and define rectal dilation, are useful for prenatal counseling and postnatal evaluation.

Prenatal Evaluation for Detection of Anorectal Atresia: Value of Ultrasound

OBJECTIVES

To investigate the applicability and value of ultrasound (US) in the diagnosis of anorectal atresia.

METHODS

Between January 2008 and January 2016, we prospectively evaluated 63,101 fetuses (gestational age, 20-38 weeks), including low- and high-risk populations using 2-dimensional US scans. An abnormal imaging finding was defined as an anal canal diameter of less than the 95% confidence interval (small anal canal) of the normal range or the absence of an anal canal and rectum. Imaging findings were considered normal on detection of an anal canal with a normal width and the absence of abnormalities. Prenatal imaging findings were confirmed by a postnatal or postmortem examination.

RESULTS

Among the investigated fetuses, 28 showed evidence of anorectal atresia on US scans, and 22 of those with anorectal atresia had additional anomalies. Six cases of isolated anorectal atresia were successfully detected during the preclusive prenatal US scans. Four cases of a low imperforate anus (including 2 covered anuses) yielded false-negative results, indicating a diagnostic rate of 87.5% (28 of 32). The normal appearance of the fetal rectum and anal canal ruled out anorectal atresia in 30 fetuses with a dilated colon. Additionally, there were 3 false-positive cases, in which a narrow anal canal was observed.

CONCLUSIONS

Identifying the abnormal appearance or absence of the fetal anal canal and rectum on preclusive US anomaly scans is useful for prenatal diagnosis or exclusion of anorectal atresia, which may help improve the detection of isolated anorectal atresia. Furthermore, a combined evaluation of the longitudinal and axial appearances of the fetal anal canal and rectum can improve diagnostic accuracy.

Isolated Fetal Cardiac Abnormalities: Are They Really Isolated?

Objective  To determine the rate of unsuspected noncardiac abnormalities in newborns suspected to have isolated cardiac abnormalities in the second trimester. Study Design  A review of the ultrasound database from the Weill Cornell Medical Center identified fetuses with a suspected cardiac abnormality from January 2006 to November 2016. Cases with prenatally suspected noncardiac structural abnormalities, abnormal fetal or neonatal karyotype or microarray, and those who delivered at an outside institution or underwent abortion were excluded. Neonatal records were reviewed to confirm prenatal findings and to identify anomalies not suspected in the second trimester. Results  Sixty-eight live births met the inclusion criteria. Five newborns (7.4%) had major abnormalities not identified in the second trimester. Three newborns had an imperforate anus. One newborn had left hydronephrosis and absent right lung, and one had hemifacial microsomia and fused ribs. All five newborns with unsuspected anomalies were in the group with suspected conotruncal anomalies, with a 11.9% rate of unsuspected anomalies versus 0% in those with nonconotruncal cardiac anomalies ( p  = 0.15). Conclusion  Patients with a suspected isolated fetal cardiac anomaly on ultrasound should be aware of the possibility of other major structural abnormalities, especially in cases of conotruncal cardiac anomalies.

How to Explore Fetal Sacral Agenesis Without Open Dysraphism: Key Prenatal Imaging and Clinical Implications

The estimated prevalence of fetal caudal dysgenesis is 1 per 100,000 births. The functional prognosis of sacral agenesis is dominated by the large spectrum of associated caudal malformations. Except for cases associated with hydrocephalus secondary to open spinal dysraphism or chromosomal anomalies, association with mental deficiency is rare. We propose a systematic prenatal approach to cases of fetal sacral agenesis based on 9 etiologic items: clinical context, type of sacral dysgenesis, associated spinal cord malformations, mobility of lower limbs, investigation of the presacral region, analysis of the gastrointestinal tract, analysis of the genitourinary tract, associated vertebral defects, and cytogenetic analysis.

Severe caudal regression syndrome with overlapping features of VACTERL complex: antenatal detection and follow up

Caudal regression is a rare syndrome with a spectrum of structural defects involving multiple organ systems. Spinal anomalies, a charecteristic feature of the entity, can vary from isolated partial agenesis of the coccyx to lumbosacral agenesis with involvement of the thoracic spine in the most severe cases. The aetiology of this syndrome is not well-known. Maternal diabetes, genetic predisposition and vascular hypoperfusion have been suggested as possible causative factors. Severe forms of the disease are commonly associated with cardiac, renal and respiratory problems with overlapping feature of VACTERL complex (vertebral, anorectal, cardiac, tracheoesophageal, renal and limb anomalies). In this case report, we describe imaging appearances of severe caudal regression syndrome, VACTERL complex associated with multisystem anomalies, detected on a screening antenatal scan during second trimester. Some unusual features of the syndrome including sternal anomaly and absent bony hemithorax are highlighted.

Prenatal diagnosis and outcome of fetal gastrointestinal obstruction

INTRODUCTION

The purpose of this study was to evaluate the accuracy of prenatal diagnosis for fetuses with gastrointestinal (GI) obstruction with correlation to postnatal outcomes.

METHODS

Fetuses diagnosed with GI obstruction (excluding esophageal and duodenal) were reviewed for those evaluated between 2006 and 2016. Prenatal diagnosis and imaging studies were compared to postnatal findings. Outcomes evaluated included diagnostic accuracy, rate of other anomalies, neonatal length of stay, incidence of short bowel syndrome, and discharge with TPN or gastrostomy.

RESULTS

Forty-eight patients were diagnosed prenatally with obstruction. Six patients were excluded owing to incomplete records and follow-up. Twelve fetuses were diagnosed with ultrasound alone, and thirty-four with ultrasound and MRI. A diagnosis of obstruction was accurate in 88.1% (n=37/42) with a positive predictive value of 91.3%, while US with MRI had an accuracy of 84.4%. Associated anomalies were highest among fetuses with anorectal obstruction (90.1%), compared to large (50%) or small bowel obstruction (28%). Survival rate was lowest for anorectal obstruction (54.5%), compared to large or small bowel obstruction (100% for both).

CONCLUSION

Fetal MRI is an accurate modality in the diagnosis of fetal GI obstruction and can complement findings characterized by ultrasound. Fetuses with anorectal obstruction have a higher rate of associated anomalies and the lowest survival.

LEVEL OF EVIDENCE

IIb.

Transient Distention of Right Posterior Located Sigma, a New Sonographic Sign for the Prenatal Diagnosis of Anal Atresia

We describe a new sonographic sign for the detection of anal atresia in the early midtrimester on transvaginal sonography. In six cases of fetal anal atresia, the finding of a transient, distended, and right-sided sigmoid colon was observed at 13-16 weeks' gestation. Three cases have undergone pregnancy termination due to multiple anomalies. In the other three, the colonic distension resolved by 19 weeks' gestation. In two of these, the finding was isolated, and no other anomalies were detected. In all six cases, anal atresia or cloaca was confirmed on postabortal autopsy or after delivery. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:160-162, 2017.

Neonate With Imperforate Anus and Meconium Streak Along the Penile Shaft

We present a neonatal male with a rectopenile fistula in the setting of imperforate anus. Reported cases of fistulae exiting on the penile shaft are exceedingly rare. The patient had a diverting colostomy performed within the first 48 hours of life and imaging later revealed no communication with the urinary tract. At 4 months of age the child was brought to the operative suite for penile exploration and posterior sagittal anorectoplasty. The patient's colostomy was reversed 4 months later. We discuss the embryology and management of imperforate anus as well as literature review.

Unilateral Fetal Renal Abnormalities: Are They Really Isolated?

OBJECTIVES

Our objective was to describe the association between unilateral fetal renal abnormalities and other major anomalies that were not apparent in the second trimester.

METHODS

A review of the ultrasound database identified fetuses with suspected unilateral renal agenesis, unilateral multicystic dysplastic kidney, and renal ectopia from 2005 to 2014. Neonatal records were reviewed to identify anomalies not suspected in the second trimester, and postnatal imaging studies were reviewed. Categorical data were compared by &x003C7;(2) analysis and the Fisher exact test.

RESULTS

We identified 102 cases, including 36 with suspected renal agenesis, 28 with suspected multicystic dysplastic kidney, and 38 with suspected renal ectopia. There were 8 cases (7.8%) with major anomalies not suspected in the second trimester. In 5 cases (4.9%), there were no associated findings in the second trimester. There were no significant differences in the rates of unsuspected abnormalities between the 3 groups. There was a trend toward a higher rate of unsuspected anomalies in the cases with a single umbilical artery compared to those with a 3-vessel cord (28.6% vs 6.3%; P= .09).

CONCLUSIONS

In fetuses with unilateral renal abnormalities, major anomalies that were not suspected in the second trimester were uncommon. However, patients should be aware of the possibility that other major anomalies could subsequently be identified, and the outcome may depend on more than postnatal renal function.

Parental subfertility, fertility treatment, and the risk of congenital anorectal malformations

BACKGROUND

Fertility treatment seems to play a role in the etiology of congenital anorectal malformations, but it is unclear whether the underlying parental subfertility, ovulation induction, or the treatment itself is involved. Therefore, we investigated the odds of anorectal malformations among children of subfertile parents who conceived with or without treatment compared with fertile parents.

METHODS

We performed a case-control study among 380 cases with anorectal malformations treated at 3 departments of pediatric surgery in The Netherlands and 1973 population-based controls born between August 1988 and August 2012. Parental questionnaires were used to obtain information on fertility-related issues and potential confounders.

RESULTS

In singletons, increased risks of anorectal malformations were observed for parents who underwent intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF) treatment compared with fertile parents (odds ratio = 2.4 [95% confidence interval = 1.0-5.9] and 4.2 [1.9-8.9], respectively). For subfertile parents who conceived after IVF treatment, an elevated risk was also found when they were compared with subfertile parents who conceived without treatment (3.2 [1.4-7.2]). Among children of the latter category of parents, only the risk of anorectal malformations with other major congenital malformations was increased compared with fertile parents (2.0 [1.3-3.3]). No associations were found with intrauterine insemination or use of hormones for ovulation induction.

CONCLUSIONS

We found evidence of a role of ICSI and IVF treatments in the etiology of anorectal malformations. However, subfertility without treatment increased only the risk of anorectal malformations with additional congenital malformations.

Genetic and nongenetic etiology of nonsyndromic anorectal malformations: a systematic review

Congenital anorectal malformations (ARMs) are one of the most frequently observed birth defects of the digestive system. However, their etiology remains elusive. Therefore, we aim to summarize and critically appraise all existing literature on the genetic and nongenetic etiology of nonsyndromic ARM and to conclude with unifying hypotheses and directions for future research. A structured literature search on English language human studies was conducted in PubMed and Embase up to October 1, 2013, resulting in 112 included articles. Research on the identification of genes underlying nonsyndromic ARM is remarkably scarce. Most studies were focused on screening of candidate genes for mutations or single-nucleotide polymorphisms, which did not yield any substantial evidence. Nongenetic factors fairly consistently found to be associated with ARM are assisted reproductive techniques, multiple pregnancy, preterm delivery, low birth weight, maternal overweight or obesity, and preexisting diabetes. This review provides indications for the involvement of both genes and nongenetic risk factors in the etiology of ARM. In future studies, large cohorts of patients with ARM from national and international collaborations are needed to acquire new hypotheses and knowledge through hypothesis-generating approaches. Challenges for future studies may also lie in the investigation of gene-gene and gene-environment interactions.

Evaluation of the development of the fetal anal sphincter with tomography ultrasonography imaging

The aim of the study described here was to examine the potential of tomography ultrasonography imaging (TUI) in evaluation of the fetal anal sphincter. In this prospective cross-sectional study of the fetal anal sphincter with TUI, 326 singleton pregnancies (mean age = 28 y, range: 22-38 y) were scanned at 19-40 wk of gestation. The fetal anal region and ischium were revealed in 320 of 326 patients (98.2%). The normal fetal anal sphincter diameter and ischial space reached maximums of 15 and 39 mm, respectively. The normal fetal anal sphincter diameter and the ischial space were plotted as a function of gestational age (GA) on a linear curve, and the regression equations for normal fetal anal sphincter diameter and ischial space as a function of GA in weeks were obtained. A scatterplot was also created that revealed a significant positive relationship between normal fetal anal sphincter diameter and ischial space. On the basis of these criteria, imperforate anus was diagnosed in one fetus. Ultrasonographic assessment of the fetal anal sphincter and the ischium with TUI is feasible. The reference values reported in this article may be useful in prenatal diagnosis of fetal anal sphincter abnormalities.

[Anorectal malformations]

Anorectal malformations (ARM) are the result of an abnormal development of the terminal part of the digestive tract interesting anus and/or rectum that occur early between the sixth and tenth week of embryonic development. They carry a malformation spectrum of severity depending on the level of disruption of the anorectal canal and of the associated caudal malformations (sacrum and spine). ARM are associated in over half the cases with other malformations that can be integrated in some cases in known syndromes. If surgical treatment to restore anatomy as normal as possible is indispensable, post-operative care is essential for these patients whose defecation mechanisms are altered, to reach if not continence, at least a socially acceptable cleanliness.

Evaluation of the perianal muscular complex in the prenatal diagnosis of anorectal atresia in a high-risk population

OBJECTIVES

To investigate whether sonographic identification of the fetal perianal muscular complex (PAMC) is of value in the prenatal detection of anorectal atresia in a high-risk population.

METHODS

During an 8-year study period, a total of 189 pregnancies at high risk for fetal anorectal atresia were prospectively examined for the presence/absence of the PAMC on axial ultrasound views of the fetal perineum. The prenatal findings were confirmed postnatally or at the time of postmortem examination.

RESULTS

The median gestational age at examination was 27 (range, 15-37) weeks. The PAMC was identified in 175 fetuses, all of which had a normal anorectal canal at the time of delivery or at postmortem examination. The PAMC was not identified prenatally in the 14 remaining cases, and the anus was absent in 11 fetuses with anorectal atresia and in two with urorectal septum malformation sequence. There was one false-positive case, in which the anus was anatomically and functionally normal but ectopically located, opening into the vaginal vestibule. Among these 14 cases of anorectal malformation, prenatal dilatation of the distal bowel was seen in nine (64.3%) and intraluminal calcified meconium or enterolithiasis in five (35.7%). Overall, absent PAMC on prenatal sonography in this high-risk population had a sensitivity of 100%, specificity of 99%, true-positive rate of 93% and false-positive rate of 7% for the diagnosis of anorectal atresia.

CONCLUSIONS

In a high-risk population, the absence of PAMC seems to be a highly sensitive and specific sonographic marker for anorectal atresia. The role of routine sonographic identification of the PAMC at the second-trimester scan to screen for cases of isolated anal atresia remains to be determined.

Sonographic evaluation of the development of the fetal rectum and anal canal

PURPOSE

To describe the sonographic (US) appearance of fetal anal canal and rectum and establish nomograms of their normal measurements.

METHODS

This was a prospective, cross-sectional study of 524 healthy women (mean age, 27 years; range, 21-37 years) with normal singleton pregnancy between 18 and 40 weeks of gestational age (GA). High-resolution transabdominal US was used to visualize and measure the normal fetal anal canal and rectum.

RESULTS

Satisfactory images and measurements of the fetal anal canal and rectum were obtained in 496 normal fetuses. The diameters of the normal anal canal and rectum were plotted as a function of GA in a sigmoid curve. The curve estimations were expressed by the following cubic regression equations with R(2) of 0.87 and 0.88, respectively (p < 0.001): anal canal diameter (mm) = 18.272 - 2.151 × GA + 0.0095 × GA(2) - 0.0011 × GA(3) , and rectal diameter (mm) = 18.545 - 2.543 × GA + 0.1237 × GA(2) - 0.0016 × GA(3) .

CONCLUSIONS

The fetal anal canal and rectum are visible sonographically between 18 and 40 weeks of GA. The knowledge of their normal US appearance and size from the second trimester of pregnancy onwards may help identify developmental anomalies.

Sonographic depiction of the fetal anus and its utility in the diagnosis of anorectal malformations

OBJECTIVES

The purpose of this study was to describe the sonographic appearance of the fetal anus and its usefulness in diagnosis of anal atresia.

METHODS

An anomaly scan was performed in 13,150 patients over 8 years. Gestational ages ranged from 16 to 38 weeks. A tangential scan of the fetal perineum was performed. The anus was seen as a hypoechoic ring representing the wall of the anal canal with a central echogenic dot representing the lumen. This appearance was seen posterior to the external genitalia. If there was failure to see this appearance, a coronal scan of the fetal pelvis was done to look for the anal canal in contiguity with the rectum and to confirm its extension up to perineum. Failure to see these two features was considered diagnostic of anal atresia.

RESULTS

On the basis of these criteria, anal atresia was diagnosed in 17 fetuses. Sixteen of these fetuses also had other associated anomalies. The appearance of the anus was useful for ruling out anal atresia in 2 fetuses with a dilated colon containing echogenic meconium balls.

CONCLUSIONS

The anus is visible on a tangential scan of the fetal perineum. It can be seen routinely during an anomaly scan to diagnose or rule out anal atresia.

Prenatal diagnosis of cloacal malformations

INTRODUCTION

Prenatal diagnosis of anorectal malformations currently occurs in 0-15.9% of screened cases. In cloacas, these numbers are unknown. We speculate that some images from prenatal ultrasound studies may suggest the diagnosis of cloaca, but are not recognized because of a lack of suspicion for this diagnosis.

METHODS

A retrospective review of the medical records of 489 patients born with cloaca was performed; 95 of them had prenatal ultrasound reports that represent the material analyzed for this study. A literature review was performed, finding 31 publications, with 68 cloaca patients detected by prenatal images. The abnormal findings of our patients were compared with those described in the literature to determine the most common abnormal prenatal images found in patients with cloaca.

RESULTS

The 95 ultrasound reports found in our patients described 270 abnormalities, the most frequent were: abdominal/pelvic cystic/mass (39), hydronephrosis (36), oligohydramnios (23), distended bowel/bowel obstruction (19), ascites (15), 2 vessel cord (14), dilated bladder (14), dilated ureter (14), polyhydramnios (10), echogenic bowel (8), multicystic kidney (8), "ambiguous genitalia" (7), hydrops fetalis (7), hydrocolpos (4), absent kidney (3), abnormal spine (3), and anorectal atresia (3). In spite of these findings, the radiologists who interpreted the studies only suspected a cloaca in 6 cases (6%). The literature review showed 212 abnormalities in 68 demonstrated cloaca patients. The most frequent were: abdominal/pelvic cystic/mass (46), hydronephrosis (44), ascites (21), oligohydramnios (20), distended bowel (11), multicystic dysplastic kidney (7), ambiguous genitalia (6), non-visualization of the bladder (6), two-vessel cord (5), dilated bladder (5), intraabdominal calcification (4), polyhydramnios (4), enterolithiasis (4), hydrometrocolpos (3), and dilated ureter (3).

CONCLUSION

We conclude that it is possible to suspect the diagnosis of cloaca, prenatally, more frequently than what currently occurs, looking at the same images but with an increased index of suspicion for cystic abdominal masses and a combination of gastrointestinal and urological abnormalities.

Application of 3-dimensional ultrasonography to imaging the fetal anal canal

OBJECTIVE

Ultrasonography has been applied previously to the assessment of the fetal anal canal. We aimed to examine the potential of 3-dimensional ultrasonography (3DUS) in the evaluation of the fetal anal canal and to obtain normal fetal anal canal measurements.

METHODS

Patients were recruited from an unselected population of gravidas with known gestational age (by dates or first-trimester ultrasonography) and without known fetal anomalies presenting for fetal evaluation in the ultrasound units of 2 tertiary care centers between 16 and 39 gestational weeks. In addition to the ordered scan, 3DUS imaging of the fetal anal canal was performed. Transverse and sagittal views and volumes were obtained. Measurements of the fetal anal canal anteroposterior diameter, lateral diameter, and length were performed in transverse and sagittal planes, respectively, and scatterplots of these dimensions were created. Measurements were performed and repeated on raw data sets by 2 independent observers, and the results were analyzed to estimate interobserver and intraobserver reliability.

RESULTS

A total of 186 patients were examined for this study at 16 to 39 weeks' gestation (mean, 27.4 weeks). The anteroposterior diameter of the fetal anal canal in this study group ranged from 4 to 21 mm (mean, 11.2 mm; SD, +/-3.5 mm), whereas the lateral diameter ranged from 7 to 18 mm (mean, 9.1 mm; SD, +/-3.0 mm). The length of the fetal anal canal in this study group ranged from 3 to 24 mm (mean, 14.3 mm; SD, +/-3.8 mm).

CONCLUSIONS

Ultrasonographic assessment of the fetal anal canal with 3DUS is feasible. Scatterplots were created for internal anal sphincter width and length measurements from 16 to 39 weeks' gestation. Larger studies are necessary to establish nomograms of these measurements and their application to the evaluation of pathologic cases. We speculate that 3DUS assessment of the fetal anal canal may improve detection rates of disorders involving this system.

Fetal bowel calcifications: a sign of anal atresia with rectourethral fistula

Fetal bowel calcifications were observed at 24 weeks of gestation in a male fetus, suggesting an anorectal malformation (ARM) with rectourethral fistula. At birth, the newborn presented with complex ARM including anal atresia, rectourethral fistula, and esophageal atresia. The prenatal sonographic visualization of calcifications within distended bowel should raise the suspicion of ARM including anal atresia and rectourethral fistula, the presence of such calcification depending on the timing of onset of fistula formation.

In-utero development of the fetal anal sphincter

OBJECTIVE

To investigate the in-utero development of the fetal anal sphincter using transabdominal ultrasound.

METHODS

This was a cross-sectional study in which the diameter of the fetal anal sphincter was measured sonographically once in 631 well-dated, non-anomalous fetuses scanned between 19 and 38 weeks of gestation. Visualization rates were determined. Regression analysis was used to assess the relationship between the diameter of the fetal anal sphincter and gestational age (GA), and reference values including the mean and 95% reference interval were calculated for each GA.

RESULTS

The sonographic visualization rate of the fetal anal sphincter increased with gestational age, plateauing at 90-100% between 23-34 weeks of gestation. There was a significant positive relationship between fetal anal sphincter diameter and GA, which was best described by the equation: anal sphincter diameter (mm) = - 0.014 x GA(2) + 1.107 x GA - 11.664 (R(2) = 0.62).

CONCLUSION

We have provided reference values for the in-utero development of the fetal anal sphincter throughout gestation.