First-trimester diagnosis of imperforate anus

Management and outcome of fetal abdominal cyst in first trimester: systematic review of the literature

OBJECTIVE

The detection of a fetal abdominal cyst at the first-trimester ultrasound scan is a rare event, for which the natural history and prognosis are often unknown and unpredictable, owing to various underlying etiologies. The aim of this study was to evaluate the outcome of fetal abdominal cysts detected in the first trimester to better understand their possible clinical significance and improve their clinical management.

METHODS

We present a case report of a fetal abdominal cyst detected in the first trimester, with subsequent diagnosis of congenital multiple arthrogryposis. We also performed a systematic review of the literature to determine the incidence and outcome of similar cases, which was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and registered with PROSPERO (CRD42023491729). PubMed, Web of Science and EMBASE were searched from inception to December 2023 to identify case reports and case series documenting an ultrasound diagnosis of a single fetal abdominal cyst in the first trimester.

RESULTS

Our case presented at 12 + 6 weeks' gestation with an isolated fetal abdominal cyst, which underwent spontaneous resolution in the second trimester, when multiple congenital arthrogryposis was observed. Data on a total of 60 cases of fetal abdominal cyst detected in the first trimester were extracted from the literature. Of these, 35% were associated with concurrent or late-onset structural anomalies, as in our case, and 65% were isolated. In pregnancies with an isolated fetal abdominal cyst, 54% had a live birth with a normal outcome.

CONCLUSIONS

A fetal abdominal cyst in the first trimester is usually an isolated finding with a moderate-to-good prognosis, but it could also be an early sign of other associated abnormalities, including arthrogryposis. Increased ultrasound surveillance and additional genetic testing to rule out possible associated anomalies are necessary to assess the risk of adverse pregnancy outcome and provide appropriate parental counseling. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

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.

First trimester lower abdominal cysts as early predictor of anorectal malformations

INTRODUCTION

Prenatal ultrasound diagnosis of anorectal malformations (ARMs) is challenging and often missed as direct visualization of the anal sphincter is not routinely performed, plus the technique is operator-dependent and inaccurate, also in expert hands. Other indirect signs, such as rectosigmoid overdistension or intraluminal calcifications, are occasionally present in late pregnancy. The detection of a cyst of the lower abdomen in the first trimester may be an early sign of ARM. Here we reported our experience and a review of the literature of such cases.

MATERIAL AND METHODS

Isolated cases of lower abdomen cysts encountered in the first trimester at the Prenatal Diagnosis Unit during the last 5 years were retrieved and compared with those found in literature. Post-natal clinical data were analyzed to check the presence and type of malformations.

RESULTS

A total of three cases of lower abdomen cysts were found in our center and 13 in literature. In our case series all the cysts spontaneously regressed and were no longer visible since the second trimester of pregnancy, while in literature this was reported in only 4 out of 13 cases. ARM was confirmed in all patients at birth or post-mortem.

CONCLUSIONS

The finding of a lower abdomen cyst during the first trimester of pregnancy could be an early predictive sign of ARM, even if it disappears during pregnancy. In these cases, we suggest mentioning to the parents the possibility of an ARM during the counseling and to refer the couple to a Colorectal Center.

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.

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.

Anal atresia as the diagnostic clue in VACTERL association: A first-trimester case report

Anal atresia is the most common malformation occurring in VACTERL association, but it is difficult to diagnose antenatally. We herein present a case of fetal anal atresia in VACTERL association diagnosed by ultrasonography and supported by autopsy. This case emphasizes the clues to ultrasonographic diagnosis of anal atresia at 11-13⁺⁶ weeks of gestation, promoting increased awareness of VACTERL association during first-trimester screening.

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.

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.

First trimester expression of anorectal malformation: Case report and review of the literature

A 26-years-old woman, underwent an ultrasound examination at 13.4 weeks. A cystic structure was identified in the right lower abdomen. Gradually, the cystic mass was replaced by echogenic content and eventually attained the appearance of hyperechoic bowel. At 21.2 weeks, the anal sphincter could not be demonstrated which was consistent with the diagnosis of isolated anal agenesis. Amniocentesis revealed 46XY karyotype with normal comparative genomic hybridization. After termination of pregnancy at 23 weeks, an autopsy revealed an isolated high type anorectal malformation (ARM) without fistula. We reviewed all 14 cases reported in the literature of first trimester sonographic expression of ARM.

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.

[Fetal abdominal cysts at the first trimester scan]

OBJECTIVES

Abdominal cysts are seldom detected at the first trimester scan. The aim of this study is to ascertain their outcome, which is currently not established.

METHODS

The French College of Fetal Ultrasound conducted a prospective observational study of 24months, collecting all cases of abdominal cysts discovered during the first trimester ultrasound. Cases of megacystis were excluded from the study. Ultrasound images, prenatal diagnosis expert reports and pregnancy outcomes were collected by sonographers after patient consent.

RESULTS

Ten cases of abdominal cysts were collected. The cysts had a mean diameter of 15mm. They were anechoic in 5 cases, hyperechoic in 2 cases and mixed in 3 cases. In 6 of 10 cases, complete resolution was observed at 18WG with a good post-natal outcome; the five cases with anechoic images were associated with normal pediatric examination at birth and in the case of the resolved hyperechoic image, an isolated imperforate anus was observed. In the four cases of hyperechoic or mixed images that had not resolved, the outcome was poor with four termination of pregnancies, including two cases of cloacal dysgenesis.

CONCLUSIONS

Abdominal cysts are rare at the first trimester scan. They resolve in two thirds of cases and are then associated with good outcome. When they do not resolve or when they are not strictly anechoic, they require a referral ultrasound examination at 18 and 22WG.

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.

Outcome of first-trimester fetal abdominal cysts: cohort study and review of the literature

OBJECTIVES

The aims of this study were to ascertain the outcome of fetuses with an abdominal cyst detected at 11-14 weeks' gestation in our unit and to undertake a review of cases reported in the literature.

METHODS

This was a retrospective study that included all fetuses found to have an abdominal cyst on ultrasound examination at 11-14 weeks, identified over a 14-year period. Pregnancy management and outcome were ascertained from maternal and neonatal records. We also performed a review of the literature using a systematic search strategy, to identify the outcome of similar cases and propose a management algorithm.

RESULTS

Fourteen cases were identified during the study period, of which four had associated abnormalities. Of the 10 isolated cases, the cyst had resolved at follow-up scan in eight (80.0%), one fetus died in utero at 15 weeks' gestation and the other case underwent surgery for a choledochal cyst 9 weeks after birth. An additional 19 cases were reported in the literature. In eight fetuses there were associated structural abnormalities, of which four had a diagnosis of anorectal malformation after birth. In two of these four, the cyst resolved in the second trimester. Of those cases with an isolated cyst (n = 11), the cyst resolved in seven (63.6%). The remainder were variably diagnosed as hepatic cyst, ileal duplication or choledochal cyst.

CONCLUSION

Fetal abdominal cysts at 11-14 weeks' gestation are rare. They constitute an isolated finding in the majority of cases and are usually associated with a good perinatal outcome. In view of the reported association with anorectal and other gastrointestinal malformations, perinatal assessment is recommended, even if the cyst resolves during pregnancy.

Early fetal anatomical sonography

Over the past decade, prenatal screening and diagnosis has moved from the second into the first trimester, with aneuploidy screening becoming both feasible and effective. With vast improvements in ultrasound technology, sonologists can now image the fetus in greater detail at all gestational ages. In the hands of experienced sonographers, anatomic surveys between 11 and 14 weeks can be carried out with good visualisation rates of many structures. It is important to be familiar with the normal development of the embryo and fetus, and to be aware of the major anatomical landmarks whose absence or presence may be deemed normal or abnormal depending on the gestational age. Some structural abnormalities will nearly always be detected, some will never be and some are potentially detectable depending on a number of factors.

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.

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.

Sonographic features of anorectal atresia at 12 weeks

We present the sonographic features of a fetus with anal atresia at 12 weeks of gestation. Follow-up ultrasound examination at 17 week revealed apparently normal bowel. Spontaneous miscarriage occurred at 18 weeks and postmortem examination showed anorectal atresia and arthrogryposis multiplex. It seems that dilatation of the bowel in the early pregnancy is a possible marker for anorectal atresia, and the abnormality may be overlooked if a mid-trimester scan alone is performed.

Fetal abdominal cysts in the first trimester: prenatal detection and clinical significance

OBJECTIVE

In order to determine the clinical significance of fetal abdominal cysts detected in the first trimester, we reviewed our experience with such cases collected over a 5-year period.

METHODS

Five cases in which a fetal abdominal cyst was detected by ultrasound in the first trimester were identified. Information on the ultrasound findings, antenatal course and perinatal outcome was obtained in all cases.

RESULTS

The abdominal cyst was confirmed by an early second-trimester scan at 14-16 weeks in all cases, at which time no associated anomalies were detected. The standard detailed second-trimester scan at 18-22 weeks demonstrated complete resolution in three cases. These women had an uneventful antenatal course, and normal newborn infants were delivered at term. However, one of these infants had intestinal malrotation, chronic abdominal distension and midgut volvulus requiring surgery at the age of 7 months. Among the remaining two cases in which the abdominal cyst persisted, one required prenatal aspiration at 19 weeks owing to significant enlargement and resolved. The other remained stable in size and was managed conservatively, but the infant required surgery at the age of 7 weeks owing to a choledochal cyst causing intermittent episodes of acholia.

CONCLUSION

Abdominal cysts in early pregnancy often resolve spontaneously or remain small and are usually associated with a good outcome. Nevertheless, as they can also be associated with serious underlying gastrointestinal pathological conditions, close surveillance in the perinatal period is advocated.

Association of endothelin-beta receptor (EDNRB) gene variants in anorectal malformations

Animal models have demonstrated the role of genetic influences in anorectal malformations (ARM), although the pathogenetic mechanism remains uncertain. A body of collateral evidence points to possible connection with the endothelin-beta receptor (EDNRB) gene and the endothelin system. This study investigates the EDNRB gene in patients with ARM. Resected surgical specimens of terminal colonic tissue were obtained from 14 children (6 males and 8 females) undergoing surgery for ARM correction with ethical permission. DNA samples were screened for mutations in EDNRB. Polymerase chain reaction amplification of 7 exons of EDNRB was followed by heteroduplex single-strand conformation polymorphism analysis. Heteroduplex single-strand conformation polymorphism variants were validated with automated sequencing techniques on polymerase chain reaction products showing conformational variants in acrylamide gel. All investigated patients with ARM showed mobility shift aberrations and polymorphisms in the EDNRB gene. These included one previously described polymorphism in exon 4 (831G/A) seen in association with Hirschsprung disease and 6 novel polymorphisms identified in exons 1 (178G/A), 2 (552C/T and 561C/T), and 3 (702C/T). No aberrant banding patterns were observed. The exon 1 (178 G/A) variation was identified in 2 (50%) of 4 low lesions compared with 1 (1%) of 84 control samples. The exon 3 (702C/T) single nucleotide polymorphism was present in 3 (60%) of 5 of the supralevator lesions being associated with exon 4 (831G/A). The patient with VATER associations including cardiac and limb anomalies had the 831G/A variation only. Analysis revealed statistically significant differences for the polymorphism 178G/A (P < .01, chi2 with Yates correction = 8.24) compared to controls. Potential disease-related mutations were identified in South African patients with ARM, raising the question of its potential role in the pathogenesis of this condition.

Fetal magnetic resonance imaging in the antenatal diagnosis and management of hydrocolpos

Hydrocolpos should be considered systematically when an abdominopelvic cystic mass is diagnosed in a female fetus. Because the prognosis and neonatal management of isolated hydrocolpos with spontaneous resolution differs greatly from that of hydrocolpos associated with a cloacal malformation, it is important to ascertain prenatally whether there are associated anomalies. We report the prenatal characteristics of three fetuses with hydrocolpos; in two cases there was spontaneous resolution and one infant was born with digestive tract atresia. The principal ultrasound findings were an oblong anechoic pelvic mass with or without a sagittal septum, located behind a normal bladder. On magnetic resonance imaging (MRI), the cervical imprint on the vagina confirmed the diagnosis of hydrocolpos and helped to diagnose cloacal malformation by demonstrating the absence of meconium beside the bladder on T1 sequences. Our cases show that MRI is useful for differentiating isolated hydrocolpos from hydrocolpos associated with cloacal malformation.

Imperforate anus: A relatively common anomaly rarely diagnosed prenatally

OBJECTIVE

Despite the relatively common occurrence of imperforate anus, prenatal diagnosis is rarely reported. In this study, we investigated the presence and diagnosis of imperforate anus along with strategies for improving prenatal diagnosis of the condition.

PATIENTS AND METHODS

Fetuses and infants with imperforate anus who had been examined prenatally by ultrasound at the National Center for Fetal Medicine (NCFM) from 1987 to 2004, were evaluated.

RESULTS

Of 69 cases with imperforate anus, only 11 (15.9%) were diagnosed prenatally, at a median gestation of 18 + 4 (range, 15 + 6 to 35 + 6) weeks. In all 11, dilatations of the rectum or lower part of the bowel were seen. Additional anomalies, most of them diagnosed prenatally, were present in 59/69 (85.5%) of the cases. The most frequent additional anomalies were urogenital (53.6%). The karyotype was abnormal in nine cases (13.0%). A retrospective evaluation of available videotapes of 22 cases of imperforate anus that were not diagnosed prenatally revealed that it was possible to suspect the diagnosis in 11/22 (50%) cases. Sixteen infants were born with imperforate anus without prenatal diagnosis of any abnormality. In total, 31/69 (44.9%) cases were terminated, two (2.9%) died in utero and 12 (17.4%) died postnatally. Twenty-four (34.8%) infants survived, including all 10 with isolated imperforate anus and seven of eight cases with only one additional anomaly.

CONCLUSIONS

The prenatal detection rate of imperforate anus was only 15.9%. Imperforate anus is often associated with other anomalies; in this study, 85.5% had additional anomalies. Prenatal diagnosis makes prenatal counseling possible and facilitates optimized postnatal care. We believe that the prenatal detection rate of imperforate anus could be improved. Examiners should intensify their search for typical findings of imperforate anus especially when other anomalies that frequently accompany this condition are present.

Fetal Anal Atresia Presenting as Transient Bowel Dilatation at 16 Weeks of Gestation

Congenital anal atresia is a rare abnormality which in two thirds of the cases is associated with other congenital abnormalities or syndromes. Prenatal diagnosis is usually achieved in cases with coexisting abnormalities. The diagnosis of isolated anal atresia is extremely difficult and can be suspected in the presence of colon dilatation. We present the case of a fetus in which marked dilatation of the colon was diagnosed at 16 weeks of gestation. Four weeks later the sonographic appearance of the bowel was normal and remained normal for the rest of the pregnancy. Anal atresia was diagnosed immediately after birth and corrected surgically. No other abnormalities were present. This case report illustrates that in anal atresia, bowel dilatation may be only transient.