Journal of Pediatric Urology (2013) 9, 3e6
Prenatal diagnosis of bladder exstrophy by fetal MRI Susan Goldman b, Patricia Oliveira Szejnfeld b, Atila Rondon a, Viviane Vieira Francisco b, Herick Bacelar a, Bruno Leslie a, Ubirajara Barroso Jr a, Valdemar Ortiz a, Antonio Macedo Jr a,* a b
Department of Urology, Federal University of Sa˜o Paulo, Rua Maestro Cardim, 560/215, 01323-000 Sa˜o Paulo, Brazil Department of Radiology, Federal University of Sa˜o Paulo, Sa˜o Paulo, Brazil
Received 28 March 2012; accepted 29 June 2012 Available online 26 July 2012
KEYWORDS Bladder exstrophy; Prenatal diagnosis; Magnetic resonance imaging
Abstract Purpose: To review our experience with prenatal diagnosis of bladder exstrophy by fetal magnetic resonance imaging (MRI). Bladder exstrophy can be diagnosed by ultrasonography (US) evaluation of the fetus based on absence of bladder filling, low-set umbilicus, small genitalia and lower abdominal mass, although in some instances more accurate anatomical information is desired. Material and methods: We studied three patients at mean gestational age of 27.3 weeks. The fetal MRI exam was performed on axial, sagittal, coronal planes and echo gradient in the best plan for acquisition of fetus. Images were analyzed by a group of three radiologists with experience in fetal MRI. Results: The MRI defined a lower abdominal mass prolapsing below the umbilical vessels, having the ureters ending on it in an anterior position. A cloacal malformation or a cloacal exstrophy could be excluded, as well as other accompanying spinal abnormalities. The renal system and oligohydramnios could be well documented. Conclusions: The MRI showed a detailed scenario of the abnormality with advantages over the US evaluation in regard to excluding cloacal anomalies. MRI allowed accurate sexual differentiation and may be indicated after suspected bladder exstrophy on US evaluation. ª 2012 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction
* Corresponding author. Tel.: þ55 11 32870639; fax: þ55 11 32873954. E-mail addresses:
[email protected],
[email protected] (A. Macedo).
Classic bladder exstrophy represents a congenital anomaly complex with an incidence of 1 in 30,000e50,000 live births [1]. It is characterized by musculoskeletal defects in the abdomen and pelvis, and genital defects [2]. The primary objectives of surgical management are secure abdominal closure, attainment of urinary continence and genital reconstruction [3].
1477-5131/$36 ª 2012 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jpurol.2012.06.018
4 The ideal scenario is early surgical bladder closure in the first 48 h after birth [4,5]. This achievement is possible when appropriate prenatal diagnosis is established and the patient referred to a tertiary pediatric urology facility. Ultrasonography (US) evaluation of the fetus by means of high-resolution methods is efficient to identify some anatomical defects during obstetric care based on absence of bladder filling, low-set umbilicus, small genitalia and lower abdominal mass [6,7]. However, in some instances, more accurate anatomical information is desired. Few studies have been published dealing with prenatal evaluation of bladder exstrophy [7,8]. Fetal magnetic resonance imaging (MRI) can accurately diagnose a wide variety of urinary tract disorders and must be regarded as a valuable complementary tool to US in the assessment of the urinary system, particularly in cases of inconclusive US findings [9]. We reviewed our experience with prenatal MRI of bladder exstrophy to describe our findings and correlate them with postnatal clinical presentation and surgical outcome.
Patients and methods Three healthy females presented to our institution at a mean of 27.3 weeks of gestation after undergoing prenatal US that failed to identify the bladder. Kidneys were normal sized and no evidence of hydronephrosis was found. Differential diagnosis by the sonographist included bladder exstrophy, bladder agenesis, bilateral ectopic ureters, patent urachus and nonvisualization of the bladder. Patients were referred for fetal MRI. The fetal MRI exam was performed using a 1.5 T Avanto Espree Siemens. Sequences performed were HASTE and TURBO FISP on axial, sagittal, coronal planes and echo gradient in the best plan for acquisition of fetus. Images were analyzed by a group of three radiologists with experience in fetal MRI.
Results The MRI defined a lower abdominal mass prolapsing below the umbilical vessels (Figs. 1 and 2), having the ureters ending on it in an anterior position (Fig. 3). A cloacal malformation or a cloacal exstrophy could be excluded, as well as other accompanying spinal abnormalities (Figs. 1 and 3). Based on the provided information, the surgical team scheduled bladder reconstruction for the 2nd day of life, and the clinical presentation was consistent with the information provided by the radiologists. The fetuses were delivered as planned by cesarean section. The bladder-plate was favorable in case 1 and very small in case 2. A staged treatment was proposed and the bladder was primarily closed without any attempt to create a bladder neck valve but only promoting its tubularization. The penis was left intact as an epispadia. Clinical outcome was favorable in case 1 and case 3, whereas case 2 had partial bladder dehiscence and is scheduled for surgical revision. The MRI information was very useful for planning the surgical treatment and to explain to the family about the congenital anatomical defects.
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Discussion After 13 weeks of conception, both abdominal and transvaginal US allow bladder identification in 98% of cases [7]. From the 16th week, fetal urine is mainly responsible for the amniotic fluid. Fetal bladder overfilling on the routine obstetric US program calls the attention to possible urological diseases like posterior urethral valves and prunebelly syndrome, whereas absence of filling may suggest bladder exstrophy [10]. In a recent study, a total of 43 cases were identified from 824,368 registered births for a total prevalence of 5.22 per 100,000 (95% CI 3.77e7.03) [11]. Interestingly, accuracy of prenatal diagnosis was low, with 4 cases (10%) being detected prenatally by routine US (bladder exstrophy in 3, cloacal exstrophy in 1). Another study showed that of 40 new babies with bladder exstrophy/cloacal exstrophy (BE/CE) referred, only 10 had an antenatal diagnosis [8]. Five patients did not have a diagnosis despite suspicious findings noted on antenatal scans and another three had a wrong diagnosis of BE/CE. Of the 16 referrals with antenatal suspicion of BE/ CE, 5 opted for termination. At the 20th week scan, it was possible to identify the gender of the fetus in 3/16 cases only. These data reinforce the importance of improving our accuracy in the prenatal diagnosis of bladder exstrophy. We acknowledge that postnatal diagnosis and early referral to a tertiary center can be performed in several countries, but we believe that early prenatal diagnosis should be encouraged. MRI has been emerging as an important method in the diagnosis of significant fetal anomalies [9]. In one study, the sensitivity of US and MRI for urological anomalies was 55% and 96%, respectively [12]. MRI provides more anatomical details which allow appropriate postnatal management and parental counseling. Also, it may be important in the decision to perform prenatal interventions or a pregnancy termination [2]. According to Gearhart et al., a prenatal US associated with a nonvisualized bladder, a lower abdominal mass and a normal amniotic fluid volume are suggestive of bladder exstrophy [6]. Hsieh et al. to our knowledge reported the first case of bladder exstrophy prenatally diagnosed by MRI at 32 weeks’ gestation [13]. In their case, MRI added to the US the visualization of the ureters ending in the mass and allowed the identification of the female gender. Moreover, other anomalies associated with cloacal exstrophy could be excluded. To our knowledge, we report here the second and third cases of bladder exstrophy with diagnosis confirmed by fetal MRI [14]. The US findings for both fetuses of our series could neither identify the bladder nor show detailed abdominal wall characteristics. It was not possible to identify properly the penis and testicles morphology, and not even a 3D US could rule out cloacal abnormalities associated with bladder exstrophy. Oligohydramnios was another important factor that made US evaluation more difficult. Bladder exstrophy on MRI can be noted as a mass below abdominal insertion of the umbilical cord (Figs. 1e3) with the distal ureters appearing to end in this mass (Fig. 3), anteriorly to its classical location. The scrotum can be well identified with the testicles inside in boys (Figs. 1 and 3).
Prenatal diagnosis of bladder exstrophy by fetal MRI
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Figure 1 (A) SSFP MRI sequence on the sagittal plane, (B) Haste sequence on the sagittal plane and (C) T1-weighted coronal plane. Images showing infra-umbilical abdominal wall mass (yellow arrows in A and B), low insertion of the umbilical cord immediately over the mass (red arrows in A and B). Scrotum with testicles inside (blue arrow in B). Rectum (white arrows in B and C) and anal sphincter muscle (pink arrows in C). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Initial MRI allows exclusion of cloacal exstrophy, since the key findings by this method are a large infra-umbilical anterior wall defect or cystic anterior wall structure associated with a clearly identified omphalocele and lumbosacral anomalies. The protrusion of the ileum between the two hemi-bladders defines the so-called “elephant trunklike image”, a patognomonic finding that is well defined on MRI. Absence of external genitalia might be found as well. An imperforate anus is associated with cloacal exstrophy, and so if there is MRI identification of normal recto-anal anatomy this helps exclude that diagnosis (Fig. 1) [14]. According to Goyal et al., the detection of multiple
anomalies, such as imperforate anus, spinal disorders, elephant trunk-like image, etc., would make the diagnosis of cloacal exstrophy easier [8]. Unlike US, MRI is not limited by maternal body habitus, fetal position or oligohygramnios [13]. Also, MRI provides enhanced soft tissue resolution, allowing accurate sexual differentiation. Other advantages are as follows: MRI involves non-ionizing radiation and is a non-invasive method; and faster sequences of MRI allow imaging acquisition during a single maternal breath hold, and therefore fetal motion is much less of a limiting factor nowadays [12].
Figure 2 SSFP MRI sequence on axial plane (A) and on coronal plane (B). (A) Infra-umbilical abdominal wall mass (yellow arrow) and umbilical arteries (red arrow). (B) Posterior wall of the bladder (yellow arrows). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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Figure 3 SSFP MRI sequence on axial plane (A, B and C). (A) Insertion of the umbilical cord with two arteries (red arrow). (B) Infra-umbilical abdominal wall mass with two ureteral meatus (yellow arrows) and umbilical arteries (white arrows). (C) Scrotum with testicles inside (blue arrow). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Conclusions In conclusion, we recommend MRI for detailed information on suspected bladder exstrophy after US evaluation. We recognize that this method is not required for primary diagnosis, but its main role could be to rule out accompanying bowel malformations like cloacal exstrophy and also penile malformations.
Conflict of interest/funding
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[7]
[8]
[9]
None.
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