OBGYN.net Ultrasound: Case of the Month

Diagnosis and management of fetal megavesica during the first half of pregnancy

by Josef Wisser, M.D., Ph.D., OBGYN.net Ultrasound Advisory Board Member

Introduction

Fetal megavesica is a rare syndrome caused by morphological or functional obstruction of the fetal urethra. It is the textbook example of a single cause producing a sequence of changes in fetal development. In this case dilatation of the lower and upper urinary tract, oligohydramnios and pulmonary hypoplasia may result and lead to the prune belly sequence (PBS), defined by the triad of absent or hypoplastic abdominal musculature, urinary tract anomalies and cryptorchidism (1)

Clinical severity depends on the time of intrauterine diagnosis (2,3). The earlier the diagnosis the higher the embryofetal mortality rate.

Fetal renal function has been monitored by fetal urinanalysis in the second half of pregnancy: in addition to electrolytes and osmolarity (4,5,6) the parameters identifying fetuses likely to benefit from intrauterine therapy include urine and amniotic fluid microprotein (7,8,9). The only report which showed gestational age dependence of fetal urine electrolytes and osmolarity assessed only four fetuses at 17–20 weeks (5). Recently, successful treatment of fetal megavesica in the first half of pregnancy has been published (10).

History

A 32-year-old Gravida 4, Para 3 was referred for fetal sonography at 16+4 weeks post menstrual age (16+4 wks p.m.). Family history and patient history were uneventful. She was sure of her dates, and a vaginal ultrasound at 10+3 weeks was consistent with these dates. The patient denied having any regular medication or problems during the ongoing pregnancy.

Prenatal diagnostic findings

Fetal ultrasound at 16+5 wks p.m. gave the following results:
Active fetus with head and limb measurements according to dates (BPD 40mm, femur 21mm). Amniotic fluid was normal. The fetal abdomen was markedly distended by a cystic mass measuring 35x36x39mm, which led to dilatation of the fetal upper urinary tract. Therefore, fetal megavesica was diagnosed (Fig. 1).

Fig.1. Horizontal section through the fetal abdomen at 16+5 weeks pregnancy, showing fetal megavesica and bilateral dilatation of the renal pelvis.

(Click on image for larger version)

The fetal urinary bladder was emptied by transabdominal intrauterine vesicocentesis and 25ml clear urine was collected.

Urinanalysis gave the following results:

Fetal karyotyping performed with fetal urine gave a numerically and structurally normal male result.

Six days after vesicocentesis, the urinary bladder was of normal size but showed marked muscular thickening (Fig.2). Surprisingly, there was no further overdistension of the fetal bladder and amniotic fluid remained normal throughout the further course of pregnancy. The only sign suggestive of an urinary tract problem was bilateral dilatation of fetal renal calices measuring 8mm at 36 wks. p.m. (Fig. 3).

Fig. 2. Six days after vesicocentesis, the fetal bladder is of normal size but shows thickening of bladder musculature Fig. 3. At 36 weeks, only bilateral dilatation of fetal renal pelvis could be detected.

(Click on images for larger version)

Outcome

The baby was spontaneously delivered at term, weighed 4100 grams and presented with an APGAR score of 8-9-9 and an umbilical arterial pH of 7.30.

The boy was put on prophylactic antibiotics and the pediatric evaluation showed no signs of posterior urethral valves. At two years of age the boy is doing fine.

References

  1. Manivel JC, Pettinato G, Reinberg Y, Gonzalez R, Burke B, Dehner LP. Prune belly syndrome: clinicopathologic study of 29 cases. Pediatr Pathol 1989;9:691-711.
  2. Mahony BS, Callen PW, Filly RA. Fetal urethral obstruction: US evaluation. Radiology 1985;157:221-4.
  3. Hutton KAR, Thomas DFM, Arthur RJ, Irving HC, Smith SEW. Prenatally detected posterior urethral valves: Is gestational age at detection a predictor of outcome? J Urol 1994;152:698-701.
  4. Glick PL, Harrison MR, Golbus MS, Adzick NS, Filly RA, Callen PW. Management of the fetus with congenital hydronephrosis. II. Prognostic criteria and selection for treatment. J Pediatr Surg 1985;20:376-387.
  5. Nicolaides KH, Cheng HH, Snijders RJM, Moniz CF. Fetal urine biochemistry in the assessment of obstructive uropathy. Am J Obstet Gynecol 1992;166:932-937.
  6. Nicolini U, Fisk NM, Rodeck CH, Beacham J. Fetal urine biochemistry: an index of renal maturation and dysfunction. Br J Obstet Gynecol 1992;99:46-50.
  7. Burghard R, Gordjani N, Leititis J, Bald R. Protein analysis in amniotic fluid and fetal urine for the assessment of fetal renal function and dysfunction. Fetal Ther 1987;2:188-196.
  8. Johnson MP, Bukowski TP, Reitleman C, Isada NB, Pryde PG, Evans MI. In utero surgical treatment of fetal obstructive uropathy: A new comprehensive approach to identify candidates for vesicoamniotic shunt therapy. Am J Obstet Gynecol 1994;170:1770-1779.
  9. Muller F, Dommergues M, Mandelbrot L, Aubry MC, Nihoul-Fekete C, Dumez Y. Fetal urinary biochemistry predicts postnatal renal function in children with bilateral obstructive uropathies. Obstet Gynecol 1993;82:813-820.
  10. Wisser J, Kurmanavicius J, Lauper U, Zimmermann R, Huch R, Huch A. Successful treatment of fetal megavesica in the first half of pregnancy. Am J Obstet Gynecol 1997;177:685-9.

Editor's note: Josef Wisser, M.D., Ph.D is Oberarzt (Assistant Medical Director), Department of Obstetrics, University Hospital Zurich, Switzerland. Additionally, he is a Lecturer for obstetrics and gynecology at Ludwig-Maximilians-University (LMU), Munich and a Lecturer for prenatal medicine at the Department of Obstetrics, University Hospital of Zurich, Switzerland. In 1989, he was named an Expert in ultrasound training, accredited by the German association of ultrasound in medicine (DEGUM). His complete curriculum vitae, including a list of published articles and book sections, can be found at:
http://www.obgyn.net/meet.asp?page=/all_advisors/J_Wisser
Dr. Wisser serves as an Advisory Panel Member of OBGYN.net.

He may be contacted at:

Josef Wisser, M.D., Ph.D.
Dept. Obstetrics University of Zurich
Frauenklinikstrasse 10
CH-8091 Zurich
Telephone: 0041-1-255-3947
FAX: 0041-1-255-4430
e-mail: jwm@fhk.smtp.usz.ch
or Josef.Wisser@obgyn.net

© 1998. All rights reserved.
Reproduction of this material in any form is forbidden without
the express written consent of Elecomm Corporation & OBGYN.net.