Ultrasonography during the 22nd week of pregnancy showed two abnormalities in a male fetus, i.e. left renal agenesis and a pelvic cystic mass 12 mm in diameter. No change occurred until birth except for a slight increase in cyst volume. These findings were confirmed after birth; the cystic mass was anechoic, unilocular, on the left side between the bladder and rectum, with a thin wall and of 17 mm diameter (Fig. 1). Cysto-urethrography showed no filling defect at the base of the bladder and no reflux into the genitourinary system. MAG3 isotope renography confirmed no fixation on the left side or in the cyst and no obstruction of the right ureter. Because the baby was healthy, with no urinary infection, supervision was indicated. On serial ultrasonography the cyst increased progressively to 25 mm in diameter at 15 months old; the family requested that the cyst be removed. Using laparoscopy through a 5-mm trans-umbilical port with a 30° telescope and three 3 mm operating ports, the cyst was explored on the left of the posterior bladder wall (Fig. 2). The cyst was easily separated from the peritoneum and bladder wall. Both vasa deferentia were found to directly enter the cyst; it was impossible to separate both vasa from the cyst wall. To preserve future fertility almost all the cyst was resected, leaving a narrow strip of the cyst wall on each side, along the vas (Fig. 3). Recovery was uneventful and the infant was discharged home within 48 h; 6 months later the child was asymptomatic with no visible recurrence on ultrasonography.
Most seminal vesical cysts remain asymptomatic until puberty, but with the widespread use of ultrasonography during pregnancy and infancy there are likely to be more asymptomatic cases [1,2]. The potential complications are infection, compression of the surrounding structures [3–6], infertility and malignant degeneration . Paediatric urologist must consider all these factors and not neglect the preservation of future sexual potency and fertility. A less invasive solution is indicated; laparoscopy seems appropriate for this purpose. Congenital seminal vesicle cysts are rare, usually discovered after puberty, and treated by cyst removal and section of the vas deferens. The present left seminal vesicle cyst was diagnosed at 22 weeks of gestation. At 15 months old, laparoscopy was used to remove the cyst and to preserve the both vas deferentia, by leaving a narrow strip of cyst along the vas. Most cases are reported in adults  or around puberty ; only 11 cases have been discovered before puberty [1,9–13]. To our knowledge the present case is the first reported with an antenatal diagnosis.
The differential diagnosis of cystic pelvic masses in the male fetus and neonate includes ureterocele, congenital vesical diverticulum, rectal duplication, anterior myelomeningocele, teratoma, a dysplastic kidney in an ectopic position (often associated with congenital seminal vesicle cyst), but the most difficult differential diagnosis is cyst of the urogenital sinus or Müllerian remnants . Several imaging techniques have been recommended in evaluating and differentiating pelvic cystic masses, especially ultrasonography [3–15], CT and MRI [16,17], which currently seem the ideal methods for differentiating cystic malformation of the pelvis in a young boy. They accurately show the anatomical relationships with the surrounding structures and help to plan surgical excision.
Various management protocols have been proposed, i.e. watchful waiting, aspiration of the cyst, transurethral deroofing and transvesical drainage . Surgical excision is usually recommended but because of the deep pelvic location of the cyst, several approaches have been described, including retropubic, transvesical, perineal transrectal and transanal. The laparoscopic approach to the seminal vesicles was described by Kavoussi et al. in 1993 and used in adults by Carmignani et al. and in children by Ikari et al.. The goal of surgery is to remove the cyst, preserving sexual potency and fertility; the best method seems to be a near-total cystectomy leaving only a narrow strip of cyst wall along the vas. This manoeuvre could be used on both sides and avoids dissection of the medial distal part of the cyst, where dissection could endanger the ejaculatory ducts.
In conclusion, although seminal vesicle disease requiring surgical treatment is very rare in boys, it represents (as a Müllerian remnant) an excellent indication for the laparoscopic approach. The depth of these structures is not a problem with good bladder suspension and an angled telescope. Care must be taken to preserve the contralateral and (if possible) the ipsilateral vasa deferentia.