***Tennesse Women"s Care, Nashville TN, * Suleymaniye Maternity Hospital, Department of Perinatology, Istanbul, Turkey, **Dept of Ob-Gyn, Academic Hospital Maastricht.

Synonyms:  Urethral Atresia

Definition: In literature, the urethral atresia is not always clear defined. Whether an absence, a partial absence or an occlusion of the urethra is affected stays unclear. In this article a total absence of the urethra is considered.

Prevalence: Urethral atresia is a rare congenital abnormality often include in the widespread spectrum of obstructive uropathies.  The antenatal detection of urethral agenesis has rarely been documented ^1,2 .   It occurs in male and female fetuses and in fetuses of diabetic mothers.

Case report: This second trimester was performed for routine assessment of fetal anomalies in a patient with unremarkable history.

The finding is this case is an enormous cystic collection that displaces and deforms the fetus. Further, there is no amniotic fluid. This combination points to a major obstruction of the bladder outlet. Several conditions can cause that such as posterior urethral valve, Urethral meatus agenesis but these usually present with some amniotic fluid. So a more severe condition like urethral agenesis was suspected. The patient elected to terminate the pregnancy in view of the dismal prognosis and after a drainage tap of the bladder the fetus was delivered:

The pathology confirmed the ultrasound findings (note the absence of external genitalia which is common).

Etiology: Unknown

Pathogenesis:   Unknown

Sonographic findings: Megacystis, hydroureter, hydronephrosis, renal dysplasia and anhydramnios sequence such as pulmonary hypoplasia, Potter face and limb deformities.

Implications for targeted examinations: Bladder outlet obstruction findings such as megacystis, hydroureter, hydronephrosis, echogenic kidney, â€keyhole sign'', ambiguous or absence of fetal external genitalia and oligo-anhydramnios and its sequences ^2,3  .

Differential diagnosis: The differential diagnosis of oligohydramnios and distended bladder could include other obstructive uropathy such as   posterior urethral valves, detrusor hypertrophy, urethral meatus agenesis or congenital urethral membranes ^1,4 . Posterior urethral valves are much more common than urethral atresia and occur in the prostatic urethra and can lead to a similar sequela of anomalies. However, in posterior urethral valves, the fetal gender, male, is a significant factor in the differential diagnosis.

Associated anomalies: Urethral atresia is found most commonly in association with other genitourinary anomalies ⁵.  Chromosomal abnormalities have been described but relation with urethral atresia is unclear .

Prognosis: The prognosis is uniformly fatal unless there is an associated urachal fistula or rectovesical fistula that allows the drainage of the bladder, or surgical intervention (shunt placement) cn be performed before renal cystic dysplasia occurs ^{3, 5, 7}.
The prognosis of drainage of the bladder with fetuses with urethral atresia is unclear since no randomized trials have been reported in literature . Case reports of successful drainage have been published ^7,9,10 ,   but also spontaneous recoveries ⁹.

Recurrence risk: Not known to be increased. Although in one study there was in increased risk of recurrence in patients with a urethral atresia ¹¹.

Management: Complete bladder outlet obstruction detected in the first or early in the second trimester is a lethal condition in the absence of spontaneous drainage or intervention. When the diagnosis is made later but before viability, the option of pregnancy termination can be offered. Teams specialized in antenatal intervention report a survival rate of 30% in the presence of poor serial urine electrolytes ¹² . Prenatal recognition of this entity at early stage might permit operative urinary diversion. There is a small number of reports of urethral atresia who underwent successful urinary decompression by intra¬ute¬rine placement of a vesico-amniotic shunt at early stage ^9,12,13 .  

References:
1)  Mogg RA. Congenital anomalies of the urethra. Br j Urol 1968; 40: 638-9.
2)  Twinning P. Urinary tract abnormalities. In Textbook of Fetal Anomalies. Twinning P, McHugo JM, Pilling DW(ed). Churchill  Livingstone, London 2000, pp: 300-301
3)  Herndon AC, Casale AJ. Early second trimester intervention in a surviving infant with postnatally diagnosed urethral atresia. J Urol 2002; 168: 1532-1533.
4)  McHugo J, Whittle M. Enlarged fetal bladders: Aetiology, management and outcome. Prenat Diagn 2001; 21: 958-63.
4)  Steinhardt G, Hogan W, Wood E, Weber T, Lynch K. Long term survival in an infant with urethral atresia. J Urol 1990; 143: 366-367.
6)  Qureshi F. Jacques S. Feldman B. Doss B. Johnson A. Evans M. Johson M. Fetal obstructive uropathy in trisomy syndromes. Fetal Diagn Ther 2000 Nov-Dec;15(6):342-7
7)  Clark T. Martin W. Divakaran T. Whittle M. Killy M. Khan K. Prenatal Bladder drainage in the management of fetal lower tract obstruction: a systematic review and meta-analysis. Obstet. Gynecol. 2003 Aug.102(2):367-382
8) Clark T. Martin W. Divakaran T. Whittle M. Killy M. Khan K. Prenatal Bladder drainage in the management of fetal lower tract obstruction: a systematic review and meta-analysis. Obstet. Gynecol. 2003 Aug.102(2):367-382
9)  Gonzales R. De Filippo R. Jednak R. Barthold J. Urethral atresia: long-term outcome in 6 children who survived the neonatal period. J. Urol. 2001 Jun;165(6Pt2):2241-4
10)  Hemdon C. Casale A. Early second trimester intervention in a surviving infant with postnatally diagnosed urethral atresia. J. Urol. 2002 Oct;168(4Pt1)675-8
11)  Reuss A. Wladimiroff J. Niermeijer M. Antenatal diagnosis of renal tract anomalies by ultrasound. Pediatr Nephrol. 1987 Jul;1(3):546-52
12)  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 appropriate candidates for vesicoamniotic shunt therapy. Am J Obstet Gynecol 1994; 170: 1770-72.
13)  Freedman AL, Bukowski TP, Smith CA, Evans MI, Johnson MP, Gonzalez R. Fetal therapy for obstructive uropathy: specific outcomes diagnosis. J Urol 1996; 156: 720-2.