Prenatal Diagnosis of Fetal Lower Urinary Tract Obstruction with Posterior Urethral Valve: A Case Report

Abstract

Background: Fetal lower urinary tract obstruction (LUTO) is a rare but potentially life-threatening congenital anomaly that can result in severe oligohydramnios, pulmonary hypoplasia, and renal dysplasia. Prenatal ultrasound is essential for early identification and evaluation of its etiology and severity.

Case Presentation: A 26-year-old woman gravida 2 para 1 at 24–25 weeks' gestation was referred due to suspicion of a fetal urinary tract anomaly. Ultrasound revealed a single intrauterine fetus in breech presentation with bilateral hydronephrosis, marked bladder distension (megacystis), and the presence of a “keyhole sign”—suggestive of posterior urethral valve. Anhydramnios was also noted, consistent with impaired fetal urine output. Based on these findings, the diagnosis of LUTO secondary to PUV was established. Conservative management was chosen, and the patient was counseled on prognosis, with plans for close follow-up.

Conclusion: This case underscores the critical role of prenatal ultrasound in the diagnosis of LUTO and the identification of key features such as the "keyhole sign" that can indicate posterior urethral valve. Accurate prenatal diagnosis enables appropriate counseling, monitoring, and preparation for potential interventions to optimize postnatal outcomes.