PRENATAL AND POSTNATAL OUTCOMES OF FOETAL MEGACYSTIS: What to expect when posterior urethral valves are excluded? A retrospective multicentre study.

Background:Foetal megacystis (FM) may be associated with a wide range of conditions beyond posterior urethral valves (PUV).This study aimed to describe the outcomes of FM cases, excluding PUV, in order to better understand the long-term consequences of these conditions and improve prenatal counselling. Methods:This retrospective multicentre study, conducted between 2009 and 2023, included pregnant women referred for suspected FM across three foetal medicine units.Patients with confirmed PUV, diagnosed either postnatally or through pathological examination following medical termination of pregnancy (MToP) or intrauterine foetal death (IUFD), were excluded.FM was defined as a longitudinal bladder diameter 7 mm between 10 and 14 gestational weeks (GW) or as an enlarged bladder that does not empty during examination for at least 40 minutes after 14 GW.Maternal information, ultrasound findings, genetic testing results, final diagnoses, and follow-up data were collected.Both MToP and IUFD cases were included. Results:Among 170 referrals, 96 cases of FM without PUV were confirmed: 31 (32.3%)live-born children, 49 (51%) MToP, and 16 (16.7%)IUFD.Overall, 66/96 (68.75%) cases were referred during the first trimester.Earlier gestational age at diagnosis was strongly associated with poor outcomes (p < 0.001 overall; p = 0.004 for males), even after excluding MToP cases (p < 0.001).All IUFD cases J o u r n a l P r e -p r o o f involved first trimester diagnoses, with 12.5% showing chromosomal anomalies.MToP occurred after a first trimester diagnosis in 83.7% of cases.Among the 31 live-born infants, four were 46, XX foetuses: two had polymalformative syndromes responsible for neonatal deaths, one had transient urinary retention, and one had bilateral vesicoureteral reflux (VUR) requiring surgery.Among the 27 live-born male infants, one neonatal death occurred.Among the remaining 26, nine (34.6%) had no urinary issues, 12 (46%) had uni-or bilateral VUR, one (3.8%)had chronic intestinal pseudo-obstruction, one (3.8%)had a VACTERL syndrome, and three (11.5%)had neurogenic bladders, one of whom required kidney transplantation.In this subgroup, VUR was significantly associated with third trimester pelvicalyceal dilatation (p = 0.047).Conclusion: This 15-year retrospective analysis confirms the heterogeneous diagnoses and prognoses associated with FM when PUV are excluded.FM in females may indicate a poorer prognosis, while VUR is common in males.Detailed prenatal ultrasound findings may help distinguish cases with favourable outcomes from those with poorer prognosis.Postnatal imaging and renal assessment remain essential.