P46Differential diagnosis in fetal obstructive uropathy

Case report A healthy 24-year-old secundigravida presented for a routine ultrasound examination at the 11th week of gestation. The scan showed a singleton pregnancy and the crown-rump length (43.8 mm) was compatible with the gestation calculated from the last menstrual period. The foetal abdomen was distended by the presence of one only cyst (12 × 7.4 mm), compatible with distension of the bladder. There was no other evident abnormality. Amniotic fluid volume was normal for the first trimester despite total urethral obstruction. At 14 weeks still birth was found and the patient delivered three days later. Diagnosis was confirmed at autopsy. Post mortem examination confirmed a phenotypically normal male foetus consistent with 14 weeks gestation and weighing 70 gr. The abdomen was distended and the abdominal wall was thin. Internal examination confirmed the presence of an enlarged bladder. There was urethral atresia, with associated dilatation of the bladder but the ureter and kidneys were normal. Internal genitals were male with normal testicles and penis. Chromosome analysis was performed on foetal skin and karyotype was 46, XY. Discussion Cloacal dysgenesis sequence (CDS) is a rare cause of fetal obstructive uropathy (FOU). The prenatal differentition of CDS from other FOU is important because CDS is not amenable to in utero surgical intervention in the form of vescicoamniotic shounts. Differential diagnosis must be made with pathologies capable of determining cystic lesions localised in the inferior foetal abdomen, such as ovarian cysts, intestinal duplications, Hirschsprung disease, colic dilatation, imperforate hymen with hydrometracolps and megacystes–microcolon syndrome. Accurate prenatal diagnosis can be difficult and requires prolonged serial observations. The above-mentioned pathologies have characteristics of relative ‘fixity’, while typical imaging of cloaca undegoes variations due to sequential filling in, or repletion, of the liquid contained in the urinary, genital and digestive components of the malformation. Moreover, intestinal obstruction is generally associated with polyhydramnios. In the first trimester diagnosis of cloaca anomalies are very difficult because there are no great changes in amniotic fluid volume and ascites rarely is present; serial examinations are required for enable definition of diagnosis.