Subdiaphragmatic extra-lobar sequestrations - a minimalistic approach to management

• Evolving understanding about indolent behaviour of congenital subdiaphragmatic lesions is changing surveillance practice • Ultrasound can adequately characterise and monitor presumed subdiaphragmatic sequestrations. • Ultrasound may be non-inferior to cross sectional imaging in characterisation of congenital subdiaphragmatic lesions Subdiaphragmatic extra-lobar sequestrations are one of a broad range of conditions presenting as an incidental antenatal finding of a suprarenal mass (SRM). With emerging evidence suggesting most of these lesions are suitable for surveillance rather than early intervention, the postnatal imaging characterisation of these lesions and surveillance algorithm is increasingly relevant. Evidence suggests subdiaphragmatic sequestrations can be adequately characterised by ultrasound alone and that their natural history is of complete or partial involution. Five patients were prospectively enrolled at Sydney Children’s Hospital following antenatal second-trimester presumptive diagnosis of SRM between February 2021-February 2024. Follow-up surveillance ultrasound was performed in the neonatal period and then regular intervals. Criteria for progression to cross-sectional imaging included lesion growth, sonographic features suggestive of malignancy (infiltrative, evidence of nodal or metastatic disease) or positive urinary catecholamines. All lesions demonstrated postnatal sonographic characteristics consistent with the antenatal diagnosis of sELS. All lesions decreased in size throughout the study period. Two patients proceeded to cross-sectional imaging, one of which demonstrated involution of the lesion and the other of which supported the diagnosis of sELS. Our small cohort suggests that antenatally presumed sELS can be adequately characterised and observed with USS alone. These results should inform larger studies to draw more robust conclusions sonographic surveillance protocols for these lesions.