Patients
This is a secondary analysis of a prospective study performed in PTB32W. From November 2017 to April 2020, every PTB32W admitted to the NICU at Hospital Puerta del Mar in Cádiz, Spain (inborn or transferred from another hospital in the first 24 hours of life) was recruited with parental consent. Infants with chromosomal abnormalities, major malformations or those who died before 36 weeks’ PMA were excluded. The local Ethics Committee approved the study protocol, with the internal number LUS-NEO-17-01. We selected the patients that received diuretics before 36 weeks’ PMA, and had more than one LU before and after beginning of treatment. Diuretics recorded were furosemide, hydrochlorothiazide and spironolactone. Diuretics were prescribed by the attending neonatologist, who was not aware of the LU results.