After institutional ethics board approval and written informed consent from parents, 197 children scheduled for routine genitourinary operation and in whom a LMA was indicated for anesthesia were included in the study. The size of the LMA was determined by choosing the size that was best matched with the auricle of the children. The results were compared with the standard method recommended by the manufacturer's weight-related guidelines. The patients were classified in different groups depending on the PLMA sizes determined by both methods. A kappa coefficient evaluated the agreement between both techniques.

Inclusion Criteria:

• ASA physical status I/II
• scheduled for genitourinary operation
• LMA was indicated for anesthesia

Exclusion Criteria:

• surgery lasting more than 3 h
• overweight or underweight patients
• gastroesophageal reflux
• risk of aspiration
• airway infection in the last six weeks
• decreased pulmonary or chest wall compliance.