Q. A 7-year-old boy is brought to your clinic with jaundice and abdominal pain. He was diagnosed with hereditary spherocytosis two years ago and has received frequent transfusions. He received a transfusion one week ago; however, he is still anemic. He does not have a fever. His abdomen is distended but soft. The spleen edge is palpated near the umbilicus. Lab tests show a hemoglobin of 7.8 g/dL, a mean corpuscular hemoglobin concentration (MCHC) of 38 g/dL, reticulocytes 18%, bilirubin 7 mg/dL, lactate dehydrogenase (LDH) 246 U/L, haptoglobin of 18 mg/dL. Abdominal ultrasound shows several stones (2-3 cm) in the gallbladder and a huge spleen. What is the prerequisite for his required current treatment?