A previously healthy 3-year-old girl presented with a 1-month history of influenzalike symptoms complicated by a 4-day history of cough, tachypnea, tachycardia, and respiratory distress when recumbent. She had recent complaints of low-back pain and left shoulder pain. There was no significant medical history.
Vital signs on admission to the hospital were as follows: temperature, 36.5°C; heart rate, 154 beats per minute; respiratory rate, 50 breaths per minute; and blood pressure, 104/64 mm Hg. Physical examination revealed an illappearing girl with moderate respiratory distress who was most comfortable lying on her left side. Examination of the left side of the chest revealed a prominent hemothorax and decreased breath sounds on the left side. Examination of the right hemithorax revealed prominent heart sounds. There was some fullness of the left side of the abdomen, and an indistinct mass was palpated in the left upper quadrant. Results of