Acute increase in a thyroid cyst during cesarean section under general anesthesia in a full-term parturient: a case report.

Background: Pregnancy is associated with thyroid nodule formation and increased size. However, an acute increase in thyroid cysts during cesarean section is unusual. Case Description: We describe the case of a 23-year-old primiparous woman at 37 weeks of gestation, without a history of thyroid disease, who underwent a cesarean section under general anesthesia. When the baby was delivered after induction of general anesthesia, the patient's airway pressure increased by approximately 5-7 mmHg, and her blood pressure increased to 170/78 mmHg. After delivery of the baby, the mother's anterior region of the neck began to swell, and ultrasonography revealed a large cystic mass. Even after aspiration of approximately 120 mL of dark brown intra-cystic fluid, the neck swelled again. Airway and blood pressure decreased after delivery and remained within the normal range until the end of surgery. Computed tomography performed after recovery from anesthesia revealed an approximately 320 mL-sized hemorrhagic cyst in the left thyroid gland with right tracheal deviation. Despite repeated aspirations and two alcohol ablations, the cyst's size increased rapidly, and the patient underwent radiofrequency ablation. Conclusions: This case indicates that rapid increases in intrathoracic and blood pressure could precipitate a rapid increase in pre-existing thyroid cysts in a parturient during delivery.