Retroperitoneal bronchogenic cyst with fluid‑fluid level: A case report and literature review.

Bronchogenic cyst is a benign lesion with congenital dysplasia. Although the occurrence of this type of cyst is rare in the retroperitoneum, the presence of fluid-fluid levels is an even rarer phenomenon in bronchogenic cysts. Therefore, it can be easily misdiagnosed due to the lack of a universal guideline of specific imaging manifestations. The present report describes the case of a patient with a bronchogenic cyst with fluid-fluid levels whilst also performing a brief literature review to summarize the findings of previous reports on this condition. A 48-year-old male individual presented with severe lower back pain without any obvious causes. A CT scan revealed a low-density cystic mass of ~3x4x6 cm in the left front of the T12-L2 area, which originated from the left crus of the diaphragm. MRI revealed a fluid-fluid level in the cyst. Anterior thoracolumbar surgery was performed to completely resect the mass. During the surgery, it was confirmed that the cyst originated from the left crus of the diaphragm and the lesion was diagnosed to be a bronchogenic cyst by pathological analysis. The patient's symptoms improved after the surgery and no recurrence of the cyst was observed during the 3-year follow-up period. The presence of a fluid-fluid level in a retroperitoneal bronchogenic cyst is rare, particularly in the abdominal aorta and paravertebral regions, rendering it easily misdiagnosed. It may be associated with protein, hemorrhage and calcium-containing mucus deposition in the cysts. In the present study, a rare case of fluid-fluid level in bronchogenic cyst was reported and a literature review was provided.