A 37-year-old patient complains of pain in the lumbar spine that is getting stronger during walking; restricted mobility, edema of the right side of abdomen. He has a history of focal tuberculosis. X-ray picture shows the destruction of the adjacent surfaces of the 1-2 vertebral bodies of the lumbar spine, vertebral body height is decreased, intervertebral foramen is undetectable. Abdominal ultrasound reveals a 15x20 cm formation in the retroperitoneal space, there are echo signals of fluid presence. What is the most likely diagnosis?