Back pain unveiled: Unexpected diagnosis of a large retroperitoneal pseudocyst - A case report

Retroperitoneal pseudocysts are rare lesions that can remain asymptomatic but may cause symptoms when they grow large. Imaging techniques like ultrasound, CT, and MRI are essential for diagnosis, and surgical excision is often recommended.

A 58-year-old woman presented with chronic lower back pain, and imaging revealed a large retroperitoneal cystic mass compressing surrounding structures. Due to symptom severity and uncertain origin, she underwent exploratory laparotomy. Intraoperatively, the mass was adherent to the inferior vena cava, right ureter, and appendix, requiring careful dissection and complete excision. The histopathology confirmed a benign unilocular cyst with chronic lymphocytic infiltration, findings compatible with a retroperitoneal pseudocyst, and the patient had an uneventful recovery.

Retroperitoneal pseudocysts are rare lesions that often present with nonspecific symptoms like vague abdominal pain, requiring imaging techniques such as CT and MRI for diagnosis. Surgical intervention is usually indicated for symptomatic or large cysts, with multidisciplinary teams essential in managing complex cases involving critical structures, as demonstrated in this case. There is no consensus on follow up after resection in the literature.

This case highlights the importance of considering retroperitoneal pseudocysts in the differential diagnosis of atypical abdominal or lumbar pain. Complete surgical resection with histopathological examination remains the cornerstone for both definitive diagnosis and symptom resolution. Given the lack of standardized guidelines on postoperative surveillance, further studies are needed to establish evidence-based follow-up protocols.