Primary hydatid cyst in the lumbar paravertebral muscle: a case report and review of literature

Abstract Background Primary intramuscular hydatid disease is an exceptionally rare form of Echinococcus granulosus infection, accounting for only 0.5–5% of cases. Paravertebral muscle involvement is particularly uncommon and often mimics other soft-tissue lesions, leading to diagnostic delays. We present an exceedingly rare case of primary lumbar paravertebral intramuscular hydatid disease occurring in complete isolation from visceral organs. Case Description A 32-year-old woman presented with chronic low back pain and no neurological deficits. Lumbar MRI revealed a well-circumscribed, multiloculated cystic lesion within the left paravertebral musculature at the L3–L5 level, measuring 46 × 42 × 60 mm, without foraminal extension or spinal canal compromise. Serological testing for hydatid disease was negative, and systemic imaging identified no additional cysts. Surgical exploration allowed en bloc excision of the lesion without rupture, followed by hypertonic saline irrigation. Histopathological examination confirmed the diagnosis of hydatid cyst. The postoperative course was uneventful, and the patient completed three months of albendazole therapy. Conclusion Primary hydatid cyst of the lumbar paravertebral muscle is an exceptionally rare entity that requires a high index of suspicion, particularly in patients from endemic regions. Because clinical findings and serology are often non-specific, MRI serves as the most informative diagnostic tool, although definitive confirmation depends on histopathology. Radical excision without cyst rupture remains the treatment of choice, complemented by postoperative albendazole therapy to reduce recurrence. Long-term surveillance is essential, and hydatid disease should be considered in the differential diagnosis of paravertebral cystic masses.