Abstract
BACKGROUND: Echinococcus species causes hydatid cyst (HC) disease, primarily affecting the liver and lungs. Bone involvement is rare (0.5%-2% of cases), with half occurring in the vertebral system. Sacral spine involvement is particularly uncommon and poses diagnostic challenges. OBSERVATIONS: A 17-year-old male with a history of HC disease presented with low back pain radiating to both lower limbs, claudication, and chronic constipation for 5 years. Imaging revealed a large, multiloculated sacral cyst extending retrorectally and presacrally from S3 to S5, involving the spinal canal, compressing the rectum, and causing sacral erosion. A diagnosis of sacral hydatidosis was made, and the patient was started on albendazole, with surgical excision planned. LESSONS: HC disease should be considered in the differential diagnosis of low back pain and constipation, especially in endemic regions. Because of its invasive nature and high recurrence rate, early diagnosis, antiparasitic therapy, and surgical intervention are essential. Proper follow-up is necessary to prevent complications, particularly in atypical presentations. https://thejns.org/doi/10.3171/CASE25109.