A primary hydatid cyst in the pelvis is rare, and usually presents with pressure symptoms affecting the adjacent abdominal organs. We describe such a cyst which protruded through the sciatic notch and presented as a gluteal swelling with a foot drop due to compression of the lumbosacral nerve roots. Surgical excision and postoperative treatment with albendazole for six weeks were effective in controlling the disease and preventing recurrence.J Bone Joint Surg [Br] 1998;80-B:1037-9. Received 2 February 1998 Accepted 6 May 1998 Hydatid disease is widely prevalent and is caused by Echinococcus granulosus. It is transmitted by the ingestion of eggs and commonly involves the liver (80%) and lung (15%) although any part of the body may be affected. We describe a case of a primary intrapelvic hydatid cyst presenting with a foot drop. So far all previous cases which have been described with a neurological deficit have been cysts of the vertebral column compressing the spinal cord or the cauda equina.
Case reportA 24-year-old woman presented with a painless swelling over the right gluteal region, which had progressively increased in size over six months. Numbness and weakness involving the right leg had been present for four days. There was no associated fever, loss of appetite, backache or history of tuberculosis. Local examination showed a cystic, non-tender swelling of about 4 cm in diameter in the right gluteal region, lying deep to gluteus maximus, and which was palpable in the right fornix on vaginal examination. A fluid thrill was present between the two sites. No swelling or mass could be felt in the abdomen and there was no spinal tenderness or deformity. Neurological examination showed weakness of the hip extensors and abductors (2/5), the hamstrings (2/5), and the muscles of the ankle and foot (0/5) on the right side as measured on the MRC scale. There was diminished sensation in the distribution of the L5, S1 and S2 roots on the affected side along with perianal anaesthesia.The clinical diagnosis was that of a benign tumour. Possibilities considered were a cystic neuroma arising from the sciatic nerve or the lumbosacral plexus, a sacral teratoma, or a hydatid cyst compressing the lumbosacral roots. The plain radiograph did not show any abnormality except for doubtful enlargement of the right sciatic notch. Ultrasonography of the abdomen revealed a large (10.7 ן 5.6 cm) hypoechoic mass with echogenic septations in the presacral area posterolateral to the uterus and extending into the right gluteal region. Both kidneys and the urinary bladder appeared normal. MRI revealed a large cystic mass in the right pelvis, with well-defined walls, situated posterior to the bladder and extending to the gluteal region through the greater sciatic notch (Fig. 1a). Aspiration of the swelling yielded approximately 15 ml of clear to straw-coloured fluid. Smear and cytospin preparation from the fluid showed acellular material with no evidence of any atypical cells or parasites. No acid-fast bacilli could be visualised in th...