外科的摘出を行った関節リウマチ患者における膝窩嚢腫破裂の1例

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Background: Popliteal cysts are often observed in patients with rheumatoid arthritis (RA) . Complications of these cysts are rupture, dissection, pseudothrombophlebitis, leg ischemia, nerve entrapment, and compartment syndrome. We describe a patient suffering from RA with a ruptured popliteal cyst that was treated by surgery.

Case: A 74-year-old patient with RA presented with sudden-onset pain and tense swelling in his right calf. Prior to hospital admission, a deep vein thrombosis (DVT) was suspected, and he was referred for evaluation and treatment. His C-reactive protein level was 3.78 mg/dL, and his D-dimer level was 3.7 μg/mL (normal level, <1.0 μg/mL) . During his evaluation for DVT, the diagnosis of a ruptured popliteal cyst (RPC) was made on enhanced computed tomography and magnetic resonance imaging. He resisted conservative management and was treated surgically. Postoperatively, the cyst disappeared completely and has not recurred.

Conclusion: A popliteal cyst is a benign lesion that results from degenerative or inflammatory disease of the knee joint. This cyst may rupture causing severe pain in the calf, with warmth, erythema, and tenderness. This may be confused with other causes of swelling and pain in the calf including deep vein thrombosis. Hence it is also described as pseudothrombophlebitis.

 After surgical resection of such cysts, general as well as local signs of inflammation improved. In difficult cases, surgery is considered to be very effective for the treatment of RPCs. In the case of failure of conservative management, surgical treatment is a good option for the treatment of RPCs.