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Age / Sex : /
Age/sex: 56/M
Chief complaint: Lt lower leg pain and swelling
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD ([email protected])
Courtesy : Sung Hwan Hong, MD., Seoul National University College of Medicine
Diagnosis: ruptured Baker's cyst
Discussion
Findings:
The axial CT images of the lower extremities reveal a subfascial fluid collection in the medial head of left gastrocnemius muscle. The right lower extremity appears normal. The axial fat-suppressed proton-density-weighted images of the right knee demonstrates fluid in the gastrocnemius/semimembranosus bursa (Baker’s cyst) and extension of fluid out of the Baker’s cyst into the fascial plane adjacent to the medial head of the gastrocnemius muscle.
Differential Diagnosis:
The MRI findings of a ruptured Baker’s cyst may be misleading. Rim enhancing fluid collections as well as subcutaneous and fascial enhancement may suggest an infectious etiology such as cellulitis, abscess, pyomyositis, pyogenic arthritis.
Discussion:
Baker’s cyst or popliteal cyst refers to distention of the gastrocnemius-semimembranosis bursa by synovial fluid. These cysts are seen frequently in patients with rheumatoid arthritis but can also occur in several other conditions including trauma, internal derangement, osteoarthritis, and other arthritities. The most common complication of Baker cyst is the rupture or dissection of fluid into the adjacent proximal gastrocnemius muscle belly, which results in a pseudothrombophlebitis syndrome mimicking symptoms of DVT. The incidence of Baker cyst rupture is 3.4-10%. A ruptured Baker cyst may present as an enlarging mass in the calf, pain, edema, and erythema of the calf. The pseudothrombophlebitis syndrome can occur with rupture of a Baker’s cyst or can also be seen secondary to compression of venous vessels by an extensive dissecting Baker’s cyst that has not ruptured. As the clinical presentation of deep venous thrombosis, pseudothrombophlebitis syndrome, and cellulitis can be similar, imaging studies are helpful. MRI or ultrasound can be used to evaluate patients with this clinical presentation. Rarely, dissection or rupture of a Baker cyst can increase pressure within the deep posterior compartment of the leg, causing posterior compartment syndrome. Dissection of Baker cysts can also cause anterior compartment syndrome, depending on the direction of dissection. A Baker cyst usually dissects through the muscles, primarily below the knee. There is evidence that almost one third of dissections are into the thigh.
References:
1. Torreggiani WC, Al-Ismail K, Munk PL, Roche C, Keogh C, Nicolaou S, et al. The imaging spectrum of Baker's (popliteal) cysts. Clin Radiol 2002;57(8):681-91.
2. Molpus WM, Shah HR, Nicholas RW, et al. Case report 731. Complicated Baker's cyst. Skeletal Radiol. 1992;21(4):266-8.
3. Munk PL, Vellet AD, Levin MF. Leaking Baker's cyst detected by magnetic resonance imaging. Can Assoc Radiol J. Apr 1993;44(2):125-8.
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