Abscess. Evaluate for "osteo" There is a lobulated collection of fluid signal intensity within the soft tissues medial to the medial malleolus. The collection is approximately 4.5 x 2 cm in transverse dimension and approximately 4.5 cm in craniocaudal dimension. Superficially, the collection lies just beneath the skin surface. Its deep margin lies against the medial malleolus and medial aspect of the distal tibial metaphysis. There appears to be mild periosteal reaction along the distal tibial metaphysis. There is mild increased signal intensity within the underlying medullary bone on the fat-suppressed T2-weighted images, but I suspect that this is reactive osteitis, as lack of signal abnormality on the T1-weighted images argues against medullary infection. Anteriorly, the collection approaches the medial aspect of the tibialis anterior tendon, but appears to lie superficial to the retinaculum. Posteriorly the collection approaches the tibialis posterior tendon.There is reticulation of the subcutaneous fat of the ankle indicating edema. This extends along the dorsum of the foot where it becomes confluent. Signal intensity of the tendons is within normal limits. Small amounts of fluid in the sheaths of the medial and lateral tendons are within normal limits. There are small amounts of fluid within the tibiotalar and subtalar joints, within normal limits. The lateral collateral ligament complex appears normal. The distal tibiofibular syndesmotic complex appears normal. Loss of normal fatty striations within the deep portion of the deltoid ligament may reflect prior sprain injury. There is edema-type signal within the head and neck of the talus which is nonspecific and may be arthritic in etiology or perhaps represent a stress reaction.
Findings compatible with the medial soft tissue abscess, with probable underlying periosteal reaction along the distal tibia perhaps reflecting early cortical osteomyelitis. Although there is mild increased signal intensity within the underlying medullary bone on fat-suppressed T2-weighted images, I suspect that this is reactive osteitis, as the fatty signal intensity on T1-weighted images is preserved. Other findings as above.