Ultrasound diagnosis of pyogenic flexor tenosynovitis in a 9-month-old infant: a rare case report.

Pyogenic flexor tenosynovitis (PFT) is an aggressive infection of the flexor tendon sheath, requiring prompt intervention to minimize adverse outcomes. The diagnosis of pediatric PFT is often delayed due to the variable presence of Kanavel's signs in children and communication difficulties. A 9-month-old male presented to the emergency department with one of four Kanavel signs. The diagnosis of PFT was delayed until ultrasound was used to identify a fluid collection within the flexor tendon sheath. He was successfully treated with surgical debridement and antibiotic therapy, achieving full recovery by 6-month follow-up. This represents the youngest reported case of PFT. Difficulties with communication and physical exam as well as the variability of Kanavel's signs in young children can delay the diagnosis of pediatric PFT. Ultrasound can be a useful adjunct when clinical history and exam are equivocal, especially in children who present prior to language acquisition.