Intern Ultrasound of the Month: Complex Abscess of the Hand & How to Evaluate for Tenosynovitis Using POCUS
The Case
35-year-old otherwise healthy male presented to the emergency department for several days of right hand pain and swelling. States he accidentally cut his hand on broken glass about 1 week prior to this. He was seen at an outside hospital at the time and discharged home. Was doing well initially but then symptoms developed over subsequent days and progressively worsened. Had limited function of his hand as a result. Denied paresthesia, fever, chills and had an otherwise negative ROS. He saw orthopedic surgery in the clinic who then sent him to the ED.
His vitals were within normal limits. Physical exam was notable for swelling, erythema, and tenderness to the dorsum of his right hand, most significant over the proximal ulnar aspect, with tense fluid collection. He had significant pain with hand flexion/extension and decreased grip strength. His 4th digit was diffusely swollen, held in slight flexion, tender to palpation over both the extensor and flexor surfaces, and pain was easily elicited with passive extension (4 of 4 Kanavel signs). Digits all had good perfusion. His wrist had slightly limited ROM due to pain. He was nontoxic appearing.
POCUS was performed to evaluate for soft tissue infection, particularly abscess/cellulitis as well as tenosynovitis. In order to help facilitate a good exam and reduce pain, a water bath was used.
POCUS findings: Top left image - large heterogenous fluid collection over his hand consistent with abscess, + cobblestoning consistent with cellulitis of surrounding area. Top right image - dorsal aspect of digit showed a small amount of nonspecific fluid. Bottom images - the volar surface of the digit is relatively normal-appearing with intact tendons and no significant peritendonous fluid or sheath thickening.
Case continued: Hand surgery was consulted and recommended MRI, which showed large abscess and extensive cellulitis of his hand abutting the extensor digitorum tendons of the 4th digit but no evidence of tenosynovitis (flexor or extensor) or osteomyelitis. Bedside I&D was performed, and 30cc of purulent fluid drained. He was treated with IV antibiotics and admitted to the hospital. His symptoms improved considerably after drainage, and his 4th digit impairment/pain was attributed to the more proximal extensor tendon involvement near his abscess. He did well overall and was discharged a few days later on antibiotics.
MRI hand showing focal fluid collection in dorsal aspect along with inflammatory changes.
So if this isn’t tenosynovitis, what does tenosynovitis look like on ultrasound???
Pyogenic Tenosynovitis
Surgical emergency of the hand. Typically results from a puncture wound that introduces bacteria (most commonly staph aureus) into the tendon sheath. As purulent fluid accumulates, it creates a high-pressure environment and can ultimately lead to ischemia and necrosis if not promptly diagnosed and treated [1].
Kanavel cardinal signs [2] are commonly used to distinguish between tenosynovitis from other similar conditions
Symmetric/fusiform swelling (“sausage digit”)
Partially flexed at rest
Tenderness along flexor tendon
Pain with passive extension
***Not well-validated. A recent study showed high sensitivity but poor specificity (51-69%) [3]
Risk factors associated with poorer prognosis: age over 40 years, diabetes, renal failure, peripheral vascular disease, polymicrobial infections, local ischemia, presence of subcutaneous purulence [4]
Definitive management: surgical decompression and irrigation + prolonged course of antibiotics [1,4]
POCUS Evaluation for Tenosynovitis
https://www.aliem.com/ultrasound-win-53m-right-index-finger-swelling/
Technique & Tips for Soft Tissue US
Use a water bath when possible — this can improve image quality & is better tolerated by pts.
Place the affected extremity in a container of water. The probe can remain a few centimeters above the affected body part so you don’t even have to touch the patient (water acts as a great conductive medium).
High frequency probe is best
Scan in two orthogonal planes (long & short axis) and fan through the area to assess extent.
Identify anatomy. Evaluate for focal fluid collection and/or cobblestoning to suggest abscess and cellulitis, respectively. For tenosynovitis, look for abnormal findings listed below. Compare to the unaffected side (extremity), especially if unsure if normal or abnormal
Apply Color Doppler to distinguish a fluid collection from vasculature and to assess for hyperemia.
Apply gentle compression — abscess contents tend to swirl with compression (“squish sign")
A quick note on tendons
Tendons appears as tightly-bound echogenic parallel lines w/ fibrillar appearance when viewed longitudinally and circular bundles when viewed in an axial plane. They’re typically highly echogenic when the probe is directly perpendicular, but as the angle of insonation changes (i.e. with fanning), it will appear more hypoechoic. This is referred to as anisotropy, an angle-dependent artifact that occurs with highly organized structures such as tendons [5]. It can easily be mistaken for fluid, but fanning the probe will help differentiate the two — fluid will maintain a hypoechoic appearance while a normal tendon’s echogenicity will change.
Normal flexor tendons seen in cross section, illustrating anisotropy. As the angle of the probe changes with fanning, the tendons’ appearance alternates between hyperechoic and hypoechoic.
POCUS Findings of Tenosynovitis [6,7]
Tendon sheath thickened and hyperemic with color doppler
Fluid surrounding the tendon
Tendon thickening > 25%
Echogenic debris in the synovial fluid
Tenosynovitis * = fluid; x = tendon; ^ = tendon sheath
https://www.aliem.com/ultrasound-win-53m-right-index-finger-swelling/
https://www.aliem.com/ultrasound-win-53m-right-index-finger-swelling/
The Evidence — How Accurate is POCUS for Tenosynovitis?
94% sensitive, 74% specific for flexor tenosynovitis if either peri-tendonous effusion or thickened synovial sheath were seen [8].
Take Home Points
Pyogenic tenosynovitis is a surgical emergency, and prompt diagnosis and treatment (emergent surgical decompression/irrigation + IV antibiotics) are essential to prevent significant morbidity. Symptoms and physical examination findings often mimic more benign, superficial soft tissue infections.
POCUS findings of fluid +/- hyperemia surrounding the affected tendon and tendon sheath thickening can help distinguish tenosynovitis from other SSTI infections, particularly in earlier stages when the clinical findings are less diagnostic. These findings are highly sensitive but less specific.
POST BY: DR. RALEIGH EMS, PGY1
FACULTY EDITING BY: DR. LAUREN MCCAFFERTY
References
Draeger R, Bynum D. Flexor tendon sheath infections of the hand. J Am Acad Orthop Surg. 2012;20(6):373-382.
Kanavel A. The symptoms, signs, and diagnosis of tenosynovitis and fascial-space abscesses. Infections of the Hand. 1912.
Kennedy CD, Lauder AS, Pribaz JR, Kennedy SA. Differentiation between pyogenic flexor tenosynovitis and other finger infections. Hand. 2017; 12(6): 585-590.
Pang HN, Teoh LC, Yam AK, Lee JY, Puhaindran ME, Tan AB. Factors affecting the prognosis of pyogenic flexor tenosynovitis. J Bone Joint Surg Am. 2007;89:1742–1748.
Noble V, Nelson B. Manual of Emergency Medicine and Critical Care Ultrasound, 2nd ed. Cambridge: Cambridge UP, 2011.
Amini, R. et al. Point of Care Ultrasound in Pyogenic Tenosynovitis: A Case Report. Bull Emerg Trauma. 2020. Jan 8(1): 41-46.
Padrez K, Bress J, Johnson B, Nagdev A. Bedside ultrasound identification of infectious flexor tenosynovitis in the emergency department. West J Emerg Med. 2015;16(2):260-2.
Jardin E, Delord M, Aubry S, Loisel F, Obert L. Usefulness of Ultrasound for the Diagnosis of Pyogenic Flexor Tenosynovitis: A Prospective Single-Center Study of 57 Cases. Hand Surg Rehabil. 2018;37(2):95-98.