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Emergency Ultrasound

Cases That Count: A 34-Year-Old Female with Finger Pain and Swelling

Lindsay Davis, MD and Marsia Vermeulen, DO, FACEP, RDMS, RDCS
NYU/Bellevue Hospital Center


Chief Complaint: finger pain and swelling

A 34-year-old right-hand dominant female with no past medical history presents to the emergency department (ED) with right index finger pain. She was bitten by a stray cat four days prior and since then has noted increasing redness, swelling and pain to the digit. On the day of presentation, she is afebrile and appears uncomfortable. She is holding her right hand with fingers in flexion. Her right index finger is diffusely swollen and erythematous, and she has pain with passive extension of the finger. Bite marks are visible at the proximal palmar aspect of the digit, without appreciable fluctuance or drainage. She has good capillary refill and is neurologically intact.  

The patient is given analgesia and x-rays are obtained, which yield no bony abnormalities or evidence of foreign body. An ultrasound is performed for further evaluation.

Image 1

Image 2


  1. What are the significant findings in the above ultrasound images?
  2. What is the pathophysiology of this condition?
  3. How can POCUS improve diagnosis of this condition?

The Role of Hand Point-of-Care Ultrasound (POCUS):

Though hand complaints comprise a small percentage of ED visits, rapid and accurate diagnosis is important. Coordination and fine motor skills of the hand are required for all facets of life, and misdiagnosis can be associated with significant morbidity and financial implications.1,2 The differential diagnosis for a painful, erythematous, swollen digit after trauma includes fracture, cellulitis, superficial abscess, foreign body, septic arthritis, and infectious tenosynovitis. POCUS is an excellent modality to distinguish between superficial soft tissue infections and more complicated deep space infections. POCUS is more sensitive than physical exam or even computed tomography (CT) for soft tissue abscess.3,4 A fluid collection in the deep compartments of the hand or within the tendon sheath signify more serious pathologies that may require surgical intervention; early recognition of these conditions can expedite necessary treatment and specialist involvement. POCUS can also be used to identify foreign bodies, including those that are radiolucent and thus not visible on plain film.5,6

POCUS examination of the hand is best performed by using a high-frequency linear transducer to visualize superficial structures. Ease of exam and image quality can be improved by using a water bath. The patient’s hand is submerged in a basin of water and the probe is placed in the water aimed at the area of interest without making direct contact with the skin. The water serves as a conducting medium and allows for high quality images despite the difficult anatomical terrain of the hand.7

Answers to Questions:

  1. What are the significant findings in the above ultrasound images?

    Both images are longitudinal views of the index finger demonstrating anechoic fluid surrounding the fibrous hyperechoic flexor tendon, concerning for infectious flexor tenosynovitis (FTS), given the clinical context of the case. Also demonstrated is cobblestoning of the subcutaneous tissue, consistent with cellulitis.

  2. What is the pathophysiology of this condition?

    Infectious tenosynovitis is an infection of the tendon and the synovial sheath, resulting in a collection of purulent fluid in the potential space between the visceral and parietal layers of the tendon sheath. It can be caused by infection via direct inoculation (trauma), contiguous spread from adjacent tissues, or hematologic spread. While tenosynovitis can occur in any joint, the most common location for tenosynovitis is in the flexor tendons of the hand and wrist, known as flexor tenosynovitis.8 The common flexor sheath travels through the carpal tunnel into the palm of the hand and contains the flexor digitorum superficialis and flexor digitorum profundus tendons. Flexor tenosynovitis is a surgical emergency. Many tendon sheaths communicate with other deep space compartments of the hand, allowing for rapid spread of infection.8 Delay in treatment (empiric antibiotics and surgical irrigation and debridement) can lead to significant morbidity, including tendon rupture, permanently restricted movement, tissue necrosis, and amputation.9

  3. How can POCUS improve diagnosis of this condition?

    Providers often rely on physical exam to diagnose this potentially devastating infection, utilizing Kanavel’s four cardinal signs originally described over 100 years ago: fusiform swelling of the digit, pain with palpation over the flexor tendon sheath, the finger held in flexion for comfort, and pain with passive extension.10 However, a negative exam does not rule out the condition, and these findings are not reliably present in children and adolescents.11 While there are few cases reported in the literature using POCUS to diagnose FTS in the ED, ultrasound has been shown to be more sensitive than clinical exam for diagnosing FTS and in some studies even outperforms MRI.12-16 Pairing POCUS with physical exam findings may therefore improve early identification and management of infectious tenosynovitis.


When presented with a patient in the ED with a clinical presentation concerning for infectious FTS, POCUS can be used to increase diagnostic confidence and expedite care.17


  1. National Hospital Ambulatory Medical Care Survey. 2010 Emergency Department Summary Tables. Available at: http://www.cdc.gov.ezproxy.med.nyu.edu/nchs/data/ahcd/nhamcs_emergency/2010_ed_web_tables.pdf
  2. Rosberg H, Carlsson K, Dahlin L. Prospective study of patients with injuries to the hand and forearm: costs, function, and general health. Scand J Plast Reconstr Surg Hand Surg. 2005;39(6):360-9.
  3. Gaspari R, Davno M, Briones J, et al. Comparison of computerized tomography and ultrasound for diagnosing soft tissue abscesses. Crit Ultrasound J. 2010 Apr 172;4(1):5.
  4. Tayal V, Hasan N, Norton H, et al. The effect of soft-tissue ultrasound on the management of cellulitis in the emergency department. Acad Emerg Med. 2006 Apr;13(4):384-8.
  5. Budhram GR, Schmunk JC. Bedside ultrasound aids identification and removal of cutaneous foreign bodies: a case series. J Emerg Med. 2014 Aug;47(2):e43-8.
  6. Dumarey A, De Maeseneer M, Ernst C. Large wooden foreign body in the hand: recognition of occult fragments with ultrasound. Emerg Radiol. 2004 Jul;10(6):337-9.
  7. Blaivas M, Lyon M, Brannam L, et al. Water bath evaluation technique for emergency ultrasound of painful superficial structures. Am J Emerg Med. 2004 Nov;22(7):589-93.
  8. Draeger RW, Bynum DK Jr. Flexor tendon sheath infections of the hand. J Am Acad Ortho Surg. 2012 Jun;20(6):373-82.
  9. Pang HN, Teoh LC, Yam AK, et al. Factors affecting the prognosis of pyogenic flexor tenosynovitis. J Bone Joint Surg Am. 2007 Aug;89(8):1742-8.
  10. Kanavel A. Infections of the hand (1st edition). Lea and Febiger, Philadephia and New York. 1912.
  11. Brusalis CM, Thibaudeau S, Carrigan RB, et al. Clinical characteristics of pyogenic flexor tenosynovitis in pediatric patients. J Hand Surg Am. 2017 May;42(5):388.
  12. Schecter WP, Markison RE, Jeffrey RB, et al. Use of sonography in the early detection of suppurative flexor tenosynovitis. J Hand Surg Am. 1989 Mar;14(2 Pt 1):307-10.
  13. Jeffrey RB Jr, Laing FC, Schecter WP, et al. Acute suppurative tenosynovitis of the hand: diagnosis with ultrasound. Radiology. 1987 Mar;162(3):741-2.
  14. Backhaus M, Kamradt T, Sandrock D, et al. Arthritis of the finger joints: a comprehensive approach comparing conventional radiography, scintigraphy, ultrasound and contrast-enhanced magnetic resonance imaging. Arthritis Rheum. 1999 Jun;42(6):1232-45.
  15. Hmamouchi I, Bahiri R, Srifi N, et al. A comparison of ultrasound and clinical examination in the detection of flexor tenosynovitis in early arthritis. BMC Musculoskelet Disord. 2011 May 8;12:91.
  16. Marvel BA, Budhram GR. Bedside ultrasound in the diagnosis of complex hand infections: a case series. J Emerg Med. 2015 Jan;48(1):63-8.
  17. Padrez K, Bress J, Johnson B, et al. Bedside ultrasound identification of infectious flexor tenosynovitis in the emergency department. West J Emerg Med. 2015 Mar;16(2):260-2.
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