Bedside Ultrasound Identification of Infectious Flexor Tenosynovitis in the Emergency Department


Infectious flexor tenosynovitis (FTS) is a surgical emergency. If not treated promptly, infectious FTS carries significant morbidity including loss of function of fingers, necrosis of the tendon, and even digit amputation (1).

Infection can be caused in three ways: direct inoculation, contiguous spread, or hematogenous spread, as seen in cases of disseminated gonococcal infection. Tenosynovitis occurs when fluid collects between the visceral and parietal layer of the tendon, the most common location being in the hand and wrist.

Traditionally, diagnosis of infectious FTS is centered on the tetrad known as Kanavel’s signs (swelling of the finger, finger held in partially flexed position, pain on palpation of the flexor tendon, and pain on passive extension of the finger). While Kanavel’s signs are specific for infectious FTD, in a study of 41 participants with infectious FTS, only 54% of patients taken to the operating room (OR) had all of these signs (2). The gold standard of diagnosis remains surgical exploration and drainage. MRI can aid in the diagnosis of FTS, but this is rarely available in the ED. While radiographs may be obtained to look for trauma, osteomyelitis or a foreign body, they offer minimal to no additional benefit in diagnosing infectious FTS.   

This article presents a case of a 58-year-old man where point of care ultrasound (POCUS) identified tissue necrosis and fluid along the flexor tendon sheath of the hand, aiding in the rapid diagnosis of FTS, adding to the limited body of literature supporting use of POCUS for early diagnosis of infectious FTS.

Bedside Ultrasound Identification of Infectious Flexor Tenosynovitis in the Emergency Department

Clinical Question

Can point of care ultrasound be used in the emergency department to diagnose infectious FTS?

Methods & Study Design

• Design 

Case report.

• Population 

58 year old male with hypertension, diabetes and end stage renal disease.

• Intervention 

POCUS looking for fluid in flexor tendon sheath. Appropriate technique is shown in the image below, with a linear ultrasound probe placed on the palmar side of the wrist crease. Common findings of FTS are hypoechoic or anechoic fluid surrounding the flexor tendons.

ultrasound flexor tendons
Padrez et al. West J Emerg Med 2015, 16(2)

• Outcomes  

Accurate diagnosis of FTS



The physicians found a moderate amount of fluid and echogenic material within the tendon sheath, as noted in the image below. Orthopedics was consulted and patient was started on broad spectrum antibiotics and taken to the operating room. They found extensive pus within the flexor tendon sheath and cultures grew Staph aureus


ultrasound flexor tenosynovitis
Padrez et al. West J Emerg Med 2015, 16(2)

Strength & Limitations

The POCUS exam the authors describe is practical and useful. This could feasibly be performed by clinicians with relatively little ultrasound training. As mentioned, FTS is a surgical emergency and remains largely a clinical diagnosis, so any modality that helps bring more certainty to the diagnosis, and lead to quicker definitive treatment, is welcome.

It is unclear what the level of ultrasound training was for the physicians who performed this exam. Another note, it may be difficult to distinguish rheumatologic from infectious causes of tenosynovitis using ultrasound, so clinical context is always important. They also mentioned this can only aid in increasing your suspicion for FTS, it cannot be used to rule it out. 

Authors Conclusion

POCUS may be an ideal adjunct for the ED physician in the evaluation of a patient with suspected infectious FTS 

Our Conclusion

We agree with the authors conclusions that POCUS can be a useful adjunct to clinical exam in diagnosing FTS, with the understanding that POCUS cannot rule out FTS or distinguish rheumatologic from infectious process.

The Bottom Line 

POCUS can be a useful adjunct to clinical exam in diagnosing FTS. Use the linear probe and place at the palmar side of the wrist crease, look for hypoechoic or anechoic material around the flexor tendons with possible thickening of the tendon itself. 


This post was written by Betial Asmerom. Review and further commentary was provided by Charles Murchison, MD, Emergency Ultrasound Fellow at UCSD and Amir Aminlari, MD, Ultrasound Faculty at UCSD.


  1. Mamane, W. et al. Infectious flexor hand tenosynovitis: State of knowledge. A study of 120 cases. J. Orthop. 15, 701–706 (2018).
  3. Hubbard, D., Joing, S. & Smith, S. W. Pyogenic Flexor Tenosynovitis by Point-of-care Ultrasound in the Emergency Department. Clin. Pract. Cases Emerg. Med. 2, 235–240 (2018).
  5. Padrez et al. Bedsound Ultrasound Identification of Infectious Flexor Tenosynovitis in the Emergency Department. West J Emerg 2015. 16 (2). 



Case # 14: Whirlpool swirling, twisting and turning

A 13-year-old male presents to the emergency department with right testicular pain for one-hour duration. The pain began while having a bowel movement. He had no nausea or vomiting. His exam is notable for a high riding right testicle and tenderness to palpation over the right testicle.

Vitals: T: 97.8, HR: 106, BP: 135/79, RR: 16, Sat: 96% on RA

A bedside ultrasound of the testicles is performed. What do you see?

Answer and Learning Points


These ultrasound images demonstrates limited flow into the right testicle suggestive of testicular torsion. Manual detorsion was performed at the bedside using the “open-the-book” maneuver with subsequent ultrasound demonstrating return of flow to the right testicle. Urology was consulted, and the patient was scheduled for an outpatient orchiopexy.

Learning Points

The acute scrotum is a presentation that requires timely evaluation and management by the emergency physician. Of all causes of acute scrotum, testicular torsion is the diagnosis that requires the most emergent action because of the limited time window of testicular salvageability.1 Unfortunately, in many clinical settings including urgent cares, clinics, and rural community emergency rooms, it can be challenging to confirm our clinical suspicion in a timely fashion because of the difficulty in obtaining an official scrotal ultrasound. For this reason, POCUS is an important tool for emergency physicians in the diagnosis of patients with acute scrotum.

Ultrasound findings of testicular torsion:

Loss or reduction of color Doppler flow/Spectral Doppler tracings to affected testicle (Must compare to other testicle)

Affected testicle becomes more heterogeneous than other testicle

Adhikari, S. R. (2008). Small parts - Testicular ultrasound. Retrieved from

Thickened, hypoechoic mediastinum

Prando D. Torsion of the spermatic cord: the main gray-scale and doppler sonographic signs. Abdom Imaging. 2009 Sep-Oct;34(5):648-61. doi: 10.1007/s00261-008-9449-8. Review. PubMed PMID: 18709404. 

Whirlpool sign6


Marissa Wolfe, MS4; Amir Aminlari, MD, Emergency Ultrasound Fellowship Director at UCSD


  1. Mellick LB, Sinex JE, Gibson RW, Mears K. A Systematic Review of Testicle Survival Time After a Torsion Event. Pediatr Emerg Care. 2017 Sep 25. doi: 10.1097/PEC.0000000000001287. [Epub ahead of print] PubMed PMID: 28953100.
  2. Sharp VJ, Kieran K, Arlen AM. Testicular torsion: diagnosis, evaluation, and management. Am Fam Physician. 2013 Dec 15;88(12):835-40. Review. PubMed PMID: 24364548.
  3. Wang S, Scoutt L. Testicular torsion and manual detorsion. Ultrasound Q. 2013 Sep;29(3):261-2. doi: 10.1097/RUQ.0b013e3182a2d129. PubMed PMID: 23945494.
  4. Adhikari, S. R. (2008). Small parts - Testicular ultrasound. Retrieved from
  5. Prando D. Torsion of the spermatic cord: the main gray-scale and doppler sonographic signs. Abdom Imaging. 2009 Sep-Oct;34(5):648-61. doi: 10.1007/s00261-008-9449-8. Review. PubMed PMID: 18709404.
  6. Kalfa N, Veyrac C, Lopez M, Lopez C, Maurel A, Kaselas C, Sibai S, Arena F, Vaos G, Bréaud J, Merrot T, Kalfa D, Khochman I, Mironescu A, Minaev S, Avérous M, Galifer RB. Multicenter assessment of ultrasound of the spermatic cord in children with acute scrotum. J Urol. 2007 Jan;177(1):297-301; discussion 301. PubMed PMID: 17162068.
  7. Vijayaraghavan SB. Sonographic differential diagnosis of acute scrotum: real-time whirlpool sign, a key sign of torsion. J Ultrasound Med. 2006 May;25(5):563-74. PubMed PMID: 16632779.

Case # 10: A Mechanical Issue

A 32 year old male was carrying a heavy pipe overhead with his right arm and slipped falling forward, onto the right side. He notes pain in the right shoulder, worse with any movement. His right arm is flexed and internally rotated for comfort.

Vitals: T 98.6 HR 95 BP 143/91  RR 14 O2 98% on RA

A bedside ultrasound of the right shoulder is performed, what is the next best step in management?

Screen Shot 2017-11-18 at 11.09.45 AM

Answer and Learning Points


Shoulder dislocation reduction. The ultrasound image shows anterior displacement of the humeral head with respect to the glenoid fossa consistent with an anterior shoulder dislocation. A hematoma is also noted within the joint space which is very commonly associated with a traumatic shoulder dislocation. 

Ultrasound diagnosis of anterior shoulder dislocation

Learning Points

    • Ultrasound is useful for both the initial diagnosis and reduction confirmation of a shoulder dislocation, as well as for intra-articular injection of local anesthetic; however in a traumatic dislocation, an initial x-ray should be obtained to evaluate for any associated fracture.
    • To perform the exam, a low frequency curvilinear transducer should be used. The operator should stand behind the patient, on the side of the affected shoulder, and place the ultrasound system directly in front of the patient for easy visualization. The probe should be placed on the posterior aspect of the scapula, parallel and just inferior to the scapular spine. This will allow direct visualization of the glenohumeral joint.
  • Proper probe placement for evaluation of glenohumeral joint.
    • In a normal shoulder the glenoid and humeral head articulate nicely and this can be appreciated on ultrasound with internal and external rotation of the patient's arm, however with dislocation, the humeral head and glenoid will not be aligned. In anterior dislocation, the humeral head will be deep to the glenoid, while in a posterior dislocation, the humeral head will be more superficial to the glenoid.
  • Normal glenohumeral ultrasound anatomy
    • Ultrasound is especially useful to confirm successful shoulder relocation and prevent both a prolonged stay in the emergency department waiting for a post reduction x-ray, as well as re-sedation if this was required for a difficult shoulder reduction.
    • Lastly, this same ultrasound view can be used for in-plane needle guidance to provide intra-articular anesthesia using a lateral needle entry approach.
    • For a 5 minute video tutorial on  ultrasound for shoulder dislocation , click here to watch this excellent video at 5 Minute Sono.
In vivo shoulder reduction!

Case # 8: A Case of Comparision

A 40 year old male presents to the emergency department with pain to the entire right thumb and wrist for 1 day.  He notes that he suffered a small puncture wound to his right thumb 1 day ago while working on his car.  The patient has notable circumferential, non-erythematous swelling to his right thumb with tenderness along the flexor tendon. There is also fullness of the dorsum of his wrist. He is holding his fingers flexed and has pain radiating into the wrist with any movement of his fingers or wrist, especially with extension of his fingers.

Vitals: T 98.7 HR 90 BP 132/81  RR 13 O2 98% on RA

A bedside ultrasound is performed, what is the next best step in management?

Normal Left Thumb in Long Axis

Normal Left Thumb in Long Axis

Abnormal Right Thumb in Long Axis

Abnormal Right Thumb in Long Axis

Answer and Learning Points


Empirical antibiotic therapy and orthopedic surgery consultation for infectious flexor tenosynovitis (FTS).  The patient meets 4 out of 4 Kanavel's signs and has ultrasound evidence of FTS suggested by a thickened tendon with surrounding anechoic fluid.

Short Axis View of Right 1st Digit demonstrating hypoechoic fluid surrounding tendon.

Learning Points

    • FTS is often a clinical diagnosis and examination (Kanavel's signs) is thought to have high sensitivity (91.4-97.1%) but low specificity (51.3-69.2%) for infectious FTS [2]; however a negative exam does not rule it out completely.
      • Kanavel's signs include:
        • Finger held in slight flexion
        • Fusiform swelling
        • Tenderness along the flexor tendon sheath
        • Pain with passive extension of the digit
    • FTS is treated with empirical antibiotic  therapy as well as early surgical debridement and drainage. Delays in diagnosis can lead to local spread of infection, compartment syndrome and necrosis.
    • While there is not high quality evidence describing the use of emergency department point of care ultrasound (POCUS) to diagnose FTS, previous radiographic studies have found ultrasound to be more sensitive than clinical exam for detecting tenosynovitis [3].
    • Common ultrasound findings for FTS include:
      • Hypoechoic or anechoic edema or debris within the tendon sheath
      • +/- thickening of the tendon sheath
    • The ultrasound examination should be performed using a linear probe, examining the affected tendon (and normal tendon on other hand for comparison), in both the longitudinal and transverse plane.
      • Small rocking or fanning motions should be used to ensure perpendicular orientation of the probe to the tendon to avoid artifact secondary to anisotropy.
    • As in all uses of POCUS in the emergency department setting, findings should be interpreted in conjunction with clinical examination and history when evaluating for infectious FTS. We believe POCUS for infectious FTS can be used to increase diagnostic certainty and even expedite care and aggressive treatment however a normal exam should not be used to rule out this diagnosis.


This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.


    1. Padrez, K., Bress, J., Johnson, B., & Nagdev, A. (2015). Bedside Ultrasound Identification of Infectious Flexor Tenosynovitis in the Emergency Department. Western Journal Of Emergency Medicine, 16(2), 260-262. doi:10.5811/westjem.2015.1.24474
    2. Kennedy CD, e. (2017). Differentiation Between Pyogenic Flexor Tenosynovitis and Other Finger Infections. - PubMed - NCBI . Retrieved 21 October 2017, from
    3. 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;12(1):91.