Septic Arthritis and Arthrocentesis

A 33 y/o male comes to the ED for fever, knee swelling and pain.
He has a history of joint surgery because of trauma, and prothesis, dating 4 years before.
He is HIV positive
He presents feverish (38°C), the left knee is swollen and hot.
WBC 34.000/μL, CRP 109 mg/L, PCT 0,05 ng/mL.
As we have seen in previous post, history, clinical examination and serum test are not useful to rule out or in a septic arthritis. It’s time to perform arthrocentesis: sWBC: 60x109, sLactate: 10 mmol/L


Are this findings useful?

Conclusion 

Although arthrocentesis is not a risk-free procedure, synovial fluid analysis is essential for the diagnosis. 

sWBC count has been studied in several trials but a significant heterogeneity was noted so it should not be used in isolation to rule in or rule out the diagnosis of septic arthritis, anyway it should augment the entire clinical evaluation.

Synovial lactate, instead, has consistently demonstrated desirable diagnostic properties to rule in septic arthritis using a threshold of >10 mmol ⁄ L. 

Bibliography 

C. R. Carpenter et al;

Evidence-based Diagnostics: Adult Septic Arthritis

Acad Emerg Med Aug 2011, vol 18 n 8. 

see previous...


Ilenia Spallino

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Septic Arthritis

A 33 y/o male comes to the ED for fever, knee swelling and pain.

He has a history of joint surgery because of trauma, and prothesis, dating 4 years before.

He is HIV positive

He presents feverish (38°C), the left knee is swollen and hot.

WBC 34.000/μL CRP 109 mg/L PCT 0,05 ng/mL

Are history, clinical examination, serum test enough to rule out or in a septic arthritis?

Conclusion 

No finding from the history significantly decreases or increase the probability of septic arthritis (SA), included hystory of HIV infection; only recent joint surgery (<3 months ago) or a joint prosthesis with skin infection, significantly increases the risk of septic arthritis, but attention, the absence does not rule out SA!

Data about physical examination and hystory are inconcludent, the presence or absence of classical clinical signs (pain with motion, limited motion, tender swelling, joint effusion, increased heat redness, fever > 37.5°C, axial load pain) is not useful to rule in or rule out septic arthritis.

Serum test like WBC, ESR, CRP are not useful, instead Procalcitonin is generally specific with very poor sensitivity. 

…..So what?

To be continued...

Bibliography 

C. R. Carpenter et al;

Evidence-based Diagnostics: Adult Septic Arthritis

Acad Emerg Med Aug 2011, vol 18 n 8. 

Ilenia Spallino

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Soft tissue abscess: clinical plus ultrasound evaluation

Male 65 y/o, he complains pain and swelling in left groin, he has history of hypertension. He has not fever. Clinical examination shows swelling, skin is hot and  eritematous.






Is it an abscess, a cellulitis or something else? 

Conclusion 

To use ultrasound on eritematous and swelling skin is very helpful 

Abscesses presents as a spherical structure with “pus in movement”.  

Celluliti’s morphology, instead, has a “cooblestoning effect”, with diffuse hyperechogenicity of subcutaneous fat.

Ultrasonography is a useful adjunct to clinical evaluation of soft tissue infection, it increases diagnostic accuracy and guides treatment decision.

Bibliography 

BT Squire, JC Fox, C Anderson

ABSCESS: applied bedside sonography for convenient evaluation of superficial soft tissue infections

Acad Emerg Med July 2005, Vol. 12, No. 7 

DW Struk, PL Munk

Imaging of softs tissue infections

Radiol Clin of N Am vol 39 n2 Mar 2001

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Ciro Paolillo

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