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Three Part Question

In [patients presenting to the emergency department with a soft tissue infection] does [point of care ultrasound] use help to [distinguish and quantify cellulitis vs. abscess formation]?

Clinical Scenario

You review a young adult (or child) in the emergency department with a soft tissue infection. Upon clinical examination you are unsure whether there is a cutaneous abscess present. You wonder whether bedside ultrasound will help you make a definitive diagnosis.

Search Strategy

Medline (1946 to May 2014) and Embase (1980 to 2014 week 23) were both searched with the following string: [exp Abscess/ OR abscess.mp OR absces$.mp OR exp Cellulitis/ OR exp Furunculosis/ OR exp Carbuncle/OR exp Soft Tissue Infections/ OR exp Fasciitis] AND [exp Ultrasonography/ OR exp Diagnostic Imaging/ OR ultraso$.mp]

This gave a very high yield and thus the searches were limited with the terms “English Language’, “Human” and “Diagnosis (Maximises specificity)”

A further search of the Cochrane Library of Systematic Reviews was also performed with the use of keywords as the [exp] search term is not valid for this particular database.

Search Outcome

This gave a total of 485 papers. 31 were read thoroughly. This gave a total of 7 relevant studies. 3 of the 31 papers were literature reviews relevant to the question. All papers had their references reviewed to ensure no papers were missed.

Additionally there was 1 ongoing interventional trial located on the National Institute for Health website: www.clinicaltrials.gov. Trial numbers: NCT01557426 which may provide additional future evidence.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Marin et al. 2013 Philadelphia, USA	"Convenience sample of 387 lesions in 348 children aged 2 months - 19 years presenting to the ED with signs of an isolated SSTI requiring treatment with systemic antibiotic therapy. This group had CE examination of the lesion by the treating physician who decided whether an abscess was clinically evident or not. Following this they had a US examination by a blinded study physician who recorded their findings. A control group of 442 lesions in 370 children had CE but no US performed. All groups were followed up for 2 days after discharge from the ED. "	Prospective Cohort Study	"1. Clinically evident lesions requiring drainage (defined as pus expressed at time of ED visit or within 2 days) "	"CE+US didn’t improve detection compared to CE alone. CE - 94.7% sensitivity, 84% specificity CE+US - 93.1% sensitivity, 81.4% specificity"	"Very short 2 day follow up could increase number of false negatives in lesions that may require drainage. Blinding methods not 100%"
			2. Lesions not clinically evident that may require drainage	"CE + US did improve detection CE 43.7% sensitivity, 42.0% specificity CE+US - 77.6% sensitivity, 61.3% specificity"
Iverson et al. 2011 Michigan, USA	"Convenience sample of 65 children (6months - 18 years) presenting to the Paediatric Emergency Department (PED) with clinical signs and symptoms suggestive of SSTI. This group had a clinical examination where a diagnosis of cellulitis vs. abscess was made along with a decision regarding the need for I&D. A blinded physician then performed a US scan."	Prospective Cohort Study	1. The effect of bedside US on diagnosis of SSTI when compared to clinical examination alone.		"Small sample size No follow-up performed, no return hospital visits looked for - some patients may have returned. 9 US examinations (13%) poorly performed but still included in results. "
			2. The effect of US on management of SSTI
Berger et al. 2011 California, USA	40 adult ED patients seen and treated for SSTI suspicious for underlying abscess. All patients had a clinical examination of their lesion and then 2 US scans of the lesion - 1 by a senior clinician and 1 by a novice.	Prospective Observational Study	1. The presence of pus expressed during I&D	"US sensitivity for positive I&D - 97% specificity - 67% CE sensitivity for positive I&D - 76% specificity -83%"	"Very small sample size - therefore results not statistically significant. No follow-up performed. Only patients with high suspicion of underlying abscess were included.
			2. The ability of a novice to detect abscess on US scan	Novices opinions agreed with senior clinicians in all but 1 patient (2.5%)
Sivitz et al. 2010 Rhode Island, USA	"50 children (under 18 years) presenting with an area of SSTI. These patients had assessment and documented management by treating physician which was either surgical (i.e. lesion requires I&D) or medical (IV or oral antibiotics). All patients then had a US scan performed. These results were then made aware to the treating physician who decided whether a management change was required. "	Prospective Observational Study	How often US changed the management of patients	"Surgically managed group (clinically evident lesion) - management changed in 30% Medically managed group (no clinically evident lesion) - management changed in 17%"	"Small number of patients with different numbers in surgical vs. medical management. Differences between study and treating clinicians - sometimes they were the same person. No blinding. No control group"
			"Specificity & sensitivity of original clinical examination & management plan compared to US. Positive I&D used as gold standard for abscess diagnosis. Unsuccessful drainage or uneventful follow-up = no abscess."	"CE had 75% sensitivity & 80% specificity. US had 90% sensitivity & 83% specificity. "
Tayal et al. 2006 North Carolina, USA	Convenience sample of 126 adult patients presenting to the ED with evidence of cutaneous tissue infection. Treating physicians performed CE and decided whether lesions required drainage. Lesions then had US scan and management plan was reviewed.	Prospective Observational Study	How often US changed the management of patients	"Lesions thought to require drainage on CE - management changed in 73% Lesions not thought to require drainage on CE - management changed in 48% "	"Small number of patients. No blinding. No control group.
Squire et al. 2005 California, USA	Convenience sample of 135 adult patients presenting to the ED with signs of soft tissue infection. The physician performed CE and then recorded whether they believed an abscess was present. Treating physicians then performed US scans.	"Prospective Clinical Trial "	1. Detection of true abscess (confirmed by either obtaining pus on I&D or failure of lesion to resolve)	"CE - 86% sensitivity, 70% specificity. CE + US - 98% sensitivity, 88% specificity"	"High proportion of patients (20%) lost to follow up. Differences in experience of staff performing US examinations. Not blinded. No control group.
			2. How often US changed the diagnosis to correct one	Diagnosis changed in 18 cases. US was correct for 17 of these (94%)
Nisha et al. 2013 Chennai, India	34 patients (aged 14-71) with odontogenic infections involved the superficial and deep fascial spaces of the head and neck. All lesions had US examination. Those deemed to be cellulitis on CE + US had medical management. Those deemed to be abscess had surgical exploration	Diagnostic Study	"Cellulitis - whether lesion resolved with 5 days of antibiotics. Abscess - The presence of pus on surgical exploration"	"Clinical examination had a sensitivity of 0.65 and specificity 0.32 Ultrasound had a sensitivity of 1.0 and a specificity of 0.957"	"Small study size and therefore results may not be statistically significant. No information about who performed the US scans. Doesn’t appear to be blinded. No control group. Cases of cellulitis excluded from sensitivity and specificity analysis of US!

Comment(s)

SSTI = skin and soft tissue infection; CE = clinical examination; US = ultrasound Despite the small sample sizes in the majority of the studies and the generally lack of blinding it does appear that the use of ultrasound examination helps in the diagnosis of cellulitis vs. abscess, particularly in regard to lesions which appear to be abscess free on clinical examination.

Clinical Bottom Line

In cases of cellulitis or suspected abscess US should be used to check for the presence of abscess. US does not need to be used to confirm the diagnosis if there is definite abscess present on clinical examination.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.

References

1. Marin, Jennifer R., et al. Emergency Ultrasound‐assisted Examination of Skin and Soft Tissue Infections in the Pediatric Emergency Department. Academic Emergency Medicine 2013; 20.6: 545-553
2. Iverson, Katrina, et al. The effect of bedside ultrasound on diagnosis and management of soft tissue infections in a pediatric ED he American Journal of Emergency Medicine 2012; 30.8: 1347-1351
3. Berger, Tony, et al. Bedside ultrasound performed by novices for the detection of abscess in ED patients with soft tissue infections. The American Journal of Emergency Medicine 2012; 30.8: 1569-1573
4. Sivitz, Adam B., et al. Effect of bedside ultrasound on management of pediatric soft-tissue infection The Journal of Emergency Medicine 2010; 39.5: 637-643
5. Tayal, Vivek S., et al. The Effect of Soft‐tissue Ultrasound on the Management of Cellulitis in the Emergency Department Academic Emergency Medicine 2006: 13.4: 384-388
6. Squire, Benjamin T., John Christian Fox, and Craig Anderson. ABSCESS: applied bedside sonography for convenient evaluation of superficial soft tissue infections Academic Emergency Medicine 2005; 12.7: 601-606
7. Aarthi Nisha, V., et al. The Role of Colour Doppler Ultrasonography in the Diagnosis of Fascial Space Infections-A Cross Sectional Study Journal of Clinical and Diagnostic Research 2013; 7.5: 962