Case Presentation by Dr.Kevin Belen, MD
CC: “My left arm hurts.”
HPI: 39-year-old male presents to the emergency department complaining of left arm pain. The patient has a history of intravenous drug use and “skin popped” in the left upper arm earlier this week. The patient first noticed some mild pain and redness at his left shoulder 4 days ago that has slowly been spreading. He had ignored it until 2 days ago when he developed a fever and nausea, with pain that worsened with arm movement. The patient presented to the emergency department today because he is unable to move his left arm without excruciating pain and foul-smelling fluid began to drain from his arm this morning.
Constitutional: Subjective fever and chills
ENT: No sore throat
Respiratory: No SOB
Cardiovascular: No chest pain
GI: Nausea, no vomiting
GU: No hematuria
Musculoskeletal: Pain with movement at left shoulder/upper arm
Skin: Redness, foul smelling fluid from wound at left shoulder/upper arm
Neuro: No weakness, numbness or tingling
Psych: No depression
PMH: Hx of IVDA, multiple abscess I&D in emergency department, denied HTN, HIV or DM
Social: Homeless, +Tobacco, ½ pint of vodka per day, active drug use via IV and “skin popping”
Vitals: BP 156/98 Pulse 110 RR 16 Temp 39.2 oral Pulse ox 100% room air
Constitutional: Thin male, Moderate distress apparent with movement of left arm, slightly diaphoretic
HEENT: No conjunctival pallor, sclera anicteric, oropharynx is dry
Respiratory: Clear to auscultation bilaterally
Cardiovascular: Tachycardic rate & regular rhythm, S1, S2, no murmurs or gallops. +2 bilateral radial pulses.
Abdomen: Soft, no abdominal tenderness
Back: No spinal, paraspinal muscle, or CVA tenderness
Musculoskeletal: Significant tenderness with passive and active ROM at left shoulder. Tender to palpation along the left clavicle, shoulder joint, and proximal half of humerus. Strength at this joint unable to be assessed secondary to pain. Full strength and ROM throughout right upper and bilateral lower extremities. +2 edema about left shoulder joint.
Skin: Remarkable for erythema at the left shoulder from mid clavicle to mid humerus, tender to palpation through area of erythema, small black eschar approximately 2 cm in diameter overlying the lateral deltoid muscle where patient states he skin popped, foul-smelling thin gray fluid.
Neurologic: Awake, alert & oriented x3, sensation intact grossly through the bilateral upper and lower extremities.
Emergency Department Course:
Following the physical examination a focused bedside soft tissue ultrasound examination was performed yielding the following two images.
1. What is the most appropriate interpretation of the ultrasound findings?
A. Cobble-stoning appearance and subcutaneous abscess
B. Linear hyperechogenicity consistent with foreign body
C. Anechoic areas representing perifascial fluid and hyperechoic areas representing emphysema
D. Inadequate and patient should undergo an MRI
2. How would you best treat this patient?
A. Discharge with oral Trimethoprim and Sulfamethoxazole (Bactrim) and Cephalexin (Keflex)
B. Perform beside abscess I&D and follow up with PCP
C. Perform joint aspiration and admit to Medicine for IV abx
D. Consult Surgery for emergent debridement
E. Consult Surgery to remove retained needle tip and I&D abcess
3. In a bacterial culture, what would be the most common single isolate for this condition?
A. Staphylococcus aureus
B. Staphylococcus epidermidis
C. Group A streptococcus
Answers & Discussion:
This patient presents with a history, physical exam, and ultrasound findings consistent and suggestive of necrotizing fasciitis. Necotizing fasciitis (NF) is an uncommon but potentially lethal soft-tissue infection with mortality rates ranging from 6 to 76% and carries a high morbidity. NF results in progressive destruction of the muscle fascia and overlying subcutaneous fat. The muscle tissue is frequently spared because of its generous blood supply. The clinical picture is similar to cellulitis which makes diagnosis sometimes difficult, however patients with NF are often noted to have pain out of proportion to exam and thus a high clinical suspicion is required as delay in diagnosis portends greater morbidity and mortality. Infection typically spreads along the muscle fascia due to its relatively poor blood supply. Initially, the overlying tissue can appear unaffected. Patients initially present with tenderness, erythema and marked subcutaneous edema. Further in the course signs of gangrene (bullae, eschars) may appear. Crepitus may be present but is not a requirement for diagnosis, and is found in only 12–36% of patients . Tissue destruction leading to thrombosis of small blood vessels and destruction of superficial nerves in the subcutaneous tissue will cause anesthesia in the involved area and may precede the appearance of skin necrosis. NF can have rapid progression and extensive destruction can occur, leading to systemic toxicity, limb loss, or death. Conditions associated with necrotizing soft tissue infection include diabetes, drug use, obesity, immunosuppression, recent surgery, and traumatic wounds .
Necrotizing fasciitis is a synergistic bacterial infection usually due to mixed flora. NF can be caused by gram-positive, gram-negative, aerobic, and anaerobic bacteria but, Group A streptococcus was the most common bacterial isolate. There are two types of necrotizing fasciitis. Type 1 is polymicrobial and involves non-group A streptococci plus anaerobes. In type 2, the pathogen is group A beta-hemolytic streptococci and the infection is typically found in the extremities. A substance in the cell wall of streptococci causes separation of the dermal connective tissue, resulting in continued inflammation and necrosis. Streptococcal necrotizing fasciitis is frequently associated with streptococcal toxic shock syndrome .
Radiographs may reveal gas in the tissues, but it is not a universal finding . If gas is visualized in the tissue, type I necrotizing fasciitis or gas gangrene caused by clostridia is most common. However, plain films show subcutaneous emphysema when there is a moderate to large amount of gas within the tissues in only 17–57% of patients .
Ultrasound is not well studied in the diagnosis of NF but there are increasing case reports. Ultrasound can offer a more rapid diagnosis than traditional imaging studies . The findings which suggest NF include thickening of the deep fascia, diffuse thickening of the overlying fatty tissue, and a fluid layer of at least 4 mm in thickness along the deep fascia. Further study regarding performance characteristics in the use of ultrasound in the diagnosis is required. Yen et al reported a sensitivity
of 88.2% and specificity of 93.3% for US in the diagnosis of NF using the aforementioned criteria. Diagnosis is further supported by the findings of subcutaneous air, which is pathognomonic for NF. Ultrasound can help distinguish NF from cellulitis. Both conditions have edema and increased echogenicity of the subcutaneous tissue, however, fluid spaces tracking along the deep fascia strongly suggest the diagnosis of NF over cellulitis .
In the case study from which the images in the case report were obtained an 8- to 12-MHz linear-array probe was used. The images above demonstrate increased echogenicity of the subcutaneous fatty tissue with interconnected thin anechoic spaces corresponding to perifascial fluid resulting in a cobblestone appearance. There was a gas layer just above the deep fascia which appears hyperechoic (Arrowheads) with posterior ‘‘dirty’’ acoustic shadowing in Figure 1. In Figure 2, there was also subcutaneous emphysema (Arrow), but there was an adjacent area of subcutaneous fat that still appeared normal at that level (M)
Treatment of necrotizing fasciitis includes resuscitation, parenteral antibiotics against S. aureus, Streptococcus, gram-negative organisms, and anaerobes as directed by Gram stain and culture findings and emergent surgical debridement,. The most important treatment is debridement, which is often extensive and often requires multiple washouts and debridements. In the case of the DRH patient from which this report is based upon, the patient underwent emergent surgical debridement. Sadly, I was foolish and did not save my ultrasound images which had similar but more impressive findings when compared to the images above.
Figure 1 shows hyperechoic soft-tissue emphysema (arrowheads) with acoustic shadowing. The overlying subcutaneous fat (F) shows increased echogenicity with interlacing anechoic spaces (arrow) representing perifascial fluid spreading along the fascial planes (cobblestone appearance).
Figure 2 shows hyperechoic focus (arrows) with posterior acoustic shadowing above the deep fascia corresponding to gas bubbles.
1. Rosen’s Emergency Medicine, Concepts and Practices, 7th edition
2. Necrotizing fasciitis: early sonographic diagnosis. J Clin Ultrasound. 2011 May;39(4):236-9.
3. UpToDate: Necrotizing soft tissue infections