On MRI, the signal on T2-WI is variable depending on the etiology. Contrast agents can be further classified as high or low osmolality, based on the iodine concentration. This can be filled at Baystate Pharmacies at 759 Chestnut Street and 3300 Main Street as well as at many local pharmacies. Computed tomography (CT) with and without contrast: indications and protocols. Ultrasound is helpful to rule out deep venous thrombosis, assess for possible foreign bodies, and guide potential diagnostic fluid aspiration.8, 13 Sensitivity of ultrasound for the diagnosis of necrotizing fasciitis is 88.2%, with a specificity of 93.3%.20, CT is the primary imaging modality in the work-up of necrotizing fasciitis given its wide availability and high spatial resolution compared to radiography or ultrasound.3 Soft-tissue gas is a pertinent CT finding, but absence of it should not exclude the diagnosis of necrotizing fasciitis if clinically suspected.1, 2,11,17 Gas within fluid collections along subfascial planes is the hallmark of necrotizing fasciitis (Figures 5 and 6).11, 21 The lack of soft-tissue gas on CT may be due to early disease, aerobic infections, or if the patient is diabetic.1, 16 The sensitivity of CT in diagnosing necrotizing fasciitis is 80%, but it lacks specificity as findings can also be seen in nonnecrotizing fasciitis.21, 22 Thickening and nonenhancement of the fascia on contrast-enhanced CT may be helpful to distinguish from nonnecrotizing fasciitis.2 Subfascial and intermuscular fluid accumulation can also be seen on CT, and may represent early findings of necrotizing fasciitis (Figure 7).21. Wong CH, Khin LW, Heng KS, Tan KC, Low CO. It is usually due to underlying bacterial sinusitis. 4. Yes neuro CTa HeaD Circle of Willis CTA Head with and without contrast Note: MRA Brain without contrast is preferred. The type of contrast agent and route of administration can increase the diagnostic yield of the study ordered. Since the epidermis is not involved, cellulitis is not transmitted by person-to-person contact. Schmid M, Kossmann T, Duewell S. Differentiation of Necrotizing Fasciitis and Cellulitis Using MR Imaging. Contrast enhancement of the pulmonary arteries is key, as embolic disease is identified as abnormal filling defects within the pulmonary arteries (Figure 2). of 20 consecutive patients with necrotizing fasciitis, CT revealed fascial thickening and fat stranding in 80%, soft tissue gas in 55%, and abscesses in 35%.22, CT is helpful in guiding surgical debridement and drainage by evaluating the extent of soft tissue and osseous involvement, identifying the potential infectious source and identifying potential complications including vascular rupture or tissue necrosis.1, 2,13,22, MRI is the gold-standard for soft-tissue infections as it provides excellent soft-tissue contrast resolution with a sensitivity of 93% for the diagnosis for necrotizing fasciitis.1, 24 Essential sequences include T1 weighted imaging to assess anatomy, and T2 fat saturated or short tauinversion-recovery sequences to look for fascial thickening and edema.3, 25 Post gadolinium sequences are helpful to delineate the extent of infection, identify abscesses and areas of necrosis, but may not be feasible in patients with acute renal failure, which is common in this patient population.3, 26, Deep fascial thickening and subfascial fluid accumulation can be seen as high signal on fluid sensitive sequences (Figures 8 and 9).21 The deep intramuscular fascia is usually protected in the setting of cellulitis, but is involved in necrotizing fasciitis.1 Fascial thickening begins in the superficial fascia and extends along the deep intermuscular fascia, not just in areas contiguous to the deep peripheral fascia.1, 18 Hyperintensity and thickness of the fascia greater than or equal to 3 mm on fat saturated T2 weighted or short tauinversion-recovery images with involvement of three or more compartments is a sensitive finding to suggest necrotizing fasciitis.3, 8,13,25,27 The absence of T2 hyperintensity within the deep fascia can essentially exclude a diagnosis necrotizing fasciitis.3, 18,21. 2017 Jun;31(2):299-324. doi: 10.1016/j.idc.2017.01.004. Measure serum creatinine before ordering CT studies with IV dye to assess for baseline renal insufficiency. Brothers TE, Tagge DU, Stutley JE, Conway WF, Del Schutte H, Byrne TK. Gothner M, Dudda M, Kruppa C, Schildhauer TA, Swol J. Fulminant necrotizing fasciitis of the thigh, following an infection of the sacro-iliac joint in an immunosuppressed, young woman, MRI in necrotizing fasciitis of the extremities. Uncomplicated cellulitis is usually treated conservatively with antibiotics and locally supportive measures. The US Preventive Services Task Force currently recommends low-dose CT without contrast, along with appropriate patient counseling, for patients with a history of smoking and an age range as detailed in the Task Force statement. As with barium agents, they must be diluted for CT compared with the concentrations used in fluoroscopy. Pitfalls of CT for deep neck abscess imaging assessment: a Citation, DOI, disclosures and article data. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. An official website of the United States government. Careers. Compared to plain radiography, ultrasound, CT and MR provide higher sensitivity and specificity for the diagnosis of necrotizing fasciitis. In C, the transplanted lung is notable for areas of air trapping in the right upper lobe on expiratory images (blue arrow), which is associated with central airway narrowing. Unauthorized use of these marks is strictly prohibited. Necrotizing fasciitis is a rapidly spreading soft tissue infection involving the deep fascial layers, which can cause secondary necrosis leading to significant morbidity and mortality.13 It most commonly affects the lower extremities accounting for approximately 50% of cases, and can affect different body parts including the perineum (as in Fourniers gangrene), and submandibular region (as in Ludwig angina). If youre ever stuck when it comes to the correct diagnostic imaging method for your patient, pick up the phone and call the radiologist or imaging facility with whom you work. There is subcutaneous emphysema (arrows) overlying the right ankle with plate and screw fixation seen (a). PDF When does chest CT QUESTIONS require contrast enhancement? A: TABLE 1 That said, it is seldom required for diagnosing cellulitis and is therefore usually ordered for suspected complications or to rule out alternative diagnoses in cases of an atypical presentation. 2 0 obj Reinert CP, Pfannenberg C, Dittmann H, Gckel B, la Fougre C, Nikolaou K, Hoefert S. J Clin Med. 1 0 obj . PDF REFERENCE GUIDE FOR ORDERING CT EXAMINATIONS - Providence (ABRS) may develop orbital, intracranial, and vascular complications including orbital cellulitis, subperiosteal , abscess, intracranial abscess, cerebritis, cavernous sinus thrombosis and aneurysm. CT Head or brain with and without contrast Note: MRI Brain with/without contrast is preferred. Marked preseptal edema and discrete contrast enhancement in the area of the affected left upper eyelid. Yu J & Habib P. MR Imaging of Urgent Inflammatory and Infectious Conditions Affecting the Soft Tissues of the Musculoskeletal System. Working in the emergency department as a nurse practitioner, I order CT scans in my evaluation of patients every day.
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