Copyright2022 ThriveAP Inc., All Rights Reserved, Key Advice for NPs & PAs with Angela Golden, DNP, FNP-C, FAANP, FOMA, Evidence-Based Wound Care for Advanced Practice Providers, Featured ThriveAP Faculty: Benjamin Smith, DMSc, PA-C, DFAAPA, Finding Your Why with ThriveAP Speaker Steven Wei, EdD, MPH, MS, PA-C, DFAAPA. Iodinated contrast agents can cause reversible acute renal failure. 1. Here is an overview of the indications for contrasted CT: CT Angiography, or CTA, is a type of contrasted CT scan used to evaluate the blood vessels. a central core consisting of necrotic inflammatory cells and local tissue peripheral halo of viable neutrophils surrounded by a 'capsule' with dilated blood vessels and proliferation of fibroblasts Terminology An abscesses is akin to an empyema, as both are defined inflammatory collections. Since the epidermis is not involved, cellulitis is not transmitted by person-to-person contact. Although classically a clinical diagnosis, imaging is a powerful adjunct to facilitate early diagnosis in equivocal cases. Signs of cellulitis are easy to appreciate on CT and MRI and include thickening of the fat, best appreciated on the preseptal space, fat infiltration, and contrast enhancement. Cellulitis. On MRI, the signal on T2-WI is variable depending on the etiology. When does chest CT require contrast enhancement? Diffuse high signal can also be seen in the muscle and subcutaneous fat.13 If subcutaneous edema is not the predominant feature, one should consider necrotizing fasciitis rather than cellulitis.1, 13 A summary of spectrum of findings for necrotizing fasciitis is summarized in Figure 10 and Table 2. Wronski M, Slodkowski M, Cebulski W, Karkocha D, Krasnodebski IW. Biomed Res Int. CT is used to accurately differentiate between superficial cellulitis and deep cellulitis. Inclusion in an NLM database does not imply endorsement of, or agreement with, Cellulitis. Emergency Medicine: Clinical Essentials. <>stream sharing sensitive information, make sure youre on a federal An official website of the United States government. 2001;176(5):1155-9. CT scanning is often the first imaging modality that is used because of its ease and availability at most medical institutions. Yu J & Habib P. MR Imaging of Urgent Inflammatory and Infectious Conditions Affecting the Soft Tissues of the Musculoskeletal System. However, if contrast must be administered within two months of iodine 131 treatment, consultation with an endocrinologist should be considered.7 Administration of iodinated contrast may provoke thyrotoxicosis, although this is rare.12, Approximately 90% of absorbed metformin is excreted by the kidneys within 24 hours. T2 weighted image with fat saturation of the left thigh demonstrates a large area of myonecrosis within the proximal rectus femoris muscle, with extensive muscular, fascial, and subcutaneous enhancement and edema, with crescentic fascial fluid collections, predominantly around the rectus femoris and sartorius, suggestive of necrotizing fasciitis. At the time the article was created The Radswiki had no recorded disclosures. Renal function should be assessed with a baseline creatinine level before administration as patients with impaired renal function are at risk for complications associated with IV contrast. Case 1: orbital and periorbital cellulitis, see full revision history and disclosures. 2020;368:m710. ADVERTISEMENT: Supporters see fewer/no ads. Emerg Radiol. Clinical presentations include skin erythema without a well-defined border, increased skin temperature, swelling of the affected area, and regional lymphadenopathy and lymphangitis. Bethesda, MD 20894, Web Policies Scout film (a) and contrast-enhanced CT (b) shows intramuscular pockets of gas (arrows) in the left lateral thigh. IV contrast may be used to visualize vasculature as well as the internal organs of the abdomen and pelvis. and transmitted securely. Additionally, systemic features such as fevers and rigors may also be present. HHS Vulnerability Disclosure, Help Necrotizing fasciitis: contribution and limitations of diagnostic imaging. 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. 07/16 RH /MF Patients with history of anaphylactic reaction should not receive contrast. CT LUMBAR SPINE W CONTRAST (IMG214) 72126 72129 72132 EXTREMITIES Fracture, Abnormal pathology. 3 0 obj It is essential to know the types of contrast agents, their risks, contraindications, and common clinical scenarios in which contrast-enhanced computed tomography is appropriate. Possible reactions are listed in Table 1.7 If a patient has had a previous minor reaction to an IV iodinated contrast agent, precontrast administration of oral or IV corticosteroids and diphenhydramine (Benadryl) may decrease their risk (Table 27 ). Necrotizing fasciitis: CT characteristics. Cellulitis occurs after disruption of the skin and invasion of the subcutaneous tissues by microorganisms that may be skin flora, such as beta-hemolytic streptococci (most often),Staphylococcus aureus(including methycillin-resistant), or other bacteria 9. The information provided is for educational purposes only. endobj Other CT findings include increase soft-tissue attenuation, subcutaneous edema and inflammatory fat stranding, which can also be seen in cellulitis.2,2123 In a study by Wysoki et al. 3. The American Academy of Radiology recommends the use of IV contrast only if care of the patient cannot be accomplished without it. Water-soluble, iodine-based contrast agents can also be given orally. Many types of contrast agents can be used in computed tomography: oral, intravenous, rectal, and intrathecal. With respect to employing CT as an imaging modality, first one should be aware of the different ty. In patients with normal renal function, repeat measurement of serum creatinine is not recommended after outpatient administration of intravenous contrast agents. Most centers use nonionic contrast agents (which are generally low osmolality) for IV contrast studies.5 The rate of major reactions (e.g., anaphylaxis, death) is the same for ionic and nonionic IV contrast agentsan estimated one in 170,000 administrationsbut nonionic contrast has a lower rate of minor reactions.6 Approximately 5% to 12% of patients who receive high-osmolality contrast have adverse reactions, most of which are mild or moderate.7 Use of low-osmolality contrast has been associated with a reduction in adverse effects. However, CT scanning with contrast involves exposure to ionizing radiation, which may increase the risk of malignancy and eye lens damage. Computed tomography (CT scan or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. Cross-sectional schematic diagram through the right thigh demonstrating the various findings of necrotizing fasciitis. Oral contrast agents are barium- or iodine-based and are used for bowel opacification. No circumscribed collection, or signs of bulbar or intraconal involvement (note the preservation of the normal intraorbital fat density). In pleural effusion, CT assessment for the presence, location, and extent of the effusion does not require contrast. No mutagenic or teratogenic effects have been shown with nonionic, low-osmolality contrast in animal studies. These experts are usually happy to help select the correct test for your patient. Accessibility CT is the most sensitive modality for soft-tissue gas detection, and compared with radiography, CT is superior to evaluate the extent of tissue or osseous involvement, show an underlying (and potentially more remote) infectious source, and reveal serious complications such as vascular rupture complicating tissue necrosis [ 10, 13 - 20 ]. The soft-tissue air deep to the fascia is seen as multiple echogenic foci (arrows) on ultrasound study (b). Horton L, Jacobson J, Powell A, Fessell D, Hayes C. Sonography and Radiography of Soft-Tissue Foreign Bodies. High Resolution Chest CT This is a specialized CT of the lungs performed without IV contrast. Normally the subcutaneous tissue is hypoechoic with few hyperechoic strands (representing connective tissue). It is also not used in patients with suspected acute stroke. Large volume of gas seen within the scrotum wall and scrotum sac on the scout image (curved black arrow), consistent with Fourniers gangrene. Related editorial: Potential Harms of Computed Tomography: The Role of Informed Consent. N Engl J Med. Fasciae of the Musculoskeletal System: MRI Findings in Trauma, Infection and Neoplastic Diseases. A paranasal sinus pathology is . Cellulitis(rare plural: cellulitides) is an acute infection of the dermis and subcutaneous tissues without deep fascial or muscular involvement. 2nd ed. Fluid tracking along deep and intermuscular fascia, which can be seen in advanced cases (d). Although many radiology departments screen for shellfish allergy, there is no cross-reactivity between shellfish and iodinated contrast. The purpose of this article is to review the imaging findings of necrotizing fasciitis as seen on radiograph, ultrasound, CT, and MRI, and to recognize the early findings in this potentially fatal disease. Patients with peripheral vascular disease or diabetes mellitusare particularly susceptible to cellulitis since minor injuries to the skin or cracked skin in the feet or toes can serve as a point of entry for infection. Please enable it to take advantage of the complete set of features! For the assessment of vascular disease, CT in most cases requires IV contrast to delineate the vessel lumen. Since the epidermis is not involved, cellulitis is not transmitted by person-to-person contact. CT without contrast in a patient with a history of interstitial lung disease and right lung trans-plant shows the patent but partially narrowed anastomotic site of the right bronchus (A) (red arrow). Epub 2020 Oct 15. sonographic hallmarks of cellulitis include abnormal echogenicity and increased thickness of the dermis with indistinct "haziness" and increased echogenicity of the subcutaneous tissue, it is often helpful to compare the area in question to the (presumably normal)contralateral side, progressive accumulation of edema in the subcutaneous tissue appears as branching, anechoic striations which impart a lobulated ("cobble-stone" appearance), presence of thickened and abnormally echogenic overlying skin will favor cellulitis over edema, linear anechoic bands of fluid deep to the subcutaneous layer favor lymphedema, ultrasound is more sensitive than MRI for the detection of a retained foreign body as the causative agent, especially if small and wooden 4,5. Copyright 2013 by the American Academy of Family Physicians. One study showed similar increases in serum creatinine levels between inpatient populations who received IV iodinated contrast and those who did not.16, Noncontrast-enhanced CT is used in patients with head trauma and acute stroke. 2022 Nov 25;10(12):2329. doi: 10.3390/microorganisms10122329. Normally the subcutaneous tissue is hypoechoic with few hyperechoic strands (representing connective tissue). Fundic gland polyps: Should my patient stop taking PPIs? CT may also be ordered for cross-sectional images of the spine with contrast in the thecal sac. Compared to plain radiography, ultrasound, CT and MR provide higher sensitivity and specificity for the diagnosis of necrotizing fasciitis. Although a very uncommon soft-tissue infection, it has significant mortality up to 7080% and constitutes a life-threatening surgical emergency.1, 2 The most important predictor of mortality is a delay in diagnosis, thus it is essential to make a prompt diagnosis.2 Clinically, the findings of necrotizing fasciitis can overlap with other soft-tissue infections including cellulitis, abscess or even compartment syndrome, but pain out of proportion to the degree of skin involvement and signs of systemic shock should alert the clinician to the possibility of necrotizing fasciitis.46 Other red flag clinical findings are listed in Table 1. Check for errors and try again. myriad of non-infective erythematous rashes, Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. While adverse effects to the fetus have not been demonstrated with IV dye, contract does cross the placenta. 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. [ 16, 17, 18] On CT scans, a preseptal cellulitis may appear as. Answer (1 of 4): You asked: Are CT scans without contrast always done before CT scans with contrast? In a 79-year-old patient with chronic thromboembolic pulmonary hypertension, CT angiography of the pulmonary artery (A) shows weblike (red arrow) and partially calcified filling defects (yellow arrow), as well as diffuse mild mosaic attenuation of lung parenchyma (B). 1Department of Radiology, Massachusetts General Hospital, Boston, MA, USA. Before Order "HAND" if entire wrist and hand. Skeletal Radiol. A 39-year-old-male with necrotizing fasciitis of the right thigh. Even in osseous infection, CT and MRI can give better anatomic delineation of the extent of infection. The CT and MRI findings in the spectrum of musculoskeletal infections are discussed and contrasted, and pitfalls in their evaluation of musculoskeletal infection are described. An official website of the United States government. Required fields are marked *. Cross-sectional imaging findings include asymmetric thickening of the fascia, soft-tissue air, blurring of fascial planes, inflammatory fat stranding, reactive lymphadenopathy, and nonenhancement of the muscular fascia. The https:// ensures that you are connecting to the Possible contraindications for using intravenous contrast agents during computed tomography include a history of reactions to contrast agents, pregnancy, radioactive iodine treatment for thyroid disease, metformin use, and chronic or acutely worsening renal disease. Cellulitis can affect any region of the body, and commonly affects a lower limb. Copyright 2016 The Cleveland Clinic Foundation. If the infection spreads to deeper tissues, complications can occur, such as soft-tissue abscess,necrotising fasciitis,infectious myositis, and/or osteomyelitis. However, IV radiologic contrast may cause transient alteration in renal function, which could impair metformin clearance, leading to a higher risk of metabolic acidosis. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. Clinical findings suggestive of necrotizing fasciitis vs cellulitis.7, There have been association with intravenous drug use as well as chronic conditions including diabetes mellitus, immunosuppression, obesity, and peripheral vascular disease.3, 8 A history of recent surgery (within the past 90 days) at the affected site has been shown to be a strong predictor for necrotizing fasciitis.7, Infection typically begins in the superficial fascial planes, then rapidly progress into the deep fascial layers, which causes necrosis secondary to microvascular occlusion.1 The rate of spread of infection is directly proportional to the thickness of the subcutaneous layers, with fastest spread seen in the lower extremities due to the lack of fibrous boundaries between subcutaneous tissue and fascia.2, 9, Necrotizing fasciitis is a clinical diagnosis since imaging findings can be nonspecific or unremarkable early in the course of the disease.1 The majority of cases are initially misdiagnosed, causing delay in diagnosis.10 Imaging appearances of necrotizing fasciitis can also overlap with other conditions, including nonnecrotizing fasciitis, dermatomyositis, graft vs host disease, or ischemic myonecrosis.1 The main utility of imaging is to determine the extent of the soft-tissue infection as well as to guide surgical planning.1, 8 If the patient is presenting with shock, imaging should not delay the initiation of treatment.1 Definitive diagnosis is based on surgical exploration and biopsy and aggressive surgical fasciotomy of necrotic tissue is required to prevent the spread of infection.7, Early findings of necrotizing fasciitis on radiography can appear similar to cellulitis including soft-tissue opacity and thickening.1113 The classical findings of dissecting gas along fascial planes in the absence of trauma is a specific sign, but is only seen in 24.855.0% of patients, and may not be seen until late in the disease (Figures 1 and 2).1, 10,12 Necrotizing fasciitis commonly affects the lower extremities, with involvement of the perineum or scrotum, classically known as Fourniers gangrene (Figure 3).3, 14,15 Soft-tissue gas is typically caused by gas-forming anaerobic infections, although this may not be present in diabetic patients.16 As such, the absence of soft-tissue emphysema does not exclude a diagnosis of necrotizing fasciitis.1. Most healthcare facilities have protocols dictating the cutoff at which IV dye may be administered in patients with impaired renal function. Zacharias N, Velmahos GC, Salama A, Alam HB, de Moya M, King DR, et al.. Hydration can decrease these risks. Nurse practitioners must be familiar with the contraindications for CT contrast administration. Axial CT with contrast enhancement obtained subsequently (B and C) shows that this abnormality corresponds to right hilar lymphadenopathy partially encasing the right pulmonary artery (arrows). The PPV was 91.3% when more than one deep neck space was involved but only 50.0% in patients with isolated retropharyngeal abscesses. JAMES V. RAWSON, MD, AND ALLEN L. PELLETIER, MD. government site. The U.S. Food and Drug Administration advises that metformin should be withheld at the time of IV contrast administration and for 48 hours afterward, and resumed only after reevaluation of renal status (i.e., return to baseline serum creatinine level).13. A 57-year-old diabetic male with pneumoscrotum. Yes neuro CTa HeaD Circle of Willis CTA Head with and without contrast Note: MRA Brain without contrast is preferred. Brothers TE, Tagge DU, Stutley JE, Conway WF, Del Schutte H, Byrne TK. It is usually due to underlying bacterial sinusitis. Disclaimer. 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. In the false-positive group, cellulitis was the most . The choice of contrast agent depends on route of administration, desired tissue differentiation, and suspected diagnosis. It is injected through an intravenous line during the examination. 5. Concerns for using IV contrast during CT include a history of reactions to contrast agents, pregnancy, treatment of thyroid disease with radioactive iodine, use of metformin (Glucophage), and chronic or acutely worsening renal disease. They are used for bowel opacification and are not nephrotoxic. Cross-sectional imaging findings include asymmetric thickening of fascia, soft tissue air, blurring of fascial planes, inflammatory fat stranding, reactive lymphadenopathy, and nonenhancement of muscular fascia. Radiology. Author disclosure: No relevant financial affiliations. Recent estimates place the number of computed tomography (CT) scans performed annually in the United States at approximately 70 million.1 Given the cost and radiation exposure, it is critical that CT is appropriate and performed with optimal technique. Shortness of breath Abdomen andPelvis Without IV contrast 1. Necrotizing fasciitis: early sonographic diagnosis. Correlation of histopathologic findings with clinical outcome in necrotizing fasciitis. Crit Rev Diagn Imaging. Swartz M. Clinical Practice. endobj BMJ. Patients with a mild allergy may be pre-medicated with an antihistamine or steroids before imaging. Premedication with antihistamines and corticosteroids is recommended in patients with a history of mild to moderate reactions to intravenous contrast agents. Reference article, Radiopaedia.org (Accessed on 01 May 2023) https://doi.org/10.53347/rID-15554. , Acuterecurrent rhinosinusitis It results in pain, erythema, oedema, and warmth. : Elsevier Health Sciences, 2013;633-644. Lactic acidosis has never been documented in patients with normal renal function who are receiving metformin. Wong CH, Khin LW, Heng KS, Tan KC, Low CO. Radiographics. AJR Am J Roentgenol. Computed tomography (CT) plays an important role in the diagnosis and treatment of many clinical conditions1 involving the chest wall, mediastinum, pleura, pulmonary arteries, and lung parenchyma. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. IV dye may cause a temporary alteration in kidney function. Preparation: Please have only a clear liquid diet for 4 hours prior to exam. 2. 2001;176(5):1155-9. and transmitted securely. References. CT head without IV contrast Usually Not Appropriate . The concentration of barium determines whether it enhances the diagnosis or causes an artifact and obscures pathology. The need for enhancement with intravenous (IV) contrast depends on the specific clinical indication (Table 1). Imaging of Musculoskeletal Soft-Tissue Infections in Clinical Practice: A Comprehensive Updated Review. If the infection spreads to deeper tissues, soft-tissue abscess, infectious myositis, necrotising fasciitis, and osteomyelitis can all be detected with CT. MRI is sensitive for distinguishing cellulitis alone from necrotising fasciitis and infectious myositis and for showing subcutaneous fluid collections and abscesses. Sign In to Email Alerts with your Email Address. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. Next imaging study. The diagnostic algorithm for lung cancer screening is evolving. Insights Imaging. The .gov means its official. Ultrasound is usually the first investigation to evaluate a clinical suspicion of cellulitis. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. Diagnosis of necrotizing soft tissue infections by computed tomography. Contrast-enhanced CT demonstrates air (arrows) and edema in the scrotum, surrounding the right testicle (a). myriad of non-infective erythematous rashes, ADVERTISEMENT: Supporters see fewer/no ads, Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. 7. Children have a lower incidence of reactions to IV contrast agents, and most of these are mild (0.18% for low-osmolality agents).7,8, Risk factors for contrast reactions include multiple drug allergies and asthma.
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