Imaging Pearls ❯ Musculoskeletal ❯ Inflammatory Disease
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- Cellulitis
Uncomplicated cellulitis is a clinical diagnosis and is treated conservatively with antibiotics and locally supportive measures. However, there is a risk for serious and rapid spread of the infection in patients with diabetes, immunodeficiency, impaired peripheral circulation or history of lymphadenectomy. For such patients in the ER, CT is used to accurately differentiate between superficial cellulitis and cellulitis associated with a deep-seated infection. In uncomplicated cellulitis, CT demonstrates skin thickening, stranding and septation of the subcutaneous fat and thickening of the underlying superficial fascia. A foreign body associated with cellulitis can be detected by CT, if present . - Necrotizing Fasciitis
Necrotizing fasciitis is a progressive, rapidly spreading infection located in the deep fascia, with secondary necrosis of the subcutaneous tissues . The speed of spread of the infection is directly proportional to the thickness of the subcutaneous layer. The occurrence of necrotizing fasciitis is relatively rare, though it is on the rise because of an increase in immunocompromised patients with HIV, diabetes mellitus, cancer, alcoholism, vascular insufficiencies and organ transplantation. It can occur after trauma or around foreign bodies in surgical wounds, though it can also be idiopathic, as in scrotal or penile necrotizing fasciitis. The majority of necrotizing soft tissue infections have gas-forming anaerobic bacteria present, usually in combination with aerobic gram-negative organisms. - Necrotizing Fasciitis
Necrotizing fasciitis is a life-threatening surgical emergency. Unfortunately, this infection can be difficult to recognize in its early stages, but it rapidly progresses. The overall morbidity and mortality is 70-80%, and one of the most important predictors of mortality is a delay in the diagnosis of necrosis. Hence, CT imaging can play a vital role in suggesting the diagnosis early and initiating rapid and successful treatment. - Necrotizing Fasciitis
The imaging findings in necrotizing fasciitis are similar to those as with cellulitis, but are more severe and show involvement of deeper structures. One specific distinguishing sign of necrotizing fasciitis is the occurrence of gas in the subcutaneous tissues due to the presence of gas-forming anaerobic organisms (Fig. 6). However, it should be noted that gas is not observed with all cases of necrotizing fasciitis. Other CT features include thickening of the affected fascia, fluid collections along the deep fascial sheaths as well as extension of edema into the intermuscular septae and the muscles (Fig. 7, 8). Following contrast enhancement, there is no demonstrable enhancement of the fascia, confirming the presence of necrosis and distinguishing non-necrotizing fasciitis from necrotizing fasciitis. Those patients with non-necrotizing fasciitis are not surgical emergencies, but they should be followed for the potential of forming necrosis. - Soft Tissue Abscess
Although most bacterial infections in the soft tissues stay localized, a soft tissue abscess may form, particularly in immunocompromised patients. The most common isolated pathogen is Staphylococcus Aureus, though in an urban emergency department population, MRSA is now cultured in 51% of patients with a soft tissue infection and such patients are more likely to present with a soft tissue abscess than patients from whom other bacteria are cultured. By CT, a well-demarcated fluid collection with a peripheral pseudocapsule showing rim enhancement is characteristic of an abscess and differentiates an abscess from simple cellulitis or fasciitis. The treatment of a soft tissue abscess is administration of appropriate antibiotics and percutaneous drainage. - Infectious Myositis
Infectious myositis is an acute, subacute or chronic infection of skeletal muscle that is most commonly seen in young adults. While viruses, bacteria (including mycobacteria), fungi, and parasites can all cause myositis, the most common infectious agent is a bacteria, namely Staphylococcus aureus, responsible for over 75% of cases. Pyomyositis or bacterial myositis, was once considered a tropical disease, but is now seen in temperate climates, particularly with the emergence of HIV infection, where, in one study, 17% of patients with pyomyositis had underlying HIV infection. In fact, some authors report pyomyositis as the most common musculoskeletal complication of AIDS, but other risk factors abound and include strenuous activity or rhabdomyolysis and a history of muscle trauma where a hematoma may form and act as a nidus for infection. Skin infections, infected insect bites, illicit drug injections, and underlying diabetes mellitus can also lead to pyomyositis. - Osteomyelitis
Osteomyelitis is an infection of the bone that can result from hematogenous spread or be secondary to direct or contiguous inoculation. In young adults, it is most commonly associated with an open fracture or direct trauma while in elderly and pediatric patients, the cause of osteomyelitis is typically bacteremia. As with other musculoskeletal infections, disease states known to predispose patients to osteomyelitis include immunosuppression, diabetes mellitus, sickle cell disease, intravenous drug abuse and alcoholism. - Osteomyelitis
Hematogenous osteomyelitis usually presents with a slow insidious progression of symptoms, while osteomyelitis due to direct inoculation is localized, with prominent local signs and symptoms. The most frequently involved bones are the tibia, wrist, femur, ribs and thoracolumbar spine. The most common pathogen cultured is Staphylococcus Aureus, although in the HIV population, 30% of the cases of osteomyelitis are due to atypical mycobacteria. It should be noted that blood culture results are positive in only 50% of patients with hematogenous osteomyelitis. - Osteomyelitis
By CT, features of bacterial osteomyelitis include overlying soft tissue swelling, periosteal reaction, medullary lucencies or trabecular coursening and focal cortical erosions. In addition, the observation of an extramedullary fat-fluid sign is a rare but specific sign for osteomyelitis. This sign is an indication of cortical breach and, thus, in the absence of trauma, confirms the presence of osteomyelitis. For chronic osteoomyelitis, CT is considered superior to MRI for the demonstration of cortical destruction, gas and sequestra. - Osteomyelitis
As stated, the most common pathogen associated with osteomyelitis is Staphylococcus Aureus. However, mycobacterial infections are of great concern in the ER of a large center city hospital. The patient group at greatest risk to develop tuberculosis is the population infected with HIV. In long bones, tuberculous osteomyelitis usually begins in the metaphysis and spreads to the epiphysis. Eventually, cortical erosion into the joint occurs. Typically, skeletal tuberculosis presents with distinct bony margins without evidence of periosteal reaction (unless occurring in children). However, the most common osseous site of disease is the spine, comprising 50% of cases, and in particular, tuberculosis affects the thoracic spine. Early infection findings by CT include vertebral osteopenia followed later by slight disc space narrowing and then, characteristic anterior corner bone destruction. Skip lesions can occur as well as spread to the posterior elements, a rare but specific sign for tuberculosis. Paravertebral soft tissue edema and abscess formation occurs and chronically, calcification in the wall of these abscesses can be detected by CT .
- Imaging of chest wall disorders
- congenital and developmental anomalies
- inflammatory and infectious diseases
- soft-tissue and bone tumors
- What is Thallasemia?
- Thalassemia is a group of inherited diseases of the blood that affect a person's ability to produce hemoglobin, resulting in anemia. Hemoglobin is a protein in red blood cells that carries oxygen and nutrients to cells in the body. About 100,000 babies worldwide are born with severe forms of thalassemia each year. Thalassemia occurs most frequently in people of Italian, Greek, Middle Eastern, Southern Asian and African Ancestry.
- The more severe form of the disease is thalassemia major, also called Cooley's Anemia. It is a serious disease that requires regular blood transfusions and extensive medical care.
- Those with thalassemia major usually show symptoms within the first two years of life. They become pale and listless and have poor appetites. They grow slowly and often develop jaundice. Without treatment, the spleen, liver and heart soon become greatly enlarged. Bones become thin and brittle. Heart failure and infection are the leading causes of death among children with untreated thalassemia major.
- National Human Genone Research Institute - “Thalassemia is an inherited multisystemic disorder with skeletal and non-skeletal manifestations. Plain-film radiography is generally adequate in defining the routine osseous abnormalities of thalassemia. The CT and MRI techniques can document the abnormal deposition of iron, ExmH, and bone marrow changes.”
Imaging features of thalassemia
M. Tunacõ, A. Tunacõ, G. Engin et al.
Eur. Radiol. 9, 1801-1809 (1999) - Extramedullary Hematopoeisis in Thallasemia: Skeletal Manifestations
- Expansion of the medulla, thinning of cortical bone, resorption of the cancellous bone and widening of diploic spaces in the skull
- Ribs most commonly involved followed by vertebral bodies, skull and other bones ((humerus, sternum,clavicle, scapula) - Extramedullary Hematopoeisis: Common Causes
- myelofibrosis
- diffuse osseous metastatic disease replacing the bone marrow
- leukaemia
- sickle cell disease
- thalassemia. - Imaging Studies before a biopsy may be valuable
- 99mTc-colloid scintigraphic imaging
- PET scanning
- MRI
- CT
- “Infectious complications are the most common reason for inpatient admission in PWID. Soft tissue infection due to intravenous injection with contaminated needles or subcutaneous/intramuscular injection may manifest as a range of disorders of varying severity which include cellulitis, abscess, myositis and necrotizing fasciitis. These infections are often polymicrobial and Staphylococcus aureus and Streptococcus pyogenes are among the most common organisms. Prompt diagnosis and determination of the extent of infection is important as more severe pathologies, such as necrotizing fasciitis, require urgent surgical management.”
The needle and the damage done: musculoskeletal and vascular complications associated with injected drug use
Francis T. Delaney , Emma Stanley and Ferdia Bolster
Insights into Imaging (2020) 11:98 https://doi.org/10.1186/s13244-020-00903-5 - "CT is required to assess for suspected abscess forma- tion in deeper locations where ultrasound assessment is limited such as the retroperitoneum or deep pelvis. In PWID, abscesses may develop in deep locations due to direct extension from the site of injection, such as from the groin into the pelvis or retroperitoneum, or as a result of haematogenous seeding of distant locations. The risk of abscess formation in association with soft tissue infection is increased in immunocompromised patients or by the presence of a retained foreign body, meaning PWID are often at an increased risk. On CT, abscesses appear as a well-defined collection with internal fluid density and a peripheral rim-enhancing pseudocapsule.”
The needle and the damage done: musculoskeletal and vascular complications associated with injected drug use
Francis T. Delaney , Emma Stanley and Ferdia Bolster
Insights into Imaging (2020) 11:98 https://doi.org/10.1186/s13244-020-00903-5 - "CT is the imaging modality of choice for mycotic aneu- rysms, although ultrasound or MR angiography may also be used for evaluation depending on the location. Gas within the aneurysm is a rare but characteristic sign which is best seen on CT. Additional imaging features more commonly seen on CT include a lobulated vascular mass, an irregular and poorly defined arterial wall and peri- aneurysmal soft tissue stranding and oedema. Inflammatory soft tissue surrounding the artery can develop a mass-like appearance and be associated with necrosis.”
The needle and the damage done: musculoskeletal and vascular complications associated with injected drug use
Francis T. Delaney , Emma Stanley and Ferdia Bolster
Insights into Imaging (2020) 11:98 https://doi.org/10.1186/s13244-020-00903-5 - “Recreational drug use continues to be a significant healthcare problem and is associated with myriad multi- system complications. Musculoskeletal and vascular complications are commonly seen and are particularly prevalent in injected drug use. Awareness of the imaging manifestations and timely diagnosis of the complications related to injected drug use is important in daily radi- ology practice as clinical presentation may be non- specific and the history of illicit drug use often not forth- coming. A focused multimodal imaging approach is typ- ically required, depending on the nature of suspected complications.”
The needle and the damage done: musculoskeletal and vascular complications associated with injected drug use
Francis T. Delaney , Emma Stanley and Ferdia Bolster
Insights into Imaging (2020) 11:98 https://doi.org/10.1186/s13244-020-00903-5
- “Although the primary imaging modality for the evaluation of inflammatory arthritis of the foot and ankle is currently magnetic resonance imaging, computed tomography may be performed in some patients and can aid in diagnosis. This article reviews a number of inflammatory arthritic conditions that involve the feet. Computed tomographic findings and the role of computed tomography in diagnosing infection, gout, and rheumatoid arthritis of the foot are discussed.”
CT of the foot: select inflammatory arthridites
Johnson PT, Fayad LM, Fishman EK
J Comput Assist Tomogr 2007 Nov-Dec;31(6):961-9
- Castleman’s Disease: Two Types
- Plasma cell type (less vascular)
- Hyaline vascular form (vascular) - Castleman’s Disease: Location
- Thorax (67-70%)
- Neck (14-40%)
- Abdomen including retroperitoneum (2-7%) - Castleman’s Disease is also known as
- Angiofollicular hyperplasia
- Giant lymph node hyperplasia "In particular the combination of ascites, elevated CA-125 levels, and pelvic and peritoneal masses found in tuberculosis can be easily mistaken for coelomic spread of ovarian cancer."
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561"Peritoneal involvement in tuberculosis is present in 5% of cases and is usually associated with widespread abdominal disease involving the lymph nodes or bowel"
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561"Spondylitis is the most common form of skeletal tuberculosis infection, accounting for 60% of cases."
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561- Musculoskeletal Infection: Who is at risk?
- HIV/AIDS patients
- IVDA patients
- Sickle cell disease
- Diabetic patients
- Periperal vascular disease
- Immunocomprimised patients - "CT provides an analysis of compartmental anatomy, thereby helping to distinguish among the various types of musculoskeletal infection and to guide treatment options."
Musculoskeletal infection: Role of CT in the Emergency Department
Fayad LM, Carrino JA, Fishman EK
RadioGraphics 2007;27:1723-1736 - “ Spondylitis is the most common form of skeletal tuberculosis infection, accounting for 60% of cases.”
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561 - “ Peritoneal involvement in tuberculosis is present in 5% of cases and is usually associated with widespread abdominal disease involving the lymph nodes or bowel.”
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561 - “ In particular the combination of ascites, elevated CA-125 levels, and pelvic and peritoneal masses found in tuberculosis can be easily mistaken for coelomic spread of ovarian cancer.”
Tuberculosis: A Benign Imposter
Tan CH et al.
AJR 2010; 194:555-561 - Fournier's Gangrene
- Described in 1883
- Unexplained fulminating gangrene of the male genitalia
- Young healthy males, no discernible cause
- Today, broader age range, Males and Females
- Source can be identified in up to 95% of cases
- Successful treatment depends on early diagnosis and aggressive surgical intervention
- 76% mortality if delay > 6 days
- 12% mortality rate if < 24 hours before surgical debridment. - Fournier's Gangrene
- Causes Are:
- Trauma: Provides access of organisms to subcutaneous tissues
- Extension of UTI
- Extension from infection in perineal area
- Comorbid conditions often present
- ETOH, DM, Malignancy, Advanced age, Prolonged hospitalization
- Clinical Presentation Fever, pain, pruritis, swelling, vesicles, discharge, crepitus - Fournier's Gangrene
- Pathogenesis:
- Severe subcutaneous infection that begins adjacent to the portal of entry (urethral, rectal, cutaneous)
- Localized cellulitis progresses to diffuse inflammatory reaction involving the deep tissue planes
- Can progress 2-3 cm per hour
- The subcutaneous infection and edema impairs blood supply and results in cutaneous and subcutaneous vascular thrombosis (Necrotizing fasciitis) - Fournier's Gangrene
- Pathogenesis:
- Most common organisms (usually 4 or more)
- Klebsiella, Proteus, Streptococcus, Staphlococcus, Peptostreptococcus, E.coli
- Organisms act synergistically to produce fascial and soft tissue necrosis
- Gas is byproduct of anaerobic metabolism (Nitrogen, nitrous oxide, hydrogen and hydrogen sulfate).