IMAGING APPROACH TO A PATIENT WITH AN ACUTE SWOLEN LEG.

DVT: QUICK FACTS• Clinical signs and symptoms of DVT are unreliable.

• If clinical signs alone were used to diagnose DVT, 42% of patients would receive unnecessary anticoagulation therapy.

• Most patients evaluated with US do not have DVT

• In 60%–80% of symptomatic patients, a diagnostic test can rule out DVT . This means that approximately seven of 10 patients could have a cause other than DVT for pain, oedema, mass, or erythema in the legs.

• Most patients who develop DVT are asymptomatic

DVT• Compression US remains the imaging procedure of choice for the investigation of

patients with suspected DVT.

• It is a highly sensitive and specific test for the diagnosis of proximal DVT in symptomatic patients.

• Management approaches that rely on two negative compression US studies obtained 1 week apart have proved to help safely exclude the diagnosis of DVT.

• Compression US is much less sensitive for diagnosing DVT following high-risk surgical procedures such as total hip or knee arthroplasty

• In the United States, the annual combined incidence of DVT and pulmonary embolism is at least 70 per 100,000 individuals

DVT• Fewer than 10% of patients with DVT will have isolated iliofemoral disease, and this

syndrome tends to occur in certain well-recognized clinical situations.

• Peripartum period (90% of cases, it will involve the left leg likely due to compression of the left common iliac vein by the right iliac artery during pregnancy.

• Pelvic mass or recent pelvic surgery is typically found in the iliofemoral veins.

• Oral contraceptive use.

• Antiphospholipid antibody syndrome.

ANATOMICAL APPROACH• The anatomic approach is the most useful strategy for characterizing the spectrum of

pathologic conditions seen in patients with symptoms that simulate DVT.

• The inferior extremity can be divided into four regions—inguinal, thigh, popliteal, and lower leg

• The differential diagnoses affecting the lower extremities include infectious, neoplastic, traumatic, inflammatory, vascular, and miscellaneous entities

INGUINAL REGIONTYPE OF ENTITY DIFFERENTIAL DIAGNOSIS

Infective Lymphangitis

Neoplastic Lymph node metastases, Soft tissue tumours(Sarcomas,Lipomas,Haemangiomas)

Vascular AV Fistula, Pseudo aneurysm, Post puncture haematoma, DVT

Traumatic Pectineal or adductor tear

Inflammatory Ileopsoas and ileopectineal bursitis, adductor tendinitis.

Miscellaneous Femoral and inguanal hernias

INGUINAL REGION: LYMPHANGITIS

• Inflammation of the lymphatic vessels.

• Usually seen with oedema, which can appear clinically similar to DVT.

• US: The presence of adenopathies and tubular dilatations that are superficial to the veins and that show no evidence of flow on colour Doppler.

• MR can help further characterize lymphangitis

INGUINAL REGION: VASCULAR LESIONS• The most common vascular pathologic conditions that simulate DVT are secondary to

catheterization of the common femoral artery:

• Hematomas

• Pseudoaneurysms

• Obese patients, large-bore sheaths, antiplatelet therapy, and postprocedural anticoagulation

• Color Doppler bidirectional flow, which appears as a “yin-yang” sign.

• The dimensions of the neck should be measured to determine whether the best treatment is to use compression therapy or to administer a thrombin injection

Less commonly from nonsurgical trauma

INGUINAL REGION: FAT RELATED LESIONS

• The symptoms of femoral hernias, especially incarcerated femoral hernias, which can produce a painful, bluish mass that is nonreducible, are similar to those of DVT

• Use of the Valsalva manoeuvre and examining the patient in supine and standing positions are essential to diagnose a hernia and to rule out DVT .

• Loss of peristalsis and a lack of mucosal blood flow can help determine if a hernia is incarcerated

VALSALVA

INGUINAL REGION: LIPOMAS

• Of the many fat-containing soft-tissue masses, lipoma is by far the most common mass seen in the subcutaneous tissue.

• Lipomas are usually asymptomatic, but when they are large and closely related to the femoral structures, they can compress the vein or nerve and exhibit symptoms similar to those of DVT.

THIGH:TYPE OF ENTITY DIFFERENTIAL DIAGNOSIS

Infective Cellulitis, Myositis, Abcesses

Neoplastic Soft tissue tumours

(Sarcomas,Lipomas,Haemangiomas, Desmoid tumours)

Vascular Haematoma, Traumatic vascular injuries,DVT

Traumatic Chronic excertional compartement syndrome, sports related injuries

Inflammatory Auto immune myositis, rhabdomyolysis, myonecrosis

THIGH: MUSCULAR LESIONS• The most frequent cause of muscular lesions is trauma.

• Muscular lesions are subdivided into:

• Contusions

• Muscle strains

• Tears

• Lacerations

THIGH: MUSCULAR LESIONS• Contusions: on rare occasions they may be confused with DVT.

• Muscle strains, tears, and lacerations often mimic DVT.

• Minor trauma: Muscular contusions with oedema in the focal lesion.

• Major trauma: Hematomas.

• Anechoic to echogenic in the first 24 hours.

• In the following 2–3 days, it becomes hypoechoic or anechoic;

• Thereafter, an increase in echogenicity can be seen

THIGH: CHRONIC EXERTIONAL COMPARTMENT SYNDROME• Classified as either acute or chronic

• The acute form of compartment syndrome is always related to trauma and therefore is not a differential diagnosis of DVT.

• In chronic compartment syndrome, recurrent pain is caused by exercise; this is because of the increase in muscle mass that is associated with exercise.

• Chronic exertional compartment syndrome primarily affects the infrapopliteal segment of the extremity, but it can also be seen in the thigh.

• On images, diagnostic clues include an increase in the size of the affected compartment and a diffuse increment of echogenicity.

• However, because US and MR imaging findings are sometimes nonspecific, comparative exploration is useful in view of the subtlety of the findings

THIGH: MYOSITIS• Common cause of muscular edema:

• Secondary to:

• Autoimmune disease, infection, vasculitis, and trauma.

• When the infection is in the thigh, myositis usually compromises the quadriceps.

• A diffuse increase in the echogenicity of the affected muscle fibers is seen in the early stages of myositis and is associated with an increase in the diameter of the muscle group.

• The natural evolution of the infection leads to formation of an abscess with central necrosis

POPLITEAL REGIONTYPE OF ENTITY DIFFERENTIAL DIAGNOSIS

Infective Cellulitis

Neoplastic Rhabdomyosarcoma, Synovial haemangioma

Vascular Popliteal artery aneurysm, Adventitial cyst of the popliteal artery, Thrombophlebitis,DVT

Traumatic Muscle contusions and haematomas, Fracture

Inflammatory Ruptured bakers cyst, Para meniscal cyst,Pes anserinus bursitis

POPLITEAL REGION: BAKER CYSTS• Most common cystic lesions seen around the knee.

• The medial gastrocnemius-semimembranosus bursa communicates with the knee joint in more than 50% of patients older than 50 years.

• Symptoms usually arise from growth or rupture of the cyst.

• Causes:

• Usually secondary to degenerative changes of the knee.

• Meniscal rupture

• Synovitis

• Chronic infectious processes

• Inflammatory arthritis(RA)

POPLITEAL REGION: POPLITEAL ARTERY ANEURYSMS

• True popliteal artery aneurysms are the most common type of peripheral artery aneurysms.

• Transverse diameter of 7 mm or more .

• Bilateral in 50%–70%.

• 6% Rupture

• Associated with aneurysms in other locations in 30%–50%.

• 45% of popliteal artery aneurysms are asymptomatic.

• Symptomatic when they rupture or compress the popliteal vein.

LOWER LEGTYPE OF ENTITY DIFFERENTIAL DIAGNOSIS

Infective Cellulitis, Abcess

Neoplastic Lipomas, Sarcomas, Haemangioma

Vascular Popliteal artery entrapment syndrome, Thrombophlebitis, anticoagulation haematoma,DVT

Traumatic Tendinitis, Fractures, tennis leg, chronic excertionalcompartement syndrome, medial tibial stress syndrome

Inflammatory Paniculitis, Nodous erythema

Miscellaneous Cardiac and renal failure, fluid overload, lymphangitis, insects bites

LOWER LEG: TENNIS LEG

• Common injury

• Middle-aged patients

• Hyperextension of the knee and forced dorsiflexion of the ankle.

• Usually associated with exercise, but it can also be caused by normal, daily activities.

• Clinically

• Sudden pain in the calf that patients describe as a “pop.”

• Over the following 24 hours, oedema and pain ensue, symptoms that simulate DVT.

LOWER LEG: MISCELLANEOUS LESIONS

• Most common:

• Venous congestion (cardiac/ renal failure and fluid overload)

• Cellulitis

• Imaging findings:

• Swelling of the subcutaneous tissue.

MUSCULOSKELETAL INFECTION: ROLE OF CT IN THE EMERGENCY DEPARTMENT

• CT is invaluable for detecting deep complications of cellulitis and pinpointing the anatomic compartment that is involved by an infection.

• CT is used to accurately differentiate between:

• Superficial cellulitis and cellulitis associated with a deep-seated infection.

• Although all patients with musculoskeletal infection will require treatment with antibiotics, CT helps guide therapy toward emergency surgical debridement in cases of necrotizing fasciitis and toward percutaneous treatment in cases of abscess formation

• Clinical parameters(CRP,WCC,ESR) for the detection of musculoskeletal infection generally lack sensitivity and specificity

MUSCULOSKELETAL INFECTION: ROLE OF CT IN THE EMERGENCY DEPARTMENT

• High risk group for serious and rapid spread of infection:

• Diabetes, immunodeficiency, impaired peripheral circulation, or a history of lymphadenectomy

• If the infection spreads to deeper tissues, deep cellulitis, myositis, necrotizing fasciitis, or osteomyelitis, abscess can occur, all of which can be excluded with CT

NECROTIZING FASCIATIS• Morbidity and mortality rate is 70%–80%

• One of the most important predictors of mortality is a delay in the diagnosis of necrosis.

• Imaging findings in necrotizing fasciitis are similar to those in cellulitis but are more severe and show involvement of deeper structures. One specific distinguishing sign of necrotizing fasciitis is the presence of gas in the subcutaneous tissues. fluid collections along the deep fascial sheaths, and extension of edema into the inter-muscular septa and the muscles.

• Contrast-enhanced CT, there is no demonstrable enhancement of the fascia, a finding that confirms the presence of necrosis and helps distinguish nonnecrotizing fasciitis from necrotizing fasciitis.

• Nonnecrotizing fasciitis does not require emergency surgery, but affected patients should be followed up because of the potential for necrosis.

PRIMARY PYOMYOSITIS• CT findings

• Enlargement of a muscle group that is disproportionate to the involvement of subcutaneous tissue helps distinguish myositis from primary cellulitis

OSTEOMYELITIS

• Young adults, it is most commonly associated with an open fracture or direct trauma.

• Elderly and pediatric patients, the cause of osteomyelitis is typically bacteremia.

• Patients at high risk to develop osteomyelitis include:

• Immunosuppression

• Diabetes mellitus

• Sickle cell disease

• Intravenous drug abuse

• Alcoholism.

OSTEOMYELITIS: ROLE OF IMAGING• Diagnosis requires two of the following four criteria, one of which is positive imaging

findings: (a) purulent material draining from the site of acute osteomyelitis,(b) positive findings at bone tissue or blood culture, (c) localized classic physical findings of bone tenderness and edema, and, as mentioned, (d) positive radiologic findings.

• Conventional xrays of acute osteomyelitis is insufficient because bone changes are not evident for 14–21 days after the onset of infection.

• Xrays are typically normal at presentation in 95% of cases, and it is not until 28 days after the onset of infection that 90% of patients demonstrate some abnormality at conventional radiography .

• MRI is the accepted modality of choice for the early detection and surgical localization of osteomyelitis.

• In the emergency department, CT is usually more readily available for establishing the diagnosis

OSTEOMYELITIS: CT FINDINGS• Soft-tissue swelling

• Periosteal reaction

• Focal cortical erosions .

• An extramedullary fat-fluid level is a rare but specific sign for osteomyelitis.

SEPTIC ARTHRITIS

• Large joints, abundant blood supply to the metaphyses are most prone to bacterial infection

• Most commonly affected joints:

• Shoulder, hip, and knee.

SEPTIC ARTHRITIS: CT FEATURES

• Joint effusion

• Bone erosions around the joint.

• Fat-fluid level can be a specific sign in the absence of trauma

LOWER LEG: ABPI• The pressures in each foot's posterior tibial artery and dorsalis pedis artery are measured

with the higher of the two values used as the ABI for that leg.

• Where PLeg is the systolic blood pressure of dorsalis pedis or posterior tibial arteries

• and PArm is the highest of the left and right arm brachial systolic blood pressure

• The ABPI test is a popular tool for the non-invasive assessment of PVD. Studies have shown the sensitivity of ABPI is 90% with a corresponding 98% specificity for detecting hemodynamically significant stenosis >50% in major leg arteries.

ABPI• ABPI LEG = P leg/ P arm

VASCULAR INJURY: HARD AND SOFT SIGNS• Hard signs of major arterial injury:

• Pulsatile hemorrhage, expanding hematoma, bruit or thrill, acute limb ischemia, and pulse deficit.

• These hard signs have been shown to be nearly 100% associated with the presence of major vascular injury and usually mandate subsequent surgical exploration .

• Soft signs

• Asymmetric pulses, abnormal ankle-brachial index, nonexpanding hematoma, or injuries determined to be within close proximity to a major neurovascular bundle.

• These soft signs of vascular injury serve as surrogates for the possible presence of such an injury and warrant observation or additional diagnostic work-up, typically with angiography

VENOGRAPHY: INDICATIONS• 1. Diagnosis of DVT in a patient:

• a. With a nondiagnostic duplex ultrasound examination or for whom a duplex examination is not technically feasible.

• b. Suspected of having infrapopliteal disease.

• c. With a symptomatic extremity status after joint replacement.

• d. With a high clinical suspicion for DVT but with a negative duplex examination.

• e. When duplex ultrasound is not available.

•

• 2. Evaluation of valvular insufficiency prior to stripping or ligation of superficial varicose veins.

• 3. Venous mapping prior to or following a surgical or interventional procedure.

• 4. Evaluation for venous malformations.

• 5. Preoperative evaluation for tumor involvement or encasement.

VENOGRAPHY CONTRA INDICATIONS• Relative contraindications include, but are not limited to:

• 1. Evidence of active cellulitis of the extremity to be imaged.

• 2. Iodinated contrast allergy.

• 3. Renal insufficiency in patients who are not on dialysis, particularly those with diabetes or congestive heart failure (CHF).

REFERENCES• Juan N. Useche, Alfredo M. Fernandez. Use of US in the Evaluation of Patients with

Symptoms of Deep Venous Thrombosis of the Lower Extremities. Radiographics 2008

• Laura M. Fayad, John A. Carrino, Elliot K. Fishman. Musculoskeletal Infection: Role of CT in the Emergency Department Radiographics November-December 2007 27:6 1723-1736;

• HamperUM, Dejong MR, Scoutt LM. Ultrasound evaluation of the lower extremity veins. Radiol Clin North Am2007; 45: 525–547

• BeamanFD, Kransdorf MJ, Andrews TR, Murphey MD, Arcara LK, Keeling JH. Superficial soft-tissue masses: analysis, diagnosis, and differential considerations. RadioGraphics2007; 27: 509–523.

• ArmfieldDR, Kim DH, Towers JD, Bradley JP, Robertson DD. Sports-related muscle injury in the lower extremity. Clin Sports Med2006; 25: 803–842.