Cheryl L. Kirby

Portal vein thrombus and infiltrative HCC: a pictoral review

Infiltrative hepatocellular carcinoma (HCC) can be overlooked on imaging. Radiologists should have a high index of suspicion for this entity in patients with chronic liver disease. Careful evaluation of the portal vein may help the radiologist diagnose infiltrative HCC, due to the high association (68%–100%) of portal vein tumor thrombus with this condition. This article will review the imaging findings of infiltrative HCC, particularly its association with portal vein thrombus, and describe imaging pitfalls and mimickers.

Morel-Lavallée lesion.

DISCUSSION A Morel-Lavallée lesion is a closed degloving injury that results in a deep fluid collection located between the subcutaneous tissues and underlying fascia (Fig. 2). Shearing forces during blunt trauma disrupt the vessels and lymphatics that perforate the deep fascia resulting in the accumulation of hemolymphatic fluid in the perifascial plane filling a potential space with blood, lymph, fat, and other debris. Morel-Lavallée lesions are most commonly found in the thigh and trochanteric regions and are often associated with pelvic, acetabular, and femoral fractures. These degloving injuries have also been described in the soft tissues overlying the knee, lumbar spine, scapular, and upper extremities. In the acute and subacute phases, patients may present with an enlarging fluctuant mass (which may or may not be painful), bruising, skin hypermobility, and/or decreased cutaneous sensation. Although these lesions are the result of a closed injury, Morel-Lavallée lesions are at risk of becoming secondarily infected in the subacute phase. Transient bacteremia that often occurs in the peritraumatic period is thought to seed the fluid collection. In 1 study, up to 46% of Morel-Lavallée lesions were culture positive at a mean time of 13 days after initial trauma. Because these collections may accumulate slowly, they may be missed on initial posttraumatic assessment. Chronic MorelLavallée lesions may develop a partial or complete fibrous capsule, and as a result, these lesions are less apt to respond to conservative management and more likely to recur after drainage. On ultrasound imaging, Morel-Lavallée lesions consist of compressible avascular hypoechoic or anechoic collections located between the deep subcutaneous fat and overlying fascia. In a retrospective review of 21 cases, acute lesions were more heterogeneous with lobulated irregular margins, whereas chronic collections were more homogeneous and flat or fusiform. As in our case (Fig. 3), fat globules may also be seen within the collection as nondependent echogenic nodules. Because these lesions are frequently large, panoramic ultrasound imaging is useful to encompass the entirety of the collection. Awareness of this entity is useful when interpreting computed tomography (CT) or magnetic resonance imaging (MRI) in posttraumatic patients. The complexity of the fluid on CT or MRI reflects its variable composition or stage of development. On MRI, acute or subacute fluid collections containing a large amount of methemoglobin may be hyperintense on T1and T2-weighted imaging. Over time, these lesions are typically hypointense to muscle on T1 and hyperintense to muscle on T2 weighting, reflecting the increasingly serous composition of the fluid. Lesions containing organizing clots, fibrin, and debris will be heterogeneously hyperintense on T2 weighting. Internal and surrounding enhancement has been described and is thought to be related to capillary formation. The presence of a partial or complete hypointense rim surrounding the lesion indicates formation of a fibrous capsule. Differential diagnoses for acute lesions include hematomas, abscesses, fat necrosis, and soft tissue neoplasms, whereas the differential diagnosis is expanded in chronic collections, which are better marginated and more homogeneous, to include seromas, bursitis, and lymphoceles. Although there is a significant overlap in the appearance of theMorel-Lavallée lesionwith these other entities, its classic location is crucial in arriving at the correct diagnosis, particularly in patients, especially children, in whom the traumatic event goes unnoticed. Treatment and management of Morel-Lavallée lesions depend on the age, size, and characteristics of the lesion. Small lesions may be treated conservatively with minimally invasive techniques, such as needle drainage or incision and drainage with compression bandages. Larger lesions traditionally have been treated with open drainage and healing by secondary intention. Recently, early treatment within 3 days of the traumatic event by percutaneous drainage and debridement has been recommended. The advantage of this approach is to reduce the risk of infection and improve healing by preserving the subdermal arterial plexus, the only remaining direct vascular supply to the skin overlying a Morel-Lavallée lesion. The presence of a fibrous capsule around a chronic Morel-Lavallée lesion impacts management because these lesions are less likely to respond to conservative treatment and more likely to recur. In these cases, surgical debridement and sclerodesis with alcohol or doxycycline have been reported to produce better results than conventional approaches.

Quality assurance case of the day: normal hypoechoic perirenal fat mistaken as the renal parenchyma in a patient with small echogenic native kidneys.

Diagnosis: Normal Hypoechoic Perirenal Fat Mistaken as the Renal Parenchyma in a Patient With Small Echogenic Native Kidneys In this patient, the length of the kidneys was overmeasured (Figs. 1A, B), and the true small echogenic kidneys were initially not appreciated (Figs. 2A, B). This error occurred because the hypoechoic perirenal fat was presumed to represent the renal cortex and the atrophic echogenic kidney was assumed to represent the typical echogenic renal sinus.

Acromioclavicular Joint Cyst.

DISCUSSION An acromioclavicular (AC) joint cyst is an uncommon complication of degenerative AC joint disease frequently associated with underlying full thickness rotator cuff tears. These cysts typically present as slowly enlarging painless masses in the elderly population, requiring imaging to exclude neoplasm. 1 There are 2 proposed etiologies for the development of an AC cyst. A type 1 cyst develops in the setting of an intact rotator cuff. This cyst is secondary to disruption of the AC articular disc with reactive synovitis and increased joint fluid from traumatic, infectious, or metabolic diseases of the AC joint. A type 1 AC cyst does not communicate with the glenohumeral joint space, and the accumulation of fluid is limited to the superficial aspect of the AC. A type 2 cyst develops in the setting of a massive rotator cuff tear. In the setting of chronic full-thickness rotator cuff tear, there is disruption of the glenohumeral joint accounting for increased production of joint fluid and upward displacement of the humeral head. Over time, the displaced humeral head and/or an inferior AC joint osteophyte erodes the inferior AC capsule, causing decompression of glenohumeral joint fluid through the subacromialsubdeltoid bursa into the AC with distension of the superior joint capsule. This phenomenon is referred to as the “Geyser sign” on conventional arthrography. Because of the different AC joint cyst etiologies, the radiologist must evaluate the integrity of the rotator cuff when an AC cyst is encountered (Fig. 2). On ultrasound, an AC cyst can present as a uniloculated or multiloculated cystic fluid collection that may contain thickened walls and internal septations and is located superior to the AC (Figs. 1A, B and 3A.)Mobile echogenic debris can be seen moving across the AC with compression. An AC cyst may also be associated with synovial hypertrophy and calcium pyrophosphate dihydrate deposition, leading to a more echogenic appearance, simulating a more ominous pathology. In these cases, correlation with additional studies can be helpful. Radiography may reveal a high-riding humeral head, degenerative changes at the glenohumeral and ACs, and findings of calcium pyrophosphate dihydrate deposition arthropathy.

CAROTID ULTRASONOGRAPHY : INTERPRETIVE ISSUES AND POTENTIAL PITFALLS

Summery Duplex color Doppler ultrasound evaluation of the extracranial carotid arteries has emerged as a cost-effective, reliable, non-invasive way to evaluate atheroselerotie disease and its complications. The accuracy of duplex color Doppler evaluation in the identification of hemodynamically significant disease can be greater than 90%. In daily practice, this accuracy can only be achieved if a variety of interpretive and technical pitfalls are overcome. The material presented in this manuscript is heavily illustrated with actual case examples obtained from retrospective correlation of the results of Duplex/color Doppler sonography and angiography. The cases provide a comprehensive visual tutorial of interpretative strategies and pitfalls.