Jeffrey Wong

Hepatic Actinomycotic Abscesses: Diagnosis and Management

ctinomycosis is a chronic suppurative and granulomatous disease usually caused by Actinomyces israelii. It is normal flora of the oropharynx, gastrointestinal tract, and female genital tract; inoculation occurs with mucosal disruption. Although most manifest as abscesses in the cervicofacial region, reports of thoracic, abdominal, pelvic, and CNS actinomycosis exist. Intraabdominally, the ileocecal region is most frequently affected. Hepatic involvement has been reported in 15% of those with abdominal disease and represents 5% of all cases of actinomycosis [1]. Gram staining and microscopy can be helpful, with the latter showing pale yellow clusters of tangled filaments surrounded by neutrophils, known as sulfur granules. To culture this bacterium, strict anaerobic processing and semiselective media in the presence of carbon dioxide is required. Without previous suspicion of actinomycosis, cultures are unlikely to elucidate the cause. Treatment consists of penicillin and drainage of the abscesses. We report two cases of hepatic actinomycotic abscesses with contrasting features, one featuring an inferior vena cava (IVC) thrombus (presumed infected) and septic pulmonary emboli.

Azygos Tip Placement for Hemodialysis Catheters in Patients with Superior Vena Cava Occlusion

Chronic central venous access is necessary for numerous life-saving therapies. Repeated access is complicated by thrombosis and occlusion of the major veins, such as the superior vena cava (SVC), which then require novel vascular approaches if therapy is to be continued. We present two cases of catheterization of the azygos system in the presence of an SVC obstruction. We conclude that the azygos vein may be used for long-term vascular access when other conduits are unavailable and that imaging studies such as magnetic resonance venography, contrast-enhanced computed tomography or conventional venography can be employed prior to the procedure to aid with planning and prevent unforeseen complications.

Transient homogeneously enhancing hepatic masses: can size predict benignity?

OBJECTIVE The purpose of our study was to test the hypothesis that, in noncirrhotic livers, large size predicts benignity of masses that homogeneously hyperenhance on arterial phase CT and then fade to isoattenuation. MATERIALS AND METHODS All multiphasic CT scans obtained at a cancer center over a 2-year period were reviewed. In consensus, three authors retrospectively identified 227 hepatic masses (> or = 5 mm) in 55 noncirrhotic patients that homogeneously hyperenhanced on arterial phase and then faded to isoattenuation: 107 masses were malignant and 120 were benign; 37 patients had benign and 18 patients had malignant masses. Two analytic approaches were pursued: per lesion and per patient. For the per-lesion analysis, the mean cross-sectional diameter of each mass was calculated and receiver operator characteristics (ROC) were assessed. For the per-patient analysis, the maximum lesion diameter was determined for each subject and logistic regression models were used to predict lesion classification (benign vs malignant) based on per-patient maximum lesion size and additional information. RESULTS Masses ranged from 5 to 84.5 mm. All 29 masses > or = 22 mm were benign. Size was a statistically significant classifier of benign versus malignant lesions in the per-lesion analysis (p = 0.024, ROC area under the curve) and a significant or trend-level predictor of tumor type in the per-patient analysis (logistic regression p values of the diameter coefficients: 0.01-0.07). CONCLUSION In noncirrhotic livers, relatively large size is a significant or trend-level predictor for benign tumors. Homogeneously hyperenhancing masses > or = 22 mm that fade to isoattenuation are benign; smaller masses may be malignant.

Equilibrium Theory of Bidensity Particle-Laden Flows on an Incline

The behaviour of inhomogeneous suspensions in a viscous oil is relevant in the context of oil spill and other oil-related disasters which may lead to the unwanted mixture of sand grains and oil. This warrants the fundamental study of the dynamics of solid particles in a thin film of viscous fluid. Specifically, sheared concentrated suspensions in a viscous fluid are subject to a diffusive mechanism called shear-induced migration that consists of “drift diffusion” and “self or tracer diffusion”. Drift diffusion causes particles to move from high to low concentrations, while tracer diffusion dictates mixing between particles of the same size. The latter mechanism becomes important in polydisperse slurries. In this chapter, we incorporate the effects of shear-induced migration and sedimentation to develop a model for the gravity-driven thin film of bidensity suspensions. We use this mathematical model to validate recent experimental results.