MRI of pediatric patients: Part 2, normal variants and abnormalities of the knee.

OBJECTIVE: The purpose of this article is to discuss MRI of the pediatric knee and familiarize the reader with conditions encountered in the pediatric population. Clinical scenarios are included to convey important concepts and to orient the learner to normal variants and abnormalities of the pediatric knee. The conditions discussed include, but are not limited to, distal femoral metaphysial irregularity, isolated popliteus tendon avulsion, juvenile idiopathic arthritis, and discoid meniscus. CONCLUSION: The knee is the joint that is most commonly imaged by MRI in children. Injury patterns and signs of other pathologic processes seen in skeletally immature patients are different from those seen in adults. Interpreting pediatric knee MRI studies may be a challenge for those unfamiliar with the evolving patterns of normal development and of the signs of conditions that are more prevalent in children. Through case scenarios, this article describes and provides images that depict conditions commonly encountered in the pediatric knee. Most of the described normal findings and abnormalities are more prevalent in the pediatric population than in adults, and a few of the conditions are, in fact, unique to pediatric patients.

Blood volume and its relation to peak O(2) consumption and physical activity in patients with chronic fatigue.

Individuals with chronic fatigue syndrome (CFS) experience a number of somatic complaints including severe, disabling fatigue, and exercise intolerance. We hypothesized that hypovolemia, through its interaction with central hemodynamics, would contribute to the exercise intolerance associated with this disorder. We examined blood volume, peak aerobic power, habitual physical activity, fatigue level, and their interrelations to understand the physiological basis of this disorder. Seventeen patients who met the Centers for Disease Control criteria for CFS and 17 age-matched controls participated in the study. Blood volume was assessed using a single bolus injection of Evans blue dye. Peak oxygen consumption was measured during exercise on an upright cycle ergometer. Supine cardiac output and stroke volumes were measured using CO(2) rebreathing. Questionnaires were used to assess habitual physical activity and fatigue. Patients displayed a trend for a 9% lower blood volume (58.3 +/- 2.1 vs. 64.2 +/- 2.5 ml/kg, P = 0.084) and had a 35% lower peak oxygen consumption (22.0 +/- 1.2 vs. 33.6 +/- 1.9 ml/kg, P < 0.001). These two variables were highly related within the patients (r = 0.835, P < 0.001) and the controls (r = 0.850, P < 0.001). Peak ventilation and habitual physical activity were significantly lower in the patients. Fatigue level was not related to any of the measured physiological parameters within the CFS group. In conclusion, individuals with CFS have a significantly lower peak oxygen consumption and an insignificant trend toward lower blood volume compared with controls. These variables were highly related in both subject groups, indicating that blood volume is a strong physiological correlate of peak oxygen consumption in patients with CFS.