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Reports of the upper limits of normal for lymph node size at abdominal computed tomography have varied from 6 to 20 mm. Establishment of an upper limit for node size by specific location, analogous to that which has been reported for mediastinal lymph nodes, was sought. Short-axis diameters of the lymph nodes were measured in 130 patients who were not likely to have enlarged abdominal lymph nodes. Seven locations were defined, and the largest nodal measurement for each was recorded. Histographic analysis and nonparametric statistical methods were used to determine threshold values for the maximum node size in each region. The upper limits of normal by location were as follows: retrocrural space, 6 mm; paracardiac, 8 mm; gastrohepatic ligament, 8 mm; upper paraaortic region, 9 mm; portacaval space, 10 mm; porta hepatis, 7 mm; and lower paraaortic region, 11 mm. Lower paraaortic lymph nodes larger than 11 mm by short-axis measurement are abnormal. In other locations, nodes smaller than 1 cm may be abnormal if the determined thresholds are exceeded.

Ultrasonograms of 38 patients and computed tomograms of 21 patients with abdominal aortic aneurysms (AAA) were retrospectively reviewed. In 69 per cent of cases in which intraluminal thrombus was demonstrated, sonography revealed a high-amplitude linear echo along the luminal surface of the thrombus. Although calcification could be easily visualized within the aortic wall by computed tomography, it was seen at the lumen -thrombus interface in only one patient. In addition, a resected aortic aneurysm with thrombus, when scanned in a water bath in vitro, demonstrated this echo pattern at the luminalthrombus interface on sonography but revealed no calcification on pathologic examination. An explanation of the source of this echo pattern and a caution against misinterpretation of this echo pattern as the aortic wall in a dissection or leaking aneurysm with hematoma are presented.

The imaging features of intrapericardial paragangliomas (pheochromocytomas) are described. MATERIALS AND METHODS. We conducted a retrospective study of the imaging features of all intrapericardial paragangliomas seen at our institution over the last 1 3 years. RESULTS. In this study, intrapericardial paragangliomas were typically located adjacent to or involved the left atrium.

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