Comparison of CT findings in symptomatic and incidentally discovered pheochromocytomas

The objective of our study was to determine the prevalence of incidental pheochromocytomas, whether their imaging characteristics differ from those of pheochromocytomas in symptomatic patients, and whether they differ from adenomas using CT densitometry.

The records from 335 adrenalectomies performed at our institution from 1995 to 2002 were reviewed, and 71 pheochromocytomas were identified. Thirty-three patients had CT examinations performed at our institution that were available for retrospective review. From electronic and hard-copy medical records, patient age and sex, the indications for imaging, and biochemistry activity were recorded. Pheochromocytomas were classified as symptomatic or incidental on the basis of clinical presentation. These groups were compared for differences in patient age, adrenal mass volume and maximal diameter based on CT dimensions, attenuation on unenhanced CT, attenuation on enhanced CT during the portal phase, the presence of calcifications, low attenuation or cystic changes, biochemical activity, and hypertension. Statistical significance was assessed with the Student's t test or chi-square test, as appropriate.

Nineteen incidental (57.6%) and 14 symptomatic (42.4%) adrenal pheochromocytomas were in the study. There was a significant difference between the two groups as to whether hypertension was present (incidental, 10/19 [52.6%]; symptomatic, 14/14 [100%]; p = 0.0025). We found a trend toward calcification present in more symptomatic patients (incidental, 0/19 [0%]; symptomatic, 4/14 [28.6%]; p = 0.0670). No statistically significant difference was noted in the mean patient age (incidental, 51.7 years; symptomatic, 45.9 years), mean volume of the mass (incidental, 74.0 cm(3); symptomatic, 78.2 cm(3)), mean maximal diameter of the mass (incidental, 5.26 cm; symptomatic, 5.33 cm), mean attenuation on unenhanced CT (incidental, 36.6 H; symptomatic, 34.2 H), mean attenuation on enhanced CT (incidental, 93.7 H; symptomatic, 104.3 H), necrosis score or biochemical activity (incidental, 17/18 [94.4%]; symptomatic, 12/14 [85.7%]). No attenuation value of any pheochromocytoma was less than 10 H on unenhanced CT (median, 35 H; range, 17-59 H).

In our study population, 57.6% of the pheochromocytomas were incidental, more than in most reported series. A history of hypertension was more frequent in the symptomatic group (p = 0.0025), but no radiologic parameters that allow differentiation of incidental and symptomatic pheochromocytomas were found. None of the pheochromocytomas had attenuation values of less than 10 H on unenhanced CT scans.