Computed tomography in the differential diagnosis of adrenal tumors

Abstract

Background. Modern methods of topical diagnostics have high accuracy and can determine the morphological structure of the adrenal tumor with high probability before surgery, but none of them has 100% sensitivity and specificity. Contrast-enhanced computed tomography is most commonly used by clinicians. The criteria for the malignancy of an adrenal tumor determined by this method continue to be discussed.The aim is to evaluate the effectiveness of contrast-enhanced computed tomography in the preoperative diagnosis of adrenal tumors and to analyze errors.Materials and methods. Contrast-enhanced computed tomography was performed in 69 patients with adrenal tumors. After morphological examination of the removed tumors, the effectiveness of preoperative diagnostics was evaluated with the determination of sensitivity and specificity of the method. If the pre- and postoperative diagnosis did not match, the causes of errors were analyzed.Results. The attenuation on unenhanced CT in adenomas ranged from 5 to 36 HU, in adrenocortical cancer — from 26 to 80 HU, in pheochromocytomas — from 25 to 99 HU. The attenuation of adenomas on unenhanced CT was significantly less than with pheochromocytomas (p=0.005) and adrenocortical cancer (p=0.012). In the venous phase, no significant differences were found, and in the delayed phase, the attenuation of adenomas was also significantly less than in malignant tumors (p=0.008, p=0.008). The median of absolute percent contrast washout in adenomas was 85%, in pheochromocytes — 59%, in adrenocortical cancer — 57%. When comparing the diagnosis before and after surgery, its non-coincidence was found in 8 cases (10.39%). Two patients (2.59%) with small tumors (diameter of 15 mm) were diagnosed with adenoma in ­combination with pheochromocytoma and adenoma before surgery. After morphological examination, the diagnosis was changed to adrenocortical cancer in combination with adenoma and «mute» pheochromocytoma.Conclusion. The sensitivity and specificity of contrast-enhanced CT in the diagnosis of adenomas was 95.61% and 94.82%, pheochromocytomas — 95% and 95.08%, adrenocortical cancer — 92.31 and 98.48%. Diagnostic errors of «mute» pheochromocytoma and adrenocortical cancer occurred with small sizes (15 mm) of adrenal tumors.