Biochemical and radiological relationships in patients with pheochromocytoma: lessons from a case control study

Abstract

SummaryBackground An elevation of fractionated plasma or urinary metanephrine (MN) or nor-metanephrine (NMN), collectively called metanephrines (MN and NMN), >4-fold above the upper limit of normal (ULN) is usually considered to be diagnostic for pheochromocytoma (PHEO). There are a greater number of false positive results when the elevations are more modest. Aim To identify biochemical and radiological features in PHEOs with modest elevations (<4-fold above ULN) of metanephrines. Methodology We retrospectively reviewed the charts of 112 patients with PHEO (10% extra-adrenal) and 208 patients with a non-PHEO adrenal mass operated from 1997-2011, who had metanephrines measured pre-operatively. We divided PHEO into group 1 (n = 90) with metanephrines ≥4-fold ULN and group 2 (n = 22) with metanephrines <4-fold ULN. The non-PHEO group was designated as group 3. Results The median (range) tumour size in group 1 and group 2 was 4Á8 cm (1Á7-22) and 3Á0 cm (1Á7-5) respectively (P < 0Á001). All patients with PHEO in group 2 had a tumour <5 cm in size. The MN fraction was elevated in about 65% of groups 1 and 2; only 2 (1%) patients in group 3 had an elevated urinary MN fraction, and none were associated with an elevated plasma MN fraction. All PHEOs had a pre-contrast attenuation ≥17 Hounsfield Units (HU). Conclusions Modest elevations (<4-fold ULN) of the NMN fraction in an adrenal mass >5 cm are almost always falsely positive. Elevations in plasma and urinary MN fraction are less likely to be false positive. The CT pre-contrast attenuation of PHEOs is >10 HU.

Hypertensive Emergency Following Embolization of a Large Adrenal Myelolipoma–Adrenal Medullary Infarction, Pheochromocytoma, or Acute Sympathetic Discharge? A Case Report and Literature Review

“…Although the authors concluded that these large functioning adrenal myelolipomas were producing catecholamines, another interpretation would be as in our case that it was related to sympathetic activation (4,5,12). The findings in our case are consistent with the recent report by Kannan et al (11). We present evidence that the plasma normetanephrines are <4-fold upper normal and the embolization and acute illness associated with this tumor resulted in a suppressible sympathetic release of catecholamines rather than autonomous secretion of them.…”

“…Hemorrhage within the tumor might increase the tissue density and HU, as was seen in this case (1,2). Pheochromocytoma precontrast attenuation values are generally >10 HU (11).…”

Adrenal Incidentalomas

“…In our experience the lowest attenuation value for adrenal PHEO has been 17 HU. 30 There has been a report of unenhanced CT attenuation values less than 10 HU in 2 patients with symptomatic adrenal PHEO. 31 However, these tumors were very small, less than 1.5 cm, and one of the reported patients had adrenal medullary hyperplasia on pathology.…”

“…Based on the accumulating data in the literature and our own experience, we only perform biochemical investigation for PHEO in patients with AIs in whom the CT attenuation value is greater than 10 HU. 30,32,33 Computed tomography washout and enhancement patterns…”

“…4,11,12,60 There are accumulating data in the literature that evaluation for PHEO in AIs with a noncontrast CT attenuation less than or equal to 10 HU is not needed. 23,30,32 Accordingly the authors only evaluate for PHEO in patients with lipid-poor AIs.…”