1568 CLINICAL EXPERIENCE WITH INCIDENTALLY DISCOVERED PHEOCHROMOCYTOMA

should be done. The metoclopramide stimulation test report- edly yields excellent specifkity.12 On the other hand, our incidental cases showed a high false-negative rate (71.4%) with the metoclopramide stimulation test and the possibility of a false-negative case (28.6%) with MIBG scanning. These results are likely to be produced by the low endocrinological potential of incidentally discovered pheochromocytomas, al- though functions exceeded the normal range. Indeed, we should integrate the results of various biochemical tests and diverse radiological studies into the diagnosis of a pheochro- mocytoma at this stage.

If an incidentally discovered tumor is proved to be a func- tioning pheochmmocytoma, treatment should theoretically be the same as that for symptomatic disease. F'razosin, an a-adrenergic blocking agent, has been used preoperatively as an alternative to phenoxybenzamine at our institute. Pre- treatment with padrenergic blockers is considered when arrhythmia or tachycardia becomes a problem.

Intraoperative management of these cases involves several concerns. Central vein pressure and arterial pressure moni- toring should be used routinely to evaluate the hemodynamic parameters and cardiac function. Enflusane or isoflurane should be used for anesthesia because both decrease myocar- did irritability.*3 Intraoperative hypertension is believed to be treated with phentolamine or nitroprueside, and propano- lo1 is excellent for the treatment of intraoperative supraven- tricular tachycardia, while patients with ventricular ar- rhythmias receive lidocaine. However, the use and regimen of these pharmacological agents vary with the administering institution. For persistent hypotension following tumor re- moval, volume replacement is required in conjunction with carefid cardiovascular monitoring.

CONCLUSIONS

We suggest that retroperitoneal incidentally discovered tumors that cannot be ruled out as pheochromocytomas should be comprehensively evaluated. Incidentally discov- ered pheochromocytomas should also be treated prudently due to the inherent unpredictable risk.

REFERENCES

1. Gross, M. D. and Shapiro, B.: Clinical Review 50: clinically silent adrenal masses. J. Clin. Endow. Metab., 77: 885, 1993.

2. Aso, Y. and Homma, Y.: A survey on incidental adrenal tumors in Japan. J. Urol., 147: 1478, 1992.

3. Ross, N. S. and Aron, D. C.: Hormonal evaluation of the patient with an incidentally discovered adrenal mass. New Engl. J. Med., 325: 1401, 1990.

4. Kobayashi, S., s k i , T., Nonomura, K., Gotoh, T., Togashi, M. and Koyanagi, T.: Clinical experience of incidentally discov- ered adrenal tumor with particular reference to cortical func- tion. J. Urol., 1M): 8, 1993.

5. Nagashima, F., Hayashi, J., Araki, Y., Sugihara, T., Nomura, M., Morichika, Y., Inoue, J., Shibata, S. and Akagi, E.: Silent mixed ganglioneuroma/pheochromromocytoma which produces a vasoactive intestinal polypeptide. Intern. Med., 32: 63,1993.

6. Whalen, R. K., Althausen, A. F. and Daniels, G. H.: Extra- adrenal pheochromocytoma. J. Urol., 147: 1,1992.

7. Crout, J. R. and Sjoerdsma. A.: Turnover and metabolism of catecholamine in patients with pheochromocytoma. J. Clin. Invest., 4 3 94, 1964.

8. Bravo, E. L.: Pheochmocybma: new concepts and future trends. Kidney Int., 40: 544, 1991.

9. Scott, H. W., Jr., Oates, J. A., Nies, A. S., Burko, H., Page, D. L. and Rhamey, R.K: Pheochromocytoma: present diagnosis and management. Ann. surg., 1sS: 587, 1976.

10. Bravo, E. L. and Gif€ord, R. W., Jr.: Current concepts. Pheochro- mocytoma: diagnosis, localization and management. New Engl. J. Med., 311: 1298, 1984.

11. Krestin, G. P., Steinbrich, W. and Friedmann, G.: Adrenal mass- es: evaluation with fast gradientecho MR imaging and Gd-

DTPA-enhanced dynamic studies. Radiology, 171: 675, 1989. 12. Kawabe, H., Itaya, Y., Suzuki, H., Kondo, K. and Saruta, T.:

Meklopramide in the diagnosis of pheochromocytoma. Jap. Heart J., 26: 557, 1985.

13. Vaughan, E. D., Jr. and Blumenfeld, J. D.: The adrenals. In: Campbell's Urology, 6th ed. Edited by P. C. Walsh, A. B. Fktik, T. A. Stamey and E. D. Vaughan, Jr. Philadelphia: W. B. Saunders Co., vol. 3, chapt. 64, pp. 2360-2412, 1992.

EDITORIAL COMMENT

These interesting observations confirm the clinical dictum that patients with incidental adrenal masses should be evaluated to rule out pheochromocytoma (reference 3 in article). In large series of patients with clinically apparent pheochromocytomas the most com- mon clinical finding is hypertension, sustained or intermittent, which is found in 90 to 95% of cases (reference 13 in article). In contrast, of the 10 patients with incidental pheochromocytomas in this series only 60% presented with hypertension. Moreover, urinary catecholamine levels were also higher in the symptomatic patients. Urinary norepinephrine levels were elevated in 8 of the 10 patients with incidental lesions, although they were rarely (2 of 10) twice the normal level. It would appear that careful evaluation of epinephrine, norepinephrine and vanillylmandelic acid wi l l identify integrated hypersecretion of catecholamines in most patients with incidental lesions. Altbough not measured in this study, plasma catecholamine levels would be assumed to be less accurate in these normotensive patients. MRI showed the characteristic bright "2-weighted image in these patients and remains the appropriate imaging study for those with suspected pheochromoeytomas, symptomatic or incidental (ref- erence 13 in article).

The final and important point made by the authors is that these patients, although normotensive preoperatively, should still be ex- pected to respond intraoperatively in a fashion similar to patients with symptomatic pheochromocytomas. Therefore, preoperative preparation with a-adrenergic antagonists or calcium channel block- era should be done in patients with incidental pheochmmocytomas. Moreover, the anesthesiologist should be fully prepared to respond with appropriate drugs in these patients just as they would in a patient with a symptomatic pheochromocytoma.

E. Darracott Vaughan, Jr. Department of Urology New York HospitallCornell Medical Center New York, New York

REPLY BY AUTHORS

Our results demonstrate that urinary catecholamine levels in in- cidentally found cases were lower than those in symptomatic cases because of weak function. Accordingly, it can be surmised that the incidence of hypertension in incidentally discovered cases may be lower than that stated in the comment. However, 15 of our 17 cases (88%) had function, which is consistent with the 90 to 95% rate of hypertension noted.

Mean values plus or minus standard deviation of plasma adrena- line, noradrenaline and dopamine in our series were 22.7 -t 59.7, 4.4 ? 5.6 and 0.7 ? 1.9 ngJml. in symptomatic cases and 0.4 2 0.7, 1.2 2 1.4 and 0 ng.1ml. in incidentally found cases (no significant difference). The limited sensitivity and specificity of plasma catechol- amine for diagnosing pheochromocytoma have been well estab- lished.'

MRI showed the characteristic bright T2-weighted image in our patients. It has also been reported that most neurogenic tumors are delineated brightly on T2-weighted images.2 Pheochromocytoma re- portedly showed marked enhancement in the early phase on TI- weighted images after the administration of gadolinium pentetic acid (reference 11 in article). Thus, in making the diagnosis of pheo- chromocytoma we integrated the results of various biochemical tests and diverse radiological studies a t this stage.

1. Krakoff, L. R.: Searching for pheochromocytoma: a new and better test? Ann. Intern. Med., 123:150, 1995.

2. Ichikawa, T., Keyama, A,, Fujimoto, H., Henma, M., Saiga, T., Matsubara, N., Ozeki, Y. and Arimizu, N.: Retroperitoned ganglioneuroma extending across the medline: MR features. Clin. Imaging, 17:19, 1993.