SAT-502 Diagnostic Facade: A Case of ESRD Complicating Pheochromocytoma Diagnosis

Abstract Disclosure: S. Modi: None. A. Sahu: None. L. Belalcazar: None. Background: The diagnosis of pheochromocytoma relies on increased catecholamine levels and typical imaging characteristics. However, end-stage renal disease (ESRD) brings diagnostic challenges, with an impact on defining clinical, biochemical, and imaging criteria. We present a case of a patient with a pheochromocytoma and discuss the diagnostic and therapeutic intricacies posed by his long history of ESRD. Clinical Case: A 43-year-old male with an 8-year history of hypertension and ESRD on dialysis presented to the hospital for excision of an infected arteriovenous graft and permcath removal. He had no symptoms suggestive of catecholamine excess. Blood pressure on admission was 144/84 mmHg and heart rate 83 beats per minute. A CT venogram with contrast, ordered for fistula workup, revealed an incidental retroperitoneal mass. Further evaluation with a CT abdomen with contrast showed a right adrenal mass measuring 4.8 x 5.4 x 6.3 cm with an attenuation of 74 Hounsfield units (HU), but an unexpected increased absolute washout of 87%. Plasma metanephrines (MN) and normetanephrine (NMN) were obtained and found to be 4.53 nmol/L (Ref 0-0.49 nmol/L) and 15.80 nmol/L (Ref 0-0.89 nmol/L), respectively, confirming the presence of a pheochromocytoma. Patient received ten days of alpha blockade with doxazosin 8 mg twice a day; metoprolol 12.5 mg twice a day was added three days prior to surgery for beta blockade. He underwent successful laparoscopic right adrenalectomy. Pathology confirmed a 5 cm pheochromocytoma. Conclusion: This case illustrates how ESRD may complicate the diagnosis of pheochromocytoma. In this patient, worsening hypertension attributed to his renal disease likely delayed the diagnosis of pheochromocytoma. Although in ESRD MN and NMN are typically elevated, they remain within 1.5 times the reference range unless a catecholamine-producing tumor is present. In our patient, the adrenal mass had characteristic high attenuation and plasma MN and NMN levels that were clearly elevated (9 and 17 times the upper limit of normal, respectively), even in the setting of ESRD. Furthermore, the patient’s underlying ESRD explains the atypical increased contrast washout seen on adrenal imaging. ESRD causes decreased renal clearance and contrast retention. Retained iodine increases tissue attenuation, elevating post-contrast HU and creating a large pre- and post-contrast difference that artificially elevates the absolute washout as seen in our patient. Presentation: Saturday, July 12, 2025