8634 Ogilvie Syndrome As A Rare Complication Of Metastatic Pheochromocytoma

Abstract Disclosure: S.K. Beeby: None. J.C. Marcayata, MD: None. D.P. Di Matteo, MD: None. F.F. Souza, MD: None. I.C. Souza, MD: None. M.F. Azevedo, MD: None. F.M. Coelho, MD: None. A. Latronico, MD: None. B.B. Mendonca: None. M.C. Fragoso: None. M.Q. Almeida: None. Background: Ogilvie's Syndrome (acute colonic pseudo-obstruction) is a rare manifestationof pheochromocytoma and paraganglioma. Its pathophysiology can be explained by thehypersecretion of catecholamines, which may reduce peristaltic activity of the gastrointestinaltract due to alpha-adrenergic stimulation. We present here the case of a patient with acuteintestinal pseudo-occlusion due to metastatic pheochromocytoma. Clinical Case: A 60-year-old male with local recurrence of pheochromocytoma presentedwith abdominal pain, anorexia, nausea, vomiting and constipation for 2 weeks. The patientunderwent left adrenalectomy and nephrectomy to resect a 7.5 cm pheochromocytoma 6years ago. On examination, his blood pressure was 186 x 122 mmHg and heart rate was 112bpm. There was abdominal distention and diminished bowel sounds. Diaphoresis was notedmainly at night. Plasma fractionated metanephrines were markedly elevated, withnormetanephrine of 50.2 nmol/L (reference range <0.9 nmol/L) and metanephrine of 0.4nmol/L (reference range <0.5 nmol/L). Abdominal CT scan showed neoplastic lesionoccupying the left adrenal space, measuring 9.0 x 5.0 x 5.5 cm, infiltrating the spleen andpancreatic tail, and para-aortic and aorto-caval lymphomegaly of 1.3 cm. The large intestinewas distended with gas and lodged stool without evident obstructive factors. He was thenstarted on a high-sodium diet and alpha-blocker doxazosin 2 mg tid and propranolol 40 mgtid. Due to the presence of significant orthostatic hypotension, amlodipine 5 mg bid wasinitiated to control blood pressure. Laxatives and enemas were not effective in relieving hissymptoms and decompression with a nasogastric tube was necessary. The patient was thenput on subcutaneous neostigmine, an acetylcholinesterase inhibitor. Unfortunately, colonicpseudo-obstruction did not revert with pharmacological treatment and parenteral nutritionwas started. Since a complete tumor resection was not possible due to extensive invasion oflarge vessels, systemic cytotoxic chemotherapy (cyclophosphamide, vincristine anddacarbazine) was initiated as an attempt to treat the colonic pseudo-obstruction. Clinical lessons: Functioning pheochromocytoma and paraganglioma should be consideredin the differential diagnosis of constipation and acute intestinal obstruction, particularly whenaccompanied by other signs and symptoms of catecholamine excess. This condition should bepromptly diagnosed and managed, as it can lead to bowel perforation with seriouscomplications. Medical management includes alpha-blocking agents and, when feasible,tumor resection has been associated with good response. Support: This work was supported by Sao Paulo Research Foundation (FAPESP) grant2019/15873-6 (to M.Q. Almeida). M.Q.A was also supported by National Council forScientific and Technological Development (CNPq) 304091/2021-9. Presentation: 6/1/2024