INTRAPULMONARY SHUNTING IN CARCINOID SYNDROME

Abstract

SESSION TITLE: Pulmonary Manifestations of Systemic Disease SESSION TYPE: Fellow Case Reports PRESENTED ON: 10/21/2019 3:15 PM - 4:15 PM INTRODUCTION: Carcinoid tumors are rare slow-growing neuroendocrine tumors. The biologic behavior of these tumors can be variable and unpredictable which may lead to unusual clinical presentations and delayed diagnosis. Carcinoid tumors release different vasoactive substances, including serotonin, histamine, and bradykinins. Release of 5-hydroxyindoleacetic acid (5-HIAA), a product of serotonin degradation, results in increased gastrointestinal motility (diarrhea), bronchoconstriction (wheezing), and vasodilation (flushing). Intra-pulmonary shunt (hepatopulmonary-like syndrome) due to pulmonary vasodilatation of the microvascular bed is exceedingly rare in carcinoid syndrome. CASE PRESENTATION: A 57-year-old man presented with chronic diarrhea and flushing. Initially, the diarrhea was believed to be related to metformin, however it persisted despite stopping this medication. Later, he developed progressive dyspnea with profound hypoxia. Hypoxemia was poorly responsive to supplemental oxygen, consistent with shunt physiology. Work up for hypoxia included an unremarkable chest radiograph and arterial blood gas with increased alveolar-arterial gradient. Chest CT angiography was negative for pulmonary embolism or parenchymal lung disease. Inhaled oxygen shunt study revealed 23.3% shunt. Agitated saline contrast echocardiography showed no evidence of intracardiac shunt, but demonstrated late bubbles (>5 beats) in the left side after agitated saline administration consistent with intra-pulmonary shunt. CT of the abdomen demonstrated enlarged and markedly heterogeneous liver concerning for metastatic disease, as well as a 2.6 x 3.0 cm mass in the small bowel mesentery, morphologically consistent with carcinoid tumor. Serum serotonin, 24 hour urine 5 HIAA, and serum chromogranin A level were abnormally elevated. Biopsy of a liver lesion confirmed a well-differentiated neuroendocrine carcinoma, classified as low grade with a Ki-67 of less than 2%. He was initiated on first line therapy with Sandostatin LAR with rapid resolution of his diarrhea. While he remains hypoxic and oxygen dependent, his subjective dyspnea has improved. DISCUSSION: Severe hypoxemia has been described in carcinoid syndrome mostly due to right to left cardiac shunts; however, carcinoid-related intrapulmonary shunt is exceedingly rare. To our knowledge, only three cases of intrapulmonary shunt in carcinoid syndrome have been reported (1-3). Similar to our patient, these were associated with metastatic disease. CONCLUSIONS: Possible mechanisms of hypoxemia in carcinoid syndrome warrant further investigation. Reference #1: Hussain A, Young ET, Greaves JD, et al. Intrapulmonary shunting causing hypoxaemia in a case of carcinoid syndrome. Clin Endocrinol (Oxf). 1994;41(4):535-537. Reference #2: Robert R, Matuchansky C, Picker F, Guitton P, Patte D. Severe hypoxemia in a case of midgut carcinoid tumor. Intensive Care Med. 1989;15(8):536-537. Reference #3: Stewart GW, Freegard SP, Keeling DH, Perrett AD. Cyanosis attributable to right to left shunt in carcinoid syndrome. Br Med J (Clin Res Ed). 1986;292(6520):589-590. DISCLOSURES: No relevant relationships by Mazen Al-Qadi, source=Web Response Consultant relationship with United Therapeutics Please note: $5001 - $20000 Added 02/14/2019 by Hubert Ford, source=Web Response, value=Travel also Consultant relationship with Actelion Please note: $1001 - $5000 Added 03/14/2019 by Hubert Ford, source=Web Response, value=Honoraria Consultant relationship with Liquidia Please note: $1-$1000 Added 03/14/2019 by Hubert Ford, source=Web Response, value=Honoraria Research Grant relationship with United Therapeutics Please note: $5001 - $20000 Added 03/14/2019 by Hubert Ford, source=Web Response, value=Grant/Research Support No relevant relationships by Amanda Kovacich, source=Web Response No relevant relationships by Autumn McRee, source=Web Response