Abstract: SA-PO387
Ectopic Adrenocorticotropic Hormone Tumor Can Present as a Chloride-Depleted Metabolic Alkalosis
Session Information
- Genetic and Diagnostic Trainee Case Reports
November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Trainee Case Report
- 902 Fluid and Electrolytes: Clinical
Authors
- Mareedu, Neeharik, Rush University Medical Center, Chicago, Illinois, United States
- Whittier, William Luke, Rush University Medical Center, Chicago, Illinois, United States
Introduction
Metabolic alkalosis (MA) often presents with hypokalemia and is either Cl-depleted (CDMA, urine Cl<15 meq/L) or Cl-resistant (CRMA, urine Cl>15 meq/L). CDMA is due to sustained loss of Cl, most commonly from either renal or GI losses, leading to pendrin inhibition. CRMA is most often due to direct tubular stimulation from either apparent or actual hyperaldosteronism.
Case Description
A 67 year old man w/ PMH of HTN presents w/ lower extremity & scrotal swelling. No OTC, herbal, or dietary supplements. Meds: Lasix, Lisinopril-HCTZ, ASA and KCl. BP 186/100, 2+ LE & scrotal edema. Serum Na 140, K 1.8, Cl 82, HCO3 45, BUN 15, Cr 0.7. ABG pH 7.58/PCO2 52/HCO3 45. Urine pH 7.5, K 33 meq/L, Na<10meq/L, Cl<10meq/L, Cr 94mg/dL, Urine K:Cr 35.1meq/g. His CDMA and kaliuresis was attributed to remote use of HCTZ & Lasix. These were held, KCl & 0.9NS was initiated, but w/ only minimal improvement in his MA & hypokalemia. His edema & HTN was exacerbated by this therapy, & follow up labs revealed Plasma Renin 1.26 ng/ml, Aldosterone 2 ng/dl, Cortisol 114.2 mcg/dl and ACTH 231 pg/ml. Imaging revealed a lung mass with mets & biopsy confirmed metastatic small cell cancer. Spironolactone resolved his HTN, edema, hypokalemia, & MA, and he is currently undergoing chemotherapy for his malignancy.
Discussion
Though initially thought to be remote use of diuretic induced CDMA, our patient’s lack of response to Cl repletion led us to search for an alternative diagnosis. After his aldosterone and renin levels returned low, we sent off ACTH & cortisol and found an ectopic ACTH producing tumor. His loop & thiazide diuretics had exacerbated his CMDA, but was not the sole underlying cause. At high concentrations, cortisol activates mineralocorticoid receptors (MR) in the cortical collecting duct, leading to epithelial Na channel (ENaC) & Na-K ATPase activation. This leads to Na reabsorption with K & H excretion through renal outer medullary K channels, thus causing HTN & hypokalemia. To maintain electrical neutrality, HCO3 is reabsorbed and Cl is secreted into the tubular lumen via pendrin. But contrary to expected, urine Cl was low in our case which makes it an unusual presentation of hypercortisolism. Treatment strategies in these patients should focus on eliminating the primary cause if possible (decreasing tumor burden) & using medications which inhibit MR (Spironolactone) or ENaC (Amiloride).