Investigating hypokalaemia – don’t be Conn’d
L Thurston, M Martineau, West Middlesex University Hospital
Case history: A 28-year-old male presented to A&E with a three-day history of diarrhoea and vomiting in April 2016. Blood tests showed severe hypokalaemia (2.3 mmol/L). Despite multiple infusions of saline with potassium chloride, serum potassium levels were slow to correct and consequently the patient self-discharged. A year later he represented to A&E with a frontal headache, a blood pressure of 220/110 mmHg and hypokalaemia confirmed on serum testing (2.5 mmol/L). Following initiation of oral potassium replacement and antihypertensive therapy (Amlodipine 10 mg OD and Ramipril 2.5 mg OD) he was discharged home however was lost to follow-up (did not attend). The following year, after a call from his GP concerning ongoing hypokalaemia, he was referred to Endocrinology for further assessment. Subsequent to biochemical correction of his hypokalaemia (2.5 mmol/L), Renin and Aldosterone testing was undertaken.
Results: Plasma Renin Activity <0.2 nmol/L/h, Aldosterone 1820 pmol/L, ratio >9100 supporting a diagnosis of primary aldosteronism. At that time his renal magnetic resonance (MR) angiogram (May 2018) was reported as normal (with both adrenal glands within normal limits and no mass lesions). As a result, he was referred for Adrenal Venous Sampling (AVS) in January 2019, results were as follows: Cortisol levels in the right and left adrenal veins (10,229 nmol/L and 8235 nmol/L respectively) indicated correct siting of the catheter. The Aldosterone/ Cortisol ratio (ACR) in the left adrenal vein was suppressed (0.4) whilst that in the right adrenal vein is markedly elevated (101) suggesting a predominantly unilateral secretion of Aldosterone from the right adrenal gland. The lateralisation index (ACRdominant/ ACRcontralateral) was 253 and the contralateral suppression index (ACRcontralateral/ ACRIVC) was 0.03, further supporting a diagnosis of unilateral disease.
Management: post-AVS he was commenced on Spironolactone which was uptitrated until serum potassium levels were >3.0 mmol/L. Blood pressure was managed with Amlodipine 10 mg OD and Doxazosin 8 mg BD. Dedicated adrenal MR imaging in May 2019 demonstrated a 22 mm lipid rich adenoma in the right adrenal gland; with a subsequent review of the original imaging confirming the presence of the same (previously missed) adenoma. As a result of the above investigations he has been referred for a right-sided laparoscopic adrenalectomy.
Discussion: This case highlights three important points.
1) Appropriate targeted investigation to ascertain the aetiology of hypokalaemia.
2) A corroborative evidence base reaffirming current Endocrine Society guidelines as to the appropriateness of when AVS is indicated. 3) Where possible the need for a multidisciplinary team approach pertaining to the management of adrenal disease – involving an (interventional) radiologist, endocrinologist and endocrine surgeon in pursuit of optimal patient care and avoidance of unnecessary and potentially harmful investigations.