A usefulness of urinary K/Cr ratio as differential diagnosis of acute hypokalemic paralysis

Abstract

Background : Acute hypokalemic paralysis, a clinical syndrome characterized by acute systemic weakness and low serum potassium, is a rare but treatable cause of acute weakness. The aim of our study is to analyze the cause of hypokalemic paralysis and to define clinical characteristics of hypokalemic paralysis. Methods : Hypokalemia was defined as a serum potassium concentration less than 3.0 mEq/L in this study. A total 31 patients with hypokalemic paralysis (male 71%, mean age; 35.7±14.3 years) have been studied retrospectively from June 1994 to March 2004 for the evaluation of clinical characteristics. According to the pathophysiology of hypokalemia, patients were divided into the potassium renal loss group (n=9) and the potassium shift group (n=14). We calculate the UK/UCr (mmol/mmol) ratio, Transtubular K+ concentration gradient (TTKG) and compared the results between two groups. Results : The cause of hypokalemic paralysis was hyperthyroidism (45.2%), medication (19.4%), renal disease (6.5%), hyperaldosteronism (3.2%), poor oral intake (3.2%), vomiting (3.2%), and unknown origin (19.4%). There was a significant difference of UK/UCr ratio (p=0.046) but no significant difference of TTKG (p=0.116) between the potassium loss and shift groups. Conclusion : The most common cause of acute hypokalemic paralysis is hyperthyroidism. The UK/UCr ratio is more useful measure than TTKG in differentiation of potassium loss and potassium shift as a cause of hypokalemia.