The Usefulness of Monitoring of Transtubular Potassium Gradient and Spot Urine Na/K Ratio in the management of Cirrhotic Ascites / 대한간학회지

BACKGROUND/AIMS: Transtubular potassium gradient(TTKG) is known as the most accurate indicator of aldosterone activity. TTKG may be used to monitor the effectiveness of aldosterone antagonist which is prescribed generally for the management of cirrhotic ascites. Spot urine [Na]/[K] ratio may also be used for the same purpose. METHODS: After measuring TTKG, spot urine [Na]/[K] ratio, and plasma aldosterone concentration in each of the 23 patients all who had cirrhotic ascites, 100 mg of spiron-olactone was prescribed to be taken daily for 5 days. When no diuretic response occurred and TTKG was more than 3.5 at the end of 5 days, the dose of spironolactone was increased by 100 mg/day at the interval of 5 days until TTKG decreased to below 3.5. Furosemide was added to the non-responders if their TTKG had dropped to below 3.5. RESULTS: Basal plasma concentration of aldosterone was higher than upper normal limit in 13(57%) patients, and correlated with TTKG significantly(r=0.60, p=0.002). TTKG was calculated to be 3.5+/-0.67 when assuming the aldosterone activity has been completely blocked. Spot urine [Na]/[K] ratio had significant negative correlation with TTKG before and after the administration of spironolactone. In most patients, diuretic response appeared with the fall of TTKG (especially below 3.5) and with the rise of spot urine [Na]/[K] ratio. In patients who did not respond to a low dose spironolactone, further treatment plan (to increase dose of spironolactone or to add furosemide) was guided by TTKG, and all were successful. CONCLUSIONS: TTKG and spot urine [Na]/[K] ratio are good indicators of aldosterone activity, and might be used as useful guidelines in the diuretic management of cirrhotic ascites.

Clinical Usefulness of Transtubular Potassium Gradient(TTKG) and Urine Ammonium in Differential Diagnosis of Hypokalemia / 대한신장학회잡지

Hypokalemia is frequently encountered in clinical medicine, the cause of which can usually be determined from the history such as with diuretic use, vomiting, or diarrhea. And measurement of urinary indices such as excretory rate of K+, random urine K+ and fractional excretion of K+ and assessment of acid-base balance have been applied to the pathophysiologic diagnosis without fruitful success. To investigate the clinical usefulness of TTKG and urine ammonium in differential diagnosis of hypokalemia, we evaluated serum electrolytes and osmolality, random(spot) urine electrolytes, osmolality and ammonium, total CO2, UNa/K, plasma aldosterone and TTKG in 7 patients with diarrhea, 6 patients with vomiting, 7 patients with 3 primary hyperaldosteronism and 4 renovascular hypertension, 6 patients with diuretic uses. With the comparison to 7 overnight fasting and acid-loaded normal controls, we obtained the following results. 1) Random measurement of the urine potassium concentration did not accurately reflect potassium wasting if the urine became concentrated. So clinical usefulness of random urine potassium concentration was limited. 2) UNa/K was useful in the diagnosis of mineralocorticoid excess such as primary hyperaldosteronism and renovascular hypertension rather than the other causes of hypokalemia. 3) TTKG was very useful in differential diagnosis of hypokalemia between potassium losses through the gastrointestinal tract (below 2) and kidney (above 10), and it had a good correlation with the aldosterone activity in the hypokalemic patients due to renal loss. 4) Random urine ammonium was a useful index in differential diagnosis of hypokalemia with acid-base disturbances. In conclusion, TTKG and random urine ammonium were very useful indices in differential diagnosis of the causes of hypokalemia.