Low normal potassium levels in acute renal failure: evidence of leptospirosis.

It has been suggested that renal involvement in leptospirosis appears to be a special form of acute renal failure characterized by a higher frequency of polyuria and the presence of hypokalemia with an elevated urinary fractional excretion of potassium [1]. The high frequency of hypokalemia is thought to be caused by a proximal or thick ascending limb of Henle tubular dysfunction [2, 3]. It has been proposed that leptospirosis should be included in the differential diagnosis in febrile patients with acute renal failure and hypokalemia [3]. However, even the presence of low normal levels of potassium in patients with acute renal failure should be an alarming sign for the diagnosis of leptospirosis. In fact, we were recently faced with a patient who presented with fever of 10 days’ duration, acute renal failure (serum creatinine 1,060 μmol/l) and marked hyperbilirubinemia (total bilirubin 560 μmol/l) with moderate increases in serum liver and muscle enzymes (CK 930 IU/l [normal values 30–220 IU/l], SGOT 219 IU/l [normal values 5–40 IU/l], SGPT 230 IU/l [normal values 5–40 IU/l]). Despite the profound deterioration of renal function and the oliguria noticed during the last few hours prior to admission, as well as the rhabdomyolysis-induced increased potassium movement from the cells into the extracellular fluid, serum potassium concentration was at low normal levels (3.8 mmol/l) with urine potassium levels 30 mmol/l. Leptospirosis was diagnosed by laboratory tests, while all other microbiological or serological tests were negative. Penicillin was given after the diagnosis. However, oliguria persisted, while the patient developed disseminated intravascular coagulation with diffuse hemorrhages and deep vein thrombosis of the lower extremities and was admitted to the emergency room. During the prolonged hospitalization urine volume was restored to about 2–3 l/day with a parallel improvement of renal function after careful rehydration. At that time, serum potassium levels ranged between 3.3 and 4.5 mmol/l.Thus, even the low normal potassium levels in febrile patients with acute renal failure should be considered further evidence indicating leptospirosis. K. Nakou, G. Liamis, M.S. Elisaf, K.C. Siamopoulos