Significance of Urine pH in Predicting Renal Outcomes for Patients with Rhabdomyolysis

Abstract

Sushil K. Mehandru, Supreet Kaur, Avais Masud, Qalb Khan, Kyrillos Rezkalla, Prit Paul Singh,Suhas Patel, Tushar J. Vachharajani, Arif Asif

Acute kidney injury (AKI) is a common complication of rhabdomyolysis. Urine pH is important in predicting the occurrence of AKI. Acidic environment plays a major role in incidence of AKI. In this case report of 32 patients with rhabdomyolysis, majority of patients with urine pH<6.5 developed AKI whereas no renal dysfunction was found in patients with urine pH>7.0, regardless of levels of creatinine kinase. Low urine pH and intratubular acidosis facilitates higher concentration of myoglobin in the tubules as well as precipitation of myoglobin and uric acid casts that results in tubular obstruction and renal dysfunction. Myoglobin has direct nephrotoxic effect in aciduria. Acidification of body fluids and aciduria are independent risk factors for acute kidney injury (AKI) in patients in the presence of met-hemoglobinuria, well documented in patients before and after coronary artery bypass graft surgery. There is, however, lack of literature regarding the role of rhabdomyolysis in predicting renal outcomes in the presence of acidosis and aciduria. Animal studies have shown that under acidic environment, myoglobin is more nephrotoxic than under alkaline conditions, however this has not been documented in humans. This is, to the best of our knowledge, the first study to correlate this phenomenon in humans. This study has wider application in patients with rhabdomyolysis. Early recognition of urinary pH may predict outcome in patients with rhabdomyolysis induced AKI.

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