Kidney injury risk during prolonged endurance running: lessons from the field

Marathon and ultramarathon runners commonly exhibit postrace rises in biomarkers of acute kidney injury. Although these perturbations are generally transient and resolve without treatment, rare but serious cases of clinically significant kidney injury in endurance athletes have been documented postrace. The purpose of this mini-review is to discuss the recent literature demonstrating a link between prolonged endurance running and acute kidney injury risk. We present the following: <i>1</i>) the primary mechanisms by which endurance exercise contributes to acute kidney injury; <i>2</i>) factors that may modulate kidney injury risk in endurance athletes; <i>3</i>) recommendations and considerations for field-based studies; and <i>4</i>) clinical implications and event-specific considerations. In brief, hemodynamic, muscular, gastrointestinal, and hydration stressors collectively contribute to increased risk for acute kidney injury during prolonged endurance running. In addition, there are several extrinsic (e.g., net elevation, temperature, humidity), intrinsic (e.g., biological sex, age, fitness), and behavioral (e.g., event hydration practices, training status) factors that likely contribute to the heterogeneous responses observed in athletes. Field studies offer unique ecological insight but introduce logistical challenges that are far less controlled than laboratory environments and therefore require important methodological considerations. Longitudinal studies are needed to determine whether repeated episodes of subclinical kidney stress contribute to any long-term decline in kidney function in habitual endurance runners or athletes.