Polyuria in Chronic Mountaineers

Yes, chronic mountaineers do suffer from polyuria due to hypoxic diuresis, which is a physiological adaptation to high altitude exposure. 1

Mechanism of High Altitude Polyuria

Hypobaric hypoxia at high altitudes triggers a fast increase in respiratory rate and tidal volume, leading to respiratory alkalosis and hypoxic diuresis 1
This diuresis is part of the body's acclimatization process to high altitude and represents a powerful physiological response to the hypoxic stimulus 2
The kidneys play a crucial role in high-altitude adaptation through regulation of body fluids, electrolyte and acid-base homeostasis 2

High altitude exposure leads to decreased circulating concentrations of antidiuretic hormone (ADH), renin, and aldosterone 2
Simultaneously, there are increased levels of natriuretic hormones, plasma and urinary epinephrine, norepinephrine, endothelin, and urinary adrenomedullin 2
Despite hyperosmolality that develops at high altitude, plasma arginine-vasopressin (ADH) concentration remains inappropriately unchanged, contributing to the diuretic response 3

Daily urine output in mountaineers can be significant, with studies showing average outputs of approximately 1557 ± 758 mL despite the challenging environment 4
Polyuria and polydipsia can be assessed by observing wetter bedding and more rapid emptying of water bottles 1
This diuretic response contributes to the development of hypovolemia as part of the adaptation process 2

The polyuria-induced fluid loss can lead to clinical signs of dehydration, which may affect performance and health at high altitude 1
Mountaineers who develop Acute Mountain Sickness (AMS) often show reduced urine output (mean 1336 mL) compared to those without AMS (mean 1655 mL), suggesting that the diuretic response may be protective 4
Prolonged exposure to high altitude may result in persistent impairment of osmoregulation, with serum osmolality rising from 290 ± 1 mOsm/kg at sea level to 302 ± 4 mOsm/kg at 6,300m 3

Chronic exposure to high altitude may lead to a condition termed "High Altitude Renal Syndrome" (HARS) 5
HARS is characterized by systemic hypertension, microalbuminuria with relatively preserved GFR, polycythemia, and hyperuricemia 5
This syndrome represents the kidney's long-term adaptation to chronic hypoxic conditions 5

Diuretic therapy should be tailored to account for clinical signs of dehydration from hypoxic diuresis or fluid gain 1
Aggressive fluid intake appears to be protective against altitude-related illnesses, though maintaining adequate hydration can be challenging due to increased insensible losses and reduced fluid intake 4
Medications that interfere with adaptation processes, such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, should be used with caution as they can reduce renal erythropoietin production 1

The polyuria observed in chronic mountaineers is primarily a physiological adaptation rather than a pathological condition 2
This diuretic response helps the body adapt to high altitude conditions but must be managed carefully to prevent dehydration 1
Understanding these renal adaptations is essential for optimizing performance and health in individuals who spend extended time at high altitudes 5