Demographics of Stone Disease—Are They Changing?

WHEN faced with extreme conditions, be it heat, cold, space or deep-sea, the body’s capacity to adapt sheds light on the physiology of health and pathophysiology of disease. In this issue of The Journal Masterson et al (page 165) evaluate the impact of a desert environment on urinary stone risk. 1 Fifty marines deployed for 1 month to the Mojave Desert submitted 24-hour urine collections before, during and after mobilization to the desert. Daily urine output decreased 68% despite an average fluid intake of 17 L per day. This decrease coupled with a decrease in urinary pH led to an increase in the supersaturation of uric acid and sodium urate. This study highlights the marked ability of the body to adapt to environmental stressors, as preservation of electrolytes and water are critical to survival in the desert. This study would have been strengthened had the Marines been placed on the same controlled diet while at home as they were when deployed. An additional study limitation is the quality of the 24-hour urine collections while deployed for training exercises in the desert. The lower creatinine excretions suggest under-collection, and confound the observations and conclusions of the study. Despite these limitations, these findings have implications on this side of the pond as agricultural workers in the arid southwest, manual laborers in foundries and other workers in extreme conditions are likely faced with similar stressors on a daily basis. Indeed, citrate supplementation may be an important adjunct to increased fluid intake in these work environments to counteract the noted decreases in urinary pH and urinary citrate on return from the desert. Studies of longer term adaptation in the desert will have added value, especially with the increased concern about global warming. Another condition to which we all adapt is that of advancing years. Perhaps our interpretation of painful stimuli or our physiological response to renal obstruction changes as we age, dulling our perception of renal colic and delaying our presentation to the emergency room. Also in this issue Krambeck et al (page 158) evaluate the impact of age on clinical presentation with symptomatic urolithiasis. 2 They report that older patients were less likely to present with characteristic renal colic, and more likely to present with fever, diarrhea and pyuria, often accompanied by urinary tract infections and bacteremia. A high index of suspicion should accompany a low threshold for imaging to diagnose stones in the geriatric population in a timely manner. Uric acid stones were more common in the elderly while calcium phosphate stones were more common in the young. These findings suggest the potential to stratify metabolic evaluation and medical therapy for stone prevention to the age of the patient. Older patients were less likely to pass their stones and more likely to require an intervention. The observations of differences in the need for and type of surgical intervention based on age are challenging to interpret. Elderly patients had more complex stones (multiple, larger, staghorn), which may have impacted the need for and selection of surgical approach. Do older patients seek advice from older urologists who may be less likely to use medical expulsive therapy or ureteroscopy? Do comorbidities impact the decision to select a specific approach? Were there differences in body mass index that impacted these decisions? These are more questions for another day.