Article Figures & Data
Tables
- Table 1.
Relationship between solute and water intake in those with normal or impaired kidney concentrating ability
Urine concentrating capacity Normal Impaired Urine osmolality (mOsmol/kg) 1200 600 Solute excretion (mOsmol) 800 800 Water needed = urine volume (ml) 670 1340 Water balance (food + oxidation − water loss; ml) 200 200 Drinking (ml) 470 1140 - Table 2.
Conditions associated with high water intake: Those in which high water intake is indicated or not indicateda
Condition Comment Conditions for which high fluid intake is indicated to prevent disease urolithiasis Generally, fluid intake should achieve a urine volume of 2.0 to 3.0 L/d Conditions for which high fluid intake is recommended because of underlying disease salt-wasting nephropathy (medullary cystic disease, other causes of chronic interstitial kidney disease) Very rare disease; high salt intake (e.g., >400 mM/d NaCl) may be required to avoid hypotension; because these patients cannot appropriately concentrate the urine, high fluid intake (e.g., >4 L/d) may be needed central and nephrogenic diabetes insipidus (genetic or acquired, e.g., lithium nephrotoxicity) These patients often cannot raise urine to levels isosmotic with plasma; often large water intakes (e.g., >5 L/d) are needed to maintain water balance and a normal plasma osmolality Conditions for which high fluid intake is not recommended inappropriately high NaCl intake (′salt gluttony′) in the patient with CKD The high NaCl intake “drives” the fluid intake; 24-h urine collection for creatinine (to assess completeness of the collection) and NaCl (to assess NaCl intake) will detect this condition; the appropriate management is to decrease salt intake primary polydipsia because of the mistaken belief that high fluid intake is good for the kidney This practice should be discouraged ↵a CKD, chronic kidney disease.