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- Michael A. Linshaw, MD*
- *Associate Professor of Pediatrics, Harvard Medical School; Department of Pediatrics-Division of Pediatric Nephrology, Massachusetts General Hospital for Children, Boston, Mass
Objectives
After completing this article, readers should be able to:
Recognize the clinical features of congenital nephrogenic diabetes insipidus
Know the different hereditary patterns of nephrogenic diabetes insipidus.
Discuss how to evaluate a child who has hypernatremic dehydration in the presence of dilute urine.
Describe the nutritional, fluid, and pharmacologic goals of therapy.
Introduction
Diabetes insipidus (DI), the inability under physiologic conditions to concentrate urine adequately, is characterized by the passage of large amounts of very dilute urine, even as the body is threatened with progressive dehydration and circulatory collapse in the presence of severe hypernatremia. Normally, about 10% to 12% of glomerular-filtered volume is reabsorbed along distal nephron vasopressin (ADH)-sensitive sites. Such reabsorption is accomplished by a responsive tubule exposed to ADH that has been secreted by stimulation of osmotic or volume receptors. Both the absence or insufficiency of ADH due to pituitary or hypothalamic dysfunction (central diabetes insipidus [CDI]) or the failure of the kidney to respond adequately to normal or high serum concentrations of ADH (nephrogenic diabetes insipidus [NDI]) can present with similar clinical features, most notably polyuria, polydipsia, and extreme thirst.
The seriousness of such a defect can be illustrated by considering a child who has an actual glomerular filtration rate of 50 mL/min. Failure to reabsorb the expected approximately 5 to 6 mL/min along ADH-sensitive sites would result in the potential loss of 300 to 360 mL/h of fluid or approximately 1 L in 3 hours. With progressive dehydration, the glomerular filtration rate would decline and blunt the fluid loss to some extent, but ensuing volume depletion, hypernatremia from water loss, and renal insufficiency could become life-threatening.
CDI occurs as a result of intracranial lesions; NDI is caused by defects in the renal concentrating process (Table 1). In NDI, congenital X-linked or autosomal inherited forms of DI …
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