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Pediatric Diabetes Insipidus Workup

  • Author: Karl S Roth, MD; Chief Editor: Stephen Kemp, MD, PhD  more...
Updated: Nov 03, 2015

Basic Laboratory Studies

In assessing patients with suspected diabetes insipidus (DI), the urine specific gravity of the first morning urine is helpful in assessing renal ability to concentrate urine. Dilute urine with a relatively high serum sodium and osmolarity effectively establishes the diagnosis. The serum sodium level may be as high as 170 mEq/L, while the serum osmolarity is greater than 300 mOsm/kg. Patients with prerenal azotemia present with severe dehydration.

In young infants, distinguishing between normal and pathologic inability to concentrate the urine may be difficult because infants generally exhibit a constitutional hyposthenuria.

An accurate 24-hour urine collection is important. The total urine output is high, and the number of osmoles excreted per day is small.

Serum potassium and calcium concentrations are important to exclude the possibility of polyuria secondary to hypokalemia or hypercalcemia, both of which interfere with renal concentrating mechanisms.


Water Deprivation Testing

The definitive diagnostic study is the water deprivation test, which can be used both to confirm the diagnosis and to distinguish between central DI and nephrogenic DI on the basis of response to a vasopressin analogue.

The water deprivation test is performed as follows:

  • Obtain baseline urine and blood for osmolality and electrolytes.
  • Deprive the patient of water after breakfast until significant dehydration occurs. Weigh the patient every 2 hours and limit dehydration to 2-5% loss of body weight.
  • Monitor urine specific gravity hourly; if the specific gravity is 1.014 or greater, terminate the test and obtain appropriate urine and blood specimens for osmolality. Limit water deprivation to 4 hours for infants and 7 hours for children.
  • If polyuria persists, administer intranasal desmopressin (see Medication), and replace urine output with fluids. After 4 hours (2 h in infants), obtain urine and blood for osmolality.

The normal response to dehydration or desmopressin includes urine osmolality greater than 450 mOsm/kg, a urine-to-serum osmolality ratio of 1.5 or higher, and an increase in urine-to-serum osmolality of 1.0 or more from baseline. A normal response should be observed in central DI and psychogenic DI but not in nephrogenic DI.


Magnetic Resonance Imaging

Cranial magnetic resonance imaging (MRI) can be used to exclude pituitary cysts, hypoplasia, and destruction secondary to mass lesions.[10] Often, the bright spot on an MRI scan that is thought to represent vasopressin-secreting neurons in the posterior pituitary is absent in patients with central DI.

Contributor Information and Disclosures

Karl S Roth, MD Retired Professor and Chair, Department of Pediatrics, Creighton University School of Medicine

Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.


James CM Chan, MD Professor of Pediatrics, Tufts University School of Medicine; Director of Research, The Barbara Bush Children's Hospital, Maine Medical Center

James CM Chan, MD is a member of the following medical societies: American Pediatric Society, Alpha Omega Alpha, American Academy of Pediatrics, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, International Society of Nephrology

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) Professor and Chair, First Department of Pediatrics, Athens University Medical School, Aghia Sophia Children's Hospital, Greece; UNESCO Chair on Adolescent Health Care, University of Athens, Greece

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) is a member of the following medical societies: American Academy of Pediatrics, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Pediatric Endocrine Society, Society for Pediatric Research, American College of Endocrinology

Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD Former Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas for Medical Sciences College of Medicine, Arkansas Children's Hospital

Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi Beta Kappa, Southern Medical Association, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Additional Contributors

Thomas A Wilson, MD Professor of Clinical Pediatrics, Chief and Program Director, Division of Pediatric Endocrinology, Department of Pediatrics, The School of Medicine at Stony Brook University Medical Center

Thomas A Wilson, MD is a member of the following medical societies: Endocrine Society, Pediatric Endocrine Society, Phi Beta Kappa

Disclosure: Nothing to disclose.

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