1. NEPHROGENIC DIABETES INSIPIDUS BY DR HU OKAFOR DEPT. OF PAEDIATRICS UNTH ENUGU

2. Introduction This is a deficiency of renal concentrating capacity with consequent polyuria and polydypsia. May be primary or secondary

3. Primary This is a heriditary condition due to a sex-linked recessive gene disorder. Found mainly in males. Female heterozygotes have been identified & show lesser degrees of urine concentrating defects. Autosomal recessive forms have been described. Results in unresponsiveness of renal tubules to ADH.

4. Pathogenesis This is uncertain but resistance of collecting tubules to effect of ADH has been suggested. Abnormal, physiologically inert ADH blocking receptor sites has also been suggested.

5. secondary Associated with disorders which cause loss of medullary concentrating gradient.This may result from torrential flow of fluid from defective proximal tubules which overwhelms the collecting tubules. Causes include:  Acute or chronic renal failure  Obstructive uropathy  Vesico-ureteric reflux  Cystic diseases of the kidney  Interstitial nephritis  nephrocalcinosis

6. Secondary causes contd. causes due to ed effect of ADH on tubules e.g  Hypokalemia  Hypercalcemia  Lithium  Amphotericin B

7. Clinical features Most present during infancy but features may be unrecognized by parents.  Polyuria & polydypsia with preference of water to milk feeds(less polyuria in breast fed babies)  Dehydration  Fever  Vomitting  Failure to thrive  Retardation of intellectual and skeletal maturation.  DEFECT IS PERMANENT BUT WITH AGE ed WATER INTAKE COMPENSATES FOR POLYURIA>

8. Lab. Features Serum Na & Cl levels are ed. Serum urea & creatinine level are ed. Urine osmolality is less than that of plasma. Even with administration of synthetic vasopressin urine concentration is unaffected. Vassopressin Test:Administer intranasal 1- desamino-8-D-arginine-vassopressin 10µg for pts. 2yrs.If urine osmolality remains ≤200mosm/kg it is confirmatory.

9. Differential diagnosis Hypokalemia Hypercalcemia Central diabetes insipidus Psychogenic polydypsia CRF Nephronopthisis

10. Treatment Water replacement Thiazides(lead to vol.depletion and increased proximal tubular absorption of NA) Indomethacin(leads to prostaglandin synthetase inhibition).