Diagnostico diferencial en la poliuria y polidipsia: variaciones cl¨ªnicas y de laboratorio en la prueba de restricci¨®n h¨ªdrica en niños.

M TROIANO,; A CHIESA; A KESELMAN,; G ROPELATO,; I BERGADA,

Lima Peru.

Congreso; XX Reunion Anual de SLEP; 2008

SLEP

Diagnosis of Central Diabetes Insipidus (CDI) is based on clinical and laboratory studies. Although the WDT is generally used for a definite diagnosis, scarce information exists in children regarding its clinical and laboratory findings. To clarify these issues we studied 31 children (aged 7.25 ¡À 5.0 years) that underwent a WDT to rule out CDI Weight and urine output were measured hourly. Initial and final plasma and urinary osmolality (freezing point), and plasma ADH (extracted RIA) were measured. Final plasma ADH was plotted on a nomogram related to serum osmolality in a normal population. The positive predictive value of a final U/P Osm ratio(f U/POsm) ¡Ü 1.5 towards an inadequate final plasma ADH was 95%, and the negative predictive value of 72%, with a diagnostic efficiency of 83%. So, patients were grouped according to the f U/POsm in: Group A (n = 20) ratio < 1.5, and B (n = 11) > 1.5. Patients from group A had a significant decrement of weight (p < 0.05) and higher urine output (p < 0.006) than group B. Increment of pADH after the test was significantly lower in group A (0.24 ¡À 1 pg/ml) vs group B (2.47 ¡À 2.8 pg/ml), p = 0.015. In summary, a decrement in body weight as well as the urine output during this test are useful information to define pediatric patients with a real incapacity to concentrate the urine. Moreover, the measuring of plasma ADH enabled us to establish that a cut-off f U/P Osm ratio ¡Ü 1.5 is likely associated with inadequate plasma ADH secretion, resulting in the best tool for the differential diagnosis in children with polyuria and polydipsia.