[Psychogenic polydipsia in a child].

At the age of 20 months a baby girl began with compulsive water drinking. The water intake reached 4,000 ml per day. The constant drinking of water created disorganization in the family life. At the age of 2 years and 9 months, the psychogenic polydipsia is confirmed, based in the patient's ability to concentrate her urine, which was demonstrated with 1-deamino-BD arginine vasopressin (DDAVP) and the water deprivation tests. Neither bacteriological, clinical, nor radiological evidences of urinary infection were found. The intravenous pyelogram revealed a unilateral and complete duplication of the collecting system. The abnormal urinary tract does not have a causal relationship with the polyuria. With progressive water deprivation, the polydispia stopped in two months. Psychogenic polydispia is rare in infants and children. The mistake and delay in diagnosis is frequency. The differential diagnosis with cranial diabetes insipidus and urological diseases may be difficult sometimes.