AVP and Polydipsia: Diabetes insipidus (DI) is a condition characterized by the body's inability to conserve water or to concentrate the urine, leading to polydipsia and polyuria.1 Nephrogenic diabetes insipidus (NDI) results from the kidney's impaired response to circulating antidiuretic hormone (ADH).1 NDI causing severe urinary tract dilatation is a rare situation that is rarely published especially in children.