A 10 year old boy is having polyuria, polydipsia,laboratory data showed (in mEq/lit) – Na– 154 K– 4.5 HCO3– 22 Serum osmolality – 295 Blood urea – 50 Urine specific gravity – 1.005 The likely diagnosis is –

Lets see each option one by one : artter's syndrome : is characterized by hypokalemia, metabolic alkalosis and normal to low blood pressure. It can be easily ruled out as the patient is having normal potassium level.  Renal tubular acidosis : is characterized by hyperchloremic metabolic acidosis with a normal serum anion gap. It is ruled out as this patient is having normal bicarbonate level (Bicarbonate level is decreased in RTA). Recurrent UTI Symptoms seen are : Fever, dysuria, frequency, urgency, suprapubic pain. It is ruled out as the above given symptoms are not mentioned in this patient. Hypernatremia (Na is 154) is not seen in UTI. iabetes insipidus : Clinical presentation of hypernatremia, polyuria, polydypsia, thin urine of low specific gravity (1.005) is suggestive of diabetes insipidus.