If all the history and clinical status data indicate the presence of pathological polyuria / polydipsia, the following blood and urine parameters should be investigated on an outpatient basis: serum osmolarity; serum sodium, potassium, calcium, glucose, urea nitrogen levels; urine osmolarity; urine specific gravity; glucosuria. Diagnostic criteria for diabetes insipidus are serum osmolarity greater than 300 washes / kg with urine osmolarity less than 300 washes / kg. If serum osmolarity is less than 270 wash / kg or urine osmolarity is more than 600 mOsm / kg, a diagnosis of diabetes insipidus is unlikely. If during the first examination of the patient the serum osmolarity is less than 300 washes / kg, but the volume of liquid drunk / excreted recorded at home indicates polydipsia / polyuria,which cannot be explained by primary polydipsia (ie, serum osmolarity is more than 270 my / kg), the patient should be tested with fluid restriction.
In the hospital setting, mainly in patients after neurosurgical operations, central diabetes insipidus is likely in cases where serum hyperosmolarity (> 300 washes / kg) is associated with urine osmolarity lower than serum osmolarity. It is always necessary to remember about excess fluid during and immediately after surgery, followed by hypo-osmolar polyuria, which can be mistakenly diagnosed as diabetes insipidus.
If all the history and clinical status data indicate the presence of pathological polyuria / polydipsia, the following blood and urine parameters should be investigated on an outpatient basis: serum sodium, potassium, calcium, glucose, serum urea levels; urine specific gravity; glucosuria. The diagnostic criteria for diabetes insipidus are: hypostenuria, i.e. the proportion of urine in all portions per day is less than 1008 in the absence of azotemia. Often the proportion is 1000-1005.