Differential Diagnosis
- Single most likely diagnosis
- Central Diabetes Insipidus (CDI): The high urine output (300 uosm) and high serum osmolality (1120) suggest an inability to concentrate urine, which is a hallmark of CDI. The normal serum sodium (sna nml) also supports this diagnosis, as CDI typically presents with hypernatremia due to the loss of free water in the urine.
- Other Likely diagnoses
- Nephrogenic Diabetes Insipidus (NDI): Although less likely than CDI, NDI could also present with high urine output and serum osmolality. However, NDI is often associated with other renal abnormalities, which are not mentioned in the question.
- Primary Polydipsia: This condition involves excessive water intake, leading to high urine output and diluted urine. However, the high serum osmolality in this case makes primary polydipsia less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Hypercalcemia: Severe hypercalcemia can cause nephrogenic diabetes insipidus, leading to high urine output and serum osmolality. Although not directly mentioned, hypercalcemia is a potentially life-threatening condition that should not be missed.
- Sepsis: Sepsis can cause acute kidney injury, leading to high urine output and serum osmolality. Although the question does not provide direct evidence of sepsis, it is a potentially deadly condition that should be considered.
- Rare diagnoses
- Psychogenic Polydipsia with underlying psychiatric disorder: This condition involves excessive water intake due to a psychiatric disorder, leading to high urine output and diluted urine. However, the high serum osmolality in this case makes this diagnosis less likely.
- Other rare causes of diabetes insipidus, such as Langerhans cell histiocytosis or sarcoidosis: These conditions are rare and typically present with other systemic symptoms, which are not mentioned in the question.