Differential Diagnosis

• Single most likely diagnosis
  • A. Water overload: The patient's low serum osmolarity, low sodium, and low potassium levels, combined with normal urine osmolarity, suggest an excess of free water in the body, which is consistent with water overload. This condition can occur in postoperative patients, especially when given IV dextrose, which can lead to hyponatremia if not balanced with adequate electrolyte replacement.
• Other Likely diagnoses
  • D. SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion): Although less likely than water overload given the context, SIADH could explain the hyponatremia and low serum osmolarity. However, SIADH typically presents with elevated urine osmolarity due to the inappropriate secretion of ADH, which is not the case here.
• Do Not Miss
  • B. Addison's disease: Although rare and less likely, adrenal insufficiency (Addison's disease) can cause hyponatremia, hypotension, and potentially agitation. It's crucial to consider this diagnosis because missing it can be fatal. However, the normal creatinine level and the absence of other typical symptoms (e.g., hypotension, hyperkalemia) make it less likely in this scenario.
• Rare diagnoses
  • C. Diabetic nephropathy: While diabetic nephropathy can lead to electrolyte imbalances, it is less likely to be the primary cause of the acute presentation of hyponatremia, hypokalemia, and low serum osmolarity in this postoperative setting, especially given the patient's well-controlled diabetes and lack of other underlying conditions.