Differential Diagnosis

The patient's presentation with diabetes mellitus (DM), coronary artery disease (CAD), lethargy, elevated white blood cell count (WBC), abnormal lymphocyte count, elevated blood urea nitrogen (BUN), creatinine, and glucose levels, along with decreased glomerular filtration rate (GFR) and low bicarbonate, suggests a complex clinical picture. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Diabetic Ketoacidosis (DKA): The patient's high glucose level (700), low bicarbonate (19), and lethargy are classic signs of DKA, a serious complication of diabetes. The elevated WBC count could be due to the stress response associated with DKA.

• Other Likely Diagnoses

  • Sepsis: The elevated WBC count (14,000) and lethargy could indicate an underlying infection. Sepsis is a concern, especially in a patient with DM, as they are more susceptible to infections.
  • Acute Kidney Injury (AKI): The elevated BUN (50) and creatinine (2.1) with a decreased GFR (33) suggest AKI, which could be due to various factors including dehydration from DKA, sepsis, or contrast-induced nephropathy if the patient recently underwent imaging studies involving contrast.
  • Hyperosmolar Hyperglycemic State (HHS): Although the glucose level is very high, the absence of explicit ketoacidosis indicators (like ketones) might suggest HHS, especially in the context of severe hyperglycemia and altered mental status.

• Do Not Miss Diagnoses

  • Myocardial Infarction: Given the patient's history of CAD and the current presentation of lethargy, it's crucial to consider myocardial infarction, as it can present atypically, especially in diabetic patients.
  • Meningitis or Encephalitis: Although less likely, these conditions can cause lethargy and have a high mortality rate if not promptly treated. The elevated WBC count could support an infectious process.
  • Septic Shock: A severe form of sepsis, septic shock is life-threatening and requires immediate intervention. The patient's lethargy and elevated WBC count, in combination with AKI, make this a critical diagnosis not to miss.

• Rare Diagnoses

  • Pancreatitis: Although less likely given the information, pancreatitis could cause abdominal pain (not mentioned), elevated WBC count, and could be associated with DKA or HHS in diabetic patients.
  • Thyroid Storm: This is a rare but life-threatening condition that can cause altered mental status, elevated WBC count, and can be associated with hyperglycemia. However, specific symptoms like exophthalmos, goiter, or a history of thyroid disease would make this more likely.