Differential Diagnosis for 100 yr old female with increased confusion

• Single most likely diagnosis
  • Urinary Tract Infection (UTI): The presence of 3-5 WBCs, moderate microscopic bacteria, and the detection of E. coli and K. pneumoniae on urine PCR strongly suggest a UTI. The patient's age and increased confusion also support this diagnosis, as UTIs can cause delirium in elderly patients.
• Other Likely diagnoses
  • Sepsis: Although not directly diagnosed, the presence of a UTI and the patient's age increase the risk of sepsis, which can also cause confusion.
  • Hypothyroidism: The patient's TSH level is slightly elevated (4.17), which may indicate hypothyroidism. However, the free T4 and free T3 levels are within normal limits, making this diagnosis less likely.
  • Dehydration: Elderly patients are prone to dehydration, which can cause confusion. Although not directly diagnosed, dehydration could be a contributing factor to the patient's symptoms.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Sepsis with urosepsis: As mentioned earlier, the patient is at risk for sepsis due to the UTI. Urosepsis is a life-threatening condition that requires prompt treatment.
  • Kidney stones with obstruction: The presence of calcium oxalate crystals and moderate microscopic bacteria could indicate a kidney stone with obstruction, which is a medical emergency.
  • Meningitis or encephalitis: Although less likely, these conditions can cause confusion and would be deadly if missed. However, there is no direct evidence to support these diagnoses.
• Rare diagnoses
  • Hypercalcemia of malignancy: The presence of calcium oxalate crystals could indicate hypercalcemia, which can be caused by malignancy. However, this diagnosis is less likely without other supporting evidence.
  • Tuberculosis (TB) of the urinary tract: Although rare, TB can infect the urinary tract and cause similar symptoms. However, there is no direct evidence to support this diagnosis.