Differential Diagnosis

The patient's presentation is complex, with a combination of symptoms that could be related to her recent urinary tract infection (UTI), her history of COPD, or other underlying conditions. Here's a breakdown of the differential diagnosis into the specified categories:

• Single Most Likely Diagnosis

  • Pyelonephritis or Sepsis: Given the patient's recent diagnosis of UTI and the worsening of her symptoms, including fever, chills, body aches, and burning on urination, pyelonephritis (an infection of the kidney) or sepsis (a systemic infection) are strong considerations. The patient's age, history of COPD, and the fact that her symptoms have not improved with initial treatment increase her risk for these complications.

• Other Likely Diagnoses

  • Pneumonia: The patient's history of COPD, shortness of breath, chest pain, and production of phlegm could indicate a respiratory infection such as pneumonia, especially in the context of her recent illness and potential for aspiration due to vomiting.
  • Gastroenteritis: Although the patient's diarrhea has resolved, the combination of abdominal pain, nausea, and vomiting could suggest a gastrointestinal infection.
  • Cholecystitis or Biliary Colic: The diffuse abdominal pain could also be indicative of a biliary issue, especially if the pain is localized to the right upper quadrant.

• Do Not Miss Diagnoses

  • Pulmonary Embolism (PE): Given the patient's shortness of breath, chest pain, and history of recent illness, PE is a critical diagnosis not to miss. The patient's age and potential for immobility increase her risk.
  • Myocardial Infarction: Chest pain and shortness of breath could also be indicative of a cardiac issue such as myocardial infarction, which is crucial to rule out, especially in a patient with risk factors for cardiovascular disease.
  • Perforated Viscus: Severe, diffuse abdominal pain could indicate a perforation, which is a surgical emergency.
  • Sepsis due to Another Source: While the UTI is a likely source of sepsis, other sources such as pneumonia, intra-abdominal infection, or even a skin infection should be considered, especially if the patient does not respond to treatment for the presumed source.

• Rare Diagnoses

  • Inflammatory Bowel Disease (IBD) Flare: Although less likely given the acute presentation, an exacerbation of IBD could present with similar gastrointestinal symptoms.
  • Pancreatitis: Abdominal pain, nausea, and vomiting could be indicative of pancreatitis, though this would typically be associated with more specific symptoms and laboratory findings.
  • Mesenteric Ischemia: This is a rare but critical condition that could present with severe abdominal pain out of proportion to physical examination findings, especially in older patients with risk factors for vascular disease.