Differential Diagnosis for a 64-year-old Male with Suspected Pyelonephritis and Nephritis

Single Most Likely Diagnosis

• Pyelonephritis: This is the most likely diagnosis given the patient's symptoms of fever, chills, dysuria, and flank pain, which are classic for an upper urinary tract infection. The presence of a right-sided CVA (cerebrovascular accident) could be unrelated or potentially related to a septic embolus in the setting of endocarditis, but the primary presentation suggests pyelonephritis.

Other Likely Diagnoses

• Sepsis: Given the patient's fever, chills, tachycardia, and potential source of infection (pyelonephritis), sepsis is a likely consideration. Sepsis can lead to organ dysfunction, including renal impairment, which could exacerbate or complicate the patient's nephritis.
• Nephrolithiasis: Kidney stones could cause severe pain and dysuria, and if an obstructing stone is present, it could lead to pyelonephritis. The patient's symptoms of pain and dysuria could be consistent with nephrolithiasis.
• Acute Kidney Injury (AKI): The patient's presentation with nephritis and potential pyelonephritis could lead to or be complicated by AKI, especially if there is an obstructive cause or if the patient is septic.

Do Not Miss Diagnoses

• Endocarditis: Although less likely, endocarditis could explain the CVA (if due to a septic embolus) and the systemic symptoms of fever and chills. It's crucial not to miss this diagnosis due to its high morbidity and mortality.
• Aortic Aneurysm or Aortic Dissection: Severe back or abdominal pain could be indicative of an aortic aneurysm or dissection, which are life-threatening conditions requiring immediate intervention.
• Pulmonary Embolism: While the primary symptoms suggest a urinary tract issue, it's essential to consider pulmonary embolism, especially if the patient has risk factors or if there are any respiratory symptoms, due to its potential for high mortality.

Rare Diagnoses

• Vasculitis: Conditions like ANCA-associated vasculitis could present with renal involvement (nephritis) and systemic symptoms but are less common than other diagnoses listed here.
• Tuberculosis: Although rare in many parts of the world, genitourinary tuberculosis could present with chronic symptoms similar to pyelonephritis and nephritis, including flank pain and dysuria.

Diagnostic Plan

1. Urinalysis and Culture: To confirm the diagnosis of pyelonephritis and identify the causative organism.
2. Blood Cultures: Especially if sepsis or endocarditis is suspected.
3. Imaging: Ultrasound or CT scan of the abdomen to evaluate for nephrolithiasis, obstruction, or other complications.
4. Renal Function Tests: To assess for AKI.
5. Cardiac Evaluation: If endocarditis is suspected, consider echocardiography.

Pharmacological Plan

1. Antibiotics: Empiric antibiotic therapy for pyelonephritis, with adjustment based on culture results.
2. Pain Management: For flank pain and dysuria.
3. Supportive Care: For sepsis or AKI, including fluid management and potential dialysis.

Non-Pharmacological Plan

1. Fluid Management: Adequate hydration to help prevent AKI and support blood pressure.
2. Monitoring: Close monitoring of vital signs, urine output, and renal function.
3. Surgical Intervention: If an obstructing stone or other condition requiring surgery is identified.