Differential Diagnosis

The patient presents with dysuria, high-grade fever, and raised GGT on liver function tests (LFTs), but clear urine and blood cultures. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Pyelonephritis or upper urinary tract infection (UTI) with atypical presentation: Despite the clear urine culture, the symptoms of dysuria and high-grade fever could still suggest an upper UTI, especially if the culture was taken after partial treatment or if the causative organism is not typical.
• Other Likely diagnoses
  • Prostatitis: Especially if the patient is male, given the symptoms of dysuria and high-grade fever without a clear source of infection from cultures.
  • Interstitial cystitis: Could present with dysuria, but typically does not cause high-grade fever; however, it's a consideration given the absence of infection evidence.
  • Tubulointerstitial nephritis: Can cause dysuria and systemic symptoms like fever, often associated with allergic reactions or certain medications.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Septic shock from an unknown source: Despite clear cultures, the high-grade fever and systemic symptoms could indicate a severe infection that has not been identified yet.
  • Intra-abdominal infection or abscess: Could cause systemic symptoms like fever and might not always be directly related to urine or blood culture results.
  • Endocarditis: Although less likely, it's a critical diagnosis not to miss, as it can present with fever and systemic symptoms without an obvious source of infection.
• Rare diagnoses
  • Malacoplakia: A rare condition that can affect the urinary tract and present with symptoms similar to a UTI, but without positive cultures.
  • Xanthogranulomatous pyelonephritis: A rare form of chronic pyelonephritis that can present with non-specific symptoms and might not always have positive cultures.
  • Fungal infections of the urinary tract: More common in immunocompromised patients, but could be a consideration if bacterial cultures are negative and the patient has risk factors.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including any additional symptoms, physical examination findings, and potentially additional diagnostic tests to narrow down the cause of the symptoms.