Differential Diagnosis

The patient's symptoms and laboratory results suggest a possible kidney infection. Here's a differential diagnosis organized into categories:

• Single most likely diagnosis

  • Pyelonephritis: The presence of E. coli in the UTI PCR test, elevated C-reactive protein (17mg/l), and creatinine serum level (42 micromol/l) along with pain in the side and back are all consistent with a kidney infection (pyelonephritis). The elevated CRP indicates an inflammatory response, and the presence of E. coli is a common cause of urinary tract infections that can ascend to the kidneys.

• Other Likely diagnoses

  • Lower Urinary Tract Infection (UTI): Although the presence of E. coli and symptoms could suggest a lower UTI, the pain in the side and back, along with the elevated creatinine, leans more towards an upper urinary tract infection (pyelonephritis).
  • Musculoskeletal pain: The pain in the side and back could also be attributed to musculoskeletal issues, but the laboratory findings and the presence of E. coli make this less likely.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Sepsis: Although less likely given the information, any infection can potentially lead to sepsis, especially in vulnerable populations. The elevated CRP is a marker of inflammation, and while it's currently attributed to a localized infection, monitoring for signs of sepsis (e.g., fever, hypotension, altered mental status) is crucial.
  • Kidney stones with infection: If a kidney stone is obstructing the urinary tract and causing an infection, it's a medical emergency. The pain in the side and back could be consistent with this diagnosis, and the presence of E. coli indicates an infection.

• Rare diagnoses

  • Perinephric abscess: This is a rare but serious condition where an abscess forms next to the kidney, often as a complication of pyelonephritis. It would present with severe pain, fever, and possibly systemic signs of infection.
  • Emphysematous pyelonephritis: A rare, severe infection of the kidney where gas is formed in the kidney tissue. It's more common in diabetic patients and presents with severe symptoms, including pain, fever, and vomiting.