investigations

Last edited 11/2018 and last reviewed 06/2021

Diagnosis is based on the history and examination, the finding of bacteria and pus cells in the urine, and growth of the organism. Note that, in the early stages, pus cells may not be excreted in the urine, as a result of the affected kidney 'shutting down'. Thus one negative MSU does not exclude the diagnosis.

Other possible investigations:

• plain abdominal X-ray - may show a stone; 90% of urinary tract stones are radio-opaque
• ultrasound - may reveal dilated collecting system
• CT - when performed before, immediately after, and at delayed intervals from contrast material injection, is the preferred modality for evaluating acute bacterial pyelonephritis (1)
  • also preferred over conventional radiography and ultrasonography (US) for assessing emphysematous pyelonephritis

IVU (rarely used) - may reveal a temporarily non-functioning kidney on the affected side

Reference:

• Craig WD et al. Pyelonephritis: Radiologic-Pathologic Review.RadioGraphics 2008; 28(1).