Diagnosis

• pyuria may occur but is not a consistent finding. It may be sterile (1)
  
• chronic pyelonephritis may cause hypertension (especially common in children). Since arterial narrowing is common in the damaged kidney, activation of the renin-angiotensin system due to renal ischaemia has been suggested as a pathogenetic mechanism (2)
  
• IVP: (3)
  • small, scarred kidneys
  • blunting of the calyces
  • cortical thinning over pelvo-calyceal lesions
    
    
• renal biopsy:
  • plasma cell infiltration predominates - occurs between the tubules that are atrophic or ballooned
  • periglomerular fibrosis
  • glomeruli - variable appearance - may be normal or hyalanised

(Note - renal biopsies are now rarely performed to make a diagnosis of chronic pyelonephritis, as imaging techniques have improved considerably and results of the biopsy do not alter treatment.)

Other findings, such as uraemia, acidosis, hypocalcaemia and hyperphosphataemia are described under chronic renal failure

Reference

1. Wennerstrom M, Hansson S, Jodal U, et al. Primary and acquired renal scarring in boys and girls with urinary tract infection. J Pediatr. 2000 Jan;136(1):30-4.
2. Peh S. Chronic pyelonephritis: the significance of renal renin and the vascular changes in the human kidney. J Pathol. 1991 Apr;163(4):343-9.
3. Urological Infections. European Association of Urology, 2020