Introduction An acute infection of cortex May progress to chronic pyelonephritis most commonly seen in girls with vesiculouteral reflux (reflux type) lower urinary tract obstructions (obstructive type) Other complications include: perinephric abcess, renal papillary necrosis, sepsis Presentation Presents with: nausea vomiting fever flank pain urinary frequency dysuria urgency Acute Pyelonephritis Evaluation Urinary Sediment findings include: clumps of neutrophils (pyuria) scattered RBC bacteria with the presence of WBC casts Microscopic analysis may show > 5 leukocytes/hpf a bacterial pathogen Gold standard is clean catch urine culture with >100,000 bacteria/ml Histology shows neutrophils filling the renal tubular lumens Chronic Pyelonephritis Evaluation Intravenous pyelogram findings: dilation of the calyces with cortical thinning (obstructive type) "blunting" of the calyces with overlying scars (reflux type) Microscopic findings "thyroidization" of tubules due to eosinophilic casts contained in the tubules