A 57-year-old male is admitted to the hospital for a suspected kidney infection (likely pyelonephritis). The patient is placed on intravenous antibiotic therapy but continues to have a temperature of 103degF after 3 days of therapy. The urine culture grows lactose fermenting GNB which is pan drug sensitive On examination, he appears ill and has marked left flank tenderness. Ultrasound depicts the following finding What is the most likely diagnosis?

1st image shows the pink colonies suggestive of E. coli on MacConkey agar (Lactose fermenters) 2nd image USG-KUB suggestive of a perinephric abscess. This 55-year-old male who is suspected of having kidney infection is not improving despite appropriate antibiotic therapy. Pyelonephritis is an infection of the kidney parenchyma usually caused by an ascending infection of bacteria. Manifests as fever, flank tenderness, white cells in the urine, and serum leukocytosis. E. coli is isolated, which is the bacterium that most often causes urinary tract infections. The ultrasound examination is performed to rule out complications of pyelonephritis. The two most common complications would be a nephrolithiasis or ureterolithiasis (kidney stone) and perinephric abscess. Intervention is required before improvement is seen. The abscess must be drained, usually by placement of a percutaneous catheter under radiologic guidance.