A boy is suffering from acute pyelonephritis. The most specific investigation is

The answer is A Acute pyelonephritis is a bacterial infection causing inflammation of the kidneys and is one of the most common diseases of the kidney.Pyelonephritis occurs as a complication of an ascending urinary tract infection (UTI) which spreads from the bladder to the kidneys and their collecting systems.Symptoms usually include fever, flank pain, nausea, vomiting, burning on urination, increased frequency, and urgency. The 2 most common symptoms are usually fever and flank pain. E. coli is the most common bacteria causing acute pyelonephritis due to its unique ability to adhere to and colonize the urinary tract and kidneys.Histopathology will usually reveal necrosis or putrid abscess formation within the renal parenchyma. The renal tissues are infiltrated with neutrophils, macrophages and plasma cells. However, architecture is not completely disorganized.The presence of white blood cells within or upon casts strongly suggests pyelonephritis, direct infection of the kidney. They may also be seen in inflammatory states, such as acute allergic interstitial nephritis, nephrotic syndrome, or post-streptococcal acute glomerulonephritis.