Reviewed by Rishi Desai, MD, MPH
Pyelonephritis is an inflammation of the kidney tissue, calyces, and renal pelvis. It is commonly caused by bacterial infection that has spread up the urinary tract or traveled through the bloodstream to the kidneys. Severe cases of pyelonephritis can lead to pyonephrosis (pus accumulation around the kidney), sepsis, kidney failure and even death. Clinical presentation of acute pyelonephritis is a patient complaining of flank pain, fever, nausea, vomiting. Multiple bouts of acute pyelonephritis can result in chronic pyelonephritis with accumulation of eosinophilic casts that resemble thyroid tissue on histology.