Chronic pyelonephritis occurs in patients at risk for repeated bouts of acute pyelonephritis, and is thus most often the result of complicated acute pyelonephritis. However, not all have preceding overt signs of acute pyelonephritis, such as fever, malaise, or flank pain. Patients present with nonspecific signs of chronic kidney disease. Urinalysis typically shows pyuria, often with microscopic hematuria, occasionally white blood cell casts and positive urine cultures. Chronic pyelonephritis due to structural abnormalities occurs more often in infants and children younger than 2 years.