A child with recurrent urinary tract infections is most likely to show:

Reflux is the most common cause of pyelonephritis and is found in 30% to 50% of children presenting with urinary tract infection. In primary reflux, the child (on average, between 2 and 3 years of age) usually presents with symptoms of pyelonephritis or cystitis. Ref:Kligman, Behrman, Jenson, Stanton (2008), Chapter 539, "Vesicoureteral Reflux", In the book, "Nelson's Textbook of Pediatrics", Volume 2, 18th Edition, New Delhi, Page 2229