The most common anomaly of the upper urogenital tract is

UPJ stenosis is the most common abnormality in childhood and is more frequent in male children, characterized by narrowing usually on the left sideOverall, position & shape of the kidney being most common oneHorseshoe kidney is the most common and most frequently found renal abnormality among men.(Refer: OP Ghai's Textbook of Pediatrics, 8th edition, pg no. 470)