AQP2 and congenital anomaly of kidney and urinary tract: In contrast to normal kidneys, in CAKUT kidneys, AQP1 demonstrated an irregular localization and a weaker expression in the proximal tubules, especially dilated ones, while AQP2 expression, normally found only apically and in a subset of distal tubules, was present in some dilated proximal tubules and throughout the cytoplasm of many distal tubules.