Primary obstructive megaureter (POM) is dilatation of ureter due to a functional obstruction at distal ureter. It could be seen all ages. It is the second cause of intrauterin hydronephrosis. It is seen uncommonly in adults. The male to female ratio is 4/1. It is usually unilateral (it is seen at left ureter more than 3-4 times to right ureter) and it is bilateral %15-25 of cases. Although it is known as a nonhereditary anomaly, some familial cases have also been reported. Most of the cases are asymptomatic and detected incidentally. The most common symptom is urinary infection in childhood and flank pain in adults. Most of the patients heal spontaneously.