What is primary megaureter?
Primary megaureter is congenital narrowing at the UVJ that results from an abnormal proportion of muscle fibers and fibrous tissue in the distalmost 3 to 4 cm of the ureter. It occurs more commonly than previously realized and can be either obstructive or nonobstructive. When primary megaureter is obstructive, the degree of obstruction is variable and seems to improve in many cases over time. Most often, this condition is detected incidentally on prenatal US. Postnatal US and urography reveal a variable degree of dilation of the ureter and collecting system on the affected side ( Figure 88-6 ). Occasionally, a short narrow segment of ureter may be seen through US at the UVJ. VCUG typically shows absence of reflux, although VUR may be present in 10% of cases.