Ureteral dissection(UD)is a rare condition which occurs when urine through the injured intima formed a urine-filled compartment separating intima and tunica media. Ureteral rupture will happen when the pressure in the UD is over than the bearable pressure range of the extima. UR is generally caused under the premise of ureteral obstruction, as found in the two cases originating from extrinsic malignant oppression and ligation of distal ureter. The male patient is obvious that ureteral wall was intruded by the malignant tumor form a precondition and urine flows through injured intima to form UD. With increasing pressure over normal load, urine-filled dissection bursts, consequently urine mixing contrast diffuse around periureteral space with illuminous hyper-density in enhanced CT scan .
The female patient might be spontaneous UR because most reported spontaneous UR occurs after surgical operation like hysterectomy. Unfortunately, there is no relative mechanism about the process of UD during spontaneous UR reports, so this notion was based on speculation of molecular mechanism of smooth muscle cell. Morphologically, ureter is a tube surrounded by loose mesenchymal cells more easy to change shape when encountering to outer force, but lasting stimulation from high pressure of obstructive ureteral cavity makes its flexibility reduce, so more damage to the wall of ureter, injured intima always occurring in the relatively weak religion (proximal ureter with two-layer mucosa however distal segment has three) .
In order to better identify the UD through radiology imaging, we should distinguish between ureteral double lumens and UD. Ureteral double lumens are a rare kind of ureteral duplication that normal ureteral lumen partially or completely separates into two pieces but it was fused at end of the split . So it is a clear discrimination between the two diseases through signs of concentric circles and rupture in the enhanced CT with contrast extravasation.
In conclusion, UD can be easily diagnosed by enhanced CT and/or retrograde pyelography with obvious double-lumen sign, concentric circle and low intensity line-shaping intima along with extension of ureter. UR caused by UD is fewly reported. UR is rare but fatal, mostly due to ureteral stones and iatrogenic injury, however no specific cause found in almost a quarter of patients . So here two cases add another specific cause for UR, giving a method to prevent UR especially in patients with acute abdominal or flank pain prior to urinary tract symptom. Ureteral dissection is a transient process before ureteral rupture happens, it is just the short time that worthy considering diagnosis of UR so that proper treatment can be taken in expeditious manner.