Case 23 -  Renal obstruction without IV conrast

This patient has an obstructed right kidney.  This is a non contrast exam so you have no information about the nephrogram.  However, there is right sided hydronephrosis.  Both the renal pelvis and calyces are dilated.  There is perinephric stranding and also a small amount of peripelvic stranding.  There is hydroureter.   Stranding around the ureter can be caused by inflammation from a passing stone.  A large stone is seen in the bladder at the UVJ.  There is bladder wall edema around the stone.  The stone is embedded in this edema.  It does not fall dependently in the bladder.   A second, larger, bladder stone is seen in the dependent portion of the bladder.

You should have noticed that the scans for renal stones are done in the prone position.  If you did not notice this look again at the orientation of the air fluid levels on this scan and on the scan from Case 22.  The fluid is anterior.  The patient is prone and the images have been rotated.  Scanning prone helps facilitate contrast emptying of the renal pelvis.  Is also allows you to evaluate for bladder wall edema.  If a UVJ stone stays at the UVJ then it is stuck in edematous bladder wall.  It is still obstructing the ureter.

The urologists always want to know the size of the stones you see.  If less than 4 mm they usually do not intervene.  If greater than 4 mm they will decide based on the clinical condition.

There are also punctate non-obstructing stones in the left kidney.  This is important because after passing the symptomatic stone the patient may have recurrent episodes of pain when the other stones pass.

This patient has a large prostate that projects into the bladder medial to the UVJ.  This may contribute to the difficulty in passing this stone.

Take home point

• Scans are performed prone.  A stone at the UVJ is stuck in an edematous bladder wall.
• On non contrast scans findings of renal obstruction include hydronephrosis, perirenal and peripelvic stranding, and hydroureter.