Detecting residual stone fragments on KUB CT post ESWL & DJ Stenting

   Detecting residual stone fragments post ESWL & DJ Stenting   

Fig. 1 a/b/c/d (left to right in serial)

Fig: 1a, in axial plane in bone window shows two densities. Red arrow is stone. Fig 1b in coronal oblique plane shows the stone fragment as a bump (red arrow), breaking the smooth contour. Fig 1c in 3D VRT shows the calculus (black arrow). Fig. 1d, is a different patient, zoomed image. The stent is red in color and the stone fragment is blue in color (red arrow)

Post ESWL, stone fragments may remain in the collecting system and ureter. 

Quite often these are seen along the DJ Stent. 

Since,  these are fragments with low HU value and not well formed like calculus, they get camouflaged with the density of stent. 

How to visualize:

1. See in the bone window in axial and coronal planes. The stent is usually denser than the stone fragments

2. See in 3D VRT - look for any bumps along the stent margins

2. Do dual energy scan - Usually the stent appears red and the stone appears blue if composed of calcium

Fig. 2 a/b/c/d (left to right in serial)

Fig: 2a: Thin MIP in oblique coro plane in soft tissue window shows local bulge on the lateral aspect of the stent and is of same density (white arrow). Fig 2b: Thin MIP in oblique coro plane in bone window, shows the local bulge on the lateral aspect of the stent to be a residual stone  (white arrow), with different density as compared to the stent. 

Fig 2c: Axial plane in soft tissue window shows stent  (white arrow). Fig 2d: Axial plane in  bone window, at the same level as 2b, shows the local bulge on the lateral aspect of the stent to be a residual stone  (white arrow), with different density as compared to the stent. 

Prepared by Dr. Sharad Maheshwari

27.10.2022

Updated: 01.11.2022