A Retrospective Analysis of Effect of Hounsfield Unit of Ureteric Calculus on Outcome of Ureteroscopic Lithotripsy

Author(s): Jayaprakasha Gangadharaiah1, N. Imdad Ali2, Paresh Sankhe3

This study was conducted to check whether computer tomography (CT) parameter
Hounsfield Unit has any bearing on outcome of ureteroscopic pneumatic lithotripsy
and as to whether it can predict success rate of ureteroscopic lithotripsy in the
management of ureteric calculus. CT Hounsfield Unit tells us about hardness of
stone, and it is primarily important in non-invasive management of ureteric and
renal calculus such as extracorporeal shock wave lithotripsy (ESWL).
We retrospectively reviewed records of 420 patients who underwent URSL from
January 2016 to January 2020. A total of 186 patients of ureteric calculus did
undergo CT in pre-operative evaluation for stone. Data of those patients was taken
for study. Intra op clearance of calculus was decided by ureteroscopy finding on
the table. All complications and difficulties of the procedure were documented.
We analysed the correlation between the outcome of the URSL and Hounsfield
unit in finding the position of the stone and size of the stone. Out of 186 study
participants, 111 (59.6 %) patients needed a single procedure for stone clearance
whereas 75 (40.4 %) needed multiple procedures for clearance. Out of 186, 22
had HU < 500, 112 had HU 501 - 1000, 52 had HU > 1000. The majority of
patients had HU between 501 - 1000HU. Complete clearance was seen in 63.6 %
of < 500 HU patients, 62.5 % of 501 - 1000 HU patients and 55.7 % of > 1000
HU patients. This difference in clearance was statistically not significant. Similarly,
the rate of complication when compared among the three groups doesn’t show a
statistically significant difference (P value 0.293). The requirement of repeat
procedure was maximum in > 1000 HU patients but the difference between the
three groups was not statistically significant. Stone migration rate was found to be
more in > 1000 HU stones (80.76 %) and this was statistically significant.
To conclude CT Hounsfield Unit’s utility in predicting the stone-free rate and
complication rate doesn’t show significant bearing in patient undergoing URSL