Category: Clinical Stones: SWL

MP31-20 - Prediction of success rate of shock wave lithotripsy using mean stone density¬ , stone heterogeneity index and Mean stone density-Stone heterogeneity index ratio in different sizes of upper tract stones.

Sun, Sep 23
2:00 PM - 4:00 PM

Introduction & Objective :

Mean stone density is the mean of HU while SHI is the defined as standard deviation of a HU on non-contrast computed tomography (NCCT).We tried to assess the role of SHI and HU-SHI ratio in determining impact on stone free rates.


Methods :

We reviewed charts of 1336 patients out of which 213 patients were included in study as their NCCT was available for the study. They had underwent first session of SWL from 2012 till 2017.152 (71.36%) patients had renal stones while 61 (28.63%) patients had ureteric stones. Variables for patients such as age, sex, location stone, mean stone size, HU, SHI, SSD, and SHI were recorded in performa from NCCT. Shock waves were delivered by using third generation Electromagnetic lithotripter. Stone free rate was defined as less than 4 mm of stone fragments on follow up X-Ray KUB after 4 weeks of the first SWL session.


Results : Mean age was 45.3±14.6 years. There were 157 (73.8%) males and 56 (26.2%) female patients. Total of 135 (63.3%) patients were stone free after one session while 78 (36.6%) patients had failed SWL procedure. Mean stone HU was 595±291 and 800±333 HU in stone free and failure groups having stone size less than 1 cm (P=0.04). While SHI values were 208±104 and 221±99 HU in the stone free and failure groups (P=0.05) having stone size less than 1 cm. SSD was significant between stone free and failure groups (10.1 vs 9.2 cm; P=0.02) for all stone sizes. On further analysis it was found that in stone size more than 1 cm the impact of SHI was significant as it was 430±58 HU and 201±53 in the stone free and failure groups (P=0.01). HU-SHI ratio was more in stone free group having stone size larger than 1 cm (P=0.04).


Conclusions :

The mean stone Hounsfield units and Skin to stone distance was significantly related to the stone free rates. While SHI was having more impact in stones size more than 1cm despite having relatively greater mean Hounsfield’s units.HU-SHI ratio was more correlated to stone free rates in stone size more than 1 cm.

Nadeem Iqbal

Resident/fellow urology
Shifa International hospital,PKLI
Islamabad, Islamabad, Pakistan

M. Umar Alam

Consultant urology
Shifa International hospital,PKI
Islamabad, Islamabad, Pakistan

Saeed Akhter

professor and Head department
Shifa International hospital,PKI
Islamabad, Islamabad, Pakistan