In this study, we used US and KUB radiographs for detecting stones in patients. The use of US alone for stone detection yields a sensitivity of 78.9% and a specificity of 83.7%. In comparison, the combined use of US and KUB radiographs has a sensitivity of 89.9% [11, 12].
US done by a single operator, Stone detected by ultrasound depend on presence of acoustic shadow, stone ≤ 5 mm does not produce shadow [13].
Fifty-eight (90.4%) small stones were found to be single and 60.3% stones were mid calyceal in this study. Forty-one (78.8%) patients had flank pain for at least 3 months; five pelvic stones were obstructive stones, while the others were non-obstructive. The reason for flank pain is not fully elucidated, but the pain subsided with ESWL.
Relief of pain after ESWL of non-obstructive renal stones might be multifactorial including stone-free status, the analgesic effect of shock wave on tissue “shock wave application can induce nerve fiber degeneration” [14]. Long-standing flank pain associated with small renal stones and no obvious obstruction is called small stone painful syndrome [8]. The rationale for treating small symptomatic and asymptomatic calculi by ESWL is to relive pain rapidly compared to the expectant therapy. Moreover, ESWL prevents the complications of hematuria, infection or stone growth and reduces the need for more invasive procedures with potentially higher morbidity [7, 9].
In our study, the stone-free rate was 77.6%. In comparison, Gürbuz et al. reported 92.5% stone-free rate and found no statistical difference between ESWL and F-URS for treating small renal pelvic stones less than 10 mm in diameter [6].
The right-sided stones exhibited statistically significant stone-free rate n.26 (89.7%) P value 0.028 compared to the other side, as the right kidney inherent better image on ultrasound as the presence acoustic window of liver, consequently more precise targeting of stone in case of non-opaque stone, also less movement of right kidney in comparison to the left lead to better hit rate, in addition gas in the left colon might reduce efficiency of ESWL on left side. [15].
In this study, ESWL either fragmented the stones (31 stone) or served as a pushing force. A total of 7 stones were migrated down the ureter after ESWL; in these cases, the shock waves played as a pushing force rather than the fragmentation role.
This propulsive effect of ESWL is similar to other techniques were used like “focused ultrasound vibration or using external physical vibration Lithecbole” to enhance stone migration or what’s called stone relocation [3, 16].
Eleven patients (21.2%) exhibited asymptomatic renal stones that were treated by ESWL, and six of them became stone-free.
In many series, the surgical intervention required in asymptomatic calyceal stones that ranged 19–25% [17, 18].
A previous study performed 4 year mean follow-up of 293 patients to evaluate the natural history of asymptomatic renal calculi and reported that ESWL was the primary therapy in 33 patients and ureteroscopy in 3 patients [19].
Thirteen stones of studied group failed to respond to ESWL. Since stone response to ESWL cannot be predicted accurately, asymptomatic patients are offered the options of RIRS or observation. Some of the advantages of ESWL include shorter operative time and hospital stay in comparison to RIRS [20].
The need for long-term follow-up for asymptomatic calyceal stones and the finding that painless silent hydronephrosis developed in 2% of patients raise concern and mandate active treatment rather than the wait-and-see approach [17].
The EAU 2018 guidelines recommend the treatment of renal stones in patients with stone growth (> 5 mm) based on de novo obstruction, patient preference, social situation (professional or traveling), solitary kidneys, women planning on getting pregnant and in patients with chronic pain [21].
Prophylactic ESWL in asymptomatic renal calyceal stones, as reported by Keeleys et al., exhibited no advantages for patients in terms of stone‐free rate, quality of life. However, the authors included only opaque lower calyceal stones that were within 15 mm in size [7].
In brief, we recommend using KUB radiography to ascertain whether the stones are opaque or lucent to help in decision of therapy. Symptomatic small renal stones visualized by KUB radiograph the role of empiric are limited.
Finally, modifying the technique and involving urologist actively in lithotripsy unit can improve ESWL outcome. ESWL will keep its role as the single noninvasive treatment in small stone management [22].
The limitation of this study is that two lithotripters with different mechanisms of stone fragmentation were used.
