Research Article: Impact of Residual Fragments following Endourological Treatments in Renal Stones

Date Published: July 5, 2012

Publisher: Hindawi Publishing Corporation

Author(s): Cenk Acar, Cag Cal.


Today, shock wave lithotripsy (SWL), percutaneous nephrolithotomy (PCNL), and flexible ureterorenoscopy (URS) are the most widely used modalities for the management of renal stones. In earlier series, treatment success of renal calculi assessed with KUB radiography, ultrasound, or intravenous pyelography which are less sensitive than CT that leads to be diversity of study results in reporting outcome. Residual fragments (RFs) after interventional therapies may cause pain, infection, or obstruction. The size and location of RFs following SWL and PCNL are the major predictors for clinical significant symptoms and stone events requiring intervention. There is no consensus regarding schedule for followup of SWL, PCNL, and flexible URS. Active monitoring can be recommended when the stones become symptomatic, increase in size, or need intervention. RFs <4 mm after SWL and <2 mm after PCNL and flexible URS could be actively monitored on an annual basis with CT. Early repeat SWL and second-look endoscopy are recommended after primary SWL and PCNL, respectively. There is insufficient data for flexible URS, but RFs can be easily treated with repeat URS. Finally, medical therapy should be tailored based on the stone analysis and metabolic workup that may be helpful to prevent regrowth of the RFs.

Partial Text

Urolithiasis is a common disorder, affecting 3% to 5% of the population in industrialized countries and gradually increasing all around the world [1, 2]. Today, shock wave lithotripsy (SWL), percutaneous nephrolithotomy (PCNL), and flexible ureteroscopy (URS) are widely used for renal stones. The overall success rates of SWL, PCNL, and URS in renal stones are 13.6–91.2% [3–5], 40–90% [6], and 34–92.2% [7, 8] in different studies, respectively. The success of these treatments also accepted free-of-stone rates in a radiologic studies such as kidney ureter bladder (KUB) radiography, ultrasonography (US), and abdominal computerized tomography (CT). CT is certainly the most sensitive method for assessing residual stones. Although CT detects stone fragments down to 1 mm in all subtypes of stones (radiolucent uric acid or cystine calculi as well as calcium-containing stones), the clinical value of being able to detect very small fragments remains debatable [9]. Besides, detecting negligible RF with CT is time-consuming and expensive. Although the renal stone protocol on newer multidetector scanners has been widely used, they lead to expose 25–50-fold higher doses of radiation than KUB radiography [10]. The advantages of ultrasound are providing comparable precision and detecting stones down to a diameter of 2 mm [11]. The clinicians suggested that evaluation of asymptomatic patients after SWL could be limited to routine radiologic studies such as KUB radiography and US [11–14].

In recent literature, several studies evaluated the fate of RFs after SWL [11–14, 18]. Spontaneous stone passage was found in 13.6% to 51.3% of the patients with mean followup between 15 and 57 months. Stone size remained stable in 17.3% to 52.6% of the patients, while stone regrowth was encountered in 21.4% to 69%. El-Nahas et al. reported that 52 (33.7%) of 154 patients had significant clinical stone event that need further intervention (mostly SWL) [18]. Osman et al. noted that 21.4% of the residual stone led to stone recurrence and need for retreatment [14]. The spontaneous clearance rate was affected by location of RF. The highest rates are seen in the ureter. In addition, many investigators emphasized that RFs are commonly localized to lower-pole calyces after SWL wherever treated in the kidney [5]. In a review, the authors concluded that 25% of the patients with CIRF will become stone-free, 50% will remain symptom-free, 20% will experience a clinically significant stone episode, and 4% to 25% of patients will need a secondary intervention, especially SWL [16]. According to this prediction, auxiliary endoscopic intervention should be considered as overtreatment in asymptomatic patients [16]. In a recent systematic review, the natural history and clinical significance of small and asymptomatic RFs after SWL were extensively discussed with data of four studies. Totally 463 patients with CIRF (<5 mm in diameter) were followed with a period of 15 months to 4.9 years. The stone-free rates were 23.8% to 78.9% and 10.7% to 41.9% of the stones remained stable. The stone size increased in 2% to 58.6% of the patients. Between 41.4% and 100% of the patients were asymptomatic while up to 58.6% had a symptomatic episode or needed intervention with a mean followup at 15 to 57 months after SWL [19]. Percutaneous nephrolithotomy is an effective minimally invasive procedure that is preformed for treatment of large and complex calculi [21]. Altunrende et al. investigated the medium-term outcome of CIRFs. They also measured 24-hour urine metabolic analysis. After PCNL, 38 patients with CIRFs followed periodically in a median time of 28.4 months. Ten (26.3%) patients had symptomatic episode that need medical therapy. The RF size was stable or decreased in 27 (71.1%) cases whilst increased in 8 (21.1%) patients. Spontaneous stone rate was 7.9% in medium term of followup. They concluded that the progression could be seen in 2-year followup, whereas presence of risk factors on 24-hour urine metabolic analysis could not predict growth of RFs [22]. Ganpule and Desai retrospectively examined in 187 patients to evaluate the fate of residual stones after PCNL [23]. 57.7% of RF was located in the lower calix, and the mean size of RF was 38.6 ± 52 mm2. Fourty-five percent of the patients were stone-free without intervention at a mean followup of 24 months. Most of the stones (65.47%) spontaneously passed in 3 months. Small RFs (<25 mm2) in renal pelvis had best clearance rate. In addition, a history of previous intervention, renal failure, metabolic abnormalities such as hyperuraecemia and hypercalciuria, size of RF, and experience of surgeon affected the fate of RF after PCNL in multivariate analysis. Raman et al. prospectively evaluated 42 patients with RF after PCNL with a median followup of 41 months [24]. They performed abdominal CT to determine the RF and classify the RF by using cut-off size as 2 mm. Sixty percent of RF was 2 mm or smaller and 79% was <5 mm. The location of RF was 47% lower, 32% middle, 24% upper pole, and 18% renal pelvis/ureter. Forty-three percent of patients experienced a stone-related event with a median time to occurrence at 32 months. Of these patients, 61% underwent auxiliary procedures such as URS, PCNL, SWL, nephrectomy, and double-J stent placement, but mostly URS. They calculated the estimated 3- and 5-year event-free probabilities were 74% and 48%, respectively. On multivariate analysis, a maximum RF size >2 mm and location in the renal pelvis or ureter independently predicted a stone-related event. The probability of needing a second surgical procedure correlated with RF size. Eight percent of patients with RFs <2 mm underwent surgical retreatment compared with 53% of patients with RFs >2 mm. These results indicate that patients with RFs >2 mm or fragments located in the renal pelvis or ureter should be treated immediately. On the other hand, some authors evaluated cost comparison of immediate second-look endoscopy against surveillance in post-PCNL RFs. They concluded that second-look endoscopy is cost advantageous in the patients with RF >4 mm following PCNL which generally leads to stone event [25].

Owing to technological advances, flexible URS has expanded its indications to include the stones in kidney [26]. The indication of flexible URS for renal stones is the stones less than 15 mm which do not respond to SWL [27]. The one of the advantages of flexible URS is the possibility of treating renal and ureteral stones in the same patient in a single session. In early series, treatment success of renal calculi was assessed with KUB radiography, US, or intravenous pyelography which are less sensitive than CT that leads to be diversity of study results. Breda et al. evaluated 51 patients with 161 renal stones (mean stone size of 6.6 mm) and they found the overall stone-free rate after single and second procedures was 64.7% and 92.2%, respectively [8]. In a different study, Perlmutter et al. evaluated the impact of stone location on success rates of flexible URS [28]. A total of 86 renal stones were treated, and the stone-free rates for upper-, middle-, and lower-caliceal stones were 100%, 95.8%, and 90.9%, respectively. They concluded that stone location does not significantly affect stone clearance rates. In a prospective randomized trial, Pearle et al. compared SWL (32 patients) and URS (35 patients) for lower-pole caliceal stones of 1 cm or less [29]. The stone-free rates of SWL and flexible URS were 35% and 50%, respectively. They concluded that there was a statistically insignificant difference in stone-free rates between SWL and URS for the treatment of small lower-pole renal calculi. However, SWL was associated with greater patient acceptance and shorter convalescence. Tanriverdi et al. evaluated the stone-free rate of flexible URS in renal calculi by classifying the RFs as the largest single fragment <2 mm, <4 mm, and >4 mm in CT [30]. The success rates were 50.4%, 62.8%, and 84.1% in stone-free, CIRF <2 mm and CIRF <4 mm, respectively. Several authors discussed medical therapy in the management of RFs after SWL or PCNL [32–36]. Fine et al. evaluated 80 patients to determine the effect of medical therapy in a retrospective study. Patients who received medical therapy had significant decrease in the stone-formation rate from a median of 1.17 to 0.00 stones per patient per year while the patients who did not receive medical therapy had a minimal decrease from a median of 1.33 to 0.77 stones per patient per year. The medically treated patients had a significantly greater stone remission rate (63.9% versus 23.1%) and lower stone burden increase (27.8% versus 61.6%) than the untreated patients. Regarding patients with CIRF, 16% of medically treated patients had fragment regrowth compared with 54.5% of the untreated patients. The authors concluded that medical therapy may alleviate stone regrowth in patients with residual stone fragments after SWL [33]. Cicerello et al. evaluated the effect of alkaline citrate therapy in patients with RF <5 mm [32]. In up to 74% of calcium oxalate patients and in up to 86% of infection stone patients, the RFs became undetectable in 1 year of followup. The undetectable RF rates of the patients were 32% and 40% in the control group for calcium oxalate and infection stones, respectively. RF regrowth rate decreased 47% to 5% in calcium oxalate patients with medical treatment. No significant difference was found for infection stones [32]. Similarly, Soygür et al. reported that among the patients with lower-pole RFs after SWL, the patients who were receiving citrate therapy showed a significantly higher stone fragment-disappearance rate (45.5% versus 12.5%) and less stone recurrence rate (56.6% versus 87.5%) compared with the control group at 12 months of followup [36]. Kang et al. evaluated the effect of medical therapy management in patients with RFs following PCNL. Patients receiving medical therapy had a lower median stone-free rate (0.02 versus 1.00 stones per patient per year) and a higher remission rate (77% versus 21%) compared with patients not receiving medical therapy. This result indicated that medical therapy can inhibit new stone formation or growth in patients with residual fragments after PCNL [34]. Afterwards, there is little evidence related to effectiveness of medical therapy in patients with RFs after flexible URS. Rebuck et al. speculated the high rate of stones remaining stable was related to medical therapy strategy in particularly lower-pole location [31]. The size and location of RFs following SWL and PCNL therapies are the major predictors for clinical significant symptoms and stone events which requiring intervention. RFs <4 mm after SWL and <2 mm after PCNL and flexible URS could be actively monitored on an annual basis with CT. Early repeat SWL and second-look endoscopy are recommended after primary SWL and PCNL, respectively. There is no sufficient data for flexible URS but RFs can be easily treated with repeat URS. Finally, medical therapy according stone analysis and metabolic workup might be helpful to prevent regrowth of the RFs.   Source: