The Natural History of Minimally Symptomatic Nonobstructing Calyceal Stones

* The primary aim is to study the natural history of single-calyx asymptomatic nonobstructing stone disease.
* The Secondary aim is to determine the predictors of the need for intervention and of cure in such population.

The prevalence and incidence of urolithiasis have been increasing worldwide. The prevalence of urinary stone disease in the U.S. had increased from 5.5% at 1994 to 8.8% at 2010. In most of the European and Asian countries, the prevalence is high. The risk of developing urolithiasis in adults appears to be higher in the western hemisphere than in the eastern hemisphere, although the highest risks have been reported in some Asian countries such as Saudi Arabia (20.1%).

Although many lines of treatment have been developed for this disease, none of these lines is completely satisfactory and many cases are still not easy to manage. The lines of treatment for renal stones include:

1. Open surgery: It includes nephrolithotomy and pyelolithotomy. Advances in endoscopic management of calculous disease promoted a rapid decrease in the use of this approach. The stone free rate (SFR) of open surgery is over 90%. Intraoperative complications, including bleeding requiring blood transfusion and pleural, vascular or ureteral injuries, represented about 37.8 %. Postoperative complications, including massive hematuria requiring blood transfusion, septicemia, urinary leakage and wound infection, were observed in 31.1%.
2. Percutaneous nephrolithotripsy (PCNL): It offers direct removal of stone fragments through the nephrostomy tract. The SFR is up to 95%. Complications such as extravasation (7.2%), blood transfusion (11.2-17.5%) or post-operative fever (21-32.1%) are common. However, severe complications are rare, e.g., urosepsis (0.3-4.7%), perforation of the colon (0.2-0.8%) or pleura (0.0-3.1%).
3. Retrograde intra-renal surgery (RIRS): With the advance in flexible ureteroscopic instrumentation and laser, the ability to access and treat intra-renal calculi has been improved \[9\]. SFR ranges between 90.9 and 93.3%. Intraoperative complications include mucosal injuries (1.5%), ureteral perforation (1.7%), significant bleeding (0.1%) and ureteral avulsion (0.1%). Post-operative complications include fever or urosepsis (1.1%), persistent hematuria (2%), renal colic (2.2%), transient vesico-ureteral reflux (4.6%), persistent vesico-ureteral reflux (0.1%) and ureteric stricture (0.1%).
4. Extracorporeal shockwave lithotripsy (ESWL): Unlike more invasive urological modalities, ESWL does not remove stones as a whole; it disintegrates them into fragments of various sizes, and these fragments must pass out of the urinary tract spontaneously \[11\]. The SFR depends on stone location, size and composition \[10\]. It ranges from 45-98%. Complications include steinstrasse (4-7%), re-growth of residual stones (21-59%), renal colic (2-4%), sepsis (1-2.7%), symptomatic hematoma (\<1%), asymptomatic hematoma (4%) and arrhythmia (11-59%).
5. Pharmacological treatement.
6. Active surveillance.

The financial burden on the U.S. health care system for urolithiasis alone costs more than $2 billion yearly. Naturally, the economic burden has a greater impact on developing countries.

The prevalence of urolithiasis in asymptomatic adults was 7.8% using low-dose non-contrast computed tomography according to a study in Wisconsin, U.S. The investigators could not find a study reporting the prevalence of asymptomatic nonobstructing calyceal stones although they encounter these cases frequently in the practice.

Single calyceal stones may present as a de novo finding, or they may be residual after PCNL, RIRS, ESWL or open surgery. Accordingly, many cases have scarring from previous surgery and/or have previous failed attempts at ESWL, so options of management are usually limited in these cases.

Research hypothesis: Substantial proportions of patients with asymptomatic nonobstructing calyceal stone(s) will not be complicated and does not require active treatment.

Eligibility Criteria:
Inclusion Criteria:

* Cases older than 18 years with renal stone disease affecting no more than one major calyx and causing neither obstruction nor bothersome pain.
* We define calyceal obstruction as calyceal dilatation with stone impaction at the calyceal neck.
* If the stones are not impacted or are casting the calyx, they are not considered obstructing.

Exclusion Criteria:

1. Gross or microscopic hematuria.
2. Patients who have difficulty to reach our tertiary center for follow-up.
3. Other pathology in the target uretero-renal unit that requires intervention, e.g., ureteropelvic junction obstruction, malignancies, ureteric stones, ...etc.
4. History of recurrent urinary tract infection.