【Introduction】
Due to the special anatomical structure of the lower calyx of the kidney and the poor drainage dynamics of the lower calyx, the treatment of lower calyx stones has always been a unique challenge in urological endoscopic treatment. The foot of the funnel part of the lower calyx, the longer funnel part, and the smaller funnel renal angle are common factors that hinder the spontaneous expulsion of fragments after stone fragmentation, thereby resulting in unstable treatment outcomes.

Due to the special anatomical structure of the lower calyx of the kidney and the poor drainage dynamics of the lower calyx, the treatment of lower calyx stones has always been a unique challenge in urological endoscopic treatment. The foot of the funnel part of the lower calyx, the longer funnel part, and the smaller funnel renal angle are common factors that hinder the spontaneous expulsion of fragments after stone fragmentation, thereby resulting in unstable treatment outcomes.

Source:Al-Rawashdah S. RIRS vs PCNL in treating lower-pole renal stones: a comparative clinical outcome study. Future Sci OA. 2026 Dec;12(1):2646277.doi: 10.1080/20565623.2026.2646277. Epub 2026 Mar 27. PMID: 41891547; PMCID: PMC13034623.


【Materials and Methods】
Included Subjects:

A total of 177 adult patients were included, all of whom had isolated renal lower calyx calculi of 1–2 cm in size. The initial treatment was either RIRS or PCNL, and imaging follow-up was completed 3 months after the operation. 

Grouping situation:

RIRS group: 85 cases

PCNL group: 92 cases

Exclusion criteria: Multiple calculi, biconical calculi, active urinary tract infection, coagulation disorders, anatomical abnormalities, pregnant patients.

Surgical Methods:

RIRS group: Utilized钬YAG laser lithotripsy, selectively placed ureteral sheath, mainly performed powderized lithotripsy, and when necessary， used basket to remove stones. Routine placement of double-J stent after the operation.

PCNL group： Established a 16–20 Fr minimally invasive percutaneous channel under ultrasound/fluoroscopy guidance， performed laser or pneumatic lithotripsy， followed by irrigation and forceps removal of stones. Left a nephrostomy tube according to the intraoperative situation.

Observation Indicators:

Baseline data, stone and anatomical parameters, operation time, fluoroscopy time, postoperative pain, decrease in hemoglobin level, length of hospital stay, perioperative complications (Clavien-Dindo classification), 3-month stone clearance rate, re-intervention and re-admission situation.

Statistical Methods:

The analysis was conducted using SPSS. A p-value less than 0.05 was considered statistically significant. There were no statistically significant differences in baseline demographic data, stone size, density, and renal calyx anatomical parameters between the two groups. The groups were comparable.

【Results】

Intraoperative and early recovery: RIRS is superior overall

Compared to PCNL, RIRS has significant advantages in minimally invasive aspects (all p < 0.001):

The operation time is shorter (72.4 vs 96.1 min)

The intraoperative fluoroscopy exposure is less (44.1 vs 98.7 s)

Postoperative pain is less severe (VAS 3.2 vs 5.7)

There is less bleeding and a smaller decrease in hemoglobin (0.7 vs 2.0 g/dL)

The hospital stay is significantly shorter (1.4 vs 3.9 d)

Clear stone efficacy: PCNL is significantly superior

Postoperative 3-month NCCT re-examination results:

The clear stone rate in the PCNL group was 93.5%, significantly higher than that in the RIRS group (78.8%, p = 0.01);

The proportion of residual small stones (< 4 mm) in the RIRS group was higher, and the rates of secondary auxiliary surgery and re-intervention were significantly higher, indicating some incomplete stone clearance and the need for a second stage treatment.

Complications and safety: RIRS has a lower risk

Overall complication rate: PCNL 39.1% vs RIRS 16.5% (p=0.002)

The PCNL group had significantly higher rates of adverse events:

Higher rates of postoperative fever and urinary tract infections

Significantly higher blood transfusion rate (12.0% vs 0)

More severe complications (Clavien-Dindo ≥Ⅲ grade) occurred (10.9% vs 1.2%)

Higher 30-day readmission rate (13.0% vs 3.5%)

【Discussion】

Core trade-off: PCNL focuses on "stone removal", while RIRS focuses on "safety"

For 1–2 cm renal calyx stones, the two mainstream minimally invasive surgical techniques have formed a clear clinical trade-off relationship:

PCNL, with its direct percutaneous approach, can thoroughly handle renal calyx stones under direct vision, without being limited by funnel angles or narrow anatomical structures, achieving a high one-time stone clearance rate and significantly reducing the risk of stone residue. However, the invasive puncture channel brings a series of perioperative burdens such as bleeding, infection, pain, and prolonged hospital stay, with significantly higher risks of severe complications and re-admission.

RIRS, operating through natural cavities, without renal puncture damage, has excellent perioperative safety, quick postoperative recovery, and almost no need for blood transfusion, making it suitable for patients with poor tolerance to trauma and a preference for rapid recovery. However, due to the anatomical limitations of the renal calyx, stone fragmentation and expulsion are difficult, and the incidence of residual fragments is high, leading to a significant increase in the rate of secondary auxiliary surgeries and re-interventions.

The changes in prospects brought about by technological advancements

In recent years, new technologies such as flexible ureteroscopy, high-power holmium laser, and negative pressure suction sheaths have been introduced. These technologies can effectively reduce the pressure within the kidney and actively suction out the stone fragments, gradually overcoming the shortcomings of traditional RIRS in dealing with lower calyx stones. In the future, it is expected that the stone clearance rate gap between RIRS and PCNL will be narrowed.

Clinical decision-making logic

For renal calyx stones less than 1-2 cm in size, they fall under the "intermediate gray indication" category. There is no absolutely optimal surgical approach. Decisions must be made on an individual basis: If one desires a single stone removal and to eliminate residual recurrence, PCNL should be prioritized; if one seeks minimally invasive safety, rapid recovery, and reduced complications, RIRS should be the preferred option.

【Final Conclusion】

For isolated stones in the lower calyx of the kidney with a diameter of 1–2 cm:

PCNL: The stone clearance rate is higher in one session, there is less residual stone, and the cure effect is better. However, the perioperative complications, bleeding, severe adverse events, and the risk of re-admission are higher, and the trauma is greater, with a slower recovery.

RIRS: It has significant advantages in minimally invasive surgery. The pain is mild, the bleeding is less, the hospital stay is shorter, and the overall safety is higher. However, the stone clearance rate is lower, and the risks of secondary intervention and auxiliary surgery are higher.

Clinical recommendation: The treatment plan should be individualized. It should be based on the patient's renal anatomical morphology, stone characteristics, underlying comorbidities, and personal wishes. A reasonable balance should be struck between "complete stone clearance" and "surgical safety and rapid recovery".