Intraoperative X-Ray Guidance for Endourological Stone Surgery: Fluoroscopic Workflow, Radiation Dose Optimization, and Emerging Image-Guided Technologies

Abstract

Endourological stone surgery frequently relies on intraoperative X-ray fluoroscopy for guidewire and access sheath placement, retrograde pyelography, stent positioning, and percutaneous renal access. Although radiation exposure from an uncomplicated procedure is usually limited, recurrent imaging and interventions contribute to cumulative patient exposure, and repeated procedures result in occupational exposure among operating-room personnel. This narrative review examines fluoroscopic workflows in ureteroscopy, retrograde intrarenal surgery, percutaneous nephrolithotomy, and endoscopic combined intrarenal surgery, with particular emphasis on dose metrics, determinants of exposure, and practical optimization. Readily implementable measures consistent with the as-low-as-reasonably-achievable (ALARA) principle include low-dose and pulsed fluoroscopy, reduced pulse rates, collimation, last-image hold, optimized C-arm geometry, protective equipment, dosimetry, feedback, and team training. Evidence also supports fluoroscopy-free or fluoroscopy-minimized ureteroscopy and retrograde intrarenal surgery in selected patients, as well as ultrasound-guided percutaneous nephrolithotomy, including hybrid ultrasound-fluoroscopy workflows. Endoscopically assisted puncture, three-dimensional reconstruction, image fusion, navigation, augmented reality, and computer vision span different stages of clinical maturity; AI-assisted dose optimization remains experimental and lacks endourology-specific clinical validation. Standardized multidimensional reporting of patient and staff dosimetry, evidence-based technology classification, and procedure- and complexity-specific benchmarks are needed. Prospective multicenter studies should evaluate integrated image-guided workflows using clinically relevant outcomes, including radiation dose, stone-free outcomes, complications, operative time, usability, and cost.

1. Introduction

Urolithiasis is a recurrent condition that often requires repeated imaging, surveillance, and intervention. Modern endourological stone surgery has shifted much of stone management away from open or highly invasive procedures toward ureteroscopy (URS), flexible ureteroscopy or retrograde intrarenal surgery (RIRS), percutaneous nephrolithotomy (PCNL), and endoscopic combined intrarenal surgery (ECIRS). Contemporary guidelines from the European Association of Urology (EAU) and the American Urological Association continue to identify these procedures as central components of surgical stone management [1,2,3].

Intraoperative imaging is integral to these procedures. Among the available modalities, X-ray fluoroscopy remains widely accessible, rapidly interpretable, and closely integrated into endourological workflows. It may be used to confirm the positions of guidewires, catheters, ureteral access sheaths, puncture needles, dilators, nephrostomy sheaths, stents, and radiopaque stones. Fluoroscopy also provides an external spatial reference when endoscopic visualization is confined to the lumen or collecting system and tactile information is indirect.

The same imaging modality that facilitates endourological surgery also creates an obligation to optimize radiation safety. Fluoroscopy exposes patients to ionizing radiation and surgeons and operating-room staff to scatter radiation. Although the dose associated with an uncomplicated URS or RIRS procedure is often limited, stone disease frequently recurs, and patients may undergo repeated non-contrast computed tomography (CT), plain radiography, fluoroscopic procedures, and additional interventions over many years. Endourologists and other operating-room personnel may likewise accumulate occupational exposure across numerous procedures.

International radiation-protection recommendations specify an occupational effective-dose limit of 20 mSv per year averaged over defined 5-year periods, provided that the effective dose does not exceed 50 mSv in any single year [4]. For the lens of the eye, the recommended occupational equivalent-dose limit is 20 mSv per year averaged over 5 years, with no single year exceeding 50 mSv [5].

The EAU Urolithiasis Guideline explicitly addresses radiation exposure during endourology. It recommends departmental radiation-protection protocols, adherence to the as-low-as-reasonably-achievable (ALARA) principle, measurement and reporting of fluoroscopy time, dosimeter use, low-dose and pulsed fluoroscopy, collimation, last-image hold, avoidance of unnecessary digital acquisition, protective garments and eyewear, and appropriate positioning of the surgeon and C-arm [1]. The goal is not to eliminate fluoroscopy from every procedure, but to use it deliberately, quantify exposure accurately, reduce avoidable imaging, and incorporate alternative guidance when appropriate.

A further challenge concerns dose measurement. Fluoroscopy time is easy to record and is commonly reported in urological studies, but it does not fully characterize patient dose. It does not account for dose rate, beam area, patient size, C-arm geometry, magnification, pulse rate, or digital acquisition. Medical-physics guidance emphasizes that fluoroscopy time, kerma–area product (KAP), cumulative air kerma, peak skin dose, and effective dose describe different aspects of exposure and are not interchangeable [6,7,8,9]. More comprehensive dosimetric reporting is therefore required in endourological research.

This review summarizes the clinical use of intraoperative X-ray guidance in endourological stone surgery, the interpretation of patient and occupational dose metrics, the determinants of radiation exposure, and practical ALARA-based strategies. It also examines fluoroscopy-free and fluoroscopy-minimized procedures, ultrasound-guided PCNL, endoscopically assisted puncture, three-dimensional reconstruction, image fusion, navigation, augmented reality, and computer-vision approaches. Unlike reviews focused primarily on radiation exposure or fluoroscopy-free techniques alone, this review maps procedure-specific fluoroscopic checkpoints in URS/RIRS, PCNL, and ECIRS and links those checkpoints to multidimensional dosimetry, practical dose reduction, and the clinical maturity of alternative image-guidance technologies.

2. Review Scope, Literature Search, and Study Selection

This narrative review was informed by literature searches of PubMed/MEDLINE, Scopus, and Web of Science from database inception through 30 July 2026. Search concepts combined terms related to urolithiasis and the procedures within scope (ureteroscopy, retrograde intrarenal surgery, percutaneous nephrolithotomy, and endoscopic combined intrarenal surgery) with terms related to fluoroscopy, radiation dose, occupational exposure, ultrasound guidance, image fusion, navigation, augmented reality, computer vision, and artificial intelligence. To improve reproducibility of the revised review, the database-specific search strategies and Boolean combinations used for the focused literature update are provided in Supplementary Table S1.

Eligible sources included English-language clinical guidelines, consensus or radiation-protection documents, systematic reviews and meta-analyses, randomized or prospective clinical studies, and other original human studies directly addressing intraoperative imaging, patient or staff dosimetry, radiation-reduction strategies, or clinically relevant image-guidance technologies. For emerging technologies with limited clinical evidence, selected technical, phantom, feasibility, or materials studies were also considered when directly relevant to intraoperative guidance or radiation reduction; these studies were explicitly identified as emerging or experimental in the evidence synthesis.

Studies focused exclusively on diagnostic imaging without perioperative relevance, non-stone procedures, or technologies without a plausible link to intraoperative guidance or radiation exposure were excluded. Shock-wave lithotripsy was outside the scope of this review because its fluoroscopic workflow and treatment process differ from endoscopic and percutaneous stone surgery.

Because this article was designed as a narrative rather than a systematic review, a PRISMA-style study-selection process and screening counts were not prespecified; retrospective counts were not presented because they could not be reconstructed reliably without implying a systematic-review methodology that was not used. No formal risk-of-bias assessment or quantitative synthesis was performed. The revised manuscript was structured with reference to the principles of the Scale for the Assessment of Narrative Review Articles (SANRA), with particular attention to transparency of the literature search, evidence weighting, referencing, and clinically relevant endpoint data [10].

3. Clinical Role of Intraoperative X-Ray Imaging

Intraoperative fluoroscopy serves several practical functions in endourological stone surgery. It provides an external spatial reference in a setting in which endoscopic visualization is confined to the lumen or collecting system, tactile feedback is indirect, and instrument position cannot always be determined from endoscopy alone. The need for fluoroscopy varies according to procedure type, stone location, patient anatomy, prior stenting, surgeon experience, and the availability of complementary imaging such as ultrasound.

In semirigid URS, fluoroscopy may be used to confirm guidewire passage beyond a stone, perform retrograde pyelography when the anatomy or degree of obstruction is uncertain, guide balloon dilation when required, and confirm ureteral stent position. For uncomplicated distal ureteral stones, experienced surgeons may substantially reduce or avoid fluoroscopy when guidewire passage, ureteroscopic advancement, stone fragmentation, and stent placement can be adequately confirmed by direct visualization and tactile feedback. Selective fluoroscopic confirmation remains appropriate when guidewire position is uncertain or when anatomy, obstruction, prior reconstruction, or procedural difficulty increases the consequences of malposition.

In flexible URS and RIRS, fluoroscopy may be used for retrograde pyelography, ureteral access sheath placement, assessment of collecting-system anatomy, and final stent positioning. Reduced-radiation and ultralow-dose protocols have demonstrated marked reductions in fluoroscopy time without increasing operative time or complications in selected procedures [11,12]. A prospective multicenter randomized trial subsequently evaluated a standardized fluoroscopy-free RIRS workflow in selected patients with renal stones measuring 20 mm or less [13]. Systematic reviews and meta-analyses have also reported broadly comparable stone-free and complication outcomes between fluoroscopy-free and conventional endourological procedures, although the evidence is derived largely from selected patients and experienced operators [14,15].

Fluoroscopy-guided PCNL commonly entails repeated imaging during collecting-system opacification, calyceal access, guidewire placement, tract dilation, sheath positioning, and assessment of residual radiopaque stones. The EAU guideline identifies PCNL as a stone intervention associated with comparatively high patient radiation exposure [1]. Nevertheless, the magnitude of exposure varies substantially according to case complexity, access technique, equipment settings, and operator practice.

ECIRS combines antegrade and retrograde approaches and may require the coordinated use and interpretation of fluoroscopic, endoscopic, and ultrasound information. Fluoroscopy can confirm retrograde catheter position, puncture trajectory, antegrade guidewire passage, tract dilation, and device location. Concurrent retrograde endoscopic visualization and ultrasound-assisted access may reduce the number of fluoroscopic checks. ECIRS therefore exemplifies the broader transition from fluoroscopy-dependent surgery to multimodal image-guided surgery. The procedure-specific fluoroscopic workflow is illustrated in Figure 1.

4. Radiation Dose Metrics and Determinants

Fluoroscopy time has traditionally been the principal radiation metric reported in endourology. It is simple, widely available, and useful for quality improvement because it reflects an operator behavior that can be modified directly. Nevertheless, fluoroscopy time is not a measure of dose. A brief exposure at a high dose rate, with a large field, magnification, unfavorable C-arm geometry, or a large patient, may deliver more radiation than a longer exposure obtained under optimized low-dose conditions. Conversely, identical fluoroscopy times may correspond to different patient and staff doses because of differences in beam collimation, pulse rate, source-to-skin distance, image-receptor position, and digital acquisition [6,7,8,9]. The principal dose metrics are summarized in

Table 1. Radiation dose metrics relevant to endourological stone surgery.

Dose Metric	Definition	Interpretation and Limitations	Recommended Reporting or Use
Fluoroscopy time (s or min)	Total duration for which fluoroscopy is active	Simple and auditable; however, it does not account for dose rate, field size, pulse rate, patient size, geometry, magnification, or digital acquisition [6,7,8,9]	Report routinely, but not as the sole dose metric
Kerma-area product (KAP; historically DAP) (Gy·cm2)	Air kerma integrated over the irradiated field	Reflects X-ray output and field size; useful for population-level comparisons of stochastic risk, but not organ specific [6,7,8,9]	Patient-dose comparison and benchmarking
Cumulative air kerma (mGy or Gy)	Air kerma at the interventional reference point	Useful surrogate for potential skin dose; not equivalent to absorbed skin dose [6,7,9]	Report when available, especially for prolonged PCNL or ECIRS
Entrance skin dose (Gy)	Absorbed dose at the skin-entry site	Clinically intuitive, but requires direct measurement or model-based estimation	Consider in prolonged or high-dose procedures
Peak skin dose (Gy)	Highest absorbed dose to any skin region	Most relevant to deterministic skin injury; generally unavailable without dose mapping [6,9]	Dedicated dosimetry or unusually prolonged procedures
Effective dose (mSv)	Tissue-weighted estimate of whole-body stochastic risk	Allows approximate cross-procedure comparisons; calculated, population-based, and unsuitable for assessing deterministic effects [8]	Use only when a stated, validated conversion method is applied
Eye-lens equivalent dose (mSv)	Equivalent dose to the lens of the eye	Relevant to occupational cataract risk; strongly dependent on dosimeter placement [5,6]	Occupational studies using eye-level dosimetry
Extremity dose (mSv)	Equivalent dose to the hands or fingers	Relevant near the primary beam; ring dosimetry may not capture the maximally exposed finger	Consider in access-heavy PCNL or dedicated occupational studies
Staff whole-body dosimetry (mSv)	Occupational dose measured beneath or over protective garments	Supports longitudinal surveillance; inconsistent positioning reduces validity [1,4,5]	Specify dosimeter type, location, shielding, and monitoring interval

Abbreviations: DAP, dose-area product; ECIRS, endoscopic combined intrarenal surgery; KAP, kerma–area product; PCNL, percutaneous nephrolithotomy.

.

KAP, historically reported as dose–area product, represents the integral of air kerma across the irradiated beam area and reflects both X-ray output and field size. Cumulative air kerma is measured or calculated at a defined interventional reference point and is more closely related to the potential magnitude of skin dose, although it is not equivalent to the absorbed dose at the patient’s skin. Peak skin dose estimates the highest dose delivered to any region of skin and is most relevant to deterministic skin injury during prolonged fluoroscopically guided interventions. Effective dose applies tissue-weighting factors to provide a population-based estimate of whole-body stochastic risk; it is calculated rather than measured directly and should not be interpreted as a patient-specific absorbed dose [6,7,8,9].

Occupational dosimetry requires a distinct framework. Occupational exposure arises predominantly from radiation scattered by the patient. Dose is influenced by the operator’s position relative to the patient and X-ray source, C-arm orientation, distance from the scattering volume, shielding, procedural duration, and equipment settings. Dosimeters should be worn consistently, positioned according to institutional policy, and reviewed at predefined intervals. Studies should report whether dosimeters were worn beneath or over protective garments and whether eye-lens or extremity monitoring was performed [1,4,5,6].

The determinants of radiation exposure can be organized into patient-, procedure-, equipment-, and operator-related domains. In URS, longer operative duration and surgeon-specific practice were independently associated with fluoroscopy time, whereas stone size, multiplicity, radiolucency, preoperative stenting, and stone-free status were not associated with fluoroscopy time in that cohort [16]. Equipment-related determinants include dose mode, pulse rate, beam collimation, magnification, C-arm geometry, digital acquisition, and the use of last-image hold [1,6,7,8,9,17]. Structured radiation-safety training can reduce fluoroscopy time during resident-performed URS [18].

Body habitus warrants particular consideration because automatic exposure-control systems may increase X-ray output to maintain image quality in larger patients. During PCNL, ultrasound assistance reduced fluoroscopy time and radiation dose across body mass index groups, although successful ultrasound-guided access was less frequent in patients with obesity [19]. In a study of provider exposure during PCNL, stone burden, staghorn configuration, operative duration, and fluoroscopy duration were associated with greater exposure in univariable analyses, whereas fluoroscopy duration remained independently associated with attending-urologist exposure [20]. These findings support procedure- and operator-specific dose monitoring rather than reliance on a single universal fluoroscopy-time threshold.

The relationship among complementary dose metrics is summarized in Figure 2.

5. Patient Radiation Exposure

Patient exposure during endourological stone surgery is generally lower than that encountered during many prolonged interventional radiology or cardiovascular procedures, but it is not negligible. In patients with recurrent urolithiasis, cumulative exposure may arise across the entire care pathway, including diagnostic CT, emergency imaging, follow-up radiography, fluoroscopic intervention, and repeat procedures. Radiation safety should therefore be considered throughout the course of stone disease rather than within a single operation.

Quantitative comparison across studies is challenging because fluoroscopy systems, dose settings, patient characteristics, procedural complexity, and reported dosimetric quantities differ substantially. Representative multidimensional radiation-exposure data are summarized in

Table 2. Representative multidimensional radiation-exposure data in endourological stone surgery.

Study	Procedure/Population	Fluoroscopy Time	KAP/DAP	Air Kerma/Cumulative Radiation Dose	Effective Dose
Danilovic et al., 2019 [21]	Adult unilateral URS; ¼-dose vs. standard-dose fluoroscopy	74.5 ± 84.8 vs. 88.3 ± 90 s	0.23 ± 0.52 vs. 1.15 ± 2.74 mGy·m2	3.6 ± 4.5 vs. 16.2 ± 19.3 mGy	NR
Hein et al., 2021 [22]	RIRS; multicenter, before vs. after radiation-awareness training	130.8 vs. 77.4 s	565.8 vs. 357.8 *	NR	NR
Vassileva et al., 2020 [23]	Semirigid/flexible URS, RIRS, mini-PCNL, PCNL; 7 centers	0.1–14 min overall	Semirigid URS 0.13–2.51; flexible URS 0.10–2.90; RIRS 0.80–1.79; mini-PCNL 1.39–9.90; PCNL 2.40–17.50 Gy·cm2 †	Maximum Ka,r 377 mGy	NR
Zampini et al., 2021 [24]	US-guided PCNL; supine vs. prone	86.32 ± 7.7 vs. 51.00 ± 5.1 s	NR	NR	2.92 ± 0.32 vs. 5.30 ± 0.70 mSv
Cheng et al., 2023 [25]	PCNL; standard-dose vs. low-dose protocol	147.62 ± 73.94 vs. 123.59 ± 67.02 s	NR	48.88 ± 36.84 vs. 11.68 ± 7.01 mGy	NR
De Coninck et al., 2024 [26]	Systematic review, 65 studies	Heterogeneous	Up to 8920 mGy·cm2 (URS); 28,700 mGy·cm2 (PCNL)	Up to 46.99 mGy (URS); 430.8 mGy (PCNL)	Up to 6.07 mSv (URS); 33 mSv (PCNL)
De Coninck et al., 2026 [27]	Strict-ALARA endourological cohort	Median 15 s (URS); 3 min 17 s (PCNL)	Median 158.5 mGy·cm2 (URS); 3440 mGy·cm2 (PCNL)	NR	NR

Abbreviations: ALARA, as low as reasonably achievable; DAP, dose–area product; Ka,r, cumulative air kerma at the patient entrance reference point; KAP, kerma–area product; NR, not reported; PCNL, percutaneous nephrolithotomy; RIRS, retrograde intrarenal surgery; URS, ureteroscopy; US, ultrasound. * DAP units were not harmonized across participating centers in Hein et al.; values should therefore be interpreted only as within-study comparisons. † Vassileva et al. reported center-specific median PKA ranges; the values shown summarize the reported ranges rather than pooled patient-level estimates.

. These values should be interpreted as study-specific estimates or ranges rather than universal reference doses. Importantly, fluoroscopy time alone does not consistently predict radiation dose, because dose rate, patient habitus, field size, geometry, pulse rate, and acquisition settings also contribute substantially to exposure.

The studies summarized in Table 2 illustrate that fluoroscopy time should not be interpreted as a direct surrogate for radiation dose. Dose varied substantially across procedures and institutions, and reductions in equipment output could markedly lower radiation exposure even when fluoroscopy time changed little. Patient habitus, case complexity, procedural position, fluoroscopy settings, and imaging strategy should therefore be considered alongside fluoroscopy time when interpreting radiation exposure.

Early direct dosimetry during URS demonstrated measurable but generally low patient and staff exposure and provided important historical evidence for last-image hold and shielding [28]. However, absolute dose values from studies performed with older fluoroscopy systems should be interpreted as historical rather than directly extrapolated to contemporary pulsed, low-dose C-arm technology. A subsequent validated anthropomorphic-phantom study incorporating clinical fluoroscopy times estimated a median effective dose of 1.13 mSv in non-obese male patients, with a range of 0.31–7.17 mSv [29]. These estimates should not be interpreted as patient-specific absorbed doses or generalized across body sizes, equipment generations, and procedural settings.

Protocol modification can substantially reduce exposure. Greene et al. reduced mean fluoroscopy time from 86.1 to 15.5 s, an 82% reduction, without increasing mean operative time or complications during uncomplicated URS [11]. In a simulated URS model, pulsed fluoroscopy reduced fluoroscopy time by 76% and radiation dose by 64% relative to continuous fluoroscopy, while image quality remained adequate for most simulated guidewire-placement and stone-localization tasks [17]. These findings support procedure-specific low-dose settings and brief, question-driven fluoroscopic pulses.

Pediatric data illustrate how exposure may differ across procedures, although the findings should be interpreted within their original clinical setting. In a single-center pediatric cohort, median fluoroscopy times were 1.6 min for primary URS, 2.1 min for stent placement followed by URS, 2.5 min for bilateral URS, and 11.7 min for PCNL. The estimated median effective dose was 3 mSv for ureteroscopic procedures and 16.8 mSv for PCNL [30]. These cohort-specific estimates should not be extrapolated directly to adult patients or contemporary low-dose protocols.

Pregnancy warrants particular attention because the justification for ionizing radiation should be especially strict. When intervention is necessary, ultrasound and direct endoscopic guidance should be preferred when they provide sufficient information for safe treatment. Fluoroscopy should not be regarded as absolutely prohibited when radiographic confirmation is necessary for maternal or procedural safety; rather, its use should be limited to clearly defined indications and optimized using brief pulsed imaging, tight collimation, low-dose settings, avoidance of unnecessary acquisition, and careful procedural planning [1,31]. Contemporary reviews support ureteroscopy as a feasible treatment option during pregnancy when performed in experienced centers with appropriate obstetric support [31].

In reproductive-age patients who are not pregnant, the principal concern is cumulative rather than immediate tissue injury from a single uncomplicated procedure. Radiation counseling should therefore consider the entire stone-care pathway, including repeated diagnostic imaging, fluoroscopically guided interventions, and potential future procedures.

Patient dose during PCNL varies considerably across institutions, eras, access techniques, and levels of case complexity. PCNL warrants particular attention because renal access and tract creation may require repeated imaging, especially when multiple tracts, difficult anatomy, or complex stones are present. Rather than characterizing PCNL as uniformly high dose, studies should report case complexity, access method, fluoroscopy settings, and equipment-derived dose indices to allow appropriate interpretation of exposure.

A 2024 systematic review of 65 studies confirmed wide variation in patient radiation exposure across endourological procedures. Across heterogeneous studies, the reported effective dose reached values up to 33 mSv for PCNL and 6.07 mSv for URS [26]. These upper reported values should not be interpreted as reference doses or expected exposure for contemporary practice; rather, they illustrate the magnitude of between-study variability and the need to report procedure type, case complexity, equipment settings, and multiple dosimetric parameters.

6. Occupational Radiation Exposure

Occupational exposure during endourological surgery arises primarily from scatter radiation generated when the primary beam passes through the patient. The operator closest to the patient and beam generally receives the greatest exposure, whereas assistants, nurses, anesthesia personnel, and observers receive lower but nonzero exposure depending on their position, shielding, and time spent in the room.

PCNL is the endourological procedure most extensively studied in this context. Early monitoring studies demonstrated measurable exposure among medical personnel during PCNL, although recorded levels were low when appropriate precautions were used [32,33]. Subsequent studies confirmed that staff exposure varies according to professional role and dosimeter location [32,34]. A broader review of fluoroscopically guided procedures also included PCNL among the interventions for which operator exposure has been quantified [35]. Because much of the early occupational dosimetry evidence was obtained using older fluoroscopic systems and practice patterns, the absolute exposure values reported in these studies should be interpreted as historical rather than directly extrapolated to contemporary low-dose practice [32,33,34].

A 2024 systematic review of 21 studies likewise found substantial heterogeneity in urologist exposure and identified PCNL, particularly prone PCNL, as the procedure associated with the greatest occupational exposure; eye and hand exposure were also highest in prone PCNL [36].

Four practical principles are immediately applicable. First, time matters: unnecessary fluoroscopy should be avoided, and procedural movement should be observed using brief pulses rather than continuous screening. Second, distance matters: staff who are not actively involved in a fluoroscopic step should move away from the patient and beam. Third, shielding matters: lead or lead-equivalent aprons, thyroid collars, protective eyewear, and table- or ceiling-suspended shields reduce exposure. Fourth, geometry matters: unnecessary magnification and extreme C-arm angulation should be avoided, the detector should be positioned close to the patient, and the X-ray source should generally be placed beneath the patient when feasible [1,6,7,8,9].

Occupational radiation safety should not rely on individual practice alone. A departmental protocol should specify who wears dosimeters, where they are positioned, how often readings are reviewed, and how unexpected values trigger corrective action. Reducing fluoroscopy time does not provide a complete measure of staff dose, but structured training and feedback remain practical means of reducing avoidable exposure [18]. Pregnancy among endourologists warrants particular occupational consideration; a recent review emphasizes that consistent shielding, low-dose and pulsed fluoroscopy, personal dosimetry, and institutional radiation-safety policies can substantially reduce occupational exposure during pregnancy [37].

7. Practical Dose-Reduction Strategies Based on ALARA

The ALARA principle should be operationalized as a defined perioperative workflow rather than treated as a general slogan. Radiation-safe endourology begins with preoperative planning, continues through question-driven intraoperative imaging, and concludes with dose documentation, feedback, and quality improvement. Procedure-specific determinants and radiation-sparing options are summarized in

Table 3. Procedure-specific fluoroscopic workflows and radiation determinants.

Procedure	Main Fluoroscopic Steps	Key Determinants	Radiation-Sparing Options
URS	Guidewire confirmation; retrograde pyelography; stone localization; dilation; stent positioning	Operative duration and surgeon-specific practice [16]	Reduced-radiation protocols [11]; pulsed fluoroscopy [17]; last-image hold [28]; fluoroscopy-free or minimized URS in selected patients [14,15]
RIRS	Retrograde pyelography; access sheath placement; collecting-system orientation; stent positioning	Independent dose determinants remain incompletely defined	Ultralow-dose or selective fluoroscopy [12]; fluoroscopy-free workflow for selected renal stones [13]; investigational navigation or AR [38]
PCNL	Collecting-system opacification; puncture; guidewire confirmation; tract dilation; sheath placement; residual-stone assessment	Body habitus; stone burden; staghorn configuration; operative and fluoroscopy duration [19,20]	Ultrasound-guided or hybrid access [19,39,40,41]; low-dose pulsed fluoroscopy and collimation [1]; endoscopically assisted puncture [42,43]; 3D planning [1]
ECIRS	Retrograde catheter placement; collecting-system mapping; puncture coordination; tract dilation; antegrade–retrograde device confirmation	Complex stone distribution and prolonged two-team procedures may increase imaging requirements	Retrograde target visualization and ultrasound-assisted puncture [42,43]; selective fluoroscopy; investigational fusion or navigation [44]

Abbreviations: 3D, three-dimensional; AR, augmented reality; ECIRS, endoscopic combined intrarenal surgery; PCNL, percutaneous nephrolithotomy; RIRS, retrograde intrarenal surgery; URS, ureteroscopy.

, while a layered ALARA framework is illustrated in Figure 3.

Preoperative imaging should be reviewed to define stone location, collecting-system anatomy, adjacent organs, and anticipated access difficulty so that exploratory fluoroscopy can be minimized. During surgery, fluoroscopy should answer a specific safety or positioning question rather than be used continuously.

Brief pulsed fluoroscopy, low-dose settings, reduced pulse rates, collimation, last-image hold, and avoidance of unnecessary digital acquisition should be used whenever image quality remains adequate [1,6,11,17].

C-arm geometry should also be optimized: the detector should be kept close to the patient, the source-to-skin distance maximized when practical, and unnecessary magnification or extreme angulation avoided [1,6,7,8,9]. Staff not involved in an imaging step should increase their distance from the patient and use appropriate shielding.

Dose reduction is most sustainable when it is embedded in training and quality improvement. Recent clinical data demonstrate that strict adherence to an ALARA-based workflow can markedly reduce DAP and fluoroscopy time during both URS and PCNL without compromising stone-free or complication outcomes [27]. Fluoroscopy time, KAP, and cumulative air kerma should be recorded when available, reviewed with nonpunitive feedback, and interpreted in the context of procedure complexity [11,17,18,27].

8. Fluoroscopy-Free and Fluoroscopy-Minimized Endourological Surgery

For this review, “fluoroscopy-free” and “zero-fluoroscopy” refer to procedures completed without intraoperative fluoroscopic exposure; these terms are often used interchangeably in the literature. “Fluoroscopy-minimized” refers to procedures in which fluoroscopy is intentionally restricted to predefined safety-critical steps or used as a rescue tool when endoscopic, tactile, or other imaging information is insufficient. These strategies represent extensions of ALARA-based practice rather than an obligation to achieve zero fluoroscopy in every case.

In semirigid URS, guidewire placement may be performed under cystoscopic and ureteroscopic visualization, stone fragmentation is performed under direct vision, and distal stent position can be confirmed cystoscopically. However, difficult ureteral anatomy, impacted stones, strictures, prior reconstruction, or uncertain guidewire position may increase the value of fluoroscopic confirmation. Careful patient selection and explicit conversion criteria are therefore essential.

Fluoroscopy-free RIRS has undergone more rigorous evaluation. A prospective multicenter randomized trial found that a standardized fluoroscopy-free workflow was noninferior to conventional RIRS for treatment success in selected patients with renal stones measuring 20 mm or less, with fluoroscopy available when conversion was considered necessary [13]. Systematic reviews and meta-analyses have similarly reported comparable stone-free and complication outcomes between fluoroscopy-free and conventional endourological procedures [14,15]. Most recently, a 2026 systematic review and meta-analysis of randomized studies from the FUTURE Collaborative found comparable efficacy and safety between fluoroless and fluoroscopy-guided URS, with only a minimal increase in operative time for fluoroless URS [45]. Nevertheless, careful patient selection and access to rescue fluoroscopy remain important, particularly in complex anatomy or difficult access.

A pragmatic approach is to stratify procedures according to anticipated complexity. Straightforward cases may be considered for a fluoroscopy-free workflow when managed by experienced operators. Cases of intermediate complexity may be managed using fluoroscopy-minimized protocols that reserve imaging for guidewire confirmation, access sheath placement, difficult orientation, or stent positioning. In highly complex cases, procedural safety should take precedence over an arbitrary zero-fluoroscopy target, and fluoroscopy, ultrasound, endoscopy, or combined guidance should be used as required.

The learning curve must also be considered. Trainees should first acquire competence in fluoroscopic anatomy, dose-conscious technique, guidewire behavior, access sheath resistance, and rescue strategies. In training settings, an explicitly taught fluoroscopy-minimized protocol may be safer and more reproducible than default fluoroscopy-free surgery. Future studies should report operator experience, trainee involvement, case complexity, conversion criteria, and the reasons for fluoroscopy use.

9. Alternative and Multimodal Guidance for PCNL and ECIRS

PCNL may offer the greatest opportunity for alternative guidance to reduce radiation exposure in endourological surgery. Conventional fluoroscopy provides rapid two-dimensional visualization of collecting-system opacification, puncture trajectory, guidewire position, tract dilation, and sheath placement, but it uses ionizing radiation and provides limited soft-tissue information. Ultrasound provides real-time visualization of the kidney, hydronephrosis, target calyx, renal parenchyma, surrounding viscera, and puncture needle without ionizing radiation.

Systematic reviews and meta-analyses have found broadly comparable stone-free and overall complication outcomes between ultrasound-guided and fluoroscopy-guided PCNL [39,40]. A more recent meta-analysis also reported a shorter duration of radiation exposure with ultrasound guidance, although substantial between-study heterogeneity limits the precision of the pooled estimate [40]. Ultrasound can visualize adjacent tissues and may assist in selecting a tract that avoids neighboring organs [1]. Nevertheless, ultrasound-guided access is operator-dependent, and image quality or access success may be reduced in patients with obesity, nondilated collecting systems, complex calyceal anatomy, or deeply located target calyces.

Hybrid ultrasound–fluoroscopy workflows offer a pragmatic transition. Ultrasound can be used for renal localization, calyceal targeting, and needle advancement, whereas fluoroscopy is reserved for guidewire confirmation, tract dilation, sheath placement, or difficult anatomy. Prospective cohort studies have shown that ultrasound-guided access and dilation can reduce fluoroscopy use during PCNL [41]. Ultrasound assistance also reduced fluoroscopy time and radiation dose across body mass index groups, although successful ultrasound-guided access was less frequent in patients with obesity [19].

Endoscopically assisted puncture is another radiation-sparing option, particularly during ECIRS. Simultaneous flexible ureteroscopy can identify the target calyx and provide direct visualization of needle entry into the collecting system. Foundational clinical experience demonstrated that flexible ureteroscopic assistance could facilitate percutaneous access in selected patients with complex collecting systems or challenging body habitus [42]. In a multicenter retrospective cohort of ultrasound-guided mini-ECIRS, ureteroscopy-assisted puncture was associated with shorter fluoroscopy duration and favorable selected surgical outcomes [43]. Because ultrasound or fluoroscopy may still be used to assess the extrarenal trajectory and create the tract, the technique is more accurately described as ureteroscopy-assisted or endoscopically assisted puncture rather than universally fluoroscopy-free access.

Future practice is therefore likely to be multimodal rather than restricted to a single guidance modality. Fluoroscopy is rapid and familiar but uses ionizing radiation; ultrasound is radiation-free and provides soft-tissue information but is operator-dependent; endoscopy provides direct intraluminal visualization but limited extraluminal orientation. Implementation should also be considered: fluoroscopy-minimized workflows may require mainly protocol standardization and training, whereas ultrasound-guided access requires equipment availability and a learning curve, and advanced navigation or fusion platforms may introduce substantial capital cost, setup time, maintenance, and workflow complexity. Hybrid ultrasound-fluoroscopy pathways may therefore offer a practical transition in centers developing ultrasound expertise.

A practical procedure- and complexity-based approach to modality selection is shown in Figure 4.

10. Emerging Image-Guided Technologies

Emerging image-guided technologies should be considered according to both their potential value and their clinical maturity. Three-dimensional reconstruction and selected image-fusion or navigation approaches may improve spatial planning, whereas augmented-reality, robot-assisted navigation, computer vision, and AI-enabled dose optimization remain at earlier stages of validation. The aim should not be technological novelty alone, but provision of the spatial information required at each procedural step with the lowest reasonable radiation burden, acceptable workflow, and justifiable cost.

Three-dimensional CT reconstruction is among the most readily accessible emerging tools. Preoperative CT already provides information on stone size, density, and location; collecting-system anatomy; skin-to-stone distance; and relationships to adjacent organs. Three-dimensional reconstruction can present this information more intuitively when planning complex PCNL or ECIRS, procedures in anomalous or horseshoe kidneys, and cases involving a retrorenal colon. The EAU guideline acknowledges the potential value of three-dimensional planning but emphasizes the need for further clinical validation [1].

Image-fusion and navigation systems are being investigated as potential means of reducing reliance on repeated fluoroscopic localization. One early system projected a tracked ultrasound puncture trajectory onto fluoroscopic images and was evaluated in laboratory experiments and a single clinical case [44]. An augmented-reality and human–robot collaboration framework for percutaneous renal puncture improved targeting performance in an experimental setting but has not established clinical effectiveness or radiation reduction during PCNL [46].

Advances in X-ray detector and scintillator materials may also contribute to future improvements in imaging efficiency. A recent study of heavy-metal-free ZnSeTe quantum-dot-based liquid scintillators demonstrated high-sensitivity, high-resolution X-ray imaging performance [47]. Although this technology has not been evaluated in endourological fluoroscopy or shown to reduce clinical radiation exposure, it represents an example of upstream detector innovation that could ultimately support more dose-efficient imaging systems.

For ureteroscopy, the Navigated Augmented Reality Visualization for Ureteroscopic Surgery (NAVIUS) system combines preoperative three-dimensional imaging, electromagnetic scope tracking, and augmented-reality visualization. Initial evaluation in kidney phantoms demonstrated improved collecting-system coverage and reduced subjective task load, but patient outcomes and radiation exposure were not assessed [38]. Registration accuracy, respiratory motion, collecting-system deformation, fluid irrigation, scope deflection, workflow complexity, and cost remain important barriers to clinical translation.

AI-assisted dose optimization should currently be classified as experimental in endourological stone surgery. Potential applications include recommending lower-dose settings, identifying repeated or unnecessary fluoroscopic events, automating radiation-event logging, and providing operator-level feedback; however, endourology-specific prospective studies demonstrating radiation reduction, clinical benefit, and cost-effectiveness are lacking. Such applications should therefore be treated as research hypotheses rather than established clinical strategies.

Computer vision has been used to segment stones and laser fibers in ureteroscopic video [48]. In that study, turbid fluid, specular reflections, camera and renal motion, motion blur, bleeding, and stone debris were identified as factors that impair image quality and segmentation performance rather than as segmentation targets [48]. Whether endoscopic video analysis can improve intrarenal orientation, residual-fragment detection, or lithotripsy efficiency sufficiently to reduce fluoroscopy remains uncertain.

Emerging technologies should be evaluated against clinically meaningful comparators. A system that reduces fluoroscopy but increases operative time, cost, technical failure, or complications may not improve overall care. Clinical studies should therefore report radiation dose, stone-free outcomes, complications, reintervention, operative time, cost, usability, registration or tracking accuracy, and learning-curve effects. The current evidence and clinical maturity of radiation-sparing and image-guided approaches are summarized in

Table 4. Radiation-sparing and image-guided approaches according to current evidence and clinical maturity.

Approach	Radiation-Sparing Mechanism or Potential Role	Main Limitations	Evidence and Clinical Maturity
Fluoroscopy-free URS	Endoscopic and tactile guidance without planned fluoroscopy	Requires careful patient selection, operator experience, and a rescue strategy	Clinically supported. Systematic reviews and meta-analyses in selected patients [14,15]
Fluoroscopy-free RIRS	Standardized RIRS without planned fluoroscopy	Access sheath placement and orientation may be difficult; generalizability to complex stones is limited	Clinically supported. Prospective multicenter RCT and systematic-review evidence for selected renal stones ≤20 mm [13,14]
Ultrasound-guided PCNL	Real-time renal access without ionizing radiation during ultrasound-guided steps	Operator-dependent; access may be more difficult in patients with obesity or nondilated collecting systems	Clinically supported. Systematic reviews, meta-analyses, and prospective cohorts [19,39,40,41]
Combined ultrasound–fluoroscopy PCNL	Ultrasound for localization and puncture; selective fluoroscopy for confirmation	Reduces but does not eliminate radiation exposure	Clinically supported. Prospective and observational cohort evidence [19,41]
Endoscopically assisted puncture	Retrograde visualization of the target calyx and needle entry	Requires simultaneous retrograde access, team coordination, and often complementary imaging	Emerging. Small clinical series and a multicenter retrospective cohort [42,43]
Three-dimensional CT reconstruction	Patient-specific visualization of stones, the collecting system, and adjacent organs	Provides static preoperative information; requires segmentation and registration	Emerging. Observational planning studies summarized in the EAU guideline [1]
Image fusion and tracked navigation	Registers imaging with tracked instruments to improve spatial orientation	Registration error, motion, deformation, cost, and workflow burden	Emerging. Feasibility studies, phantom evaluation, and a single early clinical case [44]
AR- or robot-assisted PCNL access	Trajectory visualization and/or robotic puncture guidance	Experimental systems with limited clinical validation	Experimental. Experimental system and user evaluation [46]
NAVIUS for ureteroscopy	Electromagnetic scope tracking with 3D maps and AR overlays	Phantom-only evaluation; no clinical or radiation-outcome data	Experimental. Kidney-phantom user study [38]
Endoscopic computer vision	Automated segmentation of stones and laser fibers	Affected by turbid fluid, reflections, motion blur, bleeding, and debris	Emerging. Development and external-test dataset study [48]
AI-assisted dose optimization	Proposed support for dose settings, event detection, logging, and feedback	No endourology-specific prospective clinical validation	Experimental. Conceptual or proposed application

Abbreviations: 3D, three-dimensional; AI, artificial intelligence; AR, augmented reality; CT, computed tomography; EAU, European Association of Urology; PCNL, percutaneous nephrolithotomy; RCT, randomized controlled trial; RIRS, retrograde intrarenal surgery; URS, ureteroscopy.

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11. Reporting Standards and Procedure-Specific Benchmarking

The literature on radiation exposure in endourology remains heterogeneous. Many studies report fluoroscopy time alone, whereas fewer report KAP, cumulative air kerma, estimated effective dose, or staff dosimetry. Definitions of stone-free status vary, follow-up imaging methods differ, and case complexity is reported inconsistently. These differences limit comparisons across institutions and impede the development of meaningful benchmarks.

Future studies should report a standardized minimum dataset. The proposed minimum reporting framework is summarized in

Table 5. Proposed minimum reporting dataset for studies of radiation exposure in endourological stone surgery.

Domain	Minimum Variables
Study context	Study period; single- vs. multicenter setting; fluoroscopy system/model when available
Patient/stone	BMI/body habitus; stone location; size/volume; relevant anatomy; hydronephrosis; complex/staghorn configuration where applicable
Procedure	URS/RIRS/PCNL/mini-PCNL/ECIRS; operative time; access method; number of PCNL tracts; operator experience; trainee participation
Radiation	Fluoroscopy time; KAP/DAP; cumulative air kerma when available; pulse rate; dose mode; collimation; digital acquisitions
Guidance strategy	Conventional/minimized/free fluoroscopy; ultrasound; hybrid; endoscopic assistance; navigation/fusion; conversion/rescue fluoroscopy
Outcomes	Stone-free definition; postoperative imaging modality/timing; complications; reintervention; conversion/technical failure
Occupational studies	Staff role; dosimeter type/location; shielding; operator position; C-arm orientation; monitoring period

Abbreviations: BMI, body mass index; DAP, dose–area product; ECIRS, endoscopic combined intrarenal surgery; KAP, kerma–area product; PCNL, percutaneous nephrolithotomy; RIRS, retrograde intrarenal surgery; URS, ureteroscopy.

and encompasses study context, patient and stone characteristics, procedural complexity, fluoroscopy and dosimetry parameters, image-guidance strategy, clinical outcomes, and occupational dosimetry when applicable.

At minimum, contemporary fluoroscopy studies should report fluoroscopy time together with at least one equipment-derived dose metric, preferably KAP/DAP and/or cumulative air kerma when available. Fluoroscopy time alone should not be considered sufficient for quantitative comparison of patient radiation exposure.

Procedure-specific reporting is essential. A distal ureteral stone treated by semirigid URS should not be compared directly with a staghorn stone treated by PCNL. Studies should report stone size or volume, location, radiopacity, hydronephrosis, prior stenting, ureteral access sheath use, operative time, surgeon experience, trainee participation, anatomic abnormalities, number of PCNL tracts, access method, patient position, and complications. For PCNL and ECIRS, puncture should be categorized as fluoroscopy-guided, ultrasound-guided, combined ultrasound–fluoroscopy, endoscopically assisted, or navigation-assisted.

Stone-free definitions also require standardization. Residual-fragment thresholds commonly include the absence of residual fragments or fragments measuring 2, 3, or 4 mm or less. The follow-up imaging modality must be stated because CT detects small residual fragments more sensitively than ultrasonography or plain radiography. Studies using different imaging methods should not be compared without acknowledging this distinction.

Procedure-specific radiation benchmarks may be useful, but they should account explicitly for case complexity and relevant procedural characteristics. A clinically meaningful benchmark should not consist of a single universal fluoroscopy time; rather, it should represent a reference distribution for comparable procedures and levels of case complexity. A large UK multicenter study demonstrated the feasibility of procedure-specific reference levels using both DAP and fluoroscopy time and also identified substantial interinstitutional variation, supporting procedure-specific rather than universal benchmarks [49]. Institutions could track median fluoroscopy time, KAP, and cumulative air kerma separately for uncomplicated URS, RIRS for defined renal-stone burdens, standard PCNL, mini-PCNL, and ECIRS. Review of outliers could identify equipment problems, training needs, or workflow inefficiencies.

Recent systematic reviews reinforce the need for multidimensional and procedure-specific dose reporting. A 2024 systematic review of patient exposure found wide variation across endourological procedures and identified PCNL as generally associated with the highest exposure, while emphasizing the absence of procedure-specific reference dose limits [26]. A separate 2024 systematic review of urologist exposure found substantial between-study heterogeneity and greater occupational exposure during PCNL, particularly for the eyes and hands in prone procedures [36]. Recent multidisciplinary fluoroscopy-safety recommendations also emphasize standardized training, institutional oversight, monitoring, and minimum safety standards across fluoroscopy-using specialties [50]. These data support procedure- and complexity-specific benchmarking rather than a single universal fluoroscopy-time target.

For benchmarking to become clinically meaningful, future multicenter studies should apply the same minimum dataset and compare integrated radiation-safe workflows using standardized patient and staff dosimetry. Such studies should report procedure complexity, clinical outcomes, implementation burden, and cost in addition to radiation metrics.

Radiation safety should also be integrated into endourology education. Trainees should learn radiation physics, dose metrics, fluoroscopic anatomy, C-arm geometry, protective equipment, and low-dose workflows early in their training. Simulation may allow practice in guidewire placement, access sheath insertion, renal puncture, and C-arm positioning without exposing patients or staff. Radiation exposure should be measured and reviewed within the same quality framework applied to infection prevention and surgical safety.

12. Limitations of This Review

This review has several limitations. It is a narrative review and did not include a formal risk-of-bias assessment or quantitative meta-analysis. The available literature is heterogeneous with respect to procedure type, patient selection, fluoroscopy equipment and settings, reported dose metrics, operator experience, and definitions of clinical outcomes. The literature-selection process may therefore be affected by selection bias, and direct numerical comparisons between studies should be interpreted cautiously. Evidence for several emerging technologies is based on small clinical series, phantom studies, feasibility work, or conceptual applications, which limits conclusions regarding clinical effectiveness and radiation reduction.

13. Clinical Take-Home Recommendations

• Use fluoroscopy selectively at predefined safety-critical checkpoints rather than as continuous routine imaging.
• Do not use fluoroscopy time as the sole radiation metric; record KAP/DAP and cumulative air kerma when available, together with patient and procedural context.
• Consider fluoroscopy-free or fluoroscopy-minimized URS/RIRS in appropriately selected cases and experienced hands but prioritize procedural safety over an arbitrary zero-fluoroscopy target.
• Use ultrasound-assisted or hybrid ultrasound-fluoroscopy guidance during PCNL/ECIRS when local expertise and equipment are available.
• Treat navigation, augmented reality, robot-assisted guidance, computer vision, and AI-assisted dose optimization according to their evidence level; several remain emerging or experimental and require prospective clinical and dosimetric validation.

14. Conclusions

Intraoperative X-ray fluoroscopy remains a valuable component of endourological stone surgery, but its use should be deliberate and proportional to procedural need. For most uncomplicated procedures, measured radiation exposure is limited; nevertheless, dose varies widely across procedures and settings, is generally greater for PCNL than for URS, and may accumulate in patients undergoing recurrent imaging and interventions. The magnitude of long-term clinical harm from a single contemporary procedure is difficult to quantify precisely, so radiation protection should focus on avoiding unnecessary and repeated exposure while maintaining procedural safety.

Radiation-safe endourology requires more than simply shortening fluoroscopy time. It requires multidimensional dose reporting, low-dose and pulsed fluoroscopy, collimation, last-image hold, optimized C-arm geometry, appropriate shielding, consistent dosimetry, team training, and feedback. Fluoroscopy-free or minimized URS/RIRS and ultrasound-guided or hybrid PCNL can reduce reliance on ionizing radiation in selected patients when performed by appropriately trained teams.

The future of stone surgery is unlikely to be fluoroscopy-free in every case, but it should be image-guided and radiation-conscious in every case. Alternative and emerging technologies should be adopted according to their clinical evidence, feasibility, and cost rather than novelty alone. Standardized patient and staff dosimetry, procedure- and complexity-specific benchmarking, and prospective multicenter evaluation of integrated workflows are needed to define meaningful benchmarks and determine which technologies translate into safer and more efficient care.