Authors: Daniel Pérez-Fentes, Esteban Emiliani, Ernesto Donoso, Alba García-Catalán, Lucía Mosquera-Seoane, Beatriz Ulloa-Iglesias, María E. Martínez-Corral
Categories: Review, Kidney stone, Urolithiasis, Percutaneous nephrolithotomy, Pregnancy, Outcome
Source: Asian Journal of Urology
Authors: Daniel Pérez-Fentes, Esteban Emiliani, Ernesto Donoso, Alba García-Catalán, Lucía Mosquera-Seoane, Beatriz Ulloa-Iglesias, María E. Martínez-Corral
Urinary stones in pregnancy are usually managed conservatively or with temporary drainage, but in some cases, intervention is needed. Percutaneous nephrolithotomy (PCNL) is generally avoided due to its invasiveness and the requirement for fluoroscopy. This study aimed to review the literature on the use of PCNL in pregnancy, focusing on its safety, efficacy, feasibility, and technical aspects.
A narrative literature review was conducted using PubMed, Embase, and Scopus databases, covering the period from January 2000 to March 2024. The search terms included “percutaneous nephrolithotomy”, “PCNL”, “pregnancy”, and relevant variations thereof. The initial search retrieved 27 articles, of which only six studies involving 14 patients met the inclusion criteria.
The reviewed studies included patients aged 23–34 years who underwent PCNL between 8 weeks and 28 weeks of gestation. Preoperative evaluations were exclusively based on ultrasound imaging, with stone sizes ranging from 8 mm to 48 mm. Indications for PCNL were persistent pain despite urinary diversion or reluctance to undergo stent replacement. Fluoroscopy was avoided in 13 patients. No maternal or fetal complications were reported.
PCNL appears to be a safe and feasible treatment option for selected cases of urinary stone disease during pregnancy. It should be performed in experienced centers, with proper patient counseling and a multidisciplinary approach to ensure the best outcomes.
Urinary stones are estimated to affect 1–8 in 1000 pregnant individuals, with a similar incidence to the non-pregnant population [1,2]. Stone formation is often attributed to anatomical changes in the urinary tract during gestation, alongside increased glomerular filtration rate, resulting in additional urinary excretion of sodium, calcium, and urate [3,4].
Although the majority of stones during pregnancy are asymptomatic or can be passed without complications, in some situations they can pose a serious problem to the mother and the fetus, necessitating urinary drainage or interventional treatment [[5], [6], [7]].
Regarding interventional treatment, percutaneous nephrolithotomy (PCNL) has been considered contraindicated during pregnancy due to its invasive nature and the potential risks associated with fluoroscopy, commonly employed during the procedure. The use of fluoroscopy in pregnant patients raises concerns about radiation exposure and its potential adverse effects on the developing fetus.
Despite these concerns, sporadic reports in the literature describe the utilization of PCNL in pregnant individuals. However, due to the scarcity of published data and the inherent risks involved, the safety, efficacy, and feasibility of PCNL in this specific population remain areas of uncertainty.
This paper aims to address this gap in knowledge by systematically reviewing the existing literature on PCNL in pregnancy. By analysing and synthesizing available evidence, we seek to shed light on the technical aspects of performing PCNL in pregnant patients, as well as to evaluate its safety, efficacy, and overall feasibility as a treatment modality during gestation. Furthermore, we aim to provide comprehensive insights into the technical considerations associated with this challenging procedure in pregnant women.
A narrative literature review was conducted to identify relevant studies on PCNL in pregnancy. The search was performed in electronic databases, including PubMed, Embase, and Scopus, from January 2000 to March 2024. The search strategy utilized a combination of Medical Subject Headings (MeSH) terms and keywords related to “percutaneous nephrolithotomy”, “PCNL”, “pregnancy”, and relevant variations thereof. A Boolean operator (AND) was used to refine search queries. This search strategy retrieved 27 results.
Inclusion criteria for study selection were predefined based on the Population, Intervention, Comparison, Outcome, and Study design (PICOS) framework as (a) Population: pregnant individuals with urinary stone disease undergoing PCNL; (b) Intervention: fluoroscopy-guided or fluoroless PCNL procedures; (c) Comparison: not applicable to non-comparative studies; (d) Outcome: safety, efficacy, maternal-fetal outcomes, and technical considerations; (e) Study case reports, case series, cohort studies, and clinical trials reporting outcomes of PCNL in pregnancy.
Studies were excluded if they did not meet the specified criteria or were not available in English. Two authors (Pérez-Fentes D, Martínez-Corral ME) screened titles and abstracts of retrieved records to identify potentially eligible studies. Full-text articles of selected records were then assessed for eligibility. Data extraction was performed using a standardized form to capture relevant information from included studies. Extracted data included study characteristics (author, publication year, and study design), patient demographics (age, gestational age, and stone characteristics), procedural details (PCNL technique, anesthesia type, and fluoroscopy use), maternal outcomes (complications and stone clearance rates), fetal outcomes, and any reported technical considerations specific to PCNL during pregnancy. Data synthesis involved a narrative summary of findings from included studies.
We identified six studies [[8], [9], [10], [11], [12], [13]] encompassing a total of 14 patients who underwent PCNL during pregnancy, all meeting the predetermined inclusion criteria for analysis.
Patients, aged between 23 years and 34 years, underwent the procedure between the 8th and 28th gestational weeks. Primary indications for intervention during pregnancy included refractory pain despite urinary diversion or reluctance to undergo double-J or nephrostomy tube placement. Preoperative assessment relied solely on ultrasound imaging, with stone sizes ranging from 8 mm to 48 mm. Notably, CT scans were not performed for any patient in the included studies.
Surgical procedures were performed in both supine and prone positions, utilizing either general or spinal anesthesia. Ultrasound guidance was predominantly used for puncture and dilation, with fluoroscopy employed in only one case. Among the patients, three had a pre-existing nephrostomy tube, which was utilized for dilation purposes. Specific details regarding the method of dilation were lacking in the majority of studies, with only Hosseini et al. [13] mentioning the use of metallic dilators. Percutaneous tracts were dilated to sizes ranging from 22 French to 30 French. Hospital stays post-procedure varied from 1 day to 6 days, with no reported perioperative complications. Importantly, all cases were reported to be stone-free following the procedure without any complications to the fetus.
This information has been synthesized in Table 1, complemented by the authors' personal experience to enrich the scientific evidence, as well as to address some technical considerations within this domain.Table 1Studies on percutaneous nephrolithotomy in pregnancy.Table 1StudyCase, nAge, yearGestational weekIndicationStone size, mmPreoperative diagnostic imagingNephrostomy prior to surgeryPatient positionAnesthesiaFluoroscopic guidanceDilation methodTract size, FrHospital stay, dayComplicationSFR, %Shah et al., 2004 [8]13314Unwilling to maintain nephrostomy tube18USYesNSNSYesNSNSNSNo100Toth et al., 2005 [9]13111Asymptomatic8USNoProneRegionalNoNS264No100Fregonesi et al., 2013 [10]12422Refractory pain despite ureteral stent27USNoSupineNSNoNSNS1No100Giusti et al., 2016 [12]12713Refractory pain and encrusted DJ stent40USYesNSNSNoNS226No100Basiri et al., 2016 [11]325–34a16–28aRefused urinary diversion and severe pain despite nephrostomy24–42aUS alone or US plus an MRINo (2 cases); yes (1 case)SupineRegionalNoNS28–30a1–2aNo100Hosseini et al., 2017 [13]723–32a8–13aBad tolerance to DJ and/or refused urinary diversion18–48aUSNoProneGeneralNoMetallic272–3aNo100Pérez-Fentes et al.b, 202312128Severe pain and encrusted DJ stent40USYesSupineGeneralNoMetallic162No100SFR, stone-free rate; DJ, double-J; Fr, French; NS, not specified; US, ultrasound.aValues are presented as range.bPersonal experience of the authors, not included in the narrative review.
Between 70% and 80% of stones encountered during pregnancy typically pass spontaneously, making conservative management the preferred approach. However, in instances where calculi lead to obstruction of the upper urinary tract, complications such as fever, infection, sepsis, and uncontrolled pain may arise, necessitating interventional treatment [14].
Temporary drainage with either a stent or nephrostomy is the primary treatment approach in such scenarios during pregnancy. However, this method presents several drawbacks. Stents tend to encrust more rapidly during pregnancy, requiring exchange every 4–6 weeks [15,16]. Moreover, they can cause significant pain and discomfort and are more prone to dislodgement [17]. As a result, some patients may opt for definitive treatment rather than undergoing multiple sessions of stent exchange, especially considering the impact on their well-being.
Ureteroscopy (URS) emerges as the primary option when conservative treatment is unattainable or unsuccessful. URS has proven to be a safe and effective procedure during pregnancy, with the European Association of Urology guidelines positioning it with 1b level of evidence as an alternative strategy for ureteral stones in this population [[18], [19], [20]]. However, the feasibility of URS is contingent upon stone volume, and in cases of complex or high-volume calculi, it may require extended operating times and potentially multiple surgeries for a complete stone removal. In such scenarios, PCNL emerges as a more efficient treatment option, despite its associated increased morbidity, along with other technical considerations specific to the pregnant population.
PCNL is generally not recommended during pregnancy due to concerns regarding the duration of anesthesia, the requirement for fluoroscopy, and the need for prone positioning [21]. However, advancements in anesthesia techniques, various technical refinements, and the ability to perform the surgery in a supine position have mitigated some of these challenges for pregnant women [22].
The primary indication for PCNL observed in this review was among patients presenting with large stones and complications associated with urinary diversion methods such as double-J stents or nephrostomy tubes, resulting in significant discomfort. Additionally, PCNL was considered for patients who declined the maintenance of these catheters throughout pregnancy and sought definitive treatment. While flexible URS has shown promise as a less invasive approach in interventional stone management, its efficacy in addressing large and complex stones is limited by prolonged operating times and potential complications, including an increased risk of residual stone fragments or the need for subsequent surgical interventions [23,24]. In this regard, we believe that the indication for PCNL in Toth et al.’s study [9] is controversial, as an 8 mm stone could have been successfully managed retrogradely with flexible URS, thus avoiding the risks associated with a percutaneous approach.
Regardless of the chosen definitive treatment approach, the literature consistently recommends delaying intervention until the second trimester to minimize the risk of miscarriage [25,26].
Patient selection, multidisciplinary decision-making involving obstetricians, radiologists, and anesthesiologists, and comprehensive patient counseling regarding potential risks are essential when considering PCNL procedures during pregnancy.
As with any patient undergoing PCNL, a preoperative urine culture is imperative, and antibiotic treatment is necessary if significant bacteriuria is detected.
Concerning imaging modalities, an ultrasound scan emerges as the primary screening tool for pregnant females, being the safest and most frequently used diagnostic method. Although CT is the preferred method for evaluating stones in the general population, its potential teratogenic effects preclude its use during the first trimester of pregnancy.
The American Urological Association recommends low-dose CT, limiting radiation exposure to a maximum of 50 mGy, as an alternative imaging modality in the second and third trimesters of pregnancy when ultrasound findings are inconclusive [27]. The European Association of Urology advises against routine imaging repetition in pregnant patients but advocates for the use of radiologic procedures when clinically indicated. However, in our review, none of the cases utilized preoperative CT for surgical planning. MRI without gadolinium, capable of identifying stones as filling defects, is also proposed as a secondary imaging option in the first trimester when ultrasound imaging fails to secure a diagnosis [[28], [29], [30]].
Lastly, patient counseling should include provisions for access to neonatal and obstetric services, with consideration given to corticosteroid administration for viable fetuses to promote lung maturation and mitigate the risk of premature labor.
The primary objectives of anesthesia for non-obstetric surgeries, including PCNL, are to prioritize maternal safety, maintain the pregnancy, and safeguard fetal well-being. Standard preoperative evaluation protocols apply to pregnant patients, although surgery is typically deferred until the second trimester to mitigate the risk of spontaneous abortion and preterm labor.
While anesthetic agents are not generally considered teratogens at standard perioperative doses, minimizing medication exposure during pregnancy is prudent due to uncertainties regarding potential adverse effects [31].
Maintaining fetal well-being during PCNL involves optimizing uteroplacental perfusion and avoiding factors that could compromise fetal oxygenation and circulation. Although regional anesthesia is often favored to minimize fetal drug exposure and avoid the need to manage the airway, evidence supporting its superior safety over general anesthesia is lacking. While PCNL under regional anesthesia has demonstrated its safety and feasibility in the general population, PCNL is typically performed under general anesthesia [32].
Our review revealed limited information regarding the specific anesthetic techniques utilized, with only three publications specifying the approach [9,11,13]. Among these, seven cases were performed under general anesthesia, while four cases were performed under regional anesthesia. Lastly, performing PCNL during pregnancy necessitates access to neonatal and pediatric services, and careful monitoring of the fetal heart rate before and after the procedure is essential for ensuring fetal safety [33].
One of the main reasons for contraindicating PCNL during pregnancy, in addition to the need for fluoroscopy to guide procedural steps, is the challenge of positioning the patient in the prone position. The supine position, advocated by Valdivia Uría et al. [34], improves access to the airway for the anesthesiologist and reduces the risk of fetal compression against the surgical table. However, pure supine positioning may also compress the vena cava and aorta due to the enlarged uterus, particularly in the third trimester. In such cases, it is advisable, if feasible, to position the patient slightly on the left side with the pregnant uterus tilted leftward to alleviate vena cava compression [35].
Furthermore, supine positioning enables the adoption of a combined approach for endoscopic combined intrarenal surgery (ECIRS), potentially improving stone clearance rates and reducing operative time. Additionally, ECIRS allows the endoscopic control of puncture and dilation manoeuvres if a flexible ureteroscope can be introduced at the beginning of the procedure [36].
PCNL has traditionally been performed using X-ray guidance for puncture and dilation. Recently, ultrasound has been integrated into PCNL procedures, either as a standalone modality or in combination with fluoroscopy, offering several advantages. Ultrasound allows for precise visualization of the kidney and pelvicalyceal system, facilitating accurate targeting while reducing the risk of injury to surrounding structures [37].
In this review, 13 out of 14 patients underwent a fluoroless procedure, underscoring the growing adoption of ultrasound-guided PCNL.
Performing a fluoroless PCNL demands a certain level of expertise [38]. Ultrasound puncture is relatively straightforward when the calyx of access is dilated or there is a stone as a target [39]. The surgeon must navigate the needle towards the desired calyx, either using a free-hand technique or a needle-holder, tracking the entire trajectory of the needle. Guidewire placement into the renal pelvis and ureter is also easily controlled under ultrasound (Fig. 1; the patient has signed informed consent to have this anonymized figure used for publication). However, the most challenging step to manage under ultrasound is tract dilation, mainly due to the movement of the kidney when advancing the dilators. In our opinion, the optimal method to monitor the depth of dilation is endovision control through a flexible ureteroscope [40].Figure 1Guidewire (red arrow) placement controlled under ultrasound.Figure 1
Alternatively, if this option is not feasible, some authors suggest measuring the skin-to-calyx distance prior to dilation and using this information to advance the dilators into the kidney. Furthermore, balloon dilators, which offer radial dilation of the tract and cause less kidney mobility than other methods for dilation, can be advantageous [41,42].
Finally, haptic feedback and observing urine outflow from the dilator or Amplatz sheath lumen are also helpful.
However, even when a fluoroless PCNL is intended, it is essential to have the C-arm in the operating room to address any potential difficulties that may arise. X-ray imaging should be readily available during the procedure if required and used in adherence to as low as reasonably achievable (ALARA) principles. Lead shielding of the pelvis can be an option to reduce radiation exposure to the fetus, but sometimes it may inadvertently increase the dose delivered to both the patient and fetus if the shielding is positioned under the direct X-ray beam.
To minimize the risk of bleeding and facilitate percutaneous access creation without X-rays, some authors [8,12] advocate for the placement of a nephrostomy tube prior to PCNL, utilizing the mature tract for access.
We recently employed this approach in a 21-year-old woman in her 28th gestational week, presenting with severe pain and upper tract obstruction due to an encrusted stent with a 40 mm stone in the renal pelvis of the right kidney and a 30 mm stone in the bladder, as well as encrustations along the ureteral portion of the stent.
To alleviate her pain, drain the obstructed kidney, and mature the tract for PCNL, we placed a nephrostomy tube in the middle calyx under ultrasound guidance. The PCNL procedure was conducted 2 weeks later, in the Galdakao-modified supine Valdivia position, which allowed simultaneous treatment of the bladder and renal calculi, thereby reducing operating time. Furthermore, since in this position an airbag is positioned under the patient’s right flank, a 30-degree left lateral tilt is achieved, which minimizes the risk of aortocaval compression and supine hypotension syndrome [43].
Tract dilation was achieved in one shot under ultrasound guidance up to 16 Fr using the MIP-M set by Karl Storz (Tuttlingen, Baden-Württemberg, Germany) through the nephrostomy tract (Figure 2, Figure 3; the patient has signed informed consent to have these anonymized figures used for publication). This approach facilitated the dilation without any bleeding. The entire stone burden and the stent were successfully removed within 106 min, leaving only a nephrostomy tube as drainage, which was removed the day after. The patient was discharged after 2 days without complications, and the condition of the fetus was confirmed to be perfect.Figure 2Use of a mature tract, previously established with a nephrostomy tube, for percutaneous nephrolithotomy.Figure 2Figure 3Percutaneous tract dilation using the MIP-M set under ultrasound control.Figure 3
This narrative review stands out as one of the few comprehensive assessments of PCNL during pregnancy, offering valuable insights into the technical nuances of this complex scenario. A primary limitation of this review is the paucity of data on PCNL during pregnancy, encompassing only six publications with a total of 14 patients. As a result, many of the recommendations provided rely heavily on expert opinions and exhibit a low level of evidence. Furthermore, this review is susceptible to publication bias, as it is plausible that additional PCNL cases during pregnancy have been conducted but remain undocumented in the literature.
The evidence synthesized in this review demonstrates that PCNL is a viable and safe option for managing complex stone cases during pregnancy. Although the indications for PCNL in pregnancy are limited, in specific cases, it can be an effective solution to urinary stone-related complications that may jeopardize maternal and fetal well-being.
When planning a PCNL during pregnancy, thorough evaluation of each patient’s clinical status, stone characteristics, gestational age, and the potential impact of the intervention on both maternal and fetal health is crucial. Such considerations underscore the importance of shared decision-making within the multidisciplinary team and with the patient, wherein the pros and cons of PCNL are carefully weighed against alternative treatment options.
Due to the unique challenges that PCNL in pregnancy represents, it should be performed in experienced centers. Technical refinements such as the possibility to conduct the surgery in the supine position, the performance of a fluoroless procedure, the combination of retrograde and anterograde approaches in ECIRS, and the miniaturization of endoscopes can help minimize morbidity and improve outcomes in the pregnant population.
Overall, although the experience with PCNL in pregnancy is limited, current evidence suggests that it can be a safe and feasible therapeutic option in carefully selected cases. This approach requires a nuanced and individualized strategy, guided by close collaboration among specialists. Further studies are essential to confirm the broader application of this procedure and to establish its safety and efficacy in the context of pregnancy.
Study concept and design: Daniel Pérez-Fentes, Esteban Emiliani, María Elena Martínez-Corral, Lucía Mosquera-Seoane, Ernesto Donoso.
Data acquisition: Daniel Pérez-Fentes, María Elena Martínez-Corral.
Data analysis: Daniel Pérez-Fentes, María Elena Martínez-Corral.
Critical revision of the manuscript: Daniel Pérez-Fentes, Esteban Emiliani, María Elena Martínez-Corral, Alba García-Catalán, Beatriz Ulloa-Iglesias.
The authors declare no conflict of interest.