Bakhman G. Guliev — M.D., Dr. Sc. (Med), Full Prof.; Prof., Head, Urology Centre with Robot-assisted Surgery
St. Petersburg
Ali E. Talyshinskiy — Resident
St. Petersburg
Evgeniy O. Stetsik — M.D., Urologist; Postgraduate student
St. Petersburg
Murad U. Agagyulov — M.D., Urologist; Postgraduate student
St. Petersburg
Introduction. The non-biological simulators presented in the literature are far from the real human anatomy and are primarily aimed at developing the skill of the pyelocalyceal system (PCS) puncture without the possibility of imitating various intraoperative scenarios.
Purpose of the study. To describe the manufacturing and initial testing of the ultrasound-guided PCS puncture simulator with arbitrary placement of bone landmarks and a kidney model, along with the use of a retrograde view during PCS puncture.
Materials and methods. This study included training for 5 resident and 2 urologists. Each participant performed the puncture 5 times using an 18-gauge ultrasound-guided needle. A comparison was made between the number of attempts to form access, the duration of the puncture and its correctness (puncture into the small calyx through the papilla), as well as the correctness of determining the target calyx. The trajectory of the needle was retrogradely assessed using a semi-rigid ureteroscope, and the anatomical identification of the selected calyx was assessed using our mobile application.
Results. The total number of attempts was 49 and 14 among residents and urologists, respectively. The average duration of the puncture step was 25.2 and 12.0 seconds. In 9/25 cases, residents were able to correctly analyze visual ultrasound information to determine the target calyx. When a contrast agent was injected into the PCS after 63 punctures, no contrast leakage was found.
Conclusion. The proposed PCS puncture simulator allows to develop to develop all the necessary skills for cost-effective training of young urologists in the technique of percutaneous access.
Введение. Небиологические тренажёры перкутанной нефролитотрипсии (ПНЛ) далеки от реальной анатомии человека и нацелены в первую очередь на развитие навыка пункции чашечно-лоханочной системы (ЧЛС) без возможности имитации различных интраоперационных сценариев.
Цель исследования. Описать производство и первичную апробацию тренажёра для пункции ЧЛС почки под ультразвуковым (УЗ)-контролем с произвольным расположением костных ориентиров и модели почки, а также использование ретроградного контроля при пункции ЧЛС.
Материалы и методы. В данной работе на тренажёре обучали пять клинических ординаторов и двух урологов. Каждый включённый в работу участник выполнял пункцию (до зафиксированного вхождения в полость почки через малую чашечку) 5 раз с помощью иглы 18 калибра под УЗ-наведением. Проводилось сравнение количества попыток формирования доступа, длительность пункции и её корректность (прокол в малую чашечку через сосочек), а также правильность определения таргетной чашечки. Траектория иглы оценивалась ретроградно с помощью полужесткого уретероскопа, а анатомическая идентификация выбранной чашечки — с помощью разработанного нами мобильного приложения.
Результаты. Общее количество попыток составило 49 и 14 среди ординаторов и врачей, соответственно. Средняя длительность пункционного этапа у них равнялась 25,2 и 12,0 секунд соответственно. В 9 из 25 случаев ординаторы смогли правильно проанализировать визуальную УЗ-информацию для определения таргетной чашечки. При введении контрастного вещества в ЧЛС после 63 пункций затека контраста обнаружено не было, что указывает на длительную пригодность предложенного тренажёра.
Заключение. Предложенный тренажёр для пункции почки позволяет развивать все необходимые навыки, является экономичным для обучения молодых урологов технике перкутанного доступа.
Percutaneous nephrolithotripsy (PCNL) is an endourological intervention, which is complicated in mastering and requires over 60 performed operations for significant experience [
The study aimed to describe the manufacturing and initial testing of the ultrasound-guided PCS puncture simulator with an arbitrary placement of bone landmarks and a kidney model, along with the use of a retrograde view during PCS puncture training of residents.
The computed tomography (CT) urography images of a patient with a stone (2.3 cm) in the left kidney pelvis were obtained after the patient signed informed consent. CT images were analyzed with the software DICOM Viewer (RadiAnt, Poznań, Poland). After 3D reconstruction of the excretory phase, the following structures were identified for further printing: 11th and 12th ipsilateral ribs, a fragment of an iliac wing, and the PCS of the affected kidney. Further, the left half of the lumbar area and the kidney parenchyma were identified for the formation of the respective molds. The data of the mentioned structures were saved in STL format and sent to a bioengineer for their preparation for 3D printing. Polylactide (PLA) was used as a material for the 3D printing of bone structures and body contours. The latter consists of the following parts: inferomedial, superolateral, and anterior walls made of metal to provide a fast gelatin conduction-type cooling down. The medial wall of the mold had a mounted plate for manual fixation of bone structures with magnets. The kidney mold is also made of PLA. A water-soluble printed kidney PCS was placed into the mold (Figure 1).
Figure 1. Printed molds for embedding the body with a metal plate on the medial wallfor fixing the ribs and a fragment of the iliac bone (A)and for embedding the kidney with an in-located soluble pyelocalyceal system (B)
For better imitation of the kidney parenchyma properties, multicomponent silicone with 0–30 Shore was used. A Malecot 20 Ch catheter was used for a ureter.
Gelatin composition. Gelatin composition for filling the body mold directly depends on the echogenicity of the ultrasound (US) picture and sensations of resistance during the puncture. In this direction, the publication of Gadgieva et al. [
Simulator assembly. CT images were used to identify the spaces between the 11th and 12th ribs and iliac wing, the distance between the mentioned bone landmarks and kidney, as well as the orientation of the kidney. Bone structures were placed on the medial wall of the body model considering the data obtained earlier. For stabilization of the kidney model obtained in space with regard to its poles and medial edge, magnet threads were attached, which allowed the authors to identify its orientation and depth of location in the simulator. When all components were placed, both body mold walls were connected and located vertically on a metal wall with further filling with gelatin. The filled mold was placed in a refrigerator for 24 hours to solidify (Figure 2).
Figure 2. The resulting kidney model with a Malecot catheter installed as a ureterand with thread fixators to determine the depth and location of the kidney (A)in the kidney puncture simulator after filling and solidifying of gelatin (B)
Simulator evaluation. The study included five first- and second-year residents (Group 1) and two urologists with experience of individual PCNL performance of > 60 surgeries (Group 2). Each participant made five puncture attempts (the authors counted the number of punctures in the small calix through the papilla) using an 18 gauge US-guided needle.
Figure 3. Ultrasound view of the modeled "parenchyma" and the pyelocalyceal system (A).Retrograde infusion and fluid outflow after successful approbation puncture (B)
The authors made a comparison between the number of attempts to form access, the duration of the puncture, and its correctness, as well as the precision of determining the target calyx. Finally, after puncture, the participants identified the punctured calix according to the US image. For more precise identification, the needle trajectory was retrogradely evaluated using a semi-rigid ureteroscope. The anatomical determination of the target calix was performed with the mobile application InsKid (Inside Kidney) developed by the authors (Figure 4) [
Figure 4. Retrograde evaluation of the needle puncture coursethrough the calyx of the upper (A), middle (B), and lower (C) groups.Virtual endoscopy view (center and right figures)obtained using a mobile application to accurately determine the punctured calyx
After the simulator approbation by the groups, a contrast agent was injected into the renal cavity to check its consistency and suitability for further application.
Statistical analysis. There was performed using IBMÒ SPSS Statistics 23 (SPSS: IBM Company, IBM SPSS Corp., Armonk, NY, USA). The variability of the data was described using the mean values with the specification of the maximal and minimal values. To evaluate continuous and discrete data, the Student test was used. Nominal data were assessed using the c-square test. The difference was significant at p < 0.05.
Residents and urologists made a total of 49 and 14 puncture attempts, respectively, into the small calix through the papilla. The mean time of puncture stage was 25.2 and 12.0 seconds. Only in nine cases, residents could analyze properly the visual US images for correct calyx targeting, which shows the lack of experience in percutaneous manipulation (Table).
Table. Training performance among residents (Group 1) and urologists (Group 2)
Parameter | Group 1 | Group 2 | p |
Attempts, n | 49 | 14 | – |
Puncture time, sec | 25.2 (8.0–59.0) | 12.0 (7.0–21.0) | < 0.05 |
Correct calyx targeting | 9/25 | 10/10 | < 0.05 |
After 63 punctures (total number of punctures in both groups), a contrast agent was injected. No leakage was detected, which indicated the long-term durability of the proposed simulator.
PCNL almost completely replaces open surgery in patients with nephrolithiasis [
Currently, young specialists have some difficulties in acquiring skills in PCNL performance. Not all urological units specialize in the surgical treatment of nephrolithiasis, which limits the number of patients enrolled for skills training without a decrease in the effectiveness of surgical interventions. Second, not all units have a C-arm, which negatively affects the training in this technique either.
The most promising training method is the application of simulators [
Virtual reality simulators can be used without a real C arm and for puncture training in various scenarios, which is an advantage for qualitative preparation of surgeons for real-time practice with no potential harm to patients. An example of such a simulator is the PERC Mentor Suite (Simbionix Ltd., Beit Golan, Airport City, Israel) [
Simulators based on animal tissues and organs primarily involve the application of pig kidneys because of the multi-calyx structure of their PCS. Strohmaier et al. [
The application of non-biological simulators solves the issues that face the users of VR and biological simulators. They are simple in use, structurally variable, and provide long-term service within several months if stored adequately. However, their disadvantage lies in unrealistic human anatomy.
The authors believe that the study by Ali et al. [
A simulator that is simpler in design was described by Aro et al. [
A more available option is the formation of PCS from a disposable glove placed into a rectangular cavity filled with gelatin, which was described in the study by Septian et al. [
The described examples show that an increase in similarity to real human anatomy increases the cost and time required for the preparation of such simulators. A simpler approach to the imitation of kidney PCS results in a decrease in the real anatomic properties of the model.
To avoid such drawbacks, the authors of the present study proposed some solutions. First, the application of the described composition provides a significant volume of filler without affecting its reutilization. Second, the contour of the simulator shaped as a human lumbar area and the application of the 11th and 12th ipsilateral ribs and a fragment of an iliac bone with their manual positioning on the medial wall of the simulator provide a real anatomy model of a given patient. Moreover, these structures can be placed relative to each other and relative to the silicon kidney, which artificially changes the difficulty of such training and prepares the trained surgeons for various scenarios. The application of various density materials to fill the body model and make a kidney provides a urologist with reliable tactile feedback during puncture. Third, the application of pink silicon to make a kidney and a catheter of a sufficient diameter to imitate a ureter makes it possible to perform retrograde nephroscopy, which can be used for the control and evaluation of a puncture demonstrated in the present study. The described solutions provide not only the training of puncture skills, but also the following stages of PCNL imitation.
Despite the described advantages, this simulator has its drawbacks. The preparation of a silicon kidney is a limiting factor because, after irreversible changes, a new kidney needs to be made, which takes around 12 hours. The tissues between the skin and kidney are made of homogenous gelatin, which does not provide tactile feedback when the needle goes through the fascia and muscles. It is impossible to assess artery damage during training because the proposed simulator does not contain artificial vessels. Despite these drawbacks, the results of the study confirm the feasibility of the proposed simulator to train young specialists and to prepare experienced urologists for various PCNL scenarios.
The proposed and approbated method of preparation of a simulator for kidney puncture training allows the specialists to develop the required skills and provides an economic solution for training of the young specialists. The application of the retrograde puncture control and mobile application navigation during the identification of certain parts of the PCS highlights the mistakes made by the surgeon, which increases the quality of the training process.
The authors declare that there are no conflicts of interest present.