The Tomato Model

Percutaneous renal access (PCA) is one of the most difficult intervention in endourology. Hands-on training is a useful tool for a good understanding of the puncturing technique, reducing the learning curve, and lowering risks of complications during first procedures. The ideal surgical simulator should efficiently improve trainees' skills, be easily accessible, low-cost, and realistic. We aim to present novel fluoroscopy-guided PCA simulator named TOMATO model.

The model can be easily built in few minutes using low-cost items: yoga mat, cotton wool, forceps, needle-driver, scalpel, 0 silk suture, chiba needle, small pebble (1 cm ca) and a few kidney-shaped tomatoes. The yoga mat is fold in half, sutured with silk, placed on the operating table, and thanks to the friction created between the mat and sheet underneath there is no need for other fixating methods. Once placed inside the yoga mat, the tomato is held still in the position by the cotton wool, which is placed around the vegetable. The tomato imitates the real renal structure. Therefore is ideal for this use, and there is no need for liquid-contrast enhancement. The goal is achieved when the operator manages to move the pebble with chiba needle during pulsed fluoroscopy. The model was tested 3 times by 3 endourologists and by 10 residents in training with no experience as first operators. A 7-items questionnaire (1-10 rating scale) was administered to the participants in order to evaluate the utility of the model. Trainees' kidney access time (KAT) and radiation time (RT) were assessed at the first use and after 1 hour of training (circa 15 attempts to reach the target per resident).

The model allowed residents' significant reduction of the KAT and RT. KAT passed from 114 (144.25-89) to 72.5 (97.25-49.5) seconds (P = .04) while RAT passed from 82 (89.75-56) to 51.5 (60.25-35.75) seconds (P < .001). The residents particularly appreciated the high-fidelity reproduction of the anatomy that the model offers, and its' usefulness for learning the puncturing technique, giving it 8.5 and 10 points, while the same items were rated 7.7, and 9.3 by the experts, respectively. Trainees felt that their skills could be improved by using this model. The main issue was finding the materials mimicking the real-life tissues and their different characteristics.

TOMATO model might be a helpful and creative way to start learning the steps of kidney puncturing using low-cost materials and we believe its' strength is being easily reproducible in all urology units.