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Ultrasound guided kidney biopsy is a relatively safe procedure, yet it can result in catastrophic complications or inadequate diagnosis.
The use of realistic models improves the competency of healthcare providers utilizing ultrasound to supplement standard of care treatment, these models can be prohibitively expensive. We aimed to make a low-cost model with realistic properties to offer a high level of training to many nephrologists.
We have developed two handmade models to perform US guided kidney biopsy:
Model 1: A Sheep kidney was immersed in a 5% solution of gelatin with psyllium husks. 50 grams of gelatin powder was added to 950 mL of water and then heated to 60◦ Celsius with continuous stirring till complete dissolution of all powder. 30 grams of psyllium husks were added to the solution. Psyllium husks enhances the texture simulating the subcutaneous tissues in ultrasound images. The solution is then poured in layers to the container and left in refrigerator to become in a firm consistency. The sheep kidney was then immersed in the firm mixture and covered by the final layer of the solution to make a smooth surface.
The model represents very good characteristics for training of US guided kidney biopsy [Figure 1] , with excellent visualization and needle tracking by US making it almost a realistic model.
However, this model has three main limitations: 1. It should be used in cooled rooms.
Gelatin solution totally changes from solid to liquid form in room temperature after 1- 3 hours. 2. The pressure of ultrasound probe cracks model surface after multiple trials [Figure 2]. 3. The needle track is still visible and left behind after removal of the needle from this model. These limitations make the model only suitable for 10 – 15 trials . The cost was about 6 USD/ model.
Model 2: To improve the quality of our model, a starch-based model was done. 100 grams of starch is stirred in 900 mL cold water till it becomes totally dissolute. The mixture is then heated on medium temperature with continuous movement till it become boiled. After boiling, the mixture becomes thicker gradually. It is lift from heat and poured in layers with the sheep kidney inside. After cooling, the surface of the model is covered with a 1 mm thick layer of rubber silicone.
This model seems to have the same US characteristics of the previous model, but surprisingly it avoids all limitations of the previous one. Starch-based mixture never liquify in room air before 3 – 4 days. Starch solution has some self-healing properties that make needle tracks is almost invisible after needle removal. The surface silicon layer prevent damage done by US probe. This model is suitable for more than 50 trials. It costs only 7 USD/ model.
Our models were tested by eminent professors who agreed on the importance of its realistic properties. We succeeded to train more then 170 nephrologists in three large governorates in Egypt with these models in our hands-on workshops [Figure 3].
The ability of our models to mimic the texture and ultrasound image generated by real tissue can allow for realistic, hands-on training for ultrasound guided kidney biopsy in low income countries.