An interactive teaching device simulating intussusception reduction

Abstract

Intussusception is relatively uncommon, occurring in 0.5 to 2.3 cases per 1,000 live births in the USA. Radiology residents, therefore, have few opportunities to participate in intussusception reduction during training, and practicing radiologists encounter it infrequently. Training is essential, as successful reduction avoids surgery. The judgment involved in reducing an intussusception is best gained with experience. We developed a training device that simulates fluoroscopic intussusception reduction with air. The device consists of a doll that contains a cylinder with similar stress and strain characteristics to the human colon. The trainee pumps air into the cylinder through a rectal tube using a standard hand-held air reduction pump. A sensor measures the pressure within the chamber and transmits readings to a computer, which displays images from actual intussusception reductions based on the pressure maintained within the device. A random component in the software gives the user a new experience each time and models uncertainties in the actual reduction process, including perforation. This intussusception reduction simulator can enhance resident education, giving residents the opportunity to practice this technique before employing it on a real patient. The simulator can also help practicing radiologists become more comfortable with intussusception air reduction.

Fig. 1

Plastic tubing with the instructor’s external release valve (arrow) connects the aneroid gauge and bulb insufflator to the cylinder within the doll. Additional tubing extends from the doll to a pressure sensor and is transmitted via USB cable to a computer

Fig. 2

Probability of the four possible events as a function of achieved pressure. The probability of perforation increases rapidly after reaching 140 mmHg (diamond). Regression (square) is more likely at low pressures. Early on in the procedure (triangle), probability of progression, or reduction of the intussusceptum, is relatively high, but as the duration of the procedure increases the probability of reduction (x) is much lower

Fig. 3

Flow chart of the MATLAB algorithm. The pressure sensor transmits readings to the computer every 0.5 s. Based on the pressure and the stage of reduction, the computer calculates the probability of advancing to the next stage, retrogressing to the previous stage, and perforating the bowel. The computer then compares these probabilities to a random number and decides what event, if any, will occur. The process then repeats for the next pressure reading

Fig. 4

Supine pre-procedural radiograph of patient with intussusception demonstrates a soft-tissue mass in the right upper abdomen and several mildly dilated loops of bowel

Fig. 5

Fluoroscopic image of patient during a reduction procedure. Air now fills most of the colon, and the soft-tissue mass of the intussusceptum is now in the ascending colon

Fig. 6

Fluoroscopic image of a patient immediately after successful reduction of intussusception demonstrates absence of soft-tissue mass and gas filling multiple small bowel loops

Fig. 7

Inverted modified radiograph of a patient with perforation demonstrates gas outlining bowel loops, liver and spleen