Press firmly, but not too hard, or else Patrick says "Ow!"
Other lines of prerecorded dialogue include "That's cold!" and "You're rather thorough, aren't you?"
This responsive rump - officially called a "mixed-reality human" - is just a research tool for now, and has not been added yet to the medical school's formal curriculum.
But it seems to help, said D. Scott Lind, chairman of the med school's department of surgery.
"You don't want someone who doesn't know what they're doing examining a private part of your body," Lind said.
Therein lies a key goal of medical simulation, a field that dates at least to the mid-1700s, when a Frenchwoman named Madame du Coudray used mannequins to train midwives.
Mannequins remain widely used in medical schools, but they generally cannot give feedback. Medical students also practice their craft on actors pretending to be patients, but actors cost money and typically do not have tumors or other pathology that students must learn to recognize.
Mixed-reality patients such as Patrick potentially provide the best of both worlds, Lind said.
The Drexel physician and his colleagues also have developed a similar mannequin for breast exams. It contains two simulated tumors - one near the surface, and one deep inside that students often miss, said Drexel surgical resident Larry Greenawald, a member of the project team.
It all began a decade ago when Lind was at the University of Florida College of Medicine. He and Benjamin Lok, an associate professor of computer science at Florida, started developing virtual patients with headaches, abdominal pain, and other ills.
These "patients" could interact with students, but they existed only on-screen. A few years later, Lok and Lind heard about surgeon Carla Pugh, now at the University of Wisconsin, who had added pressure sensors to mannequins.
They proceeded to create simulators that combined both elements - the mannequin and the on-screen portion. That meant students could practice both speaking and touching.
To make the prostate exam simulator, the researchers began with a silicone model of a rear end, made by a British company, Limbs & Things. They added pressure sensors and also the on-screen component.
The patient was originally named Harold, but the name was changed to Patrick because it stands for "prostate virtual interactive character," Lok said. Sort of.
For now, Patrick's spoken dialogue must be activated by a human being - the instructor who is overseeing the medical student. Eventually, the goal is to equip the simulator with voice-recognition technology so that it will be fully automated - a feature of previous virtual patients that were on-screen only.
The researchers have experimented with models that have different skin color, so that students can overcome any bias issues. Currently they are doing a study of a virtual Muslim patient who wears a head scarf.
Reena A. Parikh, a second-year Drexel med student who has helped to study the mixed-reality mannequins, said they are a valuable tool.
"It's a great way to get us ahead of the game," she said.
What about the jokes? Surely Patrick has been the butt of a few great one-liners?
A bit of nervous laughter, but so far no zingers from students. Greenawald said:
"They've been very professional."