A digital kidney is teaching researchers at the University of Waterloo about the impact of medicines on the dehydrated body.

The model has found that unless a patient is properly hydrated, taking two blood pressure drugs and an aspirin could cause acute kidney injury.

University of Waterloo professor of applied mathematics, pharmacy and biology Anita Layton said: “People who have high blood pressure are typically given a water pill, so they pee a lot to lower their blood volume and in so doing lower their blood pressure. These patients are frequently also given another drug that targets a hormonal system which will affect the kidney as well.

“A lot of people are on these two drugs, and they will be fine. But one day they might have a headache and take an aspirin, and the three of these drugs together can hurt your kidneys.”

Elderly people, those with impaired kidney function and patients taking certain drugs or drug combinations need to be mindful of their water intake, or they can face unpleasant side effects. This is because their kidneys can struggle to maintain water balance. Vital functions, like producing highly concentrated urine to get rid of waste using as little water as possible when dehydrated, can be impaired.

Layton has built the first computational model of a kidney which simulates the muscle contractions which move urine from the kidney to the bladder. The computer model simulated the effects of various drugs on the urinary system, and applied mathematical techniques to analyse the data.

The model found that in dehydrated patients, combining two blood pressure drugs and an aspirin can cause injury when there is an insufficient water balance in the body. This leads to a build-up of waste product in concentrated urine.

Layton said: “Incredibly, how mammals produce a highly concentrated urine is not well understood. We’re now a step closer to understanding how water balance is maintained in mammals.”