Humans are complex so in general if you remove an important system, you won’t live very long. This is certainly the case with the urinary system. Urination plays a very important role in what’s called homeostasis, which is the body’s ability to stay stable.

Urine is produced when blood is filtered through your kidneys. Blood needs to be constantly filtered because it accumulates waste with time. One example of accumulating waste is creatinine, which is muscle waste.

Another example is urea which is a waste product that comes from breaking down proteins. Without your kidneys filtering blood into urine, these waste products would just build up and eventually be toxic to cells. Additionally, your kidneys are like accountants that make sure that all the salts are at the right concentration in blood. This is why if you drink a lot of water, you urinate a lot. Your kidneys increase the rate of filtering blood to make sure that the salts in your blood don’t get too dilute. The opposite is also true in that if you don’t drink a lot of water you don’t urinate a lot because your kidneys decrease the filtering rate.

Every cell requires specific conditions to survive and carry out its function. The urinary system is responsible for maintaining those conditions in the blood that nourishes the cells. That’s why kidney disease is so serious. When the body loses its ability to set the right concentrations of salts and other molecules, the eventual result is cells dying. And of course, if enough important cells die, the person will die as well.

You poison yourself and die from buildup of urea, which is a chemical waste product from the breakdown of proteins.

In order to survive, a human needs all of its organ systems, so the quick answer is that without a urinary system, you would die. That isn’t an interesting enough answer though, so let’s look specifically at what would go wrong if a person spontaneously lost their urinary system. The urinary system works to remove liquid waste from the body and also maintaining the balance of ions and other small molecules in the blood. So one problem would be that you would have no way to efficiently remove water from your body. With too much water in your body, your blood volume would rapidly increase, diluting your blood, starving your cells of nutrients while simultaneously causing heart complications due to massively high blood pressure. If that didn’t kill you, the liquid waste found inside urine would build up inside your blood and likely poison your cells. Every body system is important in its own specific way, and the urinary system is no exception. Thank you for your question!