Diabetes Insipidus: Tests & Diagnosis

Instructor: Artem Cheprasov
This lesson will teach you about the basics of diabetes insipidus, as well as the names and values of the major diagnostic tests that can be used to help diagnose it.

Extreme Thirst & Urination

Imagine you get up one day and start urinating out twenty times more urine than you usually do. Then, you guzzle water non-stop throughout the day because you're always extremely thirsty. You don't get a good night's sleep either, because you always have to run to the bathroom to avoid wetting your bed. Sounds pretty bad, right?

Well, that may happen to you if you have diabetes insipidus. Hopefully you don't. But if you're curious as to what tests may be run to diagnose it, you're in luck. That's what this lesson is about.

What Is Diabetes Insipidus?

Diabetes insipidus (DI) is a condition that causes people to urinate excessively, feel thirsty all the time, and have to go to the bathroom at night. One major cause of this condition is the inappropriate production of a hormone called antidiuretic hormone (ADH), also known as vasopressin. This hormone is produced by the brain. ADH tells the kidneys to make less urine. No ADH, as a result of something wrong with the brain, means more urine is produced.

Another major cause is the lack of an appropriate response to ADH by the kidneys. There's plenty of ADH, it's just that the kidneys are like bratty children and refuse to listen to its orders to stop making so much urine!

Either way, the kidneys produce a lot of urine, the person has to go to the bathroom all the time, and they feel extremely thirsty as a result as well. That's diabetes insipidus in a nutshell for you.

Test & Diagnoses

One of the tests that helps diagnose DI is pretty cool. You know that one of the reasons for DI is a problem in the brain. So if you could look somewhere in the body to diagnose Di, where would it be? It would be inside your head, of course.

Now, you could take an x-ray to look inside the head. The problem is an x-ray won't really show you anything. A better test that can show a lot of brain detail is called magnetic resonance imaging (MRI). Basically, this diagnostic test uses magnetic waves to create a very detailed and layered picture of your brain. This helps doctors pinpoint any potential abnormalities in the brain that may be causing DI.

Another diagnostic test that can be used is called a urinalysis. It's pretty much what it sounds like. It analyzes urine. A urinalysis can tell your doctor if your urine has bacteria in it, if there are red blood cells in there, and plenty of other things. One thing doctors look for on a urinalysis, with respect to DI, is an indication that your urine is dilute. In other words, there is a lot of water in your urine, more than usual. This is one sign of diabetes insipidus. Of course, other conditions can have dilute urine, so a urinalysis (alone) is never enough to definitively diagnose diabetes insipidus.

A better and more specific test for diabetes insipidus is called a water (fluid) deprivation test. In short, a person is told to stop drinking anything and everything for a period of time. During this test, a person's urine, blood, and ADH values are closely monitored. These values are then carefully analyzed to determine if a person has DI or not.

Sometimes, a person is given an injection of vasopressin as well. If a person produces less urine thanks to this injection, then this likely indicates the person's DI stems from a problem in the brain. The problem being, a lack of production and thus a shortage of ADH. If the person keeps making lots of urine despite the injection, then we'd have to suspect the kidneys are the ones at fault (they're not responding to it despite lots of ADH being made by the brain).

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