What tests and procedures diagnose diabetes insipidus?
A healthcare professional can diagnose a person with diabetes insipidus based on;
Medical and Family History
Taking a medical and family history can help a health care provider diagnose diabetes insipidus. A health care provider will ask the patient to review his or her symptoms and ask whether the patient's family has a history of diabetes insipidus or its symptoms.
A physical exam can help diagnose diabetes insipidus. During a physical exam, a health care provider usually examines the patient's skin and appearance, checking for signs of dehydration.
Urinalysis tests a urine sample. A patient collects the urine sample in a special container at home, in a health care provider's office, or at a commercial facility. A health care provider tests the sample in the same location or sends it to a lab for analysis. The test can show whether the urine is dilute or concentrated. The test can also show the presence of glucose, which can distinguish between diabetes insipidus and diabetes mellitus. The health care provider may also have the patient collect urine in a special container over a 24-hour period to measure the total amount of urine produced by the kidneys.
A blood test involves drawing a patient's blood at a health care provider’s office or a commercial facility and sending the sample to a lab for analysis. The blood test measures sodium levels, which can help diagnose diabetes insipidus and in some cases determine the type.
Fluid Deprivation Test
A fluid deprivation test measures changes in a patient’s body weight and urine concentration after restricting liquid intake. A health care provider can perform two types of fluid deprivation tests:
A short form of the deprivation test. A health care provider instructs the patient to stop drinking all liquids for a specific period of time, usually during dinner. The next morning, the patient will collect a urine sample at home. The patient then returns the urine sample to his or her health care provider or takes it to a lab where a technician measures the concentration of the urine sample.
A formal fluid deprivation test. A health care provider performs this test in a hospital to continuously monitor the patient for signs of dehydration. Patients do not need anesthesia. A health care provider weighs the patient and analyzes a urine sample. The health care provider repeats the tests and measures the patient's blood pressure every 1 to 2 hours until one of the following happens:
- The patient's blood pressure drops too low or the patient has a rapid heartbeat when standing.
- The patient loses 5 percent or more of his or her initial body weight.
- Urine concentration increases only slightly in two to three consecutive measurements.
At the end of the test, a healthcare provider will compare the patient's blood sodium, vasopressin levels, and urine concentration to determine whether the patient has diabetes insipidus. Sometimes, the health care provider may administer medications during the test to see if they increase a patient's urine concentration. In other cases, the health care provider may give the patient a concentrated sodium solution intravenously at the end of the test to increase the patient's blood sodium level and determine if he or she has diabetes insipidus.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a test that takes pictures of the body's internal organs and soft tissues without using x-rays. A specially trained technician performs the procedure in an outpatient center or a hospital, and a radiologist, a doctor who specializes in medical imaging who interprets the images. A patient does not need anesthesia, although people with a fear of confined spaces may receive light sedation. An MRI may include an injection of a special dye, called contrast medium. With most MRI machines, the person lies on a table that slides into a tunnel-shaped device that may be open ended or closed at one end. Some MRI machines allow the patient to lie in a more open space. MRIs cannot diagnose diabetes insipidus. Instead, an MRI can show if the patient has problems with his or her hypothalamus or pituitary gland or help the health care provider determine if diabetes insipidus is the possible cause of the patient's symptoms.