Diagnosis

Autonomic neuropathy is a possible complication of a number of diseases, and the tests you'll need depend on your symptoms and risk factors for autonomic neuropathy.

When you have known risk factors for autonomic neuropathy

If you have conditions that increase your risk of autonomic neuropathy, such as diabetes, and have symptoms of the condition, your doctor will perform a physical exam and ask about your symptoms.

If you are undergoing cancer treatment with a drug known to cause nerve damage, your doctor will check for signs of neuropathy.

When you don't have risk factors for autonomic neuropathy

If you have symptoms of autonomic neuropathy but no risk factors, the diagnosis can be more involved. Your doctor will probably review your medical history, discuss your symptoms and do a physical exam.

Your doctor might recommend tests to evaluate autonomic functions, including:

• Autonomic function tests. These tests measure how your heart rate and blood pressure respond during exercises such as deep breathing and forcefully exhaling (Valsalva maneuver).

• Tilt-table test. This test monitors the response of blood pressure and heart rate to changes in posture and position, simulating what occurs when you stand up after lying down. You lie flat on a table, which is then tilted to raise the upper part of your body. Normally, your body narrows blood vessels and increases heart rate to compensate for the drop in blood pressure. This response may be slowed or abnormal if you have autonomic neuropathy.

  A simpler test for this response involves standing for a minute, then squatting for a minute and then standing again while blood pressure and heart rate are monitored.

• Gastrointestinal tests. Gastric-emptying tests are the most common tests to check for digestive abnormalities such as slow digestion and delayed emptying of the stomach (gastroparesis). These tests are usually done by a doctor who specializes in digestive disorders (gastroenterologist).
• Quantitative sudomotor axon reflex test. This test evaluates how the nerves that regulate your sweat glands respond to stimulation. A small electrical current passes through capsules placed on your forearm, upper and lower leg, and foot, while a computer analyzes the response of your nerves and sweat glands. You might feel warmth or a tingling sensation during the test.
• Thermoregulatory sweat test. You're coated with a powder that changes color when you sweat. While you lie in a chamber with a slowly increasing temperature, digital photos document the results as you begin to sweat. Your sweat pattern might help confirm a diagnosis of autonomic neuropathy or suggest other causes for decreased or increased sweating.
• Urinalysis and bladder function (urodynamic) tests. If you have bladder or urinary signs and symptoms, a series of urine and bladder tests can evaluate bladder function.
• Ultrasound. If you have bladder signs and symptoms, your doctor might do an ultrasound in which high-frequency sound waves create an image of the bladder and other parts of the urinary tract.