Polyuria is excessive urination. Many people who experience this fairly common symptom only notice at night when they keep waking up to use the bathroom. Polyuria is different than urgency. It does not indicate a frequent urge to urinate, but rather that the body is producing more than 2.5 liters of urine every day, depending on fluid intake.
Nocturnal polyuria occurs when the body produces an excessive amount of urine at night. Defining this is difficult, though, as everyone's definition of "nighttime" is unique. If nocturnal polyuria relates to light levels or circadian rhythm, a fixed time defines when night begins. If it connects to sleep, a patient-defined bedtime is used.
One potential cause of polyuria is diabetes insipidus (DI), a rare disorder that renders the body incapable of regulating fluid balance, causing extreme thirst and polyuria. Daily urine outputs for someone with DI exceed three liters, in some cases. DI does not have a cure but the symptoms are manageable with synthetic hormones, a low-salt diet, and enough water intake to avoid dehydration.
Diavetes insipidus causes polyuria because the kidneys cannot concentrate urine effectively. Antidiuretic hormone (ADH) controls the amount of water excreted by the kidneys. DI prevents the brain from producing ADH, or hinders the kidneys' ability to respond to it, resulting in polyuria. Head injuries, tumors, autoimmune diseases, and infections can cause DI.
Another condition that causes polyuria is diabetic ketoacidosis (DKA). This occurs when the body has too little insulin and is unable to use glucose as a source of energy. The body begins to break down fat, some of which is turned into ketones that quickly accumulate in the blood. It also converts glycogen and proteins to make glucose. All of this causes a huge spike in blood sugar, which leads to extreme diuresis and polyuria.
Extreme thirst and polyuria are the two most common symptoms of DKA. Most people with the condition are type 1 diabetics, but between 27 and 37 percent are undiagnosed when their symptoms begin. This dangerous condition is the leading cause of death for people under 24 with type 1 diabeties. It also affects people with a specific subgroup of type 2 diabetes whose bodies are prone to making ketones.
DI and DKA are the two most common causes of polyuria, but there are some less common ones, too, including the use of diuretics, lithium, caffeine, and alcohol. High or low blood calcium levels, kidney failure, and sickle cell anemia can also cause it. Some people experience polyuria after receiving contrast die for an MRI or CT scan, but this usually only lasts for about 24 hours.
If you are experiencing polyuria that is not explained by an increase in fluid intake or medications, contact your doctor. They will likely ask you to monitor your polyuria at home by keeping track of what and how much you drink, how many times a day you urinate, the volume that your urinate, and how much you weigh every day on the same scale.
Once your doctor verifies that you are experiencing polyuria, a blood sugar check confirms or rules out diabetes. If there are no signs of diabetes, the doctor will carry out other tests, including blood chemistry, urinalysis, ADH level, and urine osmolality, to assess the concentration. The doctor may order an inpatient water deprivation test. The patient must abstain from drinking water, and medical professionals collect urine every hour to assess the concentration. This helps the doctor determine if the brain is not producing adequate ADH or if the kidneys are unable to use it properly.
Polyuria resolves by treating the underlying cause. DI treatments may include increased water intake, a low-salt diet, or desmopressin, a medication that replaces missing AHD. If a brain tumor or other abnormality is causing DI, the doctor will treat that first. DKA is usually treated in the hospital or clinic and involves fluid and electrolyte replacement and IV insulin with close monitoring.
Dehydration is the greatest danger of polyuria. If DI is the cause and the condition is treated properly, symptoms are manageable, and the person can live a normal life. DKA is more serious. If left untreated, it can result in coma, severe illness, or death. If caught early and treated in a hospital, symptoms of DKA, including polyuria, should resolve in 24 hours.
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