Polyuria - Causes and Remedies

Introduction

Polyuria is a medical condition in which the person passes an excess amount of urine. The normal urine output in a healthy individual is around two liters per day, whereas a urine output of more than three liters is suggestive of polyuria. The frequency of urination is also increased, but it may or may not be associated with polyuria.

What Is the Pathophysiology of Polyuria?

Pathophysiologically, polyuria is divided into two types:-

• Polyuria is due to the increased removal of the solutes or the substances present in the urine.

• Polyuria due to the inability to increase the solute concentration.

Water homeostasis, or regulation of water intake and loss, is achieved by the kidneys.

When water intake increases, the blood volume increases, whereas the blood osmolality (concentration of the chemical substances in the blood) decreases, resulting in a decrease in the release of ADH or antidiuretic hormone. This hormone promotes water reabsorption in the kidney ducts. Decreased ADH increases the urine volume making blood osmolality return to normal. The presence of a high concentration of solute in the renal tubes also increases urine volume.

What Are the Causes of Polyuria?

Polyuria is multifactorial. The cause could be as simple as drinking too much water or major ones like kidney failure. The causes of polyuria are broadly categorized as renal, endocrine, iatrogenic, metabolic, and psychological.

Renal Causes:

• Nephrogenic Diabetes Insipidus - This is a condition in which the kidneys are not able to respond to antidiuretic hormone or ADH. ADH is the hormone that controls the amount of water flowing through the kidneys. Disorders such as polycystic disease, sickle cell disease, kidney failure, partial blockage of the ureters, and inherited genetic disease can hamper the kidney’s ability to respond to ADH.

• Fanconi Syndrome - It is a disorder of the kidney tubes wherein it fails to reabsorb certain substances such as glucose, amino acids, bicarbonates, phosphorus, and potassium, thus causing polyuria.

• Chronic Pyelonephritis - It is the inflammation of the kidneys as a result of bacterial infection. These infections can lead to Impaired kidney function, causing polyuria.

• Chronic Kidney Disease - It is a condition in which the disease impairs kidney function causing damage to the kidneys and leading to nocturnal polyuria because of the removal of sodium ions in the urine.

Endocrine Causes:

• Diabetes Mellitus - Uncontrolled diabetes mellitus can cause polyuria because of diuresis- a condition in which the kidneys filter too much water.

• Central Diabetes Insipidus - It causes excessive removal of water in urine. In central diabetes, polyuria can occur due to trauma, injury, tumors, and brain lesions.

• Cushing’s Syndrome - It is the tumor of the pituitary gland located at the base of the skull. In this syndrome, there is excessive production of cortisol or stress hormone that leads to polyuria.

Iatrogenic Causes (Caused by Any Medical Intervention):

• Diuretics - Polyuria can occur in case an individual has been put on diuretics to remove excess water from the body in conditions like heart failure.

• Lithium - Patients with bipolar syndrome are put on Lithium. Lithium may cause overproduction of urine, thus, polyuria.

• Tetracycline - Polyuria is a side-effect of antibiotics such as tetracycline.

Metabolic Factors:

• Hypercalcemia - It is the increase in the level of blood calcium. Calcium supplementation during osteoporosis, bone cancer, or hyperparathyroidism can lead to polyuria.

• Hypokalemia - It is the decrease in the level of blood potassium in diarrhea; the use of diuretics leads to polyuria.

Psychological Causes:

• Polyuria can occur in individuals with compulsive water-drinking habits, also known as psychogenic polydipsia.

• Individuals with complicated psychotic illnesses can also develop polyuria.

• Alcohol overuse also leads to polyuria.

What Are the Symptoms of Polyuria?

The primary symptom of polyuria is the frequent passing of urine. It simultaneously increases thirst. The other symptoms are related to the factors causing polyuria.

They are:-

• Weight loss - It is a feature of Type 1 diabetes and chronic kidney disease.

• Malaise - Polyuria causes severe dehydration leading to a state of malaise.

• Headache - Pituitary tumors cause an increase in the pressure in the brain, giving rise to headaches.

• Visual Defects - A rise in the pressure of the brain due to a brain tumor may cause swelling in certain areas of the eye (papillioedema), leading to visual defects.

• Fluctuations in the Blood Pressure - Polyuria leads to dehydration which can cause an increase in the heart rate, further leading to a decrease in the blood pressure. An increase in intracranial blood pressure can cause an increase in blood pressure and a decrease in heart rate.

How Is Polyuria Diagnosed?

Polyuria is a symptom and not a medical condition. Once the symptom appears, the underlying cause of polyuria can be diagnosed.

1. History of Present Illness - The patient is enquired about the amount of fluid consumed and eliminated to distinguish between polyuria and frequency of urination.

2. Past Medical History - The patient is reviewed for associated conditions such as diabetes, sickle cell disease, hyperparathyroidism, psychiatric disorders, etc.

3. Physical Examination - General physical examinations for obesity and undernutrition suggest debilitating conditions such as cancer or an eating disorder. The Head and neck are examined for dry eyes and mouth (Sjogren syndrome). Skin examination for hyperpigmented areas (sarcoidosis). Hands and legs were examined for the presence of swelling or edema.

4. Laboratory Investigations -

• Urine Test - It is carried out to find out the presence of any abnormal substance in the urine. Glucose and ketone bodies suggest diabetes. The presence of protein indicates kidney disease. A low specific gravity suggests diabetes insipidus and polydipsia.

• Urine Osmolality - It is a test that measures the concentration of all the particles found in urine. Urine is collected for twenty-four hours and checked for osmolality. Low urine osmolality and high plasma osmolality are found in diabetes insipidus. At the same time, both low urine osmolality and low plasma osmolality occur in polydipsia.

• Protein Assessment In Urine - The presence of protein in urine samples suggests kidney disease.

5. Blood Test -

• Measurement of serum electrolytes such as calcium, sodium, and potassium.

• Measurement of the presence of drugs like Lithium in the blood.

• Fasting blood glucose for diabetes.

• Complete blood count.

• Erythrocyte sedimentation rate.

• In case the diagnosis is uncertain, then a water deprivation test should be carried out. This test measures how much urine is made and how concentrated it further becomes when no water is given to a patient for a certain period.

How Is Polyuria Treated?

Polyuria is treated depending on the condition causing it. For example, if polyuria is caused by diabetes, then controlling the blood sugar levels could diminish polyuria. Similarly, if Lithium is the cause, then discontinuation of the medicine could be useful. In severe cases of dehydration, hospitalization is required to treat the electrolyte imbalance. Thus, treating the underlying cause of polyuria could help eliminate the condition.

Conclusion

In case one is urinating frequently or getting thirsty more often, it is better to visit the physician as soon as possible. If detected early, it can be treated without any complications. In case of delay, there is a risk of the underlying conditions getting worse and more complicated. Early diagnosis and treatment are a better way to manage the health condition.