How Dehydration Affects the Kidneys

Dehydration is a common cause of hospitalization, and not only can it be fatal, it can also aggravate many health conditions. Dehydration affects the kidneys in several ways.

Normally, people continuously lose water through their skin, lungs, kidneys, and digestive tract. When more water is lost than taken in, receptors in the brain detect a lack of water in the blood and release antidiuretic hormone. This prompts the kidneys to reabsorb more water.

When blood pressure drops, the kidneys release renin (an enzyme). Renin converts a hormone called angiotensin 1 to angiotensin 2. When angiotensin 2 levels rise, the adrenal glands release another hormone called aldosterone, which increases the kidneys’ ability to reabsorb water and sodium.

Dehydration causes concentrated urine, which increases the risk of kidney stones and urinary tract infections (UTIs). Severe dehydration can also lead to acute kidney injury (AKI), which is a sudden loss of kidney function. Waste products can build up in the blood because the kidneys are not filtering blood as effectively as they should, which can be fatal if not treated promptly.

AKI doesn’t always cause symptoms. But some signs of the condition include urinating less than usual or not at all, nausea, fatigue, swelling in the legs, hip pain, high blood pressure, shortness of breath, chest pain, confusion or mood changes, loss of appetite, seizures, or coma (in severe cases).

Causes that can lead to severe dehydration include:

– Inability to replace lost fluids due to difficulty moving, impaired thirst regulation, cognitive impairment, or loss of consciousness due to drug overdose.

– Water loss through the skin can be caused by excessive heat, excessive exercise, burns, or skin diseases.

– Renal water loss can be caused by diuretic use, acute or chronic kidney disease, and hyperglycemia.

– Dehydration through the digestive tract is often caused by vomiting, diarrhea or laxative use.

– Abdominal fluid loss due to pancreatitis, ascites (abnormal accumulation of fluid in the abdominal cavity), or peritonitis.

– Other causes include sepsis, side effects of certain medications, hyperthyroidism, and chronic obstructive pulmonary disease.

Older adults are more likely to become dehydrated because they often have chronic health conditions such as diabetes, kidney disease, and mobility problems.

People with kidney failure due to chronic kidney disease may be advised to reduce their fluid intake. In AKI, the doctor may recommend testing the patient’s fluid intake and urine output. If the kidney condition improves with increased fluid intake, the patient may have acute kidney failure due to reduced blood flow to the kidneys.

If the patient retains fluid during the challenge or is fluid overloaded, diuretics may be needed and potassium, phosphorus, and sodium intake monitored. However, diuretics can cause severe acute kidney failure in some cases. Patients should discuss with their doctor before changing their fluid intake.

To maintain optimal kidney health, people should keep their blood pressure below 140/90 mmHg or as targeted by their doctor, maintain healthy blood sugar levels, be physically active, and eat a kidney-friendly diet that includes more fruits and vegetables, less salt, and quit smoking.