Master, Doctor Nguyen Quang Huy, from the Department of Nephrology - Dialysis at Tam Anh General Hospital Hanoi, explains that kidneys require a sufficient blood supply to filter waste, maintain water and electrolyte balance, and stabilize the body's internal environment. When the body loses too much water, blood flow to the kidneys decreases. This forces the organs to function under unfavorable conditions, risking impaired function.

Dehydration can result from insufficient water intake, heavy sweating during work or exercise, fever, prolonged diarrhea or vomiting, or the use of certain medications that increase water excretion. Depending on the degree and duration of dehydration, the kidneys can experience the following effects.

Reduced filtration function

Kidneys filter blood to remove waste products and excess water from the body. When the body lacks water, the circulating volume decreases, subsequently reducing blood flow to the kidneys. This diminishes the glomeruli's filtration capacity.

In healthy individuals, mild dehydration with timely rehydration usually allows kidney function to quickly return to normal. However, if dehydration is prolonged or recurs frequently, the kidneys must constantly adjust to retain water for the body, increasing the workload on these organs.

Doctor advises on the risk of kidney damage due to dehydration. Photo: Tam Anh General Hospital

Acute kidney injury

One of the most concerning consequences of dehydration is acute kidney injury caused by reduced blood perfusion. When insufficient blood reaches the kidneys for an extended period, kidney cells can suffer damage, leading to a rapid decline in filtration function.

This risk is often higher in older adults and individuals with chronic kidney disease, heart failure, diabetes, or those using diuretics. If detected early and managed with proper fluid replacement, kidney function can recover. Conversely, delayed treatment can lead to more severe kidney damage.

Increased risk of kidney stones

Lack of water reduces urine volume, making it more concentrated. This allows minerals such as calcium, oxalate, or uric acid to crystallize and deposit in the urinary tract, eventually forming stones.

Drinking enough water is considered an important measure to prevent kidney stones, especially for individuals with a history of the condition.

Increased risk of urinary tract infections

Urine not only eliminates waste products but also helps remove bacteria from the urinary tract. When the body is dehydrated, reduced urine volume creates more favorable conditions for bacteria to grow, thereby increasing the risk of urinary tract infections.

If an infection is not treated promptly, bacteria can ascend to the kidneys, causing pyelonephritis (kidney inflammation). This condition can impair kidney function if it recurs frequently or treatment is delayed.

Progression of chronic kidney disease

Individuals with chronic kidney disease should drink an adequate amount of water as advised by their doctor to protect kidney function. When the body is dehydrated, reduced blood supply to the kidneys can accelerate the decline in kidney function and increase the risk of complications.

However, patients with chronic kidney disease should not arbitrarily drink excessive amounts of water but must follow their doctor's instructions. The amount of water needed depends on the disease stage, kidney filtration capacity, and any co-existing medical conditions.

Doctor Huy recommends that everyone drink enough water daily, especially when working outdoors, engaging in high-intensity exercise, or experiencing fever, diarrhea, or vomiting that causes significant fluid loss. If signs appear such as very little or no urination, persistently dark urine, extreme fatigue, severe dizziness, lower back pain, or fever accompanied by painful or frequent urination, patients should seek medical attention for kidney function assessment and timely treatment.