The first reaction we may think of regarding dehydration is thirst. Nonetheless, when the body is losing more fluid than it is consuming, the kidneys get to work and begin to change their processes to prevent as much water loss as possible. However, what happens next varies and depends on how serious the dehydration has been and whether there are other health problems involved.
The first reaction: water conservation
As soon as the body realises that the volume of circulating fluid has decreased, the level of antidiuretic hormone (ADH) rises. ADH prompts the kidneys to retain more liquid and thus to produce less and more concentrated urine. This is why urine colour changes in times of dehydration and why people urinate less frequently than usual.
Blood flow to the kidneys can fall
In dehydration, the amount of blood circulation can decrease as it continues to progress. Adequate blood flow is an important part of the function of kidneys in filtration. At the start of the dehydration stage, the body compensates for the loss by starting processes that preserve blood pressure levels and circulation to the organs that are of utmost importance. If the effects of dehydration are eliminated, kidney function may again go back to normal. However, severe dehydration, especially prolonged dehydration, can result in kidney perfusion so impaired that AKI occurs.
What happens to waste products?
Ordinarily, the kidneys extract waste from the blood and eliminate it in the form of urine. It is possible for waste products such as creatinine and urea to show up in the blood when the flow of blood to the kidneys is restricted. This explains why blood tests occasionally indicate that creatinine levels may be elevated after severe dehydration has occurred. However, one must consider the broader context of what may be happening before making conclusions about whether there has been irreversible kidney damage.
Why does dehydration become more concerning with certain medicines?
Dehydration can prove to be a critical aspect if medicines are taken that affect blood circulation in the kidney as well as fluid retention. Non-steroidal anti-inflammatory drugs may inhibit processes responsible for carrying out kidney blood circulation, leading to poor circulation. Patients who are on diuretics or some anti-hypertensive medicines may need to get specific medical advice before dehydration occurs.
The first 24 hours matter
Mild dehydration from heat, exercising, or insufficient intake of fluids can normally be addressed through fluid replenishment and addressing the underlying cause. Severe vomiting, diarrhoea, prolonged heat exposure, or inability to drink can lead to serious fluid loss needing medical assistance. Symptoms may include little or no urine, severe dizziness, confusion, extreme tiredness, a quick heartbeat, or inability to drink.
The takeaway
The kidneys are known to be excellent at managing the conservation of water, but they can only do so much. Recognising and treating severe dehydration quickly can lead to lower chances of complications such as AKI. Hydration needs differ among individuals, and therefore, there is no requirement for everyone to drink an unreasonable amount of water. What is really important is to address fluid losses, maintain proper hydration, and go to a doctor as soon as severe dehydration occurs.
The author is the Principal Director, Nephrology and Kidney Transplant, at Aakash Healthcare Multi Speciality Hospital, Dwarka.
The opinions expressed in this article are those of the author and do not purport to reflect the opinions or views of THE WEEK.
