What is Acute Kidney Injury? Symptoms, Stages, Diagnosis and Treatment Methods

What is Acute Kidney Injury?

Acute kidney injury is the sudden loss of kidney function due to various reasons. Acute kidney injury can develop within days or even hours. In the case of acute kidney injury, body fluid can increase suddenly, and waste products and electrolytes can accumulate in the body. As a result, serious complications such as end-stage renal failure and heart damage may develop. Acute kidney injury is a serious health problem that occurs when the kidneys lose their function suddenly and rapidly, and it can pose a life-threatening risk if not intervened in the early stages. The kidneys are involved in many metabolic activities in the body. The primary task of the kidneys is to remove toxins and excess fluid from the body. In addition to these, the kidneys play an important role in maintaining fluid-electrolyte balance, regulating blood pressure, supporting red blood cell production, and protecting bone health. If the kidneys lose their function suddenly and rapidly, a condition called acute kidney injury may occur. Consequently, serious health problems such as toxin accumulation in the body and impairment in fluid-electrolyte balance may develop. Acute kidney injury can occur at any age. Although acute kidney injury is rarer in children compared to adults, it is a significant health problem, especially in children hospitalized in intensive care units.

Symptoms of acute kidney injury, which can develop within hours or days, are seen more frequently in patients receiving hospital treatment. In the case of kidney failure, regardless of whether it is acute or chronic, patients may experience decreased urine production, accumulation of waste products such as urea and creatinine in the blood, and electrolyte imbalance. This can lead to irregularities in heart rhythm, nervous system disorders, and a rapid deterioration of general health. The stages of acute kidney injury are generally examined in 3 phases. When determining the stages, the increase in the amount of creatinine, a type of waste product in the urine, and the decrease in the amount of urine are taken into account. Accordingly, the stages of acute kidney injury are as follows:

Serum creatinine

Stage I

Increase of 0.3 mg/dL or more or 1.5-1.9 times the baseline value

Stage II

Increase of 2-2.9 times the baseline value

Stage III

Increase of 3 times the baseline value or an increase of more than 4 mg/dL or initiation of dialysis

Urine output

Less than 0.5 mL/kg per hour for 6-12 hours

Less than 0.5 mL/kg per hour for 12 hours or more

Less than 0.3 mL/kg per hour for 24 hours or more or no urine output for 12 hours or more

Kidney failure, which means one or both kidneys becoming unable to perform their functions, is classified into two categories: acute kidney failure and chronic kidney failure. The differences between acute kidney injury and chronic kidney failure are related to the duration of the disease's development. While acute kidney injury develops within a few hours or days, chronic kidney failure occurs as a result of long-term damage to the kidneys. If acute kidney injury is not diagnosed in the early stages and the necessary treatment is not applied, it can lead to chronic kidney disease.

What Are the Symptoms of Acute Kidney Injury?

The differences between acute and chronic kidney failure also manifest in the speed at which symptoms appear. Since chronic kidney failure develops slowly over time, symptoms are usually vague at the beginning. However, in patients who develop acute kidney injury, symptoms can appear suddenly. The main symptoms of acute kidney injury are as follows:

Edema (swelling) throughout the body,

Slowness in movements,

Blood in stool,

Flank pain,

Fatigue,

Bad breath,

Tremors in the hands,

Bruising even from minor impacts,

Loss of sensation in the body, especially in the hands and feet,

Inability to stop bleeding,

Mental confusion, especially in the elderly age group,

Loss of appetite,

Seizures,

A metallic taste in the mouth,

Nausea and vomiting,

Hypertension (high blood pressure).

If the listed symptoms are not brought under control in the early stages, acute kidney injury complications such as permanent kidney damage and end-stage liver disease may occur in patients.

How is Acute Kidney Injury Diagnosed?

Acute kidney injury is examined in 3 different categories according to its causes: prerenal, renal, and postrenal. Prerenal acute kidney injury is the most common cause of acute kidney injury. Prerenal acute kidney injury accounts for approximately 60% of all cases. In prerenal acute kidney injury, the cause of the damage is not the kidneys themselves. Prerenal acute kidney injury develops as a result of decreased blood flow to the kidney due to another reason. In other words, the most common cause of acute kidney injury is the reduction of blood flow to the kidneys due to reasons such as heart disease or low blood volume.

Renal acute kidney injury, as the name suggests, refers to acute kidney injury originating from the kidneys. Renal kidney damage accounts for approximately 35% of all acute kidney injury cases. Although there are many causes of renal acute kidney injury, severe kidney damage or bleeding, infectious diseases affecting the kidneys, and some medications used are among the most common causes.

The causes of postrenal acute kidney injury, which is the rarest type of acute kidney injury, are mostly related to the impairment of urine flow from the kidney due to reasons such as kidney stones, kidney or bladder tumors, and urinary tract obstructions. In summary, the causes of acute kidney injury can be listed as follows:

Acute tubular necrosis,

Severe dehydration (fluid loss),

Poisoning,

Some medications used,

Urinary tract obstructions,

Bleeding,

Septic shock,

Prolonged surgeries,

Severe burns.

Additionally, some studies suggest that there has been an increase in the number of acute kidney injury patients in recent years, and the reason for this is hospitalizations due to COVID-19 infection. Based on this, experts state that some infectious diseases can also cause impairment in kidney functions. Furthermore, crush syndrome, which develops as a result of the body being trapped under debris or a mass, and the mixing of substances such as potassium and phosphorus in the muscles into the blood, can result in acute kidney injury.

In patients with general fluid retention in their bodies, experts may need to perform some tests, suspecting acute kidney injury. One of the primary tasks of the kidneys is to filter the blood and remove waste products such as urea and creatinine from the body. Serum creatinine level and urine output are important among the diagnostic criteria for acute kidney injury. Therefore, acute kidney injury can be diagnosed by the rapid rise of creatinine and urea levels in the blood. In addition, experts may ask the patient to collect urine for 24 hours. As a result, the patient's urine output amount can be evaluated.

Additionally, experts frequently use imaging methods among the diagnostic methods for acute kidney injury. Ultrasonography is at the forefront of imaging methods used in the diagnosis of acute kidney injury. However, in some cases, doctors may also use imaging methods such as CT (computed tomography) and MRI (magnetic resonance imaging) to examine whether there is an obstruction in the urinary tract.

How is Acute Kidney Injury Treated?

While planning the treatment for acute kidney injury, nephrology specialists primarily aim to prevent fluid retention in the body and restore kidney function. In the first stage, the cause of the acute kidney injury is determined, and a treatment plan is prepared for that cause. For example, if the cause of kidney failure is a medication being used, the use of that medication may be urgently stopped or replaced with another medication. Acute kidney injury treatment often requires hospitalization. During this period, the following treatments may be applied to regulate some functions in the body until kidney functions are restored:

Ensuring fluid balance: Fluid deficiency or excess may be seen in the blood due to acute kidney injury. In case of fluid deficiency, intravenous fluid supplementation is provided. In case of fluid excess, the removal of fluid from the body can be ensured with diuretic medications.

Ensuring blood potassium balance: When the kidneys cannot filter potassium sufficiently, potassium levels rise; symptoms such as heart rhythm irregularities and muscle weakness may develop. Experts may prescribe some medications to bring potassium levels into the normal range.

Calcium supplementation: When the kidneys cannot filter calcium sufficiently, calcium levels in the blood drop. Intravenous calcium infusions may be administered to return calcium levels to normal.

In addition to those listed, acute kidney injury may also require dialysis. If the kidneys cannot clean waste products sufficiently, dialysis allows the blood to be cleaned via a machine. Acute kidney injury also requires changes in the diet. An example of an acute kidney injury diet could be as follows:

Foods low in potassium such as apples, peaches, and carrots,

Limiting salty foods,

Limiting the consumption of foods high in phosphorus such as milk, oatmeal, and whole grains.

If acute kidney injury is treated in the early stages, it is usually temporary. After kidney functions return to normal, patients can return to their normal diet, provided it is healthy and balanced.

Frequently Asked Questions

Depending on how much kidney function is impaired in acute kidney injury, dialysis may be applied. Dialysis may be necessary when waste products, excess fluid, and electrolyte imbalances in the body reach serious levels because the kidneys cannot perform their functions sufficiently. Acute kidney injury is the sudden and unexpected impairment of the kidneys' function to clean waste and maintain fluid balance due to various reasons such as infection, trauma, toxic substances, or side effects of some medications. The duration of dialysis sessions varies depending on the patient's general health status. Each dialysis session lasts an average of 4 hours. Experts may plan dialysis to be at most 3 sessions per week until kidney functions are restored. Existing health problems such as liver disease, kidney disease, diabetes, hypertension, heart disease, severe infection, serious health problems requiring hospitalization, trauma, and some medications used can increase the risk of acute kidney injury. The glomerular filtration rate (GFR) test is one of the kidney function tests used in the diagnosis and staging of kidney diseases. The GFR test helps to measure the amount of blood filtered per minute by the structures in the kidneys called glomeruli. While a high GFR value indicates that the kidneys are in good condition, a low GFR value may indicate that kidney functions have decreased. However, the GFR test alone is not sufficient for the diagnosis of acute kidney injury. Experts can make a definitive diagnosis by checking the serum creatinine level and urine output. With early diagnosis and appropriate treatment, acute kidney injury is temporary in most cases, but if the damage to the kidneys progresses and treatment is delayed, chronic kidney disease may develop in patients. Generally, if there is an increase of 3 times the baseline value or an increase of more than 4 mg/dL in the creatinine value, dialysis may be considered. However, when deciding on dialysis, experts also take into account the patient's general health status and urine amount. Dialysis may also be decided in cases of less than 0.3 mL/kg per hour for 24 hours or more or no urine output for 12 hours or more. Acute kidney injury can cause serious complications such as fluid imbalance in the body, electrolyte disturbances, accumulation of waste products, and heart rhythm irregularities resulting from these, as well as end-stage liver disease. The recovery time varies depending on factors such as the cause, severity, and stage of the impairment in kidney function, and the response to the applied treatment. As long as the treatment planned by the doctors is followed, acute kidney injury can heal in a short time. If treatment for acute kidney injury is not started in the early stages, it can lead to permanent kidney damage and life-threatening serious complications.

If you are experiencing symptoms of acute kidney injury, it is vital to consult our Nephrology Department specialists without delay.

As the Hisar Hospital Nephrology Department, we are with you with early diagnosis, advanced examinations, and personalized treatment methods.

You can contact us immediately to make an appointment.