Acute Kidney Injury (AKI): Causes, Symptoms, and Treatment

Acute Kidney Injury (AKI) can develop over a short period and become life-threatening if not treated promptly. It is a serious condition that causes sudden damage to the kidneys and can lead to full-blown kidney failure.

Although AKI often occurs in acute situations such as infections, trauma, or surgery, its consequences are much longer-lasting and more complicated than most people realize.

Early diagnosis and prompt treatment are crucial in preserving kidney function and preventing dangerous complications.

What is Acute Kidney Injury (AKI)?

Acute Kidney Injury (AKI), a rapidly developing kidney disorder, is when the kidneys lose their ability to filter waste and maintain homeostasis within hours to days. This is not a slow, degenerative process like chronic kidney disease (CKD), but a sudden deterioration that can cause electrolyte disturbances, toxic accumulation, and severe fluid imbalances, putting the patient at risk of multiple organ failure if not treated promptly.

Differences between AKI and CKD

AKI appears suddenly, usually due to an acute condition such as reduced renal perfusion, renal parenchymal injury, or urinary tract obstruction. CKD, in contrast, is a progressive, degenerative process that occurs over months or years. Another important difference is that AKI is reversible with appropriate treatment, whereas CKD is often irreversible.

Stages of AKI

According to the KDIGO criteria, AKI is classified into three stages based on increased serum creatinine and changes in urine output. Stage 1 has a minimal increase in creatinine or a mild decrease in urine output, while stage 3 can lead to anuria and requires intervention with renal replacement therapy such as dialysis.

Causes of Acute Kidney Injury

A variety of pathological mechanisms can trigger Acute Kidney Injury (AKI), but all lead to a common consequence: impaired kidney filtration, accumulation of toxins, and electrolyte and fluid imbalances. AKI is classified into three main groups depending on the origin: pre-renal, renal, and post-renal causes. Accurate identification of the cause plays a key role in treatment, helping to prevent progressive damage and optimize recovery.

Prerenal causes: Decreased renal perfusion

Renal blood flow deficit is the most common cause of AKI, usually resulting from:

• Severe dehydration (prolonged vomiting, diarrhea, severe bleeding)
• Renal volume depletion (congestive heart failure, cirrhosis, septic shock)
• Renal vascular obstruction (renal artery stenosis, thrombosis)

Renal causes: Damage to renal structures

Factors that directly damage the renal parenchyma include:

• Drug toxicity (NSAIDs, aminoglycosides, contrast agents)
• Interstitial nephritis, acute glomerulonephritis
• Acute tubular injury due to prolonged anemia or endogenous toxins (myoglobin in rhabdomyolysis, hemoglobin in acute hemolysis)

Postrenal causes: Urinary tract obstruction

Urinary flow obstruction can cause AKI if not promptly resolved. Common causes include:

• Large kidney stones
• Prostate enlargement
• Ureteral or bladder tumors

Each pathogenesis has serious consequences, requiring accurate diagnosis to choose the appropriate treatment direction.

Symptoms and Warning Signs

Acute Kidney Injury (AKI) often progresses rapidly, causing the patient to go from a normal state to a critical situation in a short period. Symptoms are not always obvious at first, but clinical signs become increasingly severe as the kidneys lose their ability to filter and maintain homeostasis. Early recognition of important warnings can help timely intervention, preventing irreversible damage.

Reduced urine output – The most important sign

Oliguria (little urine) or anuria (no urine) is a typical symptom of AKI, reflecting a severe reduction in the kidney's filtering ability. However, there are cases where AKI occurs even when urine output is not significantly reduced (non-oliguric AKI), making the diagnosis more complicated.

Edema and fluid accumulation

Impaired kidney function leads to fluid retention, causing swelling in the legs, ankles, around the eyes and sometimes spreading throughout the body. This condition may be accompanied by difficulty breathing due to pleural effusion or acute pulmonary edema.

Neurological and gastrointestinal disorders

The accumulation of nitrogenous waste products in the blood is neurotoxic, leading to symptoms of fatigue, confusion, headaches, and even seizures in severe cases. Patients may also experience nausea, vomiting, or anorexia due to increased blood urea.

Cardiovascular manifestations – When AKI becomes a critical situation

Electrolyte disturbances, especially hyperkalemia, can cause arrhythmias or cardiac arrest. When chest pain, palpitations, or respiratory failure appear, this can be a warning sign of a serious, life-threatening complication.

Risk Factors for AKI

Acute Kidney Injury (AKI) does not occur randomly but is often associated with a series of risk factors that impair kidney function or increase the kidney’s susceptibility to injury. Some patients are at high risk due to chronic underlying conditions, while others may develop AKI in the context of an acute illness or certain medical interventions. Early recognition of these risk factors is key to preventing and minimizing complications.

Chronic Disease: The Hidden Burden

People with diabetes and hypertension are at particular risk due to long-term damage to the renal microvasculature. Chronic kidney disease (CKD), even in mild stages, impairs the kidney’s ability to adapt to acute stress, predisposing to AKI.

Age and Physiological Decline

Older adults are at increased risk due to reduced renal blood flow over time, loss of ability to regulate blood pressure effectively, and often multiple underlying medical conditions. This reduced ability to adapt makes the kidney more vulnerable to stressors.

Drug and Toxin Effects

Non-steroidal anti-inflammatory drugs (NSAIDs), contrast agents, aminoglycosides, ACE inhibitors, and diuretics can reduce renal perfusion or cause direct toxicity, especially in patients with pre-existing renal impairment.

Hospital Environment and Critical Conditions

Hospitalized patients, especially those in the ICU, are at increased risk due to septic shock, multiple organ failure, hypovolemic shock, or procedures such as major surgery and the use of vasopressors. In these situations, the kidney becomes the victim of a cascade of adverse physiologic reactions that accelerate damage progression.

Diagnosis of Acute Kidney Injury

Accurate diagnosis of Acute Kidney Injury (AKI) requires a comprehensive approach, using a combination of tests to determine the extent of kidney damage and its cause. Early detection of AKI is important to prevent disease progression, preserve kidney function, and reduce the risk of chronic kidney failure. However, this can be challenging, as symptoms can be vague and atypical in the early stages.

Basic blood tests

Serum creatinine and blood urea nitrogen (BUN) are the standard measures of kidney function. A rapid rise in blood creatinine is an early warning sign, although age, nutritional status, and other factors must be considered.

Urinalysis and blood cultures

Urinalysis detects signs of inflammation, blood, or protein in the urine, which indicate damage at the cellular level of the kidney. Biomarkers such as NGAL (Neutrophil Gelatinase-Associated Lipocalin) or KIM-1 (Kidney Injury Molecule-1) are being studied and used to detect early kidney damage.

Imaging methods

Renal ultrasound is the first non-invasive tool to assess the size and condition of the kidneys, helping to rule out post-renal causes such as kidney stones or urinary tract obstruction. CT scan or MRI of the kidneys may be indicated in more complex cases to accurately determine the cause and extent of damage.

When AKI is diagnosed promptly and accurately, treatment strategies can be implemented immediately, improving patient prognosis.

Treatment Options for AKI

Treatment of Acute Kidney Injury (AKI) depends on the cause, the extent of kidney damage, and the patient's overall health. The main goals in treating AKI are to stabilize kidney function, improve fluid and electrolyte balance, and prevent serious complications. Timely and appropriate intervention can make a big difference in recovery and minimize long-term damage.

Fluid and electrolyte management

One of the top priorities in treating AKI is to correct fluid and electrolyte levels. Intravenous hydration may be necessary in cases of volume depletion, while diuretics may be indicated in cases of excessive fluid accumulation. However, diuretics should be used with caution, as overuse can increase the risk of renal ischemia.

Medication adjustment and discontinuation of toxic medications

Discontinuation of nephrotoxic medications such as NSAIDs, contrast agents, or aminoglycosides is important to stop further kidney damage. Sometimes, medications such as ACE inhibitors or diuretics must be adjusted in dose or discontinued, depending on the patient's renal status.

Renal replacement therapy

In severe cases of AKI, especially when there is anuria or severe electrolyte disturbances, hemodialysis or renal dialysis may become a necessary treatment option. Techniques such as continuous hemofiltration or intermittent hemodialysis help remove waste products, balance fluids, and support kidney function while the kidneys recover.

Monitoring and supportive care

Treatment of AKI is not only a direct intervention but also requires close monitoring. Close monitoring of parameters such as serum creatinine, BUN, and electrolytes, along with periodic assessment of kidney function, are crucial in adjusting the appropriate treatment strategy.

Prevention Strategies

Prevention of Acute Kidney Injury (AKI) is important in preserving long-term kidney function and reducing the risk of chronic kidney failure. Effective prevention strategies focus on controlling risk factors and educating patients and their healthcare team about ways to minimize the impact of external factors that cause kidney damage. These measures may vary depending on the patient population and specific health conditions.

Maintaining Fluid and Electrolyte Balance

Maintaining adequate hydration and electrolyte balance is key to protecting the kidneys from damage. Patients need to be adequately hydrated, especially in situations such as infection, trauma, or major surgery, to maintain blood flow to the kidneys. Monitoring and adjusting electrolytes such as potassium and sodium is essential in high-risk patients.

Control of Underlying Conditions

Care and control of underlying conditions such as diabetes and hypertension are important measures to prevent AKI. Maintaining stable blood glucose and controlling blood pressure within the target range helps minimize the kidney burden and limit damage to the renal microvasculature.

Avoid nephrotoxic drugs

Caution in the use of nephrotoxic drugs, such as NSAIDs, aminoglycosides, and contrast agents, is an integral part of the prevention strategy. Physicians should carefully evaluate the risks and benefits of prescribing these drugs, especially in patients with impaired renal function.

Education and regular health monitoring

Educating patients about the warning signs of AKI and encouraging regular monitoring of renal function are ways to detect AKI early and intervene promptly. Regular kidney function testing, especially in high-risk individuals, can help detect small changes in kidney function, allowing for prompt intervention when necessary.

Long-Term Outlook and Recovery

Acute Kidney Injury (AKI) can have serious short-term effects on kidney health. Still, a patient’s long-term outlook and recovery depend on many factors, including the cause of the disease, the extent of kidney damage, and timely interventions. Post-treatment evaluation and management are important to determine the risk of progression to chronic kidney disease (CKD) and the likelihood of a full recovery.

Long-Term Recovery and Complications

Many patients with AKI can fully recover kidney function if they receive appropriate treatment and care during the acute phase. However, for some, kidney damage can be long-term and lead to the development of CKD. Long-term complications such as high blood pressure, hyperkalemia, and chronic kidney failure can occur, requiring long-term follow-up. People who have experienced AKI are at increased risk of developing CKD in the future, especially if risk factors such as diabetes and high blood pressure are not well controlled.

Factors that influence recovery

The ability of the kidneys to recover from AKI depends on many factors, including the initial extent of kidney damage, age, overall health, and adherence to treatment regimens. Patients with underlying medical conditions such as cardiovascular disease or diabetes are more likely to recover, as their kidneys are already weakened. Furthermore, recurrence of AKI also increases the risk of permanent kidney damage.

Lifestyle changes and long-term monitoring

To improve the long-term outlook, patients must make lifestyle changes such as maintaining a healthy diet, exercising regularly, and controlling risk factors such as blood pressure and cholesterol. Regular follow-up appointments to monitor kidney function are crucial in detecting early signs of chronic kidney failure and preventing further complications.

Conclusion

Acute Kidney Injury (AKI) is a serious, life-threatening condition that can lead to serious complications if not diagnosed and treated promptly. Early recognition of the signs of AKI can help minimize kidney damage and improve prognosis.

Prevention strategies, including controlling underlying medical conditions and maintaining a healthy lifestyle, play an important role in reducing the risk of developing AKI.

With advances in treatments and monitoring of kidney function, the outlook for AKI patients is improving. However, ongoing care and comprehensive management remain key to long-term kidney health.