Acute Kidney Failure

Overview

Acute kidney failure (also called acute kidney injury) is the sudden loss of kidney function within hours or days. The kidneys normally filter the blood to remove waste products and excess fluid through urine, maintain the balance of salt and minerals, and regulate blood pressure. When these functions suddenly break down, waste products and fluid begin to accumulate in the body.

Acute kidney failure is most often seen in hospitalized patients, particularly those in intensive care. However, it can also develop at home. Severe fluid loss, certain medications, infections, or a blockage obstructing the urinary tract can all lead to this condition.

The word "acute" emphasizes that this condition develops suddenly. It is different from chronic kidney disease, which progresses silently over years; acute kidney failure starts rapidly but can often be fully or largely reversed with early and appropriate treatment. This is the most important feature that distinguishes it from chronic kidney disease.

Acute kidney failure is a serious condition that can be life-threatening. However, the good news is this: when diagnosed in time and the cause is eliminated, the kidneys can fully regain their function in most people.

Symptoms

The symptoms of acute kidney failure can sometimes be very obvious and sometimes extremely subtle. Particularly in patients in intensive care, it may show itself only through changes in blood tests without causing any symptoms at all. However, in many patients the following symptoms appear.

Acute kidney failure symptoms include the following:

• Decrease in urine output. This is one of the most common and earliest symptoms. Urine output decreases noticeably or stops completely. In some patients, urine output may be normal or even increased — this can be misleading.
• Swelling in the legs, ankles, and face. When the kidneys cannot eliminate excess fluid, this fluid accumulates in the tissues. Noticeable swelling forms in the ankles, legs, and sometimes the face. You may notice swelling under your eyes when you wake up in the morning.
• Shortness of breath. Fluid accumulation in the lungs makes breathing difficult. Lying flat becomes harder, climbing stairs becomes tiring. Sometimes you may wake up during sleep at night with shortness of breath.
• Extreme fatigue and weakness. Waste products accumulating in the blood wear the body down. A deep sense of exhaustion and weakness appears. Carrying out daily activities becomes progressively more difficult.
• Confusion and difficulty concentrating. Urea and other waste products accumulating in the blood affect brain function. Mild forgetfulness, slowed thinking, and difficulty focusing may draw attention at the outset. In advanced cases, severe confusion or impaired consciousness can develop.
• Nausea and vomiting. The accumulation of waste products in the blood leads to nausea and loss of appetite. It may be more pronounced after waking up in the morning.
• Pain in the back or side. A dull ache may be felt in the area where the kidneys are located — that is, in the back or side. This pain is particularly pronounced in cases related to kidney stones or blockages.
• Changes in urine color and smell. Urine may appear darker than normal, foamy, or bloody. Foamy urine can be a sign of protein leaking into the urine. Bloody urine is a symptom that must always be evaluated.
• High blood pressure. The kidneys play a key role in regulating blood pressure. When function is disrupted, blood pressure can rise, which increases the burden on the heart and brain.
• Itching. Waste products accumulating in the blood can cause widespread itching of the skin. It can be particularly bothersome at night.
• Muscle cramps. Electrolyte imbalances, especially disturbances in potassium and calcium levels, can cause muscle cramps and weakness.

Even when symptoms are mild or recovery has begun on its own with only changes showing in blood tests, a medical evaluation is always necessary.

When to See a Doctor

Acute kidney failure can progress rapidly. Acting without delay when symptoms are noticed is critically important.

Call 112 or go to the emergency room immediately in the following situations:

• If urination has stopped completely
• If sudden and severe shortness of breath has started
• If confusion, severe disorientation, or fainting is occurring
• If rapid swelling is developing throughout the body
• If there is heart palpitations or irregular heartbeat
• If there is severe vomiting and you are unable to eat or drink anything

See a doctor without delay in the following situations:

• If you have noticed a significant decrease in urine output
• If there is unexplained swelling in the legs or ankles
• If you are going through a serious infection and urine output has started to decrease
• If you have lost a large amount of fluid due to severe diarrhea or vomiting
• If these symptoms have appeared after taking a medication that could affect kidney function

Causes

The causes of acute kidney failure are evaluated in three main groups. This distinction shows whether the cause is before the kidneys, within the kidneys, or after the kidneys, and directly guides treatment.

Pre-renal causes (reduced blood flow):

The kidneys need a sufficient amount of blood flow to be able to work. When blood flow decreases, the kidneys gradually lose function. This is the most commonly seen group of causes.

Pre-renal causes that can lead to acute kidney failure are as follows:

• Severe fluid loss (dehydration). Severe diarrhea, persistent vomiting, excessive sweating, or insufficient fluid intake reduces the amount of blood reaching the kidneys. This is a condition frequently encountered especially in elderly people during the summer months.
• Serious bleeding. Losing a large amount of blood due to an accident, surgery, or internal bleeding endangers kidney blood flow.
• Heart failure or heart attack. When the heart cannot pump enough blood, the kidneys also cannot receive sufficient blood supply.
• Severe infections (sepsis). In dangerous infections affecting the whole body, blood pressure drops and blood flow to the kidneys decreases. Sepsis is one of the most common causes of acute kidney failure.
• Low blood pressure. A very significant drop in blood pressure for any reason disrupts kidney perfusion (the blood flow reaching the kidneys).

Intrinsic causes (damage within the kidney itself):

This is direct damage to kidney tissue itself.

Intrinsic causes that can lead to acute kidney failure are as follows:

• Certain medications. Painkillers, especially anti-inflammatory drugs such as ibuprofen and naproxen, can damage the kidneys when used for a long time or at high doses. Some antibiotics (such as gentamicin), certain blood pressure medications, and contrast agents used for imaging can also lead to kidney damage.
• Rhabdomyolysis (muscle breakdown). Due to severe crush injuries, very intense exercise, certain medications, or diseases affecting the muscles, muscle cells break apart and the substances inside them enter the bloodstream. These substances clog the kidneys and cause serious damage.
• Kidney inflammation (glomerulonephritis). Kidney inflammation originating from the immune system can damage the kidney filters.
• Contrast agent damage. The dye (contrast) used in imaging procedures such as CT scans or angiography can cause acute kidney injury in some people — especially those whose kidney function is already weak.

Post-renal causes (obstruction of the urinary tract):

Even if urine is being produced, if there is a blockage in the urinary tract, urine accumulates and damages the kidneys by creating backward pressure.

Post-renal causes that can lead to acute kidney failure are as follows:

• Kidney stones. Large stones blocking the urinary tract obstruct urine flow. They present with sudden and severe flank pain.
• Enlarged prostate. The prostate gland, which enlarges with age in men, can block urine outflow. This is a frequently seen cause especially in older men.
• Bladder or urinary tract tumors. Tumors forming in the urinary tract can lead to obstruction.
• Bladder dysfunction. The inability of the bladder to empty sufficiently due to nervous system problems leads to urine accumulation.

Risk Factors

Risk factors for acute kidney failure are as follows:

• Advanced age. In elderly individuals, kidney reserve has decreased and is more fragile against additional stress. The risk of acute kidney failure increases significantly above age 65.
• Chronic kidney disease. People who have had previous kidney problems are much more susceptible to acute injury.
• Diabetes. Diabetes weakens the kidneys and reduces their resistance to acute injury.
• Heart failure or heart disease. Insufficient functioning of the heart endangers blood flow to the kidneys.
• Liver disease. The kidneys are frequently affected in liver failure as well.
• Being an intensive care patient. Acute kidney failure is very common in patients in intensive care, where multiple risk factors are present together.
• Going through a serious infection or sepsis. Infections affecting the whole body can cause serious damage to the kidneys.
• Use of certain medications. Anti-inflammatory painkillers in particular, some antibiotics, and certain groups of blood pressure medications create a burden on the kidneys. Drinking plenty of water and monitoring kidney function during use of these medications is important.
• Major surgeries. Blood flow to the kidneys can be temporarily disrupted especially after heart and vascular surgeries.
• Not taking in enough fluid. Insufficient fluid intake especially in hot weather, during exercise, or during periods of diarrhea and vomiting increases risk.

Diagnosis

Acute kidney failure is generally diagnosed quickly with blood and urine tests. Finding the cause after the diagnosis is made is also critically important since it guides treatment.

The methods used in the diagnosis of acute kidney failure are as follows:

• Blood tests. This is the most fundamental diagnostic tool. Creatinine and urea (BUN) are the basic indicators of kidney function; a rapid rise in these values is the most important evidence of acute kidney failure. Electrolyte levels such as potassium, sodium, and bicarbonate are measured; imbalances help both with the diagnosis and with determining urgency. A blood count is evaluated for infection or anemia.
• Urine tests. Urine output is monitored. The presence of protein, blood, or special cell clusters (casts) in the urine helps us understand which part of the kidney is affected. In acute kidney failure, urine sodium level and specific gravity can help distinguish pre-renal from intrinsic causes.
• Kidney ultrasonography. The size and structure of the kidneys are imaged. Whether there is a stone or obstruction in the urinary tract is investigated. In chronic kidney disease, the kidneys shrink; this image supports the distinction between acute and chronic.
• Computed tomography (CT). Used for more detailed imaging of kidney stones, tumors, or other structures obstructing the urinary tract.
• Kidney biopsy. In cases where the cause cannot be determined, especially when kidney inflammation is suspected, a small tissue sample is taken from the kidney with a thin needle and examined under a microscope. It is not needed in every case; the decision is made based on the doctor's assessment.
• Other blood tests. Depending on the cause, special tests showing autoimmune diseases, infections, or muscle breakdown may be requested.

Treatment

The primary goal of acute kidney failure treatment is to give the kidneys the opportunity to recover. To achieve this, the cause is first eliminated, then the kidneys are supported through this process. Mild cases can be followed on an outpatient basis, while severe cases require hospitalization and even intensive care.

The methods used in acute kidney failure treatment are as follows:

• Treatment targeting the cause. This is the most critical step. The kidneys cannot recover without eliminating the cause. In fluid loss, fluid replacement is performed — that is, fluids are given intravenously to restore the water and minerals the body has lost. If there is a blockage, the stone is broken up or removed; in prostate problems, a urinary catheter is inserted. Infection is treated. The harmful medication is discontinued.
• Restoring fluid and electrolyte balance. Since the kidneys cannot maintain fluid and mineral balance, this function is supported from outside. The amount of fluid you take in and put out is carefully monitored. If potassium rises in the blood, emergency treatment is needed since it can threaten heart rhythm. Sodium and bicarbonate levels are also closely monitored.
• Medication adjustment. When kidney function is disrupted, many medications can accumulate in the body and cause harm. For this reason, the medications being used are reviewed, those harmful to the kidneys are discontinued, and doses are readjusted according to kidney function.
• Nutritional support. A special nutrition plan is needed in kidney failure. Protein intake is carefully adjusted, because both too little and too much protein can burden the kidneys. Foods containing potassium and phosphorus may be restricted. Working with a nutritionist is very helpful during this process.
• Dialysis. When the kidneys cannot adequately clear waste products and excess fluid, dialysis may be needed. Dialysis is a blood-cleaning method that temporarily takes over the work of the kidneys. In intensive care, continuous dialysis (CRRT) is generally applied; this method places less burden on the kidneys because the blood is cleaned more slowly and continuously. Dialysis is temporary in many patients; as the kidneys recover, dialysis may no longer be needed.
• Blood transfusion. If severe anemia accompanies kidney failure, a blood transfusion may be needed.
• Intensive care monitoring. In severe cases, blood pressure, heart rhythm, breathing, and level of consciousness are continuously monitored. If more than one organ is affected, supporting each of them is carried out simultaneously.

Complications

If acute kidney failure goes untreated or follows a severe course, it can lead to many important complications.

Complications that may be seen in acute kidney failure are as follows:

• High potassium (hyperkalemia). When the kidneys cannot excrete excess potassium, potassium accumulates in the blood. This can lead to heart rhythm disorders and even cardiac arrest. It is one of the most critical complications requiring emergency treatment.
• Fluid accumulation in the lungs. When excess fluid fills the lungs, breathing becomes severely difficult. This condition is called pulmonary edema and requires emergency treatment.
• Serious infections. The immune system weakens in kidney failure. Infections are both more frequent and more severe. The risk of turning into sepsis is high.
• Acidosis (acidification of the blood). When the kidneys cannot excrete the acid accumulating in the blood, the blood pH drops. This affects all organs, particularly the heart, lungs, and brain. It speeds up breathing and in severe cases impairs consciousness.
• Anemia. The kidneys secrete a hormone that stimulates red blood cell production. Deficiency of this hormone leads to anemia. Existing anemia can deepen further.
• Progression to chronic kidney disease. Even after getting through acute kidney failure, the kidneys may not fully recover in some patients. Recurrent or severe acute kidney failure in particular increases the risk of chronic kidney disease.
• Multiple organ failure. In the most severe picture, the kidneys, heart, lungs, and brain all become unable to function at the same time. This is an extremely difficult situation to manage even in intensive care.

Living with Acute Kidney Failure

Experiencing acute kidney failure is a difficult experience both physically and emotionally. However, many patients can fully recover with the right treatment and return to a life close to normal. Knowing what to pay attention to during the recovery process helps both protect your health and prevent a possible recurrence.

The Recovery Process and What to Expect

The recovery process from acute kidney failure varies greatly from person to person. In mild cases, the kidneys can fully recover within a few days to a few weeks. In severe cases, recovery can take months and in some patients the kidneys may not regain full function.

Fatigue after discharge can continue for a long time. Even if you feel well, your body is still in the process of healing. Increase your activities gradually; avoid taking on multiple demanding tasks at once. Listen to the signals your body gives you.

Regular blood tests are critically important for tracking how much kidney function has recovered. Whether blood creatinine and urea values have returned to normal, and potassium and sodium balance, should be closely monitored. Don't skip these tests; even if the kidneys seem to feel fine, silent damage may still be ongoing.

Fluid Intake and Nutrition

While recovering from acute kidney failure, fluid intake should be managed according to your doctor's recommendation. In some patients, plenty of fluid is encouraged, while in others fluid restriction may be needed. This varies from person to person; contrary to what your neighbor says or what you read online, only your doctor can determine the right amount of fluid for you.

Nutrition plays a critical role in kidney recovery. Reducing salt consumption lightens the load on the kidneys and keeps blood pressure under control. Foods rich in potassium — bananas, oranges, tomatoes, potatoes, dried legumes — may be restricted during the recovery period; however this is entirely individual, follow your doctor's recommendation. Foods containing phosphorus (dairy products, nuts, processed foods) are also sometimes limited. Protein intake also needs to be carefully planned; too little protein slows recovery, while too much protein can burden the kidneys. Consulting a renal dietitian is extremely valuable during this process.

Medication Management

After experiencing acute kidney failure, being very careful about medication use is necessary. Staying away from medications that create a burden on the kidneys both speeds up recovery and prevents recurrence.

Strictly avoid ibuprofen, naproxen, and similar anti-inflammatory painkillers (NSAIDs). These medications reduce blood flow to the kidneys and can be very dangerous for people who have experienced acute kidney failure. Paracetamol can be used for pain with your doctor's approval.

Never take any medication, herbal supplement, or traditional remedy you obtain without a prescription from a pharmacy without first asking your doctor. Products labeled "natural" or "herbal" can have serious effects on the kidneys.

Report all medications you use regularly to your doctor. Some blood pressure medications, diabetes medications, and other chronic disease medications may require dose adjustment based on kidney function.

Managing Underlying Conditions

Proper management of underlying conditions is essential to prevent acute kidney failure from occurring again.

If you have diabetes, keeping blood sugar within the target range is one of the most effective ways of protecting the kidneys in the long term. High blood sugar damages kidney vessels and makes the kidneys more vulnerable to every acute stress.

Blood pressure control is equally important. High blood pressure can be both a cause and a consequence of kidney damage. Keeping blood pressure below 130/80 mmHg is targeted through salt restriction, regular exercise, and medication treatment when needed.

If you have heart failure, pay particular attention to your heart treatment. Good heart function is essential for sufficient blood to reach the kidneys.

Protection from Dehydration

People who have experienced acute kidney failure need to be especially careful about fluid loss. When diarrhea or vomiting starts, in hot weather, or during intense exercise, fluid losses can quickly reach a critical level.

If you are unable to take in fluids by mouth due to nausea or vomiting and there is no improvement within hours, see a doctor. Elderly individuals and those with chronic conditions in particular should be much more cautious about this. Pay attention to clean water sources while traveling and be prepared for the risk of diarrhea.

Regular Follow-up

Regular nephrology (kidney disease specialist) or internal medicine follow-up is essential after experiencing acute kidney failure. Kidney function tests should be done frequently in the early period and at least once or twice a year in later periods.

Don't skip follow-up appointments. Kidney damage can progress silently; feeling well does not mean the kidneys have fully recovered. A problem detected early is much more easily managed.

Psychological Impact

Going through a serious illness, especially for those who have had an intensive care experience, can leave deep psychological marks. Anxiety, depression, and post-traumatic stress disorder can develop during this process.

Being aware of these feelings is part of recovery. Don't hesitate to seek support from a psychologist or psychiatrist if needed. Remember that your family and loved ones are also affected by this process; it may be important for them to receive support as well.

Preparing for Your Appointment

What you can do:

• Note in detail when symptoms started and how they progressed
• Mention changes in urine output and color changes
• List all medications you have taken in recent days, including painkillers and herbal supplements
• If fluid loss has occurred (diarrhea, vomiting, excessive sweating), indicate how long it lasted
• Share your chronic conditions such as diabetes, hypertension, or heart disease and the medications you use for them
• Mention if there is a family history of kidney disease
• Write your questions down in advance

Questions you can ask your doctor are as follows:

• Can my kidneys fully recover?
• How long until improvement is expected?
• Will I need dialysis?
• Which medications should I avoid?
• How much fluid should I take in?
• What should I pay attention to in terms of nutrition?
• Am I at risk of developing chronic kidney disease?
• How often should I have checkups?
• What can I do to prevent this from happening again?

Questions your doctor may ask you are as follows:

• When did symptoms start and how quickly did they worsen?
• How much fluid have you been taking in recently?
• Have you experienced diarrhea, vomiting, or excessive sweating?
• Which medications have you taken in recent days?
• Have you taken ibuprofen or a similar painkiller?
• Do you have a history of diabetes, hypertension, or kidney disease?
• Have you had kidney problems before?
• Have you recently had surgery or an imaging procedure?
• Is there kidney disease in the family?