Acute kidney injury (AKI) is a sudden drop in kidney function that happens over hours to days, usually during another illness. Chronic kidney disease (CKD) is kidney damage or reduced function that lasts 3 months or more and tends to develop slowly. AKI often gets better with prompt treatment, while CKD is managed to slow it down, and the two are more connected than many people realize.
Key Takeaways
- AKI comes on suddenly, most often within 48 hours, although it can take as long as 7 days to develop.
- CKD means the kidneys have been damaged over time and have not worked as well as they should for 3 months or more.
- Most people with AKI are already in the hospital for another reason, such as a serious infection or surgery.
- AKI damage is often reversible with prompt treatment, while advanced, long-lasting CKD usually cannot be reversed but steps can be taken to slow it.
- Having AKI raises your risk of CKD later, so a kidney check within 3 months of finishing treatment is recommended.
What Is the Difference Between Acute Kidney Injury and Chronic Kidney Disease?
The main difference is time. Acute kidney injury, sometimes called acute kidney failure, is a sudden episode of kidney damage or failure. According to the National Kidney Foundation, it most often develops within 48 hours, but it can take up to 7 days. Waste products build up in the blood, and the kidneys struggle to keep the right balance of fluid in the body.
Chronic kidney disease means the kidneys have been damaged over time and do not work as well as they should. Two common tests are a blood test called eGFR, which estimates how well your kidneys filter, and a urine test called uACR, which checks for a protein called albumin. An eGFR under 60 and/or a uACR over 30 for 3 months or more may be a sign of CKD. Our guide to what your kidney function test results mean explains these numbers.
What Causes Acute Kidney Injury?
AKI usually happens when another health problem suddenly affects the kidneys. The causes fall into three groups:
- Less blood flow to the kidneys: severe dehydration, heavy blood loss, very low blood pressure, a severe infection, heart failure, burns or major surgery.
- Direct damage to the kidneys: some medicines and substances, sepsis, or diseases that inflame the kidneys’ filters or small blood vessels.
- A blockage that stops urine from draining: kidney stones, an enlarged prostate, blood clots in the urinary tract or some cancers.
Medicines and substances that can play a part include NSAID pain relievers such as ibuprofen and naproxen, certain antibiotics, certain blood pressure medicines and iodine-based contrast dye used for imaging. AKI is especially common in hospital and intensive care patients and in older adults, and people with CKD, diabetes or high blood pressure are more likely to get it. Do not stop a prescribed medicine on your own; ask your doctor or pharmacist first. Dehydration from severe vomiting or diarrhea is another cause to know about (see dehydration and kidney health).
What Causes Chronic Kidney Disease?
The most common causes of CKD in adults are diabetes and high blood pressure. High blood sugar can damage the kidneys’ filters over time, and high blood pressure can damage the blood vessels and other parts of the filtering system. Other causes include glomerular diseases (conditions that harm the filters), polycystic kidney disease, immune system disorders such as lupus, some infections, toxic medicines and genetic conditions.
A past acute kidney injury is on that list too. Other risk factors include heart disease, obesity, smoking, a family history of kidney disease and being over 60. Because early CKD usually has no symptoms, testing is the only way to know how well your kidneys are working. If you have already been diagnosed, our article on CKD stages and treatment explains what each stage means.
Do AKI and CKD Cause Different Symptoms?
AKI symptoms can appear quickly and depend on the cause. They may include:
- Making less urine than usual, or none at all
- Swelling in the legs, ankles, feet or around the eyes
- Tiredness, weakness or confusion
- Shortness of breath, nausea, or chest pain or pressure
Some people with AKI have no symptoms, and the injury is found only through tests. CKD is quieter still: most people have no symptoms in the early stages, and many have none until it is advanced. Later signs can include poor appetite, tiredness, trouble concentrating, foamy urine, itching, muscle cramps and worsening swelling. These signs overlap with many other conditions. See 5 signs your kidneys are not working properly for more.
Can Kidneys Recover From AKI or CKD?
With a proper diagnosis and prompt treatment, AKI damage is often reversible. Cleveland Clinic notes that a mild AKI may heal within a few days, while severe cases may take at least 2 to 3 weeks or longer. Treatment targets the cause, such as fluids, antibiotics, stopping a harmful medicine or relieving a blockage. Some people need dialysis for a while, but in most cases it is temporary until the kidneys recover. If you had kidney problems before the AKI, your kidneys may not fully heal.
CKD works differently. Advanced, long-lasting CKD usually cannot be reversed, but you can take steps to protect your kidneys from more damage. NIDDK calls controlling your blood pressure the most important step. Reaching your blood sugar goals matters if you have diabetes, and two types of blood pressure medicines, ACE inhibitors and ARBs, may slow kidney disease and delay kidney failure. Your doctor decides which treatments are right for you.
Can Acute Kidney Injury Lead to Chronic Kidney Disease?
It can. After AKI, you have a higher risk of other health problems, including CKD, heart disease and stroke, and a higher chance of having AKI again. The National Kidney Foundation notes that the chance of developing kidney disease and kidney failure goes up each time an AKI happens.
That is why follow-up matters after a hospital stay where your kidneys were affected, even if you feel well when you go home. The National Kidney Foundation recommends checking your kidney health with simple tests, ideally within 3 months of finishing treatment for AKI. If none was set up, ask your primary care doctor.
When Should You Get Medical Care?
Call 911 or go to the nearest emergency room right away if you have chest pain or pressure, trouble breathing, sudden confusion or unusual behavior, fainting, or a seizure. Go to the emergency room as well if several of these happen together: you are urinating much less than usual, you feel very tired, you are not hungry, you cannot focus, and your feet or ankles are swelling.
Make an appointment with your doctor if you were treated for AKI and have no follow-up planned, if a blood or urine test showed reduced kidney function, or if you have diabetes, high blood pressure, heart disease or a family history of kidney failure and have not had your kidneys checked. Your primary care doctor can decide whether you should see a kidney specialist.
Frequently Asked Questions
Is Acute Kidney Injury the Same as Kidney Failure?
Not exactly. AKI ranges from mild kidney damage to sudden kidney failure, which is why it is sometimes called acute kidney failure. Kidney failure from CKD is long-term and is treated with dialysis or a kidney transplant.
Can You Have AKI and CKD at the Same Time?
Yes. People with CKD have a higher risk of AKI, and kidneys that were already damaged before an AKI may not fully heal afterward.
How Long Does It Take to Recover From AKI?
It depends on the cause and how severe the injury is. A mild AKI may heal within a few days, while a severe one may take at least 2 to 3 weeks or longer.
Does AKI Always Cause Symptoms?
No. Some people have no symptoms at all, and the injury is found only through blood or urine tests.
Will I Need Dialysis for AKI?
Only in more serious cases. Dialysis for AKI is usually temporary until the kidneys recover, although sometimes the damage is severe enough that it is needed long term.
Should I See a Nephrologist After a Hospital AKI?
Ask your doctor. Follow-up kidney tests come first, and your doctor can refer you to a kidney specialist if needed. In most cases you need a referral from your primary care doctor to see a nephrologist, but it may depend on your insurance plan.
Talk to ANC About Acute or Chronic Kidney Disease
ANC’s physicians, nurse practitioners and physician assistants see patients with all types of acute and chronic kidney disease, both in the clinic and in the hospital. If you have had an AKI or have been told your kidney function is low, ask your primary care doctor whether a referral makes sense. Contact ANC or call 651-772-6251 with questions.
Sources
- National Kidney Foundation: Acute Kidney Injury (AKI): Causes, Symptoms, and Treatment
- National Kidney Foundation: Chronic Kidney Disease (CKD)
- NIDDK: What Is Chronic Kidney Disease in Adults?
- NIDDK: Managing Chronic Kidney Disease
- Cleveland Clinic: Acute Kidney Injury (AKI)
Medical Disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your specific care and treatment options.
