Acute Kidney Injury: Key Questions and Answers for Patients Based on the Latest Medical Evidence

 Acute Kidney Injury (AKI) is one of the most significant and common complications in modern hospital medicine, affecting both adults and children, but with especially severe outcomes in patients with multiple underlying health conditions. In order to provide patients and their loved ones with the most up-to-date and evidence-based answers to key questions, this article draws on one of the latest and most authoritative sources in the field: the review article “Acute kidney injury, its definition, and treatment in adults: guidelines and reality,” published in 2020 in the journal Polish Archives of Internal Medicine (Volume 130, Issue 12, pp. 1074–1080).

The authors, Prof. Dr. Joanna Matuszkiewicz-Rowińska and Prof. Dr. Jolanta Małyszko, are leading nephrology experts from the Medical University of Warsaw, Poland. Their article summarizes the latest scientific findings, established diagnostic criteria, and current practices in the treatment of acute kidney injury, as well as the most common questions and challenges faced by patients and healthcare teams.

“Acute kidney injury is not simply a temporary condition—even after successful treatment, patients remain at high risk for long-term complications. Timely recognition and follow-up care are crucial for their future health.”

Expert Insights

1. What is acute kidney injury and why is it so important?

"Acute kidney injury is defined as an increase in serum creatinine levels by at least 0.3 mg/dl within 48 hours or 1.5‑fold the baseline, which is known or presumed to have occurred within the preceding 7 days, or—according to the urine output criterion—urine volume less than 0.5 ml/kg/hour for at least 6 hours."

Explanation: AKI is a condition in which the kidneys suddenly lose their ability to filter waste products from the blood. The key diagnostic criteria are a rapid rise in serum creatinine or a reduction in urine output. This matters because even small changes can indicate a serious problem that requires immediate medical attention.

2. What are the risks and long-term consequences of AKI?

"In patients requiring renal replacement therapy (RRT), the overall 90-day mortality ranges between 44% and 60%. Moreover, those who survive the hospitalization period are at risk of developing long-term complications associated with a substantial cost burden. Recent studies have consistently shown that, in both adults and children, AKI and its stage is a strong, independent risk factor for CKD development."

Explanation: AKI is not just a temporary condition—even with successful treatment, many patients remain at risk of developing chronic kidney disease (CKD), hypertension, and cardiovascular complications. The risk of death remains high in severe cases, especially when dialysis is required.

3. How reliable are the diagnostic criteria for AKI, and what are their limitations?

"Many shortcomings of the KDIGO definition result from the fact that it is based on serum creatinine levels, which are imperfect biomarkers of AKI, being affected by numerous factors... The greatest uncertainty about the value of the KDIGO classification in clinical research is the fact that the definition does not differentiate between 2 extreme forms of AKI: the functional one, formerly called prerenal azotemia, and structural tubular injury."

Explanation: While the KDIGO criteria are the most widely accepted, they have limitations. For example, serum creatinine levels are influenced by many non-kidney-related factors. The definition also doesn’t distinguish between functional (prerenal) and structural types of injury, which can lead to misjudgment of the condition.

4. What should be done if AKI is suspected? What is the proper diagnostic and treatment approach?

"The current approach to AKI includes: 1) identification and treatment of the underlying causes such as volume depletion, hypotension, use of selected drugs, or urinary tract obstruction; 2) removal of any potential insults to minimize additional injury; and 3) supportive measures to maintain optimal fluid, acid–base, and electrolyte balances. In patients with severe AKI, RRT is initiated when these measures fail to provide an adequate and safe control of homeostasis."

Explanation: The key is timely identification and treatment of the root causes (such as dehydration, low blood pressure, medications, or urinary tract obstruction). Maintaining fluid and electrolyte balance, and starting dialysis (renal replacement therapy) if needed, are critical.

5. Should AKI patients receive long-term monitoring?

"It is suggested that AKI survivors, especially those who develop AKI in the hospital, should be closely followed up, since they are at substantial risk of relapse and the subsequent development of end-stage CKD as well as other adverse outcomes including hypertension and cardiovascular disease. According to the 2012 KDIGO guidelines, patients discharged from the hospital with a diagnosis of AKI should be evaluated within 90 days for resolution and new onset or worsening of pre-existing CKD."

Explanation: Patients who have experienced AKI are often at increased risk for kidney and cardiovascular conditions. Close follow-up by a nephrologist—especially within the first 90 days after hospital discharge—is essential to prevent or manage potential chronic damage.

Frequently Asked Questions

1. What are the main causes of acute kidney injury in a hospital setting? 

Answer: The main causes of AKI in hospitals are varied and often related to serious medical conditions. These include severe infections (such as sepsis or septic shock), major surgical procedures (especially heart or abdominal surgeries), organ or stem cell transplantation, major trauma and burns, use of nephrotoxic medications (such as certain antibiotics, imaging contrast agents, and nonsteroidal anti-inflammatory drugs), acute liver disease, massive muscle or blood tissue breakdown (rhabdomyolysis, hemolysis), and urinary tract obstructions caused by stones or tumors. In many patients, the causes can be complex and the risk factors combined.

2. Why are older adults at greater risk for acute kidney injury? 

Answer: Older adults (age 65 and above) are significantly more vulnerable to AKI due to multiple underlying conditions and chronic degenerative changes in their organs. Many already have chronic kidney disease (“AKI on CKD”), which makes them more susceptible to additional damaging factors like surgeries, infections, trauma, or medications. With age, the kidneys have less ability to recover from sudden injury.

3. How is the severity of acute kidney injury determined? 

Answer: AKI severity is classified using KDIGO (Kidney Disease: Improving Global Outcomes) criteria, which define three stages based on changes in serum creatinine and urine output over time. For example:

• Stage 1: Creatinine is 1.5–1.9 times the baseline or increased by ≥0.3 mg/dl; urine output is <0.5 ml/kg/hour for 6–12 hours.

• Stage 2: Creatinine is 2–2.9 times the baseline; urine output is <0.5 ml/kg/hour for >12 hours.

• Stage 3: Creatinine is 3 times or more the baseline, or dialysis is required; urine output is <0.3 ml/kg/hour for >24 hours, or there is anuria (no urine) for >12 hours.

4. Does a rise in creatinine always mean the kidneys are severely damaged? 

Answer: Not always. Elevated creatinine may result not only from true structural kidney damage but also from temporary changes in blood volume or kidney perfusion (functional, or prerenal AKI). This can be caused by dehydration, low blood pressure, heart or liver failure. In such cases, the increase in creatinine might be a protective response by the body and may not lead to permanent damage if the cause is identified and treated promptly. This is why accurate diagnosis and clinical context are essential, rather than relying solely on lab results.

5. What errors or limitations exist in diagnosing acute kidney injury? 

Answer: Diagnosis of AKI often relies on changes in serum creatinine and urine output, but these indicators can be affected by many factors unrelated to kidney function—such as muscle mass, fluid intake, certain medications, or even lab errors. For instance, in cases of fluid overload, creatinine levels can be "diluted," underestimating the severity of the condition. Additionally, it’s not always possible to determine the baseline (normal) creatinine level before the acute episode, which can lead to inaccuracies in assessing AKI severity. In patients who do not experience a significant drop in urine output (so-called non-oliguric AKI), diagnosis can be missed or delayed.

Conclusion Acute kidney injury remains a challenge for both modern medicine and every affected patient. Highlighting the most important questions and answers—based on scientific evidence—helps build a better understanding of the disease, supports informed decision-making, and encourages active participation in treatment. The publication by Prof. Matuszkiewicz-Rowińska and Prof. Małyszko is a valuable source of current and practically applicable guidance that can help both patients and their families during the difficult stages of diagnosis, treatment, and recovery from AKI. Being informed is the first and most crucial step toward better health and successful rehabilitation.

Source Matuszkiewicz-Rowińska J, Małyszko J. Acute kidney injury, its definition, and treatment in adults: guidelines and reality. Pol Arch Intern Med. 2020; 130: 1074‑1080. https://doi.org/10.20452/pamw.15373