An Introduction to Acute Kidney Injury and its Medico-Legal Applications

by Dr Adnan Sharif, Consultant Nephrologist

Acute Kidney Injury (AKI) is a sudden and recent reduction in a person’s kidney function, which can have dramatic implications and consequences for good health.

In this article I will explain:

  • Why kidneys are so important
  • The spectrum of kidney disease – from acute to chronic
  • How to detect AKI
  • Who’s more at risk to AKI
  • Why AKI is a significant medical problem
  • How AKI may be relevant in Medico-legal cases

Why Kidneys Are So Important

Kidneys are critically important for our healthy well-being. They look after our bodies by:

  • Producing urine to remove excess water and toxins
  • Regulating water balance to ensure we don’t have too much or too little water in our body
  • Maintaining a balance of electrolytes (e.g., potassium, sodium, calcium) to help control our heart rhythm
  • Managing our acid-base balance to ensure our blood is never too acidic or alkaline
  • Controlling our blood pressure through different mechanisms to ensure our blood pressure isn’t too high or low
  • Activating vitamin D to help bone absorb calcium
  • Releasing the hormone erythropoietin which tells our bone marrow to make red blood cells

The Spectrum Of Kidney Disease – From Acute To Chronic

Patients with kidney disease can have different clinical presentations. Kidney problems will generally cause acute, sub-acute, or chronic health problems.

When a kidney abnormality is detected, often a detailed investigation of records is required to determine whether the kidney injury is acute or more chronic (referred to as chronic kidney disease which affects 10-15% of the general population).

At the acute end of the spectrum, AKI is an important medical problem that develops over hours to days and can be diagnosed in the community or after any hospital admission.

How To Detect AKI

AKI is easily diagnosed by a blood test to measure the level of creatinine in the blood. If the creatinine level has doubled, then there is severe AKI and urgent treatment is normally necessary. If the creatinine level has gone up by a lesser amount, then there may need to be follow-up checks over the next few days.

AKI can also be detected based on a drop in urine production in hospitalised people, but this is less common. Guidelines for managing AKI have been published by NICE and have been implemented as AKI bundles by many healthcare organisations.

Often people with AKI have no symptoms or have symptoms of the underlying cause that has caused AKI (e.g., infection), but some complaints people may include nausea, dehydration, peeing less than usual, confusion and/or drowsiness.

Who’s More At Risk To AKI?

AKI should be considered for individuals with acute illness. Guidance from the National Institute for Health and Care Excellent (NICE) suggests increased awareness of AKI is necessary if any of the following are likely or present:

  • chronic kidney disease (adults with an estimated glomerular filtration rate [eGFR] less than 60 ml/min/1.73 m2 are at particular risk)
  • heart failure
  • liver disease
  • diabetes
  • history of acute kidney injury
  • oliguria (urine output less than 0.5 ml/kg/hour)
  • neurological or cognitive impairment or disability, which may mean limited access to fluids because of reliance on a carer
  • hypovolaemia
  • use of drugs with nephrotoxic potential (such as non-steroidal anti-inflammatory drugs [NSAIDs], aminoglycosides, angiotensin-converting enzyme [ACE] inhibitors, angiotensin II receptor antagonists [ARBs] and diuretics) within the past week, especially if hypovolemic
  • use of iodinated contrast agents within the past week
  • symptoms or history of urological obstruction, or conditions that may lead to obstruction
  • sepsis
  • deteriorating early warning scores

Why AKI Is A Significant Medical Problem

AKI is an important medical problem because firstly it is very common. Around 1 in 4 adult hospital admissions are associated with AKI, with 1 in 2 adult critical care admissions being associated with AKI. Approximately a third of patients with AKI in the hospital develop their AKI episode during their stay in the hospital, while two-thirds of patients with AKI in the hospital had AKI at the time of admission.

The second reason why AKI is important is that it’s associated with excess death. Back in 2009, the National Confidential Enquiry into Patient Outcome and Death (NCEPOD) AKI report found that in the UK up to 100,000 deaths each year in hospitals are associated with acute kidney injury and up to 30% could be prevented with the right care and treatment.

The majority of AKI is caused by sepsis, poor hydration and medication but other causes exist including renal tract obstruction and intrinsic renal disease. AKI is associated with high mortality rates; from 8 to 18%, 22–33%, and 32–36% mortality for patients with AKI stages 1, 2, and 3 respectively, whilst in the absence of AKI, mortality runs at 2%. Even in the absence of death, AKI can have short-term and long-term health issues for survivors including heart disease, chronic kidney disease and risk for developing kidney failure.

Since the NCEPOD report, great strides have been made in hospital AKI care, including the introduction of AKI algorithms to detect AKI and national advice on what an AKI bundle should include.

There is greater awareness of clinically recognised risk factors for AKI, both modifiable (e.g., use of iodinated contrast for radiology scans, use of certain medications that can damage the kidneys) and non-modifiable (e.g., age, presence of chronic kidney disease) providing greater opportunity to prevent the development of AKI with appropriate intervention.

For example, staff should be alert to AKI risk in individual patients that may lead to increased clinical monitoring or a change in treatment. Many hospitals now have IT-based AKI alerts that notify clinical teams of the development of AKI from blood tests.

How AKI May Be Relevant In Medico-Legal Cases

As mentioned earlier, AKI is very common and can be seen in over a quarter of hospital episodes (and about half of any critical care admissions). Therefore, AKI is likely to occur in many medical-legal cases, either as the main reason for admission or more commonly as a co-existing or new complication due to admission for any other reason even if it may not be immediately obvious.

Blood test investigations almost always will include kidney function checks, both in hospitalised patients and in the community, and it is likely that a closer review of these blood results may identify kidney issues like AKI. This is important to flag up as the occurrence of AKI can have immediate and long-term consequences for health and wellbeing.

Think Kidneys is a national campaign raising awareness of the importance of kidneys for life and health, both AKI and chronic kidney disease. It is equally important for medico-legal teams to have a greater awareness of kidneys in their wide variety of cases and seek expert consult where required.

Want to Discuss Your Clinical Negligence Claim with Dr Sharif?

Dr Adnan Sharif graduated from the University of Edinburgh in 2002 and underwent his medical and nephrology training in Cardiff and Birmingham respectively while achieving his research degree in the field of post-transplantation diabetes.

He took up his Consultant Transplant Nephrologist post at the Queen Elizabeth Hospital Birmingham in 2011 and is an Honorary Associate Professor at the Institute of Immunology and Immunotherapy at the University of Birmingham.

He has an active research focus with >150 peer-reviewed publications and is currently Chief Investigator on a number of studies in nephrology and transplantation.

He is on the Board of Trustees for Kidney Research UK, Give A Kidney and the Global Kidney Foundation, and is a long-term member of the National BAME Transplantation Alliance. Dr Sharif has represented Transplant Nephrology on the British Transplantation Society Council for 2020-2023. Finally, he is an executive team member of the UK Organ Donation and Transplant Research Network.

In addition to his clinical and research interests, he is the Secretary of the non-Government Organization Doctors Against Forced Organ Harvesting (DAFOH) which campaigns against illegal and unethical organ procurement around the globe. The group was nominated for the Nobel Peace Prize in 2016 & 2017 and received the Mother Teresa Memorial Award for Social Justice in 2019.

Dr Sharif has been doing medico-legal work since 2018. He specialises in nephrology, renal medicine, dialysis, transplantation, acute kidney injury, chronic kidney disease, diabetes nephrology and inflammatory renal disease. His Claimant – Defendant ratio is 70:30.

To contact Dr Sharif for any enquiries, email

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