Epidemiology of AKI

Question 1

Define AKI and describe the characteristics

Answer 1

Definition and Characteristics
- Abrupt fall in glomerular filtration rate (GFR) (aka kidney function), potentially reversible
- Results in retention of waste products, volume dysregulation, and electrolyte imbalance
- Impairs renal physiological functions:
- Nitrogenous waste product excretion
- Water and electrolyte regulation
- Acid-base regulation

Question 2

What are some of the difficulties around AKI?

Answer 2

• true worldwide incidence is poorly understood due to under-reporting and different definitions
• KDIGO: improved data
• Data from under-resourced countries is typically sourced from studies in tertiary care hospitals

Question 3

Discuss the incidence of AKI

Answer 3

• AKI affects 13 million people annually
• seen in 20% of hospitalised adults and 25% of paediatric patients in intensive care, in high resource settings
• each episode of AKI has considerable mortality and long term adverse outcomes, including cardiovascular complications and chronic kidney disease
• in low resource settings, AKI is due to environmental factors including polluted water and endemic infections e.g. malaria
• diagnosis and treatment is often delayed or inadequate leading to increased mortality

Question 4

Describe how AKI is diagnosed and some issues

Answer 4

• Detected by measuring creatinine
• Challenges:
  
  • Early AKI may overestimate true GFR due to insufficient time for creatinine accumulation
  • Difficulty estimating true GFR after dialysis

Question 5

Discuss challenges in ascertaining AKI

Answer 5

• Clinical trials use different creatinine cut-off values for defining ARF
• Lack of consensus in quantitative definition of AKI
• Differences in AKI definition between general population, hospitalized patients, and ICU patients
• Differences between developing and developed countries

Question 6

Discuss issues with RIFLE and AKIN criteria

Answer 6

RIFLE Criteria Issues
- Confusion regarding inclusion of prerenal and obstructive aetiologies (either subsumed in or considered external)
- Utility at the bedside less clear
- RIFLE criteria based on changes in serum creatinine or urine output
- Critique of evidence behind the criteria
- Also: change in serum creatinine without baseline measures

AKIN Criteria
- Focus on change in serum creatinine and urine output
- GFR not considered for staging

Question 7

Describe KDIGO and its benefits

Answer 7

KDIGO 2012
- Considers change in serum creatinine and urine output for staging
- It is the current criteria used

AKIN vs KDIGO
- Different criteria for staging and classification of AKI
- Long-term survival analysis of AKI patients

Question 8

Describe variations in epidemiology of AKI

Answer 8

Developed Countries
- High incidence of AKI in both adults and children hospitalized with acute illness
- Age-standardized rates of AKI hospitalizations increased significantly
- Varying incidences of AKI in different studies

Under-Resourced Countries
- Factors contributing to AKI include infectious diseases, snake bites, and obstetrical complications
- Challenges in gathering accurate data due to methodological limitations
- Metropolitan regions show similarities to developed countries
- Note: under-reporting, socioeconomic and environmental influences

Community-Acquired AKI
- Acute elevation in creatinine occurring outside the hospital
- Causes include rhabdomyolysis, industrial accidents, and specific diseases including diarrhoeal HUS in UK, diarrhoea and malaria in SE Asia and amanita mushrooms in (not limited to) Nigeria

Hospital-Acquired AKI
- Incidence varies from 0.15% to 7.2% of all hospitalizations
- Caused by ischemia, toxins, and multifactorial factors
- Risk factors include
- post-operative status: haemodynamic compromise (kidneys are not prioritised), infection and sepsis, cardiac surgery
- sepsis (because blood siphoned elsewhere)
- contrast nephropathy (used in CT, indicated in low blood pressure, T2DM, CKD, volume of contrast)
- nephrotoxic antibiotics

ICU-Acquired AKI
- Common complication 30-50% in ICU admissions
- Variability in incidence based on surgical setting, primary diagnosis, and type of surgery: a third of cases of AKI in ICU

Question 9

Discuss the long term complications of AKI

Answer 9

AKI and CKD Interaction

Long-Term Implications
- AKI often leads to CKD development
- Complex interplay between AKI and CKD progression

AKI in Older Age Group
### Impact of Age
- Prevalence of AKI increases with age
- Elderly individuals with AKI experience higher mortality rates