Acute Kidney Injury (AKI) occurs as an abrupt loss of kidney function over hours to weeks and is usually reversible (but not invariably). Chronic Kidney Disease (CKD) arises as a result of progressive loss of kidney function over a period of months or years which leads to irreversible damage. This is the key difference between Acute Kidney Injury and Chronic Kidney Disease. Further differences between these two will be discussed in this article.
What is Acute Kidney Injury (AKI)?
Acute Kidney Injury has now replaced the term Acute Renal Failure (ARF). AKI is potentially treatable; however, a minor reduction of kidney function has an adverse prognosis. The common definition of AKI for practice, research and public health is as follows.
Increase in sCr by ≥ 0.3mg/dl (26.5 μmol/l) within 48 hours; or
Increase in sCr to ≥ 1.5 times baseline, which is known or presumed to have occurred within prior 7 days; or
Urine volume < 0.5ml/kg/hr for 6 hours
Two similar definitions; RIFLE – Risk, Injury Failure, Loss of function, End stage renal disease and AKIN – Acute Kidney Injury Network have also been proposed and validated for defining and staging of AKI.
Signs and Symptoms
There are several signs and symptoms associated with Acute Kidney Injury.
Skin: Livido reticularis, Maculopapular rash, Track marks
Eyes: Keratitis, Jaundice, Multiple Myeloma, Signs of diabetes mellitus, and hypertension
Ears: Hearing loss
Cardiovascular System: Irregular rhythms, Murmurs, Pericardial friction rub
Abdomen: Pulsatile mass, Abdominal tenderness, Edema
Pulmonary System: Rales, Hemoptysis
What is Chronic Kidney Disease (CKD)?
According to the national kidney foundation guidelines, CKD can be defined as,
Kidney damage for ≥ 3 months, as defined by structural or functional abnormalities of the kidney, with or without decrease in Glomerular Filtration Rate (GFR) manifest by either pathological abnormalities or markers of kidney damage, including abnormalities in the composition of the blood or urine, or abnormalities in the imaging test.
GFR < 60ml/min/1.73m2 for ≥ 3 months, with or without kidney damage.
Signs and Symptoms
Signs of metabolic acidosis, Edema – Peripheral and pulmonary, Hypertension, Fatigue, Pericariditis, Encephalopathy, Peripheral neuropathy, Restless leg syndrome, Gastrointestinal symptoms, Skin manifestation, Malnutrition, Platelet dysfunction are signs and symptoms of CKD.
What are the differences between Acute Kidney Injury and Chronic Kidney Disease?
Causes of Acute Kidney Injury and Chronic Kidney Disease
AKI: AKI occurs due to the sudden reduction of kidney function over hours to weeks.
CKD: CKD occurs due to progressive loss of renal function.
AKI: AKI is reversible in most of the times.
CKD: CKD cannot be revised.
Etiology of Acute Kidney Injury and Chronic Kidney Disease
AKI: Etiology of AKI can be divided into 3 categories; pre-renal (caused by decreased renal perfusion), intrinsic renal (caused by a process within kidneys) and post-renal (caused by inadequate drainage of urine distal to the kidneys)
CKD: CKD can be a manifestation of other chronic illnesses such as diabetes mellitus, hypertension or glomerulonephritis.
Diagnosis of Acute Kidney Injury and Chronic Kidney Disease
AKI: Early diagnosis of AKI can be difficult using traditional biomarkers such as serum cratinine as it takes more than 48 hours to appear in serum after injury. Therefore, more sensitive and specific biomarkers are needed for AKI.
CKD: CKD can be diagnosed with conventional laboratory tests.
K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis, 39, S1-266.
Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney International Supplements 2, 18-20.
ARORA, P. 2015. Chronic Kidney Disease [Online]. Available: http://emedicine.medscape.com/article/238798-overview [Accessed June 13th 2016].
BIRUTH, T. 2015. Acute Kidney Injury [Online]. Available: http://emedicine.medscape.com/article/243492-overview [Accessed June 13th 2016].
CRUZ, D. N., RICCI, Z. & RONCO, C. 2009. Clinical review: RIFLE and AKIN–time for reappraisal. Crit Care, 13, 211.
WAIKAR, S. S. & BONVENTRE, J. V. 2009. Creatinine kinetics and the definition of acute kidney injury. J Am Soc Nephrol, 20, 672-9.
“Blausen 0592 KidneyAnatomy” By Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. – (Own work, CC BY 3.0) via Commons Wikimedia
“Kidney – acute cortical necrosis” By Haymanj – Own work (own photo) (Public Domain) via Commons Wikimedia