Difficulties in diagnosing acute kidney injury post liver transplantation using serum creatinine based diagnostic criteria

Table 1 Definitions of acute kidney injury using changes in serum creatinine between the Risk Injury Failure EndStage[7], Akute Kidney Injury Network[8] and Kidney Disease Improving Global Outcomes[9] criteria

Criteria	RIFLE[7]	AKIN[8]	KDIGO[9]
Date of release	2004	2007	2012
Time interval	Diagnosis and Staging: Within 1-7 d and sustained more than 24 h	Diagnosis: Within 48 h Staging: 1 wk	Diagnosis: 50% increase within 7 d or ≥ 0.3 mg/dL (26.5 μmol/L) within 48 h
Stage 1 or R	Increased SCr 1.5-1.9 times baseline	Increased SCr 1.5-1.9 times baseline or ≥ 0.3 mg/dL (≥ 26.5 μmol/L) increase	Increased SCr 1.5-1.9 times baseline (7 d) or ≥ 0.3 mg/dL (≥ 26.5 μmol/L) increase (48 h)
Stage 2 or I	Increased SCr 2.0-2.9 times baseline	Increased SCr 2.0-2.9 times baseline	Increased SCr 2.0-2.9 times baseline
Stage 3 or F	Increased SCr 3.0 times baseline, or Increase in SCr ≥ 4.0 mg/dL (350 μmol/L) with an acute rise of ≥ 0.5 mg/dL (44 μmol/L)	Increased SCr 3.0 times baseline, or Increase in SCr ≥ 4.0 mg/dL (350 μmol/L) with an acute rise of ≥ 0.5 mg/dL (44 μmol/L)	Increased SCr 3.0 times baseline, or Increase in SCr ≥ 4.0 mg/dL (350 μmol/L)

SCr: Serum creatinine; RIFLE: Risk Injury Failure EndStage; AKIN: Akute Kidney Injury Network; KDIGO: Kidney Disease Improving Global Outcomes.

Table 2 Cohort of 329 adult patients transplanted for advanced cirrhosis

	RIFLE[7]	AKIN[8]	KDIGO[9]
Stage 1 or R	53	93	97
Stage 2 or I	28	28	28
Stage 3 or R	8	8	8
Stage 3 initiation of RRT	17	17	17

Changes in renal as assessed bt RIFLE, AKIN and KDIGO criteria for acute kidney injury for changes in serum creatinine. RIFLE: Risk Injury Failure EndStage; AKIN: Akute Kidney Injury Network; KDIGO: Kidney Disease Improving Global Outcomes; RRT: Renal replacement therapy.

Table 3 Comparison of the established methods for assessing renal function in clinical practice

	Advantages	Disadvantages
Serum marker
Creatinine	Widely available	Influenced by several factors unrelated to renal function, including dehydration and volume expansion, dietary protein, muscle mass, physical activity and thyroid hormones renal tubular secretion affected by chronic kidney disease, proteinuria and drugs not an early biomarker of acute kidney injury Absence of standardization of the laboratory methods for jaundiced patients
Clearance of exogenous marker	“Gold standard”	technical difficulties and expense make impractical for routine clinical practice stable renal function Less reliable in patients with oedema, ascites, pleural effusions and sarcopenia
Creatinine Clearance f
(24 h urine collection)	? more accurate compared to Cr	Inconvenient for outpatientsoverestimates GFR in proteinuria chronic kidney disease influenced by muscle metabolism and diet, inflammatory disease and malnutrition Unexplained variation due to incomplete urine collection and errors in urine volume measurement overestimation of GFR in patients with cirrhosis
Mathematical formulae based on Cr	Easier method compared to 24 h urine collection	Not validated for patients with changing renal function (acute kidney injury, muscle wasting disorders) Does not overcome the limitations in serum creatinine
C-G formula	Requires only gender, age, body weight	Difficult to determine body weight in patients with ascites and post LT
MDRD formula	Body weight is not needed ethnicity, gender and age are taken into account	Has not been validated in patients with chronic liver disease 6-variables formula: needs albumin, urea Only validated in stable chronic kidney disease patients

GFR: Glomerular filtration rate; Cr: Serum creatinine; C-G: Cockcroft-Gault; MDRD: Modification of Diet in Renal Disease; CKD: Chronic kidney disease; LT: Liver transplantation.