Update on the diagnosis and management of acute kidney injury

Figures & data

Table 1 RIFLE and AKIN criteria for diagnosis of AKI

RIFLE criteria (within 7 days)
Class	GFR criteria	Urine output criteria
R-Risk	Creatinine increase × 1.5 or GFR loss > 25%	0.5 < mL/kg/hour × >6 hours
I-Injury	Creatinine increase × 2 or GFR loss > 50%	0.5 < mL/kg/hour × >12 hours
F-Failure	Creatinine increase × 3 or GFR loss > 75% or creatinine increase >4 mg/dL (acute increase >0.5 mg/dL)	0.3 < mL/kg/hour × >24 hours or anuria >12 hours
L-Loss	Persistent loss of kidney function >4 weeks
E-ESKD	ESKD > 3 months
AKIN criteria (within 48 hours)
Stage	Serum creatinine criteria	Urine output criteria
1	Creatinine increase × 1.5 or creatinine increase >0.3 mg/dL	0.5 < mL/kg/hour × >6 hours
2	Creatinine increase × 2	0.5 < mL/kg/hour × >12 hours
3	Creatinine increase × 3 or creatinine increase >4 mg/dL (acute increase >0.5 mg/dL)	0.3 < mL/kg/hour × >24 hours or anuria >12 hours

Table 2 Conditions causing prerenal azotemia

Hypovolemia

Hemorrhage

Gastrointestinal losses

Third space

Burns

Peritonitis

Muscle trauma

Renal fluid losses

Overdiuresis

Impaired cardiac function

Congestive heart failure

Cardiogenic shock

Acute myocardial infarction

Pericardial tamponade

Massive pulmonary embolism

Systemic vasodilatation

Gram-negative bacteremia

Antihypertensive medications

Anaphylaxis

Cirrhosis

Increased renal vascular resistance

Anesthesia

Surgery

Hepatorenal syndrome

Prostaglandin inhibitors

NSAIDs

Renal vasoconstricting drugs

Cyclosporin

Table 3 Conditions causing postrenal azotemia

Urethral obstruction

Valves

Stricture

Bladder neck obstruction

Prostatic hypertrophy

Bladder carcinoma

Bladder infection

Functional

Autonomic neuropathy

Alpha adrenergic blockers

Bilateral obstruction of ureters (unilateral obstruction in solitary kidney)

Intraureteral

Sulphonamide, uric acid, acyclovir, anti-retroviral agent crystals

Blood clots

Stones

Necrotizing papillitis

Extraureteral

Tumor of cervix, prostate, bladder

Endometriosis

Periureteral fibrosis

Accidental ureteral ligation

Pelvic abscess or hematoma

Table 4 Conditions that cause parenchymal (intrinsic) AKI

Vascular

Large vessels

Bilateral renal artery stenosis

Bilateral renal vein thrombosis

Operative arterial cross clamping

Small vessels

Vasculitis

Atheroembolic disease

Thrombotic microangiopathies

Hemolytic uremic syndrome

Thrombotic thrombocytopenic purpura

Scleroderma renal crisis

Malignant hypertension

Hemolysis, elevated liver enzymes and low platelets syndrome (HELLP)

Glomerular

Diseases with linear immune complex deposition

Goodpasture’s syndrome

Diseases with granular immune complex deposition

Acute postinfectious glomerulonephritis

Lupus nephritis

Infective endocarditis

Immunoglobulin A (IgA) glomerulonephritis

Henoch-Schonlein purpura

Membranoproliferative glomerulonephritis

Cryoglobulinemia

Diseases with few immune deposits (“Pauci-immune”)

Wegener’s granulomatosis

Polyarteritis nodosa

Idiopathic crescentic glomerulonephritis

Churg-Strauss syndrome

Interstitium

Acute allergic interstitial nephritis

Antibiotics

Beta-lactam antibiotics (penicillins, methicillin, cephalosporins)

Rifampicin

Sulphonamides

Erythromycin

Ciprofloxacin

Diuretics (furosemide, thiazides, chlorthalidone)

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Anticonvulsant drugs (phenytoin, carbamazepine)

Allopurinol

Interstitial nephritis associated with infection, granuloma, crystals

Streptococcal

Staphylococcal

Diphtheria

Leptospirosis

Brucellosis

Legionnaire’s disease

Toxoplasmosis

Infectious mononucleosis

Salmonella typhi

Tuberculosis

Sarcoidosis

Acute uric acid nephropathy eg, tumor lysis syndrome

Hypercalcemia

Melamine toxicity

Acute tubular necrosis

Renal ischemia (50% of cases)

Shock

Complications of surgery

Hemorrhage

Trauma

Gram-negative bacteremia

Pancreatitis

Pregnancy (postpartum hemorrhage, abruptio placenta, septic abortion)

Nephrotoxic drugs (35% of cases)

Antibiotics (aminoglycosides, amphotericin, pentamidine, foscarnet, acyclovir)

Antineoplastics (cisplatin, methotrexate)

Iodine-containing x-ray contrast

Organic solvents (carbon tetrachloride)

Ethylene glycol (antifreeze)

Anesthetics (enflurane)

Acute phosphate nephropathy

Endogenous toxins

Myoglobin due to rhabdomyolysis

Hemoglobin (incompatible blood transfusion, acute falciparum malaria)

Uric acid (acute uric acid nephropathy)

Table 5 Scoring system of AKI severity based on number of granular casts and RTE cells in urinary sediment

RTE cells (per HPF)	Granular casts (per LPF)
	0 (0 Points)	1 to 5 (1 Point)	≥6 (2 Points)
0 (0 points)	0	1	2
1 to 5 (1 point)	1	2	3
≥6 (2 points)	2	3	4

Notes: Values denote total points awarded. A urine sediment score of greater than or equal to three versus zero was a significant predictor of worsening of AKI (progressing to a higher AKIN stage [Table 1], dialysis, or death).⁴⁷ Reproduced from Perazella et al.⁴⁷

Abbreviations: HPF, high-powered field; LPF, low-powered field; RTE, renal tubular epithelial.

Table 6 Urine findings in prerenal azotemia and intrinsic AKI

Laboratory test	Prerenal azotemia	ATN
Urine sodium (UNa), mEq/L	<20	>40
Urine osmolality, mOsm/kg H2O	>500	<400
Urine to plasma urea nitrogen	>8	<3
Urine to plasma creatinine	>40	<20
Fractional excretion of filtered sodium	<1	>1
Urinary sediment	Bland	“Muddy” brown granular casts, cellular debris, tubular epithelial cells

Table 7 Dose of dialysis in AKI

No of patients	Study design	Results	Ref
425 patients; single center	Dose of CVVH	Ultrafiltration at 35 or 45 mL/hour/kg better patient survival than 20 mL/hour/kg	^Citation96
160 patients; single center	Daily or alternate day hemodialysis	Daily hemodialysis better patient survival than alternate day hemodialysis	^Citation97
206 patients; single center	Increase in dialysis dose by adding CVVHDF to CVVH	CVVH + CVVHDF better patient survival than CVVH alone	^Citation98
ATN study; 1,124 patients multicenter	3/week HD (Kt/V > 1.2 per HD) or CVVH 20 mL/hour/kg versus 6/week HD or CVVH 35 mL/hour/kg	Patient survival was the same intensive versus conventional dialysis	^Citation99
RENAL study; 1,508 patients	CVVH at 25 mL/hour/kg versus 40 mL/hour/kg	Mortality at 90 days the same in intensive versus conventional dose of CVVH	^Citation100

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