I HAVE A PATIENT WITH ACUTE KIDNEY INJURY
How do I determine the cause?
Mr. T is 77-year-old man with acute kidney injury (AKI).
What is the differential diagnosis of AKI? How would you frame the differential?
CONSTRUCTING A DIFFERENTIAL DIAGNOSIS
AKI is a broad clinical syndrome defined by an abrupt decrease in kidney function over a period of hours to days, characterized by a rise in serum creatinine or a decrease in urinary output. The time frame of development and persistence of kidney damage defines a spectrum that extends to acute kidney disease (AKD) and chronic kidney disease (CKD). Table 28-1 summarizes the current diagnostic criteria and staging for AKI, AKD, and CKD, which may be relevant in the evaluation and prognostication of disease.
Table 28-1.Diagnostic criteria and staging for kidney disease. |Favorite Table|Download (.pdf) Table 28-1. Diagnostic criteria and staging for kidney disease.
|Syndrome ||Serum Creatinine (Scr)/GFR Criteria ||Evidence of Kidney Damage1 ||Staging |
|Stage2 ||Scr ||Urinary Output |
|Acute kidney injury (AKI) || |
Increase in serum creatinine by ≥ 0.3 mg/dL within 48 hours or
Increase to ≥ 1.5 times baseline within 7 days or
Urine volume < 0.5 mL/kg/h for 6 hours
|Not required for diagnosis || |
↑ by ≥ 0.3 or 1.5–1.9 times baseline
2–2.9 times baseline
3 times baseline or ≥ 4 mg/dL or dialysis
< 0.5 mL/kg/h for 6–12 hours
< 0.5 mL/kg/h for ≥ 12 hours
< 0.3 mL/kg/h for ≥ 24 hours or anuria
|Acute kidney disease (AKD)3 || ||Present for < 3 months ||No staging || || |
| || || ||GFR (mL/min/1.73 m2) || ||Albuminuria stages (AER, mg/day) |
|Chronic kidney disease (CKD)3 ||GFR < 60 mL/min for > 3 months ||Present for > 3 months || |
G1 > 90 Normal or high
G2 60–89 Mild decrease
G3a 45–59 Mild to moderate
G3b 30–44 Moderate to severe
G4 15–29 Severe
G5 < 15 Kidney failure
| || |
A1 < 30 Normal to mild
A2 30–300 Moderate
A3 ≥ 300 Severe
The framework for the differential diagnosis of AKI is a combination of anatomic and pathophysiologic, typically divided into prerenal, intrarenal, and postrenal causes:
Prerenal (due to renal hypoperfusion)
Intravascular volume depletion
Renal loss: drug-induced or osmotic diuresis (such as from hyperglycemia), diabetes insipidus
Skin and mucous membrane losses
Third spacing, such as nephrotic syndrome, pancreatitis, etc.
Decreased effective circulating volume (with or without hypotension)
Heart failure (HF), with or without cardiogenic shock...