Evaluation and Management of Impaired Renal Function

Initial Assessment

The American College of Radiology recommends determining if the renal impairment is acute or chronic by reviewing previous creatinine values and calculating the rate of change 1, 2
Categorize the cause as prerenal, intrinsic renal, or postrenal 1
Calculate estimated GFR using validated equations (CKD-EPI or MDRD) rather than relying on serum creatinine alone, especially in elderly patients or those with reduced muscle mass 2, 3
Assess for signs and symptoms of uremia, fluid overload, or electrolyte disturbances 1, 4

Complete blood count to assess for anemia, which commonly accompanies chronic kidney disease 2
Comprehensive metabolic panel including electrolytes, BUN, and creatinine 1, 4
Urinalysis with microscopic examination for casts, cells, and crystals 1, 4
Urine albumin-to-creatinine ratio (UACR) to quantify proteinuria 5, 2
Urine sodium and urea to help differentiate prerenal from intrinsic causes 6
Consider specialized urinary biomarkers in selected cases 1

Renal ultrasonography should be performed in all patients with new or worsening renal impairment to evaluate kidney size, echogenicity, and rule out obstruction 1, 2
Consider additional imaging based on clinical suspicion, such as CT with or without contrast, MRI without gadolinium, or renal Doppler ultrasound 1

Identify and discontinue potentially nephrotoxic medications (NSAIDs, certain antibiotics) 6, 2
Review medications requiring dose adjustment for renal function 2, 3
Consider holding ACE inhibitors or ARBs temporarily if acute kidney injury is present, but do not discontinue for minor increases in serum creatinine (≤30%) in the absence of volume depletion 5, 3

For diabetic patients, optimize blood pressure control with target <140/90 mmHg to reduce risk of CKD progression 5, 2
In patients with cirrhosis and AKI, perform diagnostic paracentesis to evaluate for spontaneous bacterial peritonitis 6
For immune checkpoint inhibitor-related nephritis, consider renal biopsy if AKI is refractory to steroids 7

eGFR <30 mL/min/1.73m² 5, 2
Rapid progression of kidney disease (sustained decrease in eGFR >20%) 2
Difficult management issues (resistant hypertension, electrolyte abnormalities) 5, 2
Uncertainty about the etiology of kidney disease 5, 2
Persistent significant proteinuria (UACR ≥300 mg/g) 5, 2