Describe the initial lab studies.
Serum markers: ↑ creatinine and BUN (alternatively, ↑ cystatin C)
Glomerular filtration rate: ↓ eGFR
Serum creatine-based eGFR (preferred): e.g., CKD-EPI equation, MDRD equation
Serum cystatin C-based eGFR
Describe findings of urine studies.
↑ Spot UACR: used to determine the albuminuria category for CKD staging.
↑ Spot urine protein-to-creatinine ratio (UPCR): Nephrotic-range proteinuria may be seen.
Urine dipstick: may show hematuria or proteinuria
Urine microscopy: may show abnormal urine sediment, e.g., the presence of waxy casts
Describe the US of the kidneys / urinary tract.
First-line imaging technique for the assessment of kidney structure
Consider obtaining for all patients to further support the diagnosis and help determine the etiology.
Findings that suggest chronic kidney damage include: 
↓ Kidney length (< 10 cm)
↓ Parenchymal and/or cortical thickness
↑ Cortical echogenicity
Findings that suggest specific etiologies
Ureteral or renal pelvic dilation suggests obstructive nephropathy.
Bilaterally enlarged kidneys with multiple cysts suggest polycystic kidney disease.
Describe the renal biopsy.
Not routinely indicated
Consider in either of the following situations:
Rapid and unexplained decline in eGFR
Need for diagnostic confirmation of the underlying etiology (e.g., glomerulonephritis) prior to initiating disease-specific therapy
Renal biopsy is only indicated in patients in whom the underlying cause of CKD is still unclear after noninvasive testing, the results are likely to influence management, and the potential benefits are thought to outweigh the risks.