What is the appropriate approach to understanding and treating a condition referred to as RFT (Renal Function Test)?

Understanding and Treatment Approach for Renal Function Testing

Renal Function Test (RFT) refers to a set of laboratory assessments used to evaluate kidney function, not a medical condition requiring treatment. According to KDIGO guidelines, proper terminology and assessment methods are essential for accurate evaluation of kidney health 1.

Proper Terminology and Definitions

• The term "Renal Function Test" (RFT) is not a preferred term according to KDIGO nomenclature guidelines; instead, specific kidney function assessments should be identified 1
• KDIGO recommends using the term "kidney function" rather than "renal function" except when describing specific functions (e.g., renal acidification) 1
• The term "GFR" should be used when specifically referring to glomerular filtration, while "kidney function(s)" should be used when addressing the totality of kidney functions 1

Components of Kidney Function Assessment

• Initial assessment: Serum creatinine (SCr) with an estimating equation (eGFRcr) is recommended for initial evaluation 1
• More accurate assessment: When eGFRcr is potentially inaccurate, cystatin C measurement and eGFRcr-cys should be used 1
• Highest accuracy needed: For clinical decisions requiring precise GFR measurement, use plasma or urinary clearance of exogenous filtration markers 1
• Albuminuria/proteinuria: Assessment of urine albumin-to-creatinine ratio (ACR) is essential for comprehensive kidney evaluation 1

Diagnostic Approach

• Establish chronicity (duration ≥3 months) through review of past GFR measurements, albuminuria/proteinuria results, imaging findings, or kidney pathology 1
• Do not assume chronicity based on a single abnormal eGFR or ACR measurement, as it could result from acute kidney injury (AKI) 1
• Consider kidney biopsy when clinically appropriate to evaluate cause and guide treatment decisions 1
• Evaluate for potential causes of kidney dysfunction through clinical context, personal/family history, medications, laboratory measures, imaging, and genetic testing when appropriate 1

Treatment Considerations

• For chronic kidney disease (CKD), treatment should be based on GFR category, albuminuria level, and underlying cause 1
• Consider timely referral for renal replacement therapy (RRT) planning when risk of kidney failure within 1 year is 10-20% or higher 1
• Multidisciplinary care is suggested for progressive CKD, including dietary counseling, education about RRT options, and psychosocial support 1
• Dialysis initiation should be based on symptoms and complications rather than GFR alone (typically in GFR range of 5-10 ml/min/1.73m²) 1

Continuous Renal Replacement Therapy (CRRT) Considerations

• CRRT refers specifically to extracorporeal blood purification therapies applied continuously (24 hours/day) 2
• CRRT modalities include CVVH (continuous venovenous hemofiltration), CVVHD (continuous venovenous hemodialysis), and CVVHDF (continuous venovenous hemodiafiltration) 2, 3
• Vascular access for CRRT typically uses uncuffed nontunneled dialysis catheters with right jugular vein as the preferred insertion site 3
• Anticoagulation protocol should be based on patient's bleeding risk, with regional citrate anticoagulation as first choice when appropriate 3

Common Pitfalls to Avoid

• Avoid using outdated terminology such as "renal failure," "end-stage renal disease," or "renal replacement therapy" 1
• Do not rely on single BUN and creatinine thresholds alone for initiating RRT; consider broader clinical context 1, 3
• Avoid using subclavian veins for dialysis access due to risk of thrombosis and stenosis 3
• Do not use diuretics to enhance kidney function recovery or reduce duration/frequency of RRT 1, 3

By following these evidence-based approaches to kidney function assessment and treatment, clinicians can provide optimal care while using appropriate terminology and diagnostic methods.