Should I proceed with an Ultrasound (USG) of the kidneys to confirm Chronic Kidney Disease (CKD)?

Ultrasound for Diagnosis of Chronic Kidney Disease

Renal ultrasound is not necessary to confirm the diagnosis of chronic kidney disease (CKD), as CKD is primarily diagnosed through laboratory tests including estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (ACR) measurements over at least 3 months. 1

Diagnosis of CKD: Laboratory Tests vs. Imaging

Primary Diagnostic Criteria for CKD

• CKD is defined as abnormalities of kidney structure or function present for >3 months with health implications 1
• Diagnosis requires:
  • eGFR <60 mL/min/1.73 m² and/or
  • Albuminuria ≥30 mg/g (≥3 mg/mmol) on urinary ACR
  • Persistence of these findings for at least 3 months

Role of Ultrasound in CKD

Ultrasound is not required for initial diagnosis but may be indicated in specific scenarios:

1. When to consider renal ultrasound:

   • Unexplained decline in kidney function
   • Suspected urinary tract obstruction
   • Family history of polycystic kidney disease
   • Recurrent urinary tract infections
   • Hematuria with flank pain
   • Suspected renal artery stenosis

2. Findings on ultrasound in CKD:

   • Small kidneys (<9 cm in length in adults) suggest advanced CKD 1
   • Increased echogenicity indicates parenchymal disease 2
   • Loss of corticomedullary differentiation
   • Cortical thinning
   • Irregular contours in advanced disease

Evidence-Based Approach to CKD Diagnosis

The 2024 ESC guidelines clearly state that CKD diagnosis requires:

• Measurement of serum creatinine and eGFR
• Urinary albumin-to-creatinine ratio
• Persistence of abnormalities for at least 3 months 1

The ACR Appropriateness Criteria notes that renal ultrasound has limited impact on management in patients with CKD and diabetes or hypertension, contributing to diagnosis in only 5.9% of patients and affecting management in just 3.3% 1.

When Ultrasound Is Indicated in CKD

Renal ultrasound should be considered in the following situations:

• Moderate to severe CKD to assess kidney structure 1
• To exclude renoparenchymal and renovascular hypertension 1
• History of kidney stones or obstruction 1
• Family history of autosomal dominant polycystic kidney disease 1
• Frequent urinary tract infections 1

Limitations of Ultrasound in CKD

• Normal-sized kidneys do not exclude CKD (especially in diabetic nephropathy) 2
• Ultrasound contributes to a definite diagnosis in <50% of CKD cases 3
• Findings are often nonspecific, especially in advanced CKD 3
• Technical limitations include obesity affecting visualization 4

Conclusion

For diagnosing CKD, laboratory tests (eGFR and urinary ACR) repeated over time are the primary diagnostic tools. Ultrasound provides supplementary structural information but is not necessary for confirming the diagnosis of CKD in most cases. It should be used selectively based on clinical presentation and suspected underlying causes.