Elastography Has No Established Role in PKD Management
Elastography is not recommended for routine diagnosis or management of polycystic kidney disease (PKD), as current guidelines do not include it in standard monitoring protocols. The established imaging modalities for PKD are ultrasonography and MRI for measuring total kidney volume (TKV), cyst number, and disease progression 1.
Why Elastography Is Not Used in PKD
PKD Pathophysiology Differs from Fibrosis-Based Disease
- PKD involves cyst formation and expansion, not primarily fibrosis, which is what elastography measures 2, 3, 4
- Elastography measures tissue stiffness as a surrogate for fibrosis in organs like the liver, but this mechanism does not apply to the cystic changes in PKD 1, 2
- The kidney enlargement in PKD is due to fluid-filled cysts, not the solid tissue changes that elastography is designed to detect 1
Current Guideline-Recommended Imaging for PKD
For clinical monitoring in children and adults with ADPKD, ultrasonography is the primary imaging modality, with MRI reserved for clinical trials or specific situations 1:
- Ultrasonography measures kidney size, cyst number, and can calculate TKV using the ellipsoid formula in children (when kidneys are <17 cm) 1
- MRI with planimetry is the gold standard for TKV measurement in clinical trials and for cooperative children/adolescents with larger kidneys 1
- 3D ultrasonography is emerging as a promising tool for TKV measurements but requires further validation 1
What Should Be Monitored in PKD
The 2019 international consensus recommends monitoring hypertension, proteinuria, kidney volume, cyst volume/number, and eGFR 1:
- Blood pressure measurement directly (not replaced by imaging) 1
- Albumin/creatinine ratio measured in laboratory (not dipstick) 1
- TKV by MRI in clinical trials for cooperative children 1
- Ultrasonography for symptomatic evaluation (UTIs, cyst hemorrhage, hematuria, stones, infections) 1
Limited Exception: ARPKD and Liver Fibrosis
The only context where elastography has demonstrated utility in cystic kidney disease is for detecting liver fibrosis in autosomal recessive PKD (ARPKD), not for evaluating the kidneys themselves 2:
- Transient elastography (FibroScan) detected liver fibrosis in 100% of ARPKD patients versus only 57% detection by conventional ultrasound 2
- ARPKD patients had significantly increased liver stiffness (12.0 kPa) compared to controls (4.5 kPa) and ADPKD patients (5.3 kPa) 2
- This application is for hepatic complications of ARPKD, not for renal parenchymal assessment 2
Why Research on Renal Elastography Doesn't Apply to PKD
While elastography shows promise for detecting renal fibrosis in chronic kidney disease (CKD) 3, 4, 5, 6, this research addresses a different pathophysiology:
- Studies show elastography can distinguish CKD patients from healthy controls based on fibrosis-related stiffness 5, 6
- However, PKD kidneys enlarge due to cysts, not fibrosis, making these findings non-applicable 1
- Kidney stiffness measurements are affected by vascularization, hydronephrosis, and external pressure—all confounders in PKD 3, 4
Clinical Bottom Line
Use ultrasonography for routine PKD monitoring and MRI for precise TKV measurements in clinical trials or when assessing rapid progressors 1. Focus clinical management on blood pressure control, proteinuria monitoring, and identifying patients at risk for rapid progression who may benefit from tolvaptan 7. Elastography should be reserved exclusively for assessing liver fibrosis in ARPKD patients, not for renal parenchymal evaluation in any form of PKD 2.