A Review of the Imaging Techniques for Measuring Kidney and Cyst Volume in Establishing Autosomal Dominant Polycystic Kidney Disease Progression

Abstract

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the commonest inherited renal disorder; it is defined by progressive renal cyst formation and subsequent renal enlargement that leads to end-stage renal disease. Until recently, only symptomatic treatments for ADPKD existed. However, therapies that address the underlying pathophysiology of ADPKD are now available and accurate identification of the rate of disease progression is essential. Summary: Published data on the different imaging modalities for measuring kidney and cyst volumes in ADPKD are reviewed. The advantages and drawbacks of the different techniques for calculating kidney volume from renal imaging are also examined, including the use of manual planimetry, stereology, and the ellipsoid equation, as well as the prospect of semi- and fully automatic techniques. The translation of these approaches into clinical practice and their role in informing treatment decisions is discussed. Key Messages: These new therapies require the accurate monitoring of disease progression, which along with diagnosis and prognosis, relies on the effective use of renal imaging techniques. There is growing support for the use of total kidney volume as a measure of cyst burden and as a prognostic predictor of renal function in ADPKD, showing promise as a marker of disease progression.

Renal Volume in ADPKD Patient Evaluation

“…Recently, semiautomatic or fully automated techniques for renal volume evaluation have been developed: these show good correlation with manual planimetry techniques being recommended for clinical practice [15].…”

ADPKD—what the radiologist should know

“…Manual Planimetry on MRI using manual segmentation being more reproducible for the expert operator and the former for the beginner operator. 32 Of interest, these methods show more accuracy on CT in comparison to MRI due to slice thickness and utilisation of the Cavalieri method; however, this would not be feasible due to the chronic nature of ADPKD and serial imaging requirements over decades and the radiation hazards carried by CT. MRI is therefore the most accurate method practically applicable to imaging requests, with the time requirement being the biggest factor to impact on MRI reporting adding on average at least 30 additional minutes to produce accurate reproducibility. 33 We must evaluate the additional value this carries in enhancing the radiological report, considering volume estimation is useful in such patients particularly around decision making on Tolvaptan commencement.…”

Recent advances in the clinical management of autosomal dominant polycystic kidney disease

“…Measuring TKV for use as a prognostic biomarker does not require high precision. Measurement by the ellipsoid equation as well as by means of various imaging modalities is possible 27, 37 . Another imaging approach that can be used to predict PKD progression involves the measurement of renal length.…”