The von Hippel-Lindau disease (VHL) is a hereditary cancer syndrome with multifocal, bilateral cysts and solid tumors of the kidney. Surgical management may include multiple extirpative surgeries, which ultimately results in parenchymal volume loss and subsequent renal function decline. Recent studies have utilized parenchyma volume as an estimate of renal function prior to surgery for renal cell carcinoma; however, it is not yet validated for surgically altered kidneys with multifocal masses and complex cysts such as are present in VHL.
We sought to validate a magnetic resonance imaging (MRI)-based volumetric analysis with mercaptoacetyltriglycine (MAG-3) renogram and postoperative renal function.
We identified patients undergoing renal surgery at the National Cancer Institute from 2015 to 2020 with preoperative MRI. Renal tumors, cysts, and parenchyma of the operated kidney were segmented manually using ITK-SNAP software.
Serum creatinine and urinalysis were assessed preoperatively, and at 3- and 12-mo follow-up time points. Estimated glomerular filtration rate (eGFR) was calculated using serum creatinine-based CKD-EPI 2021 equation. A statistical analysis was conducted on R Studio version 4.1.1.
Preoperative MRI scans of 113 VHL patients (56% male, median age 48 yr) were evaluated between 2015 and 2021. Twelve (10.6%) patients had a solitary kidney at the time of surgery; 59 (52%) patients had at least one previous partial nephrectomy on the renal unit. Patients had a median of three (interquartile range [IQR]: 2–5) tumors and five (IQR: 0–13) cysts per kidney on imaging. The median preoperative GFR was 70 ml/min/1.73 m2 (IQR: 58–89). Preoperative split renal function derived from MAG-3 studies and MRI split renal volume were significantly correlated (r = 0.848, p < 0.001). On the multivariable analysis, total preoperative parenchymal volume, solitary kidney, and preoperative eGFR were significant independent predictors of 12-mo eGFR. When only considering patients with two kidneys undergoing partial nephrectomy, preoperative parenchymal volume and eGFR remained significant predictors of 12-mo eGFR.
A parenchyma volume analysis on preoperative MRI correlates well with renogram split function and can predict long-term renal function with added benefit of anatomic detail and ease of application.
The manuscript discusses a study that examines the utility of preoperative MRI-based volumetric analysis for estimating renal function in patients with von Hippel-Lindau disease (VHL), characterised by multiple kidney cysts and tumours. Surgical interventions in VHL often results in a loss of kidney tissue volume and subsequent decline in renal function.
The study involved 113 VHL patients who underwent renal surgery at the National Cancer Institute between 2015 and 2021. 52% had undergone at least one prior partial nephrectomy on the renal unit. Patients were evaluated with MAG3 studies. The study found a significant correlation between preoperative split renal function determined from MAG-3 studies and MRI split renal volume on VHL patients. Parenchymal volume demonstrated an association with renal function at 12 mo. Assessing parenchyma volume on preoperative MRI can effectively estimate renal function, showing a strong correlation with renogram split function. Volumetric assessment prior to partial nephrectomy by CT scan has previously been described by several authors in sporadic RCC patients.
Measurement with MAG3 would allow for prediction of renal function postoperatively. Renal function prediction after partial nephrectomy is extremely challenging as there are several factors that interact. Warm ischemia had initially been pointed as a main factor to determine postoperative GFR. However, it was disregarded by evidence supporting the importance of other factors, such as parenchymal volume left and comorbidities assessment.
In the VHL population, there is a special need for postoperative renal function prediction since those patients undergo several surgical procedures over a lifetime and have an increased risk of CKD. MRI avoids CT radiation exposure and iodine-contrast toxicity and facilitates complex cyst assessment. Caveats of MRI use imply the current lack of availability within several health systems and the nuances associated with describing the findings. Further validation of the results presented on this retrospective analysis are required.