Not All Nephrologists Measure Kidney Size in ‘Adult’ Polycystic Kidney Disease

LONG BEACH, Calif. — Not all nephrology providers measure kidney size in patients with autosomal dominant polycystic kidney disease (ADPKD), a survey indicated.

Among 201 respondents, 80% said they assess kidney size in all patients with ADPKD, the most common genetic cause of renal failure, reported Geoff Lockwood, PharmD, MBA, medical science director of nephrology and rare disease at Otsuka Pharmaceutical in Princeton, New Jersey.

As detailed in his group’s poster presented at the National Kidney Foundation (NKF) Spring Clinical meeting, 66% of respondents ranked kidney size assessment as the top factor in determining prognosis for patients with ADPKD using a scale of 1-5 (5 being the most important), while 26% ranked it as a 4.

Of the respondents who said they assess kidney size, 88% reported that they use total kidney volume as their primary assessment modality — considered the gold-standard imaging biomarker in determining prognosis for patients with ADPKD. Nine percent said they measure kidney length instead.

Meanwhile, 48% preferred MRI for measuring kidney size, while 26% preferred ultrasound, and 24% preferred CT.

“We want doctors to understand there is more than one way to obtain total kidney volume,” Lockwood told MedPage Today. “There are options for imaging modality and calculation method, and doctors can utilize the method that fits their practice best.”

That being said, he noted that he was a bit surprised to see the split between MRI, ultrasound, and CT, especially the proportion of providers who said that they use ultrasound.

“We often hear about MRI and CT scans being used, but do not hear about ultrasounds as frequently,” he added.

There are no consensus guidelines on which imaging modality to use for ascertaining kidney size. Regardless of which type of imaging is used, prior data have suggested that measuring total kidney volume, and not just length, is best for assessing the prognosis of patients with ADPKD, which is the most prevalent form of polycystic kidney disease, and sometimes referred to as “adult PKD.”

Imaging and measurement methods also appeared to vary by the clinician’s practice setting. More respondents in academic settings said they assess kidney size in all of their ADPKD patients compared with community settings (88% vs 77%).

Of clinicians who obtained total kidney volume, 39% of those in community settings said they were provided this measure by radiology compared with 78% of those working in academic settings.

“We did not realize missing information was as common as it was reported within the study,” Lockwood noted. “Specifically, the proportion of nephrologists reporting that imaging studies are often missing the necessary data to calculate height-adjusted total kidney volume, especially in the community setting.”

As for nephrology providers who don’t measure kidney size in all of their ADPKD patients, the top reasons why were lack of information from the radiologist (88%) and issues with insurance coverage (68%). Other reasons cited included that the measure was time consuming (22%), the information wasn’t beneficial (22%), and they don’t know how to (7%).

Lack of information from radiology tended to be more of an issue for nephrology providers working in community settings, rather than academic ones (92% vs 60%). On the other hand, more nephrology providers working in academic settings had insurance coverage issues compared with those in community settings (80% vs 67%).

“Communication between nephrology and radiology is critical,” Lockwood said. “When there is open communication between nephrology and radiology, obtaining the information necessary to identify total kidney volume can be a very simple process.”

“Collaborating to create an imaging protocol or order set could help ensure imaging orders are consistent and that accurate information is being conveyed,” he added.

For this study, responses from surveyed nephrology providers in the U.S. were collected by Medical Science Liaisons from October to December 2022.

Of the survey respondents, most were practicing nephrologists (92.5%) and practiced in community settings (79.1%). The remaining 7% were advanced practitioners.

A little over half said they are currently managing five or fewer patients with ADPKD, while 44.8% said they currently have over five ADPKD patients.

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