Renal Surface Nodularity Tracks Kidney Damage, Overlaps With eGFR

Key Takeaways

• Among hypertensive adults undergoing routine health screening, 47.1% had ultrasound-detected renal surface nodularity (RSN).
• Kidney damage occurred in 5.2% of adults with grade 0 RSN, 8% with grade 1, and 27.2% with grade 2.
• Severe, but not mild, RSN remained significantly associated with composite kidney damage after adjustment, although the severe-grade association weakened after continuous eGFR adjustment.
• Readers showed substantial agreement when grading the same stored ultrasound images and stronger agreement on repeat assessment by the same reader; repeat image acquisition was not tested.

When adults with hypertension undergo renal ultrasound alongside kidney-function and urine-protein testing, an irregular kidney contour raises a clinical question: does it reflect damage captured by conventional laboratory thresholds or a different feature of the kidney? Interpreting that contour also depends on whether readers grade the images consistently. Investigators assessed both questions in a hypertensive health-screening cohort.

Investigators retrospectively assessed 871 hypertensive adults aged 18–80 years undergoing routine screening at the Taihu Lake Cadre Sanatorium of Jiangsu Province, China, between October 2025 and March 2026. Laboratory testing occurred within seven days of ultrasound. Blinded to laboratory findings, a reader graded renal surface nodularity (RSN) on one standardized stored coronal image per kidney: grade 0 was smooth, grade 1 mildly undulating, and grade 2 serrated, deeply indented, or accompanied by cortical thinning. The higher bilateral grade determined each participant’s classification. A second reader graded the same random 80-patient image subset; the original reader graded it again at least four weeks later. Kidney damage meant estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or dipstick proteinuria ≥1+. Sequential models progressively accounted for demographics, hypertension grade, diabetes, hypertension duration, cortical echo intensity, and finally continuous eGFR; investigators separately analyzed an endpoint without the eGFR component.

Smooth contours predominated, followed by mild and then severe nodularity. Mild RSN was not significantly associated with the composite kidney-damage endpoint in any model, whereas severe RSN remained significantly associated after adjustment. For grade 2 versus grade 0, the model 3 odds ratio (OR) was 7.66 before continuous eGFR adjustment; the final model 4 OR was 2.88 (95% confidence interval [CI] 1.26–6.61). Higher hypertension grade, longer hypertension duration, greater cortical echo intensity, and lower eGFR were independently associated with RSN. Agreement on the stored images was substantial between readers and stronger when the original reader graded them again.

For the endpoint excluding reduced eGFR, the grade 2 association seen before continuous eGFR adjustment was no longer significant afterward: OR 1.55 (95% CI 0.67–3.57; P = .30). Adding RSN to a model already containing eGFR did not significantly improve discrimination. Grade 2 nodularity was also observed in participants without threshold-defined kidney damage, which does not establish early structural disease.

This selected, single-center Chinese screening cohort was assessed cross-sectionally, so the findings cannot establish temporal order, causation, future prediction, or screening benefit. The composite endpoint included an eGFR threshold, while the final model also adjusted for continuous eGFR; attenuation, the proteinuria-only analysis, and limited added discrimination constrain claims of information independent of eGFR. Agreement concerned interpretation of selected stored frames, not repeat ultrasound acquisition or contours outside the selected plane. Dipstick protein testing, eGFR calculated using a modified Modification of Diet in Renal Disease (MDRD) equation, lack of direct computed tomography or histologic comparison, and possible residual confounding further qualify interpretation.

The authors concluded that ultrasound-visible renal contour grading tracked kidney damage in this hypertensive screening cohort, with substantial overlap with eGFR. They identified prospective evaluation and cross-modality comparison as ways to clarify the contour finding’s temporal and diagnostic meaning.

Clinician Questions

Which patients were excluded from the hypertensive ultrasound screening cohort for renal surface nodularity?

The renal surface nodularity analysis involved hypertensive adults undergoing routine health screening in Jiangsu, China. It excluded people with urinary infection, obstruction, or renal tuberculosis; congenital or hereditary renal disease; renal cysts or masses above the specified size threshold; prior renal surgery or infarction; marked bilateral kidney-size asymmetry; malignancy; myocardial infarction; or atrial fibrillation. Without a normotensive comparison group, the analysis cannot establish whether nodularity is specific to hypertension.

Can grade 2 renal surface nodularity on ultrasound reflect cortical thinning rather than a deep surface indentation?

Yes. In this cohort, grade 2 renal surface nodularity could reflect a serrated or nodular contour with indentation greater than one-third of cortical thickness or accompanying cortical thinning. Investigators did not separately record which feature qualified each kidney, so the proportion classified by indentation rather than cortical thinning cannot be specified.

This content is intended for healthcare professionals for educational purposes. The article and its image were developed with AI assistance and reviewed by members of the ReachMD team prior to publication. Please refer to the original source linked for the complete and most up-to-date information.