Kidney volumetry for predicting long-term outcome in acute kidney injury: A retrospective cohort study

Continuous renal replacement therapy (CRRT) is effective for severe acute kidney injury (AKI); however, predicting successful CRRT discontinuation and long-term outcomes remains challenging. Although urinary neutrophil gelatinase-associated lipocalin (NGAL) levels and kidney volume measured by computed tomography (CT) have been associated with renal prognosis, it remains unclear whether their combination improves predictive accuracy. This study evaluated whether combining urinary NGAL levels with kidney volume measured by CT improves prediction accuracy.

In this retrospective cohort study, urinary NGAL levels and height-adjusted total kidney volume (HtTKV) were assessed for their ability to predict successful CRRT discontinuation and major adverse kidney events at 90 days (MAKE90).

Among the 74 patients included, CRRT discontinuation was successful in 55 (74.3%), and MAKE90 occurred in 31 (41.9%). Urinary NGAL (area under the curve [AUC], 0.86; 95% confidence interval [CI], 0.76-0.95) was a significant predictor of CRRT discontinuation, whereas HtTKV was not. For long-term outcomes, urinary NGAL (AUC, 0.73 [95% CI, 0.61-0.85]) and HtTKV (AUC, 0.67 [95% CI, 0.54-0.80]) were significantly associated with MAKE90. Adding HtTKV to urinary NGAL significantly improved prediction of MAKE90, as demonstrated by reclassification analyses (net reclassification improvement and integrated discrimination improvement).

Adding HtTKV significantly improved the prediction of long-term MAKE90 based on NGAL levels, but not that of short-term CRRT discontinuation. These findings in this proof-of-concept study suggest that structural kidney assessment by CT volumetry may complement urinary NGAL for long-term risk stratification in patients with severe AKI requiring CRRT.