Obstructive acute kidney injury: predictors of mortality and need for renal replacement therapy

Obstructive acute kidney injury (AKI) is a significant clinical entity with varying outcomes. This study aims to describe the clinical, diagnostic, and therapeutic characteristics of obstructive AKI in a large cohort of adult patients and to identify predictors of in-hospital mortality and the need for renal replacement therapy (RRT).

We conducted a retrospective, observational single-center study at the Fondazione Policlinico Universitario A. Gemelli IRCCS (Rome, Italy). Adult patients presenting to the Emergency Department between 2018 and 2022 with KDIGO-defined AKI and a documented diagnosis of urinary tract obstruction established during the index Emergency Department evaluation were included. Multivariable logistic regression analysis was performed to identify independent predictors of in-hospital mortality and RRT requirement.

The study included 1,351 patients (median age 71 years). In-hospital mortality was 12% (n=167), and RRT was required in 6% (n=80). Independent predictors of mortality included older age, higher triage priority (OR 4.96, 95% CI 2.99-8.20), higher serum creatinine, and lower hemoglobin. A significant interaction was found between pre-existing chronic kidney disease (CKD) and RRT (OR 11.11, 95% CI 1.23-100.02), identifying a subgroup with the highest mortality risk. Predictors for RRT included admission serum creatinine (OR 1.37, 95% CI 1.16-1.62) and pre-existing CKD (OR 5.26, 95% CI 1.22-22.73).

Obstructive AKI is associated with substantial mortality, particularly in elderly patients and those with pre-existing CKD  who required RRT during hospitalization. The interaction between CKD and RRT highlights a vulnerable population where serum creatinine alone may underestimate clinical risk. Early risk stratification using functional and laboratory markers is essential to guide management.