Supplementary Material for: Critically Ill Patients Requiring Acute Renal Replacement Therapy Are at an Increased Risk of Long-Term Renal Dysfunction, but Rarely Receive Specialist Nephrology Follow-Up

<b><i>Background:</i></b> Episodes of acute kidney injury (AKI) have been associated with the development of chronic kidney disease (CKD). However, follow-up pathways for patients who have survived AKI complicating critical illness are not well established. We hypothesised that patients who had AKI requiring renal replacement therapy (RRT) in intensive care are at risk of CKD, but are rarely referred for nephrology follow-up at hospital discharge. <b><i>Methods:</i></b> We performed a retrospective analysis of all patients who survived AKI requiring renal replacement therapy in intensive care units (ICUs) in the East London region, examining renal function at baseline, hospital discharge and 3-6 months follow-up. We excluded patients who were known to renal services prior to index admission. <b><i>Results:</i></b> From 5,544 critical care admissions, we identified 219 patients who survived to be discharged, having undergone RRT for AKI, that were not previously known to renal services. Of these, 124 (57%) had creatinine measured within 3-6 months after discharge, 104 having a pre-morbid baseline for comparison. Only 26 patients (12%) received specialist nephrology follow-up. At 3-6 months follow-up, the estimated glomerular filtration rate was significantly lower than baseline (48 vs. 60 ml/min/1.73 m<sup>2</sup>; p < 0.001), with the prevalence of CKD stage III-V rising from 49 to 70% (p < 0.001). <b><i>Conclusions:</i></b> Follow-up of patients who required RRT for AKI in ICU is inconsistent despite evidence of a significant increase in the prevalence of CKD. There is strong justification for the development of robust pathways to identify survivors of AKI in order to detect and manage CKD and its complications.