ACE and acute kidney injury: In this review of serum creatinine trajectories in kidney disease, we have examined and reported on the multifarious behavior of serum creatinine in AKI; in CKD to ESRD progression, including SORO-ESRD; in otherwise non-progressing CKD; in LORFFAB; and in post-operative AKI associated with iatrogenic intra-operative hypotension on concurrent ACE inhibition.