From a Washington Post story by Matthew Brown headlined “Feinstein’s health leave is part of a long history of absent senators”:

The prolonged absence of Sen. Dianne Feinstein (D-Calif.) for health reasons poses a major challenge to Democrats as it has stalled President Biden’s judicial nominees and Republicans are unwilling to help, blocking a temporary replacement for Feinstein on the Senate Judiciary Committee.

But while Feinstein’s health problems at 89 have forced her to miss weeks and votes in Washington since February, her case is not a new one in a Congress in which senators have been absent for extended periods of time.