# Where edema comes from and how fluid leaves

Edema reflects excess filtration or inadequate lymphatic return: increased hydrostatic pressure, reduced plasma oncotic pressure, increased permeability, lymphatic obstruction, and renal sodium retention can overlap. Fluid must return to the circulation before the kidneys can excrete it. Assess the circulation, kidney response and urinary outflow; more diuretic is not a universal answer.

[Levick and Michel, revised Starling principle — PubMed](https://pubmed.ncbi.nlm.nih.gov/20200043/) · [Ellison, 2019 — PubMed](https://pubmed.ncbi.nlm.nih.gov/30936153/)

Andrew Bland, MD, FACP, FAAP