Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
Spontaneous bacterial peritonitis (SBP) is a bacterial infection of belly fluid (ascites) that happens when gut bacteria slip into the fluid—no hole in the bowel or other source you can fix with surgery.
A Dam, a Sponge, and an Unguarded Gate
Imagine a factory (your liver) that makes two critical things: a giant sponge (albumin) that soaks up water to keep it in the warehouse (blood vessels), and security guards (complement and antibodies) that patrol and kill intruders. Behind the warehouse runs a river (portal vein) carrying goods from the farm (gut). When the factory gets damaged and scarred, it becomes a broken dam—the river backs up and floods everywhere, water leaks out of the warehouse into the ground (ascites forms). At the same time, the factory stops making sponges and guards. With no sponge to hold water in and no guards on duty, the flooded ground becomes a swamp where germs multiply. Meanwhile, the farm's fence (gut tight junctions) rots from all the backup pressure and swamp moisture, so the farm's bacteria walk right through the broken fence into the swamp. Before long, you have a disease-infested swamp nobody can control.
AASLD Practice Guidance on Ascites, Spontaneous Bacterial Peritonitis, and Hepatorenal Syndrome (2021) · European Association for the Study of the Liver (EASL) Clinical Practice Guidelines on Ascites (2018) · Infectious Diseases Society of America (IDSA) · Surviving Sepsis Campaign 2021 · reviewed 2026-07-07