Updated July 2026 · 7 min read
Part of the ICU Emergencies Hub — browse every related guide in one place.
A cirrhotic patient with a belly full of fluid can be brewing a life-threatening infection with almost no fanfare — no rigid abdomen, sometimes no fever, just a subtle decline. That's spontaneous bacterial peritonitis (SBP), and it's one of the classic reasons a patient with ascites tips into the ICU with sepsis, encephalopathy, or kidney failure. The other half of this story is the procedure that both diagnoses and treats the fluid: paracentesis. This guide covers recognizing SBP, the diagnostic tap, the antibiotic-plus-albumin regimen, and the albumin rule that protects the kidneys after a large-volume drain.
In advanced liver disease, ascitic fluid pools in the abdomen and the gut wall becomes leaky, letting bacteria translocate into that fluid without any perforation or abscess to point at — hence "spontaneous." Because the source isn't a surgical catastrophe, the presentation is often quiet: instead of the board-rigid, agonizing abdomen of surgical peritonitis, SBP may show up only as a patient whose encephalopathy is worsening, whose creatinine is creeping up, or who just "isn't right." Fever and abdominal tenderness may be present or absent. That subtlety is exactly why the rule in hepatology is to have a very low threshold to perform a diagnostic tap on any decompensating patient with ascites.
Paracentesis is both the diagnostic and, for large volumes, the therapeutic tool. A diagnostic tap removes a small sample of ascitic fluid, and the single most important result is the cell count — a high polymorphonuclear (neutrophil) count in the fluid diagnoses SBP even before cultures return, which is why treatment starts on the cell count, not on waiting days for a culture. Fluid is also sent for culture (ideally bottles inoculated at the bedside), protein, and albumin to help characterize it.
| Fluid result | What it tells the team | Nursing action |
|---|---|---|
| High neutrophil (PMN) count | Diagnostic of SBP — treat now | Antibiotics + albumin without waiting for culture |
| Positive culture | Names the organism, guides narrowing | Inoculate culture bottles at bedside for yield |
| Serum-ascites albumin gradient | Confirms portal-hypertension ascites | Sample sent with a paired serum albumin |
| Grossly cloudy fluid | Raises suspicion before counts return | Flag it — heightens urgency of the tap |
The nurse's role around the tap is real: positioning, maintaining a sterile field, labeling and routing specimens quickly (the cell count is the priority), and monitoring the patient during and after for hypotension and bleeding.
SBP is treated empirically with a third-generation cephalosporin (ceftriaxone or cefotaxime) started as soon as the cell count confirms it — this is a sepsis source, and the same urgency about early antibiotics in sepsis applies. What surprises people new to hepatology is that IV albumin is given alongside the antibiotic, not as a nice-to-have but because it meaningfully reduces the risk that these patients develop hepatorenal syndrome and die. SBP is a classic precipitant of that kidney failure, and albumin supports the effective circulating volume that keeps the kidneys perfused.
Beyond diagnosis, paracentesis is used to drain tense, uncomfortable ascites — and when a large volume is removed (roughly more than 5 liters), the circulation can crash afterward. Pulling out several liters suddenly drops the pressure the fluid was exerting; the splanchnic vessels dilate further, effective volume falls, and the kidneys can be injured in a syndrome called post-paracentesis circulatory dysfunction. The prevention is simple and important: IV albumin is infused to replace large-volume removals (a set amount of albumin per liter drained). This is the recurring theme of the whole topic — albumin protects the circulation and the kidney.
Spontaneous bacterial peritonitis is infected ascites without a surgical source, and it hides — often showing up as worsening encephalopathy, rising creatinine, or vague decline rather than a rigid, painful belly — so the threshold to tap is low. The diagnosis rides on the ascitic fluid neutrophil count, and treatment starts immediately with a third-generation cephalosporin plus IV albumin, because albumin cuts the risk of the hepatorenal syndrome that kills these patients. When paracentesis is used to drain large volumes, albumin replacement prevents post-tap circulatory collapse. Across the whole topic, the nurse's leverage is thinking of SBP early, moving specimens fast, and making sure the albumin that protects the kidneys is actually delivered.
Related: Hepatorenal syndrome · Hepatic encephalopathy · Acute pancreatitis · ICU sepsis protocol
Educational content for licensed clinicians. Always follow your facility's protocol and provider orders. Not medical advice.
Get the ICU Notebook
Free investing strategies built for nurses. One email per week, no fluff.
Yes, send it freeNo spam. Unsubscribe any time.