The diagnostic threshold
New abdominal tenderness in a client with cirrhosis and ascites raises concern for spontaneous bacterial peritonitis (SBP), an infection of ascitic fluid without an obvious surgical source. An ascitic neutrophil (polymorphonuclear) count of 250 cells/mm³ or more is diagnostic of SBP. Once this threshold is reached, treatment with an IV third-generation cephalosporin plus albumin starts without waiting for the culture result.
Why the threshold matters
Ascitic fluid cultures are often negative or slow to grow even when infection is present, so diagnosis relies on the neutrophil count. A threshold of 250 cells/mm³ balances sensitivity and specificity: it identifies most true infections early enough to start treatment, while not labeling too many uninfected clients as having SBP. Because untreated SBP can progress rapidly to sepsis and kidney failure, early empirical treatment is important. Fluid is also sent for culture, ideally inoculated into blood-culture bottles at the bedside, which improves the chance of growing the organism.
| Option | Problem |
|---|
| 250 cells/mm³ | Correct diagnostic threshold |
| 500 cells/mm³ | Too high; would delay treatment of many infections |
| 100 cells/mm³ | Too low; would label many uninfected clients as infected |
| 1,000 cells/mm³ | Far too high; many infected clients never reach it |
Treatment and nursing care
Treatment combines an IV third-generation cephalosporin with albumin, which reduces the risk of kidney injury in SBP. The nurse gives antibiotics promptly, monitors temperature, mental status, urine output, and kidney function, and watches for signs of sepsis or worsening hepatic encephalopathy. SBP can also present subtly, with only confusion, fever, or worsening kidney function, so the nurse reports any unexplained change in a client with ascites.
Recognizing SBP early
Classic signs include fever, abdominal pain or tenderness, and altered mental status, but some clients have few symptoms. Any client with cirrhosis and ascites who deteriorates without a clear reason should have a diagnostic paracentesis. That is why the procedure was repeated on day 6 in this case.
Exam takeaway
Key point Remember the number 250: an ascitic neutrophil count of 250 cells/mm³ or more diagnoses SBP and triggers immediate antibiotics plus albumin.