ROSH Gastrointestinal Practice Exam

In patients with suspected spontaneous bacterial peritonitis, what white blood cell count in ascitic fluid warrants antibiotic treatment?

1. Ascitic fluid pH of 7.35

2. WBC of 275 cells/mm3 with 20% lymphocytes

3. WBC of 370 cells/mm3 with 90% neutrophils

4. WBC of 500 cells/mm3 with 40% neutrophils

The correct answer is: WBC of 500 cells/mm3 with 40% neutrophils

In the context of spontaneous bacterial peritonitis (SBP), the key factor that determines the need for antibiotic treatment is the presence of neutrophils in the ascitic fluid. A white blood cell count greater than 250 cells/mm³ is traditionally used as a threshold to initiate antibiotic therapy. In this case, the option indicating a white blood cell count of 500 cells/mm³ with 40% neutrophils is particularly noteworthy. This option shows that although 40% of the white blood cells are neutrophils, the sheer count of total white blood cells being 500 means there are potentially enough neutrophils present (which would be 200 neutrophils) to indicate a significant bacterial infection. A higher neutrophil count is classically associated with SBP, leading to the consensus that treatment should commence to prevent further complications. Other choices present lower white blood cell counts or an inadequate percentage of neutrophils, which does not meet the threshold for treating suspected SBP. Hence, the selection that identifies a total count of 500 cells/mm³ with a significant number of neutrophils accurately reflects the clinical guidelines that mandate starting antibiotics in this critical scenario.