 In nephrotic syndrome SBP can frequently affect children but only very rarely can it affect adults.Infection of the peritoneum causes an inflammatory reaction with a subsequent increase in the number of neutrophils in the fluid.Diagnosis is made by paracentesis (needle aspiration of the ascitic fluid); SBP is diagnosed if the fluid contains neutrophils (a type of white blood cell) at greater than 250 cells per mm3 (equals a cell count of 250 x106/L) fluid in the absence of another reason for this (such as inflammation of one of the internal organs or a perforation).