Final answer:
The correct SAAG value necessary to diagnose spontaneous bacterial peritonitis (SBP) is >1.1 g/dL. A SAAG higher than 1.1 g/dL indicates ascites due to portal hypertension, which is related to but not exclusive for the diagnosis of SBP.
Step-by-step explanation:
To diagnose spontaneous bacterial peritonitis (SBP), a key parameter measured is the serum-ascites albumin gradient (SAAG). The correct answer is:
b) >1.1 g/dL
The SAAG is calculated by subtracting the albumin concentration of the ascitic fluid from the albumin concentration of a serum sample taken at the same time. A SAAG of greater than 1.1 g/dL indicates that the ascites is likely due to portal hypertension, which can be associated with conditions such as cirrhosis, heart failure, or Budd-Chiari syndrome. In the context of SBP, if the patient with ascites due to portal hypertension develops an infection within the ascitic fluid without an evident intra-abdominal secondary source, SBP is considered.
Therefore, while the SAAG helps to ascertain the etiology of ascites, the diagnosis of SBP also involves additional criteria, which typically includes a positive ascitic fluid bacterial culture and an elevated ascitic fluid neutrophil count of typically greater than 250 cells/mm3.