In people with ascites, a diagnosis of peritonitis is made via paracentesis (abdominal tap): More than 250 polymorphonuclear cells per μL is considered diagnostic. In addition, Gram stain is almost always negative, whereas culture of the peritoneal fluid can determine the microorganism responsible and determine their sensitivity to antimicrobial agents. Pathology
In normal conditions, the peritoneum appears greyish and glistening; it becomes dull 2–4 hours after the onset of peritonitis, initially with scarce serous or slightly turbid fluid. Later on, the exudate becomes creamy and evidently suppurative; in people who are dehydrated, it also becomes very inspissated. The quantity of accumulated exudate varies widely. It may be spread to the whole peritoneum, or be walled off by the omentum and viscera. Inflammation features infiltration by neutrophils with fibrino-purulent exudation. Treatment
Depending on the severity of the persons state, the management of peritonitis may include:

Antibiotics are usually administered intravenously, but they may also be infused directly into the peritoneum. The empiric choice of broad-spectrum antibiotics often consist of multiple drugs, and should be targeted against the most likely agents, depending on the cause of peritonitis (see above); once one or more agents grow in cultures isolated, therapy will be target against them. Gram positive and gram negative organisms must be covered. Out of the cephalosporins, cefoxitin and cefotetan can be used to cover gram positive bacteria, gram negative bacteria, and anaerobic bacteria. Beta-lactams with beta lactamase inhibitors can also be used, examples include ampicillin/sulbactam, piperacillin/tazobactam, and ticarcillin/clavulanate.
Carbapenems are also an option when treating primary peritonitis as all of the carbapenems cover gram positives, gram negatives, and anaerobes except for ertapenem. The only fluoroquinolone that can be used is moxifloxacin because this is the only fluoroquinolone that covers anaerobes. Finally, tigecycline is a tetracycline that can be used due to its coverage of gram positives and gram negatives. Empiric therapy will often require multiple drugs from different classes. Surgery (laparotomy) is needed to perform a full exploration and lavage of the peritoneum, as well as to correct any gross anatomical damage that may have caused peritonitis. The exception is spontaneous bacterial peritonitis, which does not always benefit from surgery and may be treated with antibiotics in the first instance. Prognosis
If properly treated, typical cases of surgically correctable peritonitis (e.g., perforated peptic ulcer, appendicitis, and diverticulitis) have a mortality rate of about <10% in otherwise healthy people. The mortality rate rises to 35% in peritonitis patients who develop sepsis, and patients who have underlying renal insufficiency and complications have a higher mortality rate. Etymology
The term "peritonitis" comes from Greek περιτόναιον peritonaion "peritoneum, abdominal membrane" and -itis "inflammation". References


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