Patient presents with acute abdomen concerning for peritonitis.  Symptoms include severe abdominal pain, tenderness, rigidity, rebound tenderness, and guarding.  Possible causes under consideration include appendicitis, diverticulitis, perforated peptic ulcer, bowel perforation, pelvic inflammatory disease, or other intra-abdominal infections.  Patient reports nausea, vomiting, and decreased bowel sounds.  Fever, tachycardia, and leukocytosis are present, suggesting an inflammatory process.  Differential diagnosis includes gastroenteritis, pancreatitis, and cholecystitis.  Diagnostic workup includes complete blood count with differential, comprehensive metabolic panel, urinalysis, abdominal imaging such as CT scan with intravenous contrast, and potentially diagnostic laparoscopy or paracentesis.  Severity of peritonitis may be classified based on clinical findings and laboratory values.  Management plan includes aggressive fluid resuscitation, broad-spectrum intravenous antibiotics targeting common intra-abdominal pathogens, pain management, and possible surgical intervention depending on the underlying cause.  Patient is currently NPO and being closely monitored for clinical deterioration or signs of sepsis.  Prognosis depends on the etiology of peritonitis, timeliness of intervention, and overall patient health status.  Medical coding considerations include ICD-10 codes for peritonitis (K65.x) with appropriate specifications for underlying cause and procedural codes for any surgical or diagnostic interventions performed.  Continued monitoring and reassessment are necessary to optimize patient outcomes and minimize morbidity and mortality associated with peritonitis.