Diagnostic Considerations

Thoracic processes with diaphragmatic irritation (eg, empyema), extraperitoneal processes (eg, pyelonephritis, cystitis, acute urinary retention), and abdominal wall processes (eg, infection, rectus hematoma) may mimic certain signs and symptoms of peritonitis. Always examine the patient for the presence of external hernias to rule out intestinal incarceration.

According to Adler and Gasbarra, the following should be considered in the differential diagnosis^[10]:

Chemical irritants (eg, bile, blood, gastric juice, barium, enema or douche contents)
Chronic peritoneal dialysis
Chylous peritonitis
Eosinophilic peritonitis
Familial Mediterranean fever
Fungal infections (eg, histoplasmosis, cryptococcosis, coccidioidomycosis)
Granulomatous peritonitis (eg, parasitic infestations, sarcoidosis, tumors, Crohn disease, starch granules)
Gynecologic disorders (Chlamydia peritonitis, salpingitis, endometriosis, teratoma, leiomyomatosis, dermoid cyst)
Human immunodeficiency virus (HIV)-associated peritonitis (from opportunistic organisms)
Mesothelial hyperplasia and metaplasia
Neoplasms (eg, primary mesothelioma, secondary carcinomatosis, Pseudomyxoma peritonei)
Parasitic infections (eg, schistosomiasis, ascariasis, enterobiasis, amebiasis, strongyloidiasis)
Perforated viscus
Peritoneal encapsulation
Peritoneal loose bodies and peritoneal cysts
Peritoneal lymphangiectasis
Pyelonephritis
Sclerosing peritonitis
Splenosis
Vascular conditions (eg, mesenteric embolus, mesenteric nonocclusive ischemia, ischemic colitis, portal vein thrombosis, mesenteric vein thrombosis)
Vasculitis (eg, systemic lupus erythematosus, allergic vasculitis [Henoch-Schönlein purpura], Kohlmeier-Degos disease, polyarteritis nodosa)

Differential Diagnoses

Workup

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Media Gallery

Peritonitis and abdominal sepsis. Diagnostic and therapeutic approach to peritonitis and peritoneal abscess.
Peritonitis and abdominal sepsis. A 48-year-old man underwent suprapubic laparotomy, right hemicolectomy, and gastroduodenal resection for right colon cancer invading the first portion of the duodenum. After surgery, the patient developed abdominal pain and distention. Computed tomography (CT) scanning was used to confirm an anastomotic dehiscence. Figure A shows a contrast-enhanced scan of the abdomen and pelvis that reveals multiple fluid collections, perihepatic ascites, and mild periportal edema. A collection of fluid containing an air-fluid level is visible anterior to the left lobe of the liver. A second collection is anterior to the splenic flexure of the colon. In figure B, a third fluid collection is present in the inferior aspect of the lesser space and in the transverse mesocolon. Figure C shows the pelvis with a collection of free fluid in the rectovesical pouch.
Peritonitis and abdominal sepsis. A 78-year-old man was admitted with a history of prior surgery for small bowel obstruction and worsening abdominal pain, distended abdomen, nausea, and obstipation. In figure A, a marked amount of portal venous gas within the liver, mesenteric venous gas, and pneumatosis intestinalis are consistent with ischemic small intestine. The superior mesenteric artery appears patent. The liver has a nodular contour consistent with cirrhosis. In figures B and C, markedly distended loops of small intestine containing fluid and air-fluid levels are consistent with a small bowel obstruction. No focal fluid collections are identified.
Peritonitis and abdominal sepsis. A 35-year-old man with a history of Crohn disease presented with pain and swelling in the right abdomen. In figure A, a thickened loop of terminal ileum is evident adherent to the right anterior abdominal wall. In figure B, the right anterior abdominal wall is markedly thickened and edematous, with adjacent inflamed terminal ileum. In figure C, a right lower quadrant abdominal wall abscess and enteric fistula are observed and confirmed by the presence of enteral contrast in the abdominal wall.
Peritonitis and abdominal sepsis. Gram-negative Escherichia coli.

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Table 1. Common Causes of Secondary Peritonitis

Source Regions	Causes
Esophagus	Boerhaave syndrome Malignancy Trauma (mostly penetrating) Iatrogenic*
Stomach	Peptic ulcer perforation Malignancy (eg, adenocarcinoma, lymphoma, gastrointestinal stromal tumor) Trauma (mostly penetrating) Iatrogenic*
Duodenum	Peptic ulcer perforation Trauma (blunt and penetrating) Iatrogenic*
Biliary tract	Cholecystitis Stone perforation from gallbladder (ie, gallstone ileus) or common duct Malignancy Choledochal cyst (rare) Trauma (mostly penetrating) Iatrogenic*
Pancreas	Pancreatitis (eg, alcohol, drugs, gallstones) Trauma (blunt and penetrating) Iatrogenic*
Small bowel	Ischemic bowel Incarcerated hernia (internal and external) Closed loop obstruction Crohn disease Malignancy (rare) Meckel diverticulum Trauma (mostly penetrating)
Large bowel and appendix	Ischemic bowel Diverticulitis Malignancy Ulcerative colitis and Crohn disease Appendicitis Colonic volvulus Trauma (mostly penetrating) Iatrogenic
Uterus, salpinx, and ovaries	Pelvic inflammatory disease (eg, salpingo-oophoritis, tubo-ovarian abscess, ovarian cyst) Malignancy (rare) Trauma (uncommon)
*Iatrogenic trauma to the upper GI tract, including the pancreas and biliary tract and colon, often results from endoscopic procedures; anastomotic dehiscence and inadvertent bowel injury (eg, mechanical, thermal) are common causes of leak in the postoperative period.

Table 2. Microbial Flora of Secondary Peritonitis

Type	Organism	Percentage
Aerobic
Gram negative	Escherichia coli	60%
	Enterobacter/Klebsiella	26%
	Proteus	22%
	Pseudomonas	8%
Gram positive	Streptococci	28%
	Enterococci	17%
	Staphylococci	7%
Anaerobic	Bacteroides	72%
	Eubacteria	24%
	Clostridia	17%
	Peptostreptococci	14%
	Peptococci	11%
Fungi	Candida	2%

Table 3. Microbiology of Primary, Secondary, and Tertiary Peritonitis

Peritonitis (Type)	Etiologic Organisms		Antibiotic Therapy (Suggested)
Peritonitis (Type)	Class	Type of Organism	Antibiotic Therapy (Suggested)
Primary	Gram-negative	E coli (40%) K pneumoniae (7%) Pseudomonas species (5%) Proteus species (5%) Streptococcus species (15%) Staphylococcus species (3%) Anaerobic species (< 5%)	Third-generation cephalosporin
Secondary	Gram-negative	E coli Enterobacter species Klebsiella species Proteus species	Second-generation cephalosporin Third-generation cephalosporin Penicillins with anaerobic activity Quinolones with anaerobic activity Quinolone and metronidazole Aminoglycoside and metronidazole
	Gram-positive	Streptococcus species Enterococcus species
	Anaerobic	Bacteroides fragilis Other Bacteroides species Eubacterium species Clostridium species Anaerobic Streptococcus species
Tertiary	Gram-negative	Enterobacter species Pseudomonas species Enterococcus species	Second-generation cephalosporin Third-generation cephalosporin Penicillins with anaerobic activity Quinolones with anaerobic activity Quinolone and metronidazole Aminoglycoside and metronidazole Carbapenems Triazoles or amphotericin (considered in fungal etiology) (Alter therapy based on culture results.)
	Gram-positive	Staphylococcus species
	Fungal	Candida species

Table 4. Ascitic Fluid Analysis Summary ^[5]

Routine	Optional	Unusual	Less Helpful
Cell count	Obtain culture in blood culture (BC) bottles.	Tuberculosis (TB) smear and culture	pH
Albumin	Glucose	Cytology	Lactate
Total protein	Lactate dehydrogenase (LDH)	Triglyceride	Cholesterol
	Amylase	Bilirubin	Fibronectin
	Gram stain		Alpha 1-antitrypsin
			Glycosaminoglycans

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Author

Brian J Daley, MD, MBA, FACS, FCCP, CNSC Professor and Program Director, Department of Surgery, Chief, Division of Trauma and Critical Care, University of Tennessee Health Science Center College of Medicine

Brian J Daley, MD, MBA, FACS, FCCP, CNSC is a member of the following medical societies: American Association for the Surgery of Trauma, Eastern Association for the Surgery of Trauma, Southern Surgical Association, American College of Chest Physicians, American College of Surgeons, American Medical Association, Association for Academic Surgery, Association for Surgical Education, Shock Society, Society of Critical Care Medicine, Southeastern Surgical Congress, Tennessee Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

BS Anand, MD Professor, Department of Internal Medicine, Division of Gastroenterology, Baylor College of Medicine

BS Anand, MD is a member of the following medical societies: American Association for the Study of Liver Diseases, American College of Gastroenterology, American Gastroenterological Association, American Society for Gastrointestinal Endoscopy

Disclosure: Nothing to disclose.

Chief Editor

Praveen K Roy, MD, MSc Clinical Assistant Professor of Medicine, University of New Mexico School of Medicine

Praveen K Roy, MD, MSc is a member of the following medical societies: Alaska State Medical Association, American Gastroenterological Association

Disclosure: Nothing to disclose.

Acknowledgements

BS Anand, MD Professor, Department of Internal Medicine, Division of Gastroenterology, Baylor College of Medicine

BS Anand, MD is a member of the following medical societies: American Association for the Study of Liver Diseases, American College of Gastroenterology, American Gastroenterological Association, and American Society for Gastrointestinal Endoscopy