Spontaneous bacterial peritonitis differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Shivani Chaparala M.B.B.S [2];Ahmed Younes M.B.B.CH [3]

Overview

SBP must be differentiated from other abdominal conditions presenting with fever and abdominal pain. It also has to be differentiated from secondary peritonitis, chemical peritonitis, peritoneal dialysis peritonitis, chronic tuberculous peritonitis.

Differentiating Spontaneous bacterial peritonitis from other Diseases

Spontaneous bacterial peritonitis presents with fever and abdominal pain. Diseases presenting with similar features include:

Differentiating secondary peritonitis from spontaneous bacterial peritonitis

Characteristic	Spontaneous bacterial peritonitis	Secondary peritonitis
Presentaion	Main manifestations of peritonitis are acute abdominal pain, tenderness, and guarding, which are exacerbated by moving the peritoneum, e.g. coughing, flexing the hips, or elicitingthe Blumberg sign (a.k.a. rebound tenderness)	Similar presentation but insidious onset unlike rapid onset in SBP
Microorganism	Monomicrobial involvement is common No identifiable source of intra-abdominal infection	Polymicrobial involvement is common Identifiable source of intra-abdominal infection, with or without perforation (surgically treatable source)
Diagnostic criteria	SBP is diagnosed in the presence of: Ascitic fluid PMN count of ≥250/mm3 No evident intra-abdominal source of infection Positive ascitic fluid bacterial culture	Diagnosed in the presence of Positive ascitic fluid bacterial culture Ascitic fluid PMN count of ≥250/mm3 Evidence of a source of infection (demonstrated at surgery or autopsy], either intra-abdominal or contiguous with the peritoneal cavity
Follow-up paracentesis	Ascitic fluid usually became sterile after one dose of antibiotic	Failure of the ascitic fluid to become culture-negative despite of initial antibiotic treatment, appears to be typical of secondary peritonitis due to continuous spillage of organisms into abdominal cavity which requires surgery.

Differentiating SBP from other causes of peritonitis

Disease		Prominent clinical findings	Lab tests	Tratment
Primary peritonitis	Spontaneous bacterial peritonitis	Absence of GI perforation, most closely associated with cirrhosis and advanced liver disease. Presents with abrupt onset of fever, abdominal pain, distension, and rebound tenderness.	Most have clinical and biochemical manifestations of advanced cirrhosis or nephrosis like leukocytosis,hypoalbuminemia, Prolonged prothrombin time. SAAG >1.1 g/dL, increased serum lactic acid level, or a decreased ascitic fluid pH (< 7.31) supports the diagnosis. Gram staining reveals bacteria in only 25% of cases. Diagnosed by analysis of the ascitic fluid which reveals WBC > 500/ML, and PMN >250cells/ml. Culture of ascitic fluid inoculated immediately into blood culture media at the bedside usually reveals a single enteric organism, most commonly Escherichia coli, Klebsiella, or streptococci.	Once diagnosed,it is treated with Ceftriaxone.
	Tuberculous peritonitis	Seen in 0.5% of new cases of tuberculosis particularly in young women in endemic areas as a primary infection. Presents with abdominal pain and distension, fever, night sweats, weight loss, and altered bowel habits.	Ascites is present in about half of cases. Abdominal mass may be felt in a third of cases. The peritoneal fluid is characterized by a protein concentration > 3 g/dL with < 1.1 g/dL SAAG and lymphocyte predominance of WBC. Definitive diagnosis in 80% of cases is by culture. Most patients presenting acutely are diagnosed only by laparotomy.	Combination antituberculosis chemotherapy is preferred in chronic cases.
	Continuous Ambulatory Peritoneal Dialysis (CAPD peritonitis)	Peritonitis is one of the major complications of peritoneal dialysis & 72.6% occurred within the first six months of peritoneal dialysis. Historically, coagulase-negative staphylococci were the most common cause of peritonitis in CAPD, presumably due to touch contamination or infection via the pericatheter route. Treatment for peritoneal dialysis-associated peritonitis consists of antimicrobial therapy, in some cases catheter removal is also warranted. Additional therapies for relapsing or recurrent peritonitis may include fibrinolytic agents and peritoneal lavage. Most episodes of peritoneal dialysis-associated peritonitis resolve with outpatient antibiotic treatment.	Majority of peritonitis cases are caused by bacteria (50%-due to gram positive organisms, 15% to gram negative organisms,20% were culture negative.2% of cases are caused by fungi, mostly Candida species. Polymicrobial infection in 4%.Exit-site infection was present in 13% and a peritoneal fluid leak in 3 % and M.tuberculosis 0.1%.	Initial empiric antibiotic coverage for peritoneal dialysis-associated peritonitis consists of coverage for gram-positive organisms (by vancomycin or a first-generation cephalosporin) and gram-negative organisms (by a third-generation cephalosporin or an aminoglycoside). Subsequently, the regimen should be adjusted based on culture and sensitivity data. Cure rates are approximately 75%.
Secondary peritonitis	Acute bacterial secondary peritonitis	Occurs after perforating, penetrating, inflammatory, infectious, or ischemic injuries of the GI or GU tracts. Most often follows disruption of a hollow viscus→chemical peritonitis→bacterial peritonitis(polymicrobial, includes aerobic gram negative {E coli, Klebsiella, Enterobacter, Proteus mirabilis} and gram positive { Enterococcus, Streptococcus} and anaerobes {Bacteroides, clostridia}). Presents with abdominal pain, tenderness, guarding or rigidity, distension, free peritoneal air, and diminished bowel sounds. Signs that reflect irritation of the parietal peritoneum resulting ileus. Systemic findings include fever, chills or rigors, tachycardia, sweating, tachypnea, restlessness, dehydration, oliguria, disorientation, and, ultimately, refractory shock.		Peritoneal lavage, Laparoscopy are the treatment of choice.
	Biliary peritonitis	Most often seen in cases of rupture of pathological gallbladder or bile duct or cholangitic abscess or secondary to obstruction of the biliary tract. Seen in alcoholic patients with ascites.
Tertiary peritonitis		Persistence or recurrence of intraabdominal infection following apparently adequate therapy of primary or secondary peritonitis. Associated with high mortality due to multi organ dysfunction. It presents in a similar way as other peritonitis but is recognized as an adverse outcome with poor prognosis.	Enterococcus, Candida, Staphylococcus epidermidis, and Enterobacter being the most common organisms.	Characterized by lack of response to appropriate surgical and antibiotic therapy due to disturbance in the hosts immune response.
Familial Mediterranean fever (periodic peritonitis, familial paroxysmal polyserositis)		Rare genetic condition which affects individuals of Mediterranean genetic background. Etiology is unclear. Presents with recurrent bouts of abdominal pain and tenderness along with pleuritic or joint pain. Fever and leukocytosis are common.		Colchicine prevents but does not treat acute attacks.
Granulomatous peritonitis		A rare condition caused by disposable surgical fabrics or food particles from a perforated ulcer, eliciting a vigorous granulomatous (delayed hypersensitivity) response in some patients 2-6 weeks after laparotomy. Presents with abdominal pain, fever, nausea and vomiting, ileus, and systemic complaints, mild and diffuse abdominal tenderness.	Diagnosed by the demonstration of diagnostic Maltese cross pattern of starch particles.	The disease is self-limiting. Treated with corticosteroids or anti-inflammatory agents.
Sclerosing encapsulating peritonitis		Seen in conditions associated with long term peritoneal dialysis, shunts like VP shunts, history of abdominal surgeries, liver transplantation. Symptoms include nausea, abdominal pain, diarrhea, anorexia, bloody ascites.
Intraperitoneal abscesses		Most common etiologies being Gastrointestinal perforations, postoperative complications, and penetrating injuries. Signs and symptoms depend on the location of the abscess within the peritoneal cavity and the extent of involvement of the surrounding structures. Diagnosis is suspected in any patient with a predisposing condition. In a third of cases it occurs as a sequela of generalized peritonitis. The pathogenic organisms are similar to those responsible for peritonitis, but anaerobic organisms occupy an important role. The mortality rate of serious intra-abdominal abscesses is about 30%.	Diagnosed best by CT scan of the abdomen.	Treatment consists of prompt and complete CT or US guided drainage of the abscess, control of the primary cause, and adjunctive use of effective antibiotics. Open drainage is reserved for abscesses for which percutaneous drainage is inappropriate or unsuccessful.
Peritoneal mesothelioma		Arises from the mesothelium lining the peritoneal cavity. Its incidence is approximately 300-500 new cases being diagnosed in the United States each year. As with pleural mesothelioma, there is an association with an asbestos exposure. Most commonly affects men at the age of 50-69 years. Patients most often present with abdominal pain and later increased abdominal girth and ascites along with anorexia, weight loss and abdominal pain. Mean time from diagnosis to death is less than 1 year without treatment.	CT with intravenous contrast typically demonstrates the thickening of the peritoneum. Laparoscopy with tissue biopsy or CT guided tissue biopsy with immunohistochemical staining for calretinin, cytokeratin 5/6, mesothelin, and Wilms tumor 1 antigen remain the gold standard for diagnosis.	At laparotomy the goal is cytoreduction with excision. Debulking surgery and intraperitoneal chemotherapy improves survival in some cases.
peritoneal carcinomatosis		Associated with a history of ovarian or GI tract malignancy. Symptoms include ascites, abdominal pain, nausea, vomiting.

Differentiating spontaneous bacterial peritonitis from other diseases that may cause abdominal pain

Classification of acute abdomen based on etiology Presentation Symptoms Signs Diagnosis Comments Fever Abdominal Pain Jaundice Guarding Rebound Tenderness Bowel sounds Lab Findings Imaging Common causes of Peritonitis Primary Peritonitis Spontaneous bacterial peritonitis + Diffuse - - - Hypoactive Ascitic fluid PMN>250 cells/mm³ Culture: Positive for single organism Ultrasound for evaluation of liver cirrhosis - Secondary Peritonitis Perforated gastric and duodenal ulcer + Diffuse - + + N Ascitic fluid LDH > serum LDH Glucose < 50mg/dl Total protein > 1g/dl Air under diaphragm in upright CXR Upper GI endoscopy for diagnosis Acute cholangitis + RUQ + - - N Abnormal LFT Ultrasound shows biliary dilatation Biliary drainage (ERCP) + IV antibiotics Acute cholecystitis + RUQ + - - Hypoactive Hyperbilirubinemia Leukocytosis Ultrasound shows gallstone and evidence of inflammation Murphy’s sign Acute pancreatitis + Epigastric +/- - - N Increased amylase / lipase Ultrasound shows evidence of inflammation Pain radiation to back Acute appendicitis + RLQ - + + Hypoactive Leukocytosis Ultrasound shows evidence of inflammation Nausea & vomiting, decreased appetite Acute diverticulitis + LLQ +/- + - Hypoactive Leukocytosis CT scan and ultrasound shows evidence of inflammation Acute salpingitis + LLQ/ RLQ - +/- +/- N Leukocytosis Pelvic ultrasound Vaginal discharge Hollow Viscous Obstruction Small intestine obstruction - Diffuse - + +/- Hyperactive then absent Leukocytosis Abdominal X ray Nausea & vomiting associated with constipation, abdominal distention Volvulus - Diffuse - + - Hypoactive Leukocytosis CT scan and abdominal X ray Nausea & vomiting associated with constipation, abdominal distention Biliary colic - RUQ + - - N Increased bilirubin and alkaline phosphatase Ultrasound Nausea & vomiting Renal colic - Flank pain - - - N Hematuria CT scan and ultrasound Colicky abdominal pain associated with nausea & vomiting Vascular Disorders Ischemic causes Mesenteric ischemia +/- Periumbilical - - - Hyperactive Leukocytosis and lactic acidosis CT scan Nausea & vomiting, normal physical examination Acute ischemic colitis +/- Diffuse - + + Hyperactive then absent Leukocytosis CT scan Nausea & vomiting Hemorrhagic causes Ruptured abdominal aortic aneurysm - Diffuse - - - N Normal CT scan Unstable hemodynamics Intra-abdominal or retroperitoneal hemorrhage - Diffuse - - - N Anemia CT scan History of trauma Gynaecological Causes Ovarian Cyst Complications Torsion of the cyst - RLQ / LLQ - +/- +/- N Increased ESR and CRP Ultrasound Sudden onset sever pain with nausea and vomiting Cyst rupture - RLQ / LLQ - +/- +/- N Increased ESR and CRP Ultrasound Sudden onset sever pain with nausea and vomiting Pregnancy Ruptured ectopic pregnancy - RLQ / LLQ - - - N Positive pregnancy test Ultrasound History of missed period and vaginal bleeding References