Spontaneous bacterial peritonitis

Occurs mainly in patients with liver cirrhosis and is usually caused by gram-negative bacilli.

Associated with increased morbidity and mortality.

Has a mortality rate of 20-40% despite Antibiotic treatment.

Aerobic gram-negative organisms and streptococci are the most frequent causes.

Increasing incidence of gram-positive organisms.

An acute bacterial infection of ascitic fluid.

Generally, no source of the infecting agent is easily identifiable.

Contamination of dialysate can cause the condition among those receiving peritoneal dialysis.

Can occur in both children and adults and is a well-known complication in patients with cirrhosis.

Cirrhotic patients who have spontaneous bacterial peritonitis, 70% are Child-Pugh class C and is associated with a poor long-term prognosis.

Affects patients with cirrhosis from any cause.

Decompensated cirrhosis associated with the highest risk of developing spontaneous bacterial peritonitis, as are patients with decreased hepatic protein production or with prolonged prothrombin times.

Patients with < 1 g/dL of protein in ascitic fluid have a 10-fold higher risk of developing spontaneous bacterial peritonitis than those with a protein level greater than 1 g/dL.

SBP can occur as a complication of any disease state that produces the clinical syndrome of ascites, such as heart failure and Budd-Chiari syndrome.

Children with nephrosis or systemic lupus erythematosus who have ascites have a high risk of developing spontaneous bacterial peritonitis.

Three fourths of spontaneous bacterial peritonitis infections have been caused by aerobic gram-negative organisms.

50% of aerobic gram-negative infections are due to Escherichia coli, and 19% are due to streptococcal species.

The percentage of gram-positive infections may be increasing.

Anaerobic organisms are rare due to the high oxygen tension of ascitic fluid.

A single organism is noted in 92% of cases, and 8% of cases are polymicrobial.

Low complement levels are associated with the development of spontaneous bacterial peritonitis.

The frequency may be as high as 18% in patients with ascites.

There is a 2.7 fold increase in mortality for each hour delay in paracentesis.

No raceor gender predeliction.

Two peak ages for spontaneous bacterial peritonitisin children: the first in the neonatal period and the second at age 5 years.

Mortality rate in patients with spontaneous bacterial peritonitis ranges from 40-70% in adult patients with cirrhosis, but the rates are lower in children with nephrosis.

Mortality higher in patients with renal insufficiency.

Enteric organisms isolated from more than 90% of infected ascites fluid in spontaneous bacterial peritonitis, suggesting that the GI tract is the source of bacterial contamination.

The preponderance of enteric organisms, in combination with the presence of endotoxin in ascitic fluid and blood, suggests direct transmural migration of bacteria from the intestine, a process called bacterial translocation.

A proposed mechanism for bacterial inoculation of ascites is hematogenous transmission in combination with an impaired immune system.

Intestinal bacterial overgrowth is seen in cirrhosis, attributed to delayed intestinal transit time.

Intestinal bacterial overgrowth, impaired phagocytic function, low serum and ascites complement levels, and decreased activity of the reticuloendothelial system, contributes to an increased number of microorganisms and decreased capacity to clear them from the bloodstream, resulting in their migration into and eventual proliferation within ascites fluid.

Adults with spontaneous bacterial peritonitis typically have ascites, but most children with spontaneous bacterial peritonitis do not.

Three fourths of spontaneous bacterial peritonitis infections have been caused by aerobic gram-negative organisms, with 50% of these being Escherichia coli.

The remainder has been due to aerobic gram-positive organisms including 19% of cases due to streptococcal species.

The percentage of gram-positive infections may be increasing, with recent studies suggesting streptococci accounting for more than 30% of cases, second to Enterobacteriaceae.

Streptococci viridans infections account for the majority of streptococci isolates.

Because ascites has oxygen tension anaerobic organisms are usually not isolated in SBP.

SBP is usually associated with a single organism in more than 92% of cases, while 8% of cases are polymicrobial.

Patients with decompensated cirrhosis are at the highest risk, as are patients with low total serum protein levels, prolonged prothrombin time, and low complement levels.

Patients with protein levels in ascitic fluid of < 1 g/dL, have a 10-fold higher risk of developing spontaneous bacterial peritonitis than those with a protein level greater than 1 g/dL.

The frequency of SBP in patients with ascites may be as high as 18%.

Both genders are affected equally in the presence of ascites.

SBP has 2 peaks in childhood: neonatal period and about 5 years of age.

The mortality rate ranges from 40-70% in adult patients with cirrhosis, and is lower in children with nephrosis.

Patients with renal insufficiency have a higher risk of mortality.

Mortality may be decreasing because of advances in its diagnosis and treatment.

Asymptomatic cases have been reported in as many as 30% of patients.

Patients may experience refractory ascites, ileus, diarrhea, encephalopathy, progressive renal impairment, hypotension, abdominal tenderness that may mimic an acute abdomen, and progressive jaundice.

Clinically similar to secondary bacterial peritonitis.

All patients suspected of having spontaneous bacterial peritonitis should have diagnostic paracentesis, and blood and urine cultures.

Blood cultures are positive in as many as 33% of patients with spontaneous bacterial peritonitis.

Asymptomatic bacteruria may predispose to the development of spontaneous bacterial peritonitis.

The examination of ascitic fluid is routinely analyzed for cell count, differential, and culture.

The sensitivity of microbiologic studies increases significantly with the direct inoculation of routine blood culture bottles at the bedside with 10 mL of ascitic fluid.

An ascitic fluid neutrophil count of more than 500 cells/µL is the single best predictor of spontaneous bacterial peritonitis.

A ascitic fluid analysis of greater than 500 cells/µL has a sensitivity of 86% and specificity of 98% for the diagnosis of SBP.

Reagent strips that detect leukocyte esterase, can be read at the bedside using a portable spectrophotometric device and can achieve a 100% sensitivity in diagnosis of SBP.

Ascites lactate level of more than 25 mg/dL is 100% sensitive and specific in predicting active spontaneous bacterial peritonitis.

Combination of an ascites fluid pH below 7.35 and polymorphonuclear neutrophil count above 500 cells/µL is 100% sensitive and 96% specific for spontaneous bacterial peritonitis.

Culture-negative ascites is noted in as many as 50% of patients with SBP and may be the result of poor culturing techniques or late-stage resolving infection.

American Association for the Study of Liver Diseases recommends that adult cirrhotic patients with ascitic fluid neutrophil counts greater than 250 cells/ µL receive empiric antibiotic therapy with a cephalosporin.

Patients with a peritoneal fluid PMN count greater than 500 cells/µL should universally be admitted to the hospital and immediately treated for spontaneous bacterial peritonitis, regardless of peritoneal fluid Gram stain result.

Asymptomatic patients that have yet to have positive culture results may be managed without treatment but must undergo a follow-up paracentesis within 24-48 hours.

All symptomatic patients with a peritoneal fluid PMN count of 250-500 cells/µL should be admitted and treated for spontaneous bacterial peritonitis.

A 10- to 14-day course of antibiotics is recommended for SBP.

A repeat peritoneal fluid analysis is recommended to verify improvement in ascitic neutrophil count and improved culture results. If improvement in ascitic fluid or clinical condition does not occur within 48 hours, further evaluation is required to rule out bowel perforation or intraabdominal abscess.

Antibiotics are initially instituted empirically, to prevent death from infection.

Traditionally, a combination of an aminoglycoside and ampicillin was used to treat spontaneous bacterial peritonitis affording excellent empiric coverage of more than 90% of cases caused by gram-negative aerobes or gram-positive cocci.

The third-generation cephalosporins have been demonstrated to be as efficacious as the ampicillin/aminoglycoside combination, and it does not carry the increased risk of nephrotoxicity in cirrhotic patients.

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