Spontaneous Bacterial Peritonitis – Pearls & Pitfalls

Authors: Michael Moss, MD (@mossmj, Emergency Medicine Chief Resident, VCU Medical Center) and Stephen Miller, DO (Assistant Professor, VCU Medical Center) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Stephen Alerhand, MD (@SAlerhand)

Take-home points

• SBP cannot be ruled out by history, physical examination, or clinical judgment
• Intravenous third-generation cephalosporins are the mainstay of treatment
• Albumin may be beneficial in select patients with SBP

Introduction and Case

A 67 year-old male with history of cirrhosis is brought to the ED for altered mental status. His vitals are T 37.4, HR 98, BP 113/72, SpO2 92%, RR 20. He is alert but mildly confused. He has a distended abdomen but denies any tenderness. You wonder if his worsening clinical status could be secondary to spontaneous bacterial peritonitis (SBP).

SBP is a common diagnosis with an annual incidence of 29% in those with known ascites due to cirrhosis. It is a hallmark of advanced liver disease with mortality estimates of 31.5% at 1 month and 66.2% at 12 months.^1,2

In which patients should I consider the diagnosis of SBP?

SBP is commonly a part of the differential diagnosis in patients with a history of cirrhosis and ascites. However, the classic symptoms of fever, abdominal pain, and worsening ascites are rare. Even asymptomatic outpatients have a rate of SBP of 3.5%.³ Most importantly, physical examination and clinical gestalt cannot be used to rule out SBP. In a series of 144 ED patients with ascites undergoing paracentesis, physician judgment had a sensitivity of 76% and specificity of 34% for predicting SBP.⁴ Thus, a high suspicion for SBP must be maintained and paracentesis performed in any cirrhotic patient with ascites and any combination of hepatic encephalopathy, worsening ascites, abdominal pain, fever, leukocytosis, or renal failure.

Hospital admission alone is another indication for diagnostic paracentesis as the rate of SBP among admitted patients is estimated to be 12%, even without the presence of other signs and symptoms suggesting SBP.¹

What are diagnostic criteria for SBP? What should I order when working up SBP?

SBP is defined as ascitic fluid with > 250 PMNs or WBC > 500 without evidence of a secondary intra-abdominal, surgically treatable infection or malignancy. Fluid may also be sent for LDH and glucose though these are less helpful for establishing the diagnosis. If the etiology of the ascites is in question, fluid and serum albumin may be measured to calculate a serum-ascites albumin gradient. All samples should be sent for cell count and differential, gram stain, and culture.¹

Ascitic fluid should be placed directly in aerobic and anaerobic blood culture bottles at the bedside as it may increase culture yields from 50% to 80%.^5-7

Do cirrhotic patients with thrombocytopenia or elevated INR require transfusion prior to paracentesis?

Patients with liver disease often have an elevated INR and thrombocytopenia. While these tests may be ordered for other reasons, they are not necessary prior to performing a paracentesis. In a series of 628 patients undergoing large volume paracentesis, there were no bleeding complications even with an INR as high as 8.7 and platelets as low as 19.⁸

What treatment should be given for SBP?

Ascitic fluid is rapidly sterilized within 6 hours after a single dose of antibiotics so paracentesis should be performed prior to antibiotic administration when at all possible.¹

The preferred regimen for empiric treatment of SBP is a third-generation cephalosporin such as cefotaxime which covers the three most common bacteria: Escherichia coli, Klebsiella pneumoniae, and Streptococcus pneumoniae. An oral fluoroquinolone may be considered in low-risk patients with close outpatient follow-up. Fluoroquinolones should not be used to treat SBP in a patient receiving fluoroquinolones for SBP prophylaxis.^1,9

Albumin infusion may be beneficial in some patients with SBP. A study in 1999 showed a mortality benefit with albumin administered to all patients with SBP.¹⁰ However, newer data and guidelines now only recommend albumin administration with serum creatinine >1 mg/dL, BUN >30 mg/dL, or total bilirubin >4 mg/dL. The preferred regimen is 1.5 g/kg albumin within 6 hours of diagnosis with a subsequent dose of 1 g/kg on day 3.^1,11

Conclusion and Case Resolution

Though the patient has no overt symptoms of SBP, you perform a diagnostic paracentesis and find 297 PMN/mm³. The remainder of his laboratory studies are unremarkable. You order 2 g cefotaxime IV and admit the patient to the hospital.

SBP is very common among cirrhotic patients with ascites. Clinical suspicion cannot be used to rule out SBP and a diagnostic paracentesis should be performed in any patient admitted to the hospital or with worsening clinical status, fever, leukocytosis, or renal failure. Direct transfer of ascitic fluid into blood culture bottles will increase culture yields. Third-generation cephalosporins are the treatment of choice and albumin may be considered in more severely ill patients.

References / Further Reading

1. Runyon BA. AASLD Practice Guideline: Management of adult patients with ascites due to cirrhosis: Update 2012. Hepatology. 2013.
2. Arvaniti V, D’Amico G, Fede G, et al. Infections in patients with cirrhosis increase mortality four-fold and should be used in determining prognosis. Gastroenterology. 2010;139:1246-56, 1256.e1-5.
3. Evans LT, Kim WR, Poterucha JJ, Kamath PS. Spontaneous bacterial peritonitis in asymptomatic outpatients with cirrhotic ascites. Hepatology. 2003;37:897-901.
4. Chinnock B, Afarian H, Minnigan H, Butler J, Hendey GW. Physician clinical impression does not rule out spontaneous bacterial peritonitis in patients undergoing emergency department paracentesis. Ann Emerg Med. 2008;52:268-273.
5. Runyon BA, Antillon MR, Akriviadis EA, McHutchison JG. Bedside inoculation of blood culture bottles with ascitic fluid is superior to delayed inoculation in the detection of spontaneous bacterial peritonitis. J Clin Microbiol. 1990;28:2811-2812.
6. Runyon BA, Canawati HN, Akriviadis EA. Optimization of ascitic fluid culture technique. Gastroenterology. 1988;95:1351-1355.
7. Castellote J, Xiol X, Verdaguer R, et al. Comparison of two ascitic fluid culture methods in cirrhotic patients with spontaneous bacterial peritonitis. Am J Gastroenterol. 1990;85:1605-1608.
8. Grabau CM, Crago SF, Hoff LK, et al. Performance standards for therapeutic abdominal paracentesis. Hepatology. 2004;40:484-488.
9. Chavez-Tapia, Norberto C, Soares-Weiser, et al. Antibiotics for spontaneous bacterial peritonitis in cirrhotic patients. John Wiley & Sons, Ltd; 2009.
10. Sort P, Navasa M, Arroyo V, et al. Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis. N Engl J Med. 1999;341:403-409.
11. Sigal SH, Stanca CM, Fernandez J, Arroyo V, Navasa M. Restricted use of albumin for spontaneous bacterial peritonitis. Gut. 2007;56:597-599.