Does every patient with ascites need a tap?
Bottom line up top: Any patient with ascites who is sick enough to be admitted should have a diagnostic paracentesis in the ED, because spontaneous bacterial peritonitis (SBP) presents cryptically.
Clinical scenario
A 57-year-old man with cirrhosis and ascites presents with 4 days of left lower extremity redness and pain. Vitals: HR 84, BP 110/73, T 100.5 °F, SpO₂ 98% on room air. His left ankle and foot are swollen, warm, and erythematous, with no abscess, ulceration, or crepitus. His primary doctor started Bactrim and Keflex, without improvement. You start IV vancomycin and call for admission. The hospitalist asks whether he needs a paracentesis before admission.
What your gut says: He has an obvious infectious source for the fever, so there is no need for paracentesis. Besides, he is already on IV antibiotics.
What the evidence says
SBP is an acute infection of ascitic fluid, common in liver disease. Patients with advanced liver disease have an SBP incidence of 10–25% per year, with historically high mortality (Runyon 1988; Runyon 1988; Borzio 2001).
The classic triad of abdominal pain, fever, and increasing ascites is insensitive. Most patients have an incomplete triad, and some have only one feature.
An ED-based study found clinician sensitivity of only 76% for predicting SBP (Chinnock 2008).
Admitted patients who underwent paracentesis had lower overall mortality than those who did not, even when SBP was not suspected (Gaetano 2016).
Given how cryptic SBP is, keep a low threshold for diagnostic paracentesis in cirrhotic patients with ascites. A recommended standard approach is to tap every such patient presenting to the ED, except those with the most minor complaints (for example, a laceration or musculoskeletal injury).
Diagnosis
SBP is diagnosed by an ascitic fluid neutrophil (PMN) count > 250 cells/mm³. A total WBC count > 500–1,000 cells/mm³ is also used.
The threshold is lower in peritoneal dialysis patients (> 100 cells/mm³).
Treatment is specific
Treating another infection is not adequate coverage for SBP.
Common organisms: E. coli, S. pneumoniae, and enterococci.
Empiric therapy: a third-generation cephalosporin (for example, ceftriaxone or cefotaxime).
Albumin reduces renal failure (by 25%) and mortality (by 20%) (Sort 1999). The AASLD recommends albumin 1.5 g/kg within 6 hours, then 1 g/kg on day 3, for patients with SBP and any of the following (Runyon 2012):
serum creatinine > 1.0 mg/dL
BUN > 30 mg/dL
total bilirubin > 4.0 mg/dL
Clinical bottom line
SBP is hard to diagnose in the ED because its presentation can be subtle. Consider a diagnostic paracentesis in every ED patient with cirrhotic ascites, whatever the chief complaint.
Clinical pearls
An obvious alternative source does not rule out SBP. Tap the belly.
Send cell count with differential and culture (inoculate blood culture bottles at the bedside).
If SBP is present, start a third-generation cephalosporin and check whether the patient meets albumin criteria.
Resources
References
Runyon BA, et al. Ascitic fluid analysis in malignancy-related ascites. Hepatology. 1988;8(5):1104–1109. PMID: 3417231
Runyon BA. Spontaneous bacterial peritonitis: an explosion of information. Hepatology. 1988;8:171–175. PMID: 3338704
Borzio M, et al. Bacterial infection in patients with advanced cirrhosis: a multicentre prospective study. Dig Liver Dis. 2001;33(1):41–48. PMID: 11303974
Chinnock B, et al. Physician clinical impression does not rule out spontaneous bacterial peritonitis in patients undergoing emergency department paracentesis. Ann Emerg Med. 2008;52:268–273. PMID: 18433932
Gaetano JN, et al. The benefit of paracentesis on hospitalized adults with cirrhosis and ascites. J Gastroenterol Hepatol. 2016. PMID: 26642977
Wong CL, et al. Does this patient have bacterial peritonitis or portal hypertension? How do I perform a paracentesis and analyze the results? JAMA. 2008;299(10):1166–1178. PMID: 18334692
Runyon BA. Management of adult patients with ascites due to cirrhosis: update 2012. AASLD Practice Guideline.
Sort P, 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. PMID: 10432325
