Spontaneous bacterial peritonitis laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2] Guillermo Rodriguez Nava, M.D. [3]
Overview
Diagnosis requires paracentesis (needle drainage of the ascitic fluid). Ascites culture is negative in up to 60% of patients with clinical manifestations of spontaneous bacterial peritonitis (SBP), therefore, the diagnosis is based on the neutrophil count, which reaches its highest sensitivity with a cutoff neutrophil count of > 250/mm3.[1]
Laboratory Findings
Laboratory tests, most importantly ascitic fluid analysis is required for confirmation of diagnosis of spontaneous bacterial peritonitis.
- Complete blood count and differential count are tested to confirm infection.
- Serum electrolytes and creatinine to asses the renal function.
- Liver function tests are to performed for evaluation of cirrhosis.
- Blood cultures may be useful in sepsis
- Urine culture to rule out asymptomatic bacteriuria
Ascitic Fluid Analysis
- A high index of suspicion must exist for ascitic fluid infection in a cirrhotic patient. Given the similarities in presentation between the variants of ascitic fluid infection and the inability to clinically distinguish spontaneous from secondary peritonitis, the diagnosis of SBP should be through abdominal paracentesis as it has been shown to be safe with a low risk for complication, even in patients with marked coagulopathy and thrombocytopenia.
Diagnostic paracentesis
- Performed in all cirrhotics with ascites:
- upon admission to the hospital
- who develop any change in clinical status including fever, abdominal pain, mental status changes, ileus, or septic shock
- who develop laboratory abnormalities such as a leukocytosis, acidosis, or renal failure
- during episodes of gastrointestinal bleeding prior to the administration of antibiotics
- The following tests are recommended for suspected infection of the ascitic fluid:
- Cell counts with differential : Absoulte neutrophil count - a total count of >250 cells/mm3 confirm the diagnosis of spontaneous bacterial peritonitis.most sensitive and single best
test in diagnosing ascitic fluid infection [45]. Not all cases in which the PMN count is above this threshold represent infection, and values in this range can be seen with hemorrhage into ascites, peritoneal carcinomatosis, or pancreatic ascites. A useful distinguishing feature is that the PMN is usually not the predominant cell type in these cases
- Culture (in blood culture bottles)
- Gram’s stain
- Total protein
- Lactate dehydrogenase
- Glucose
- Amylase
- Albumin (if SAAG unknown)
- Serum-ascites albumin gradient (if not calculated before)
- When culture is positive, the most common organisms are Gram-negative bacteria (mainly Escherichia coli) and Gram-positive cocci (usually Streptococcus spp. and enterococci).[2]
- If the diagnosis is doubtful, the serum procalcitonin level has a 95% sensitivity, and 98% specificity with a 0.75 ng/mL cutoff.[3]
- Some patients may have an ascitic neutrophil count <250 cells/mm3 with positive cultures. This is known as "bacterascites". This patients should undergo a second paracentesis. Patients with signs of Systemic inflammatory response syndrome (SIRS) or in whom the repeat ascitic neutrophil count is >250 cells/mm3 should receive antibiotic therapy, if not, they should be followed up.[1]
- Albumin concentration - it is important for the calculation of serum-ascites albumin gradient , this helps us in identifying the portal hypertension and prognosis.
- Protein concentration - low protein concentration is noticed in cases of spontaneous bacterial peritonitis which differentiates it from secondary bacterial peritonitis where it is normal.
References
- ↑ 1.0 1.1 European Association for the Study of the Liver (2010). "EASL clinical practice guidelines on the management of ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome in cirrhosis". J Hepatol. 53 (3): 397–417. doi:10.1016/j.jhep.2010.05.004. PMID 20633946.
- ↑ Caly WR, Strauss E (1993). "A prospective study of bacterial infections in patients with cirrhosis". J Hepatol. 18 (3): 353–8. PMID 8228129.
- ↑ Viallon A, Zeni F, Pouzet V, Lambert C, Quenet S, Aubert G; et al. (2000). "Serum and ascitic procalcitonin levels in cirrhotic patients with spontaneous bacterial peritonitis: diagnostic value and relationship to pro-inflammatory cytokines". Intensive Care Med. 26 (8): 1082–8. PMID 11030164.