Can clear ascitic fluid appearance rule out spontaneous bacterial peritonitis?

Review article: spontaneous bacterial peritonitis--bacteriology, diagnosis, treatment, risk factors and prevention

BACKGROUND

Spontaneous bacterial peritonitis (SBP) is a severe and often fatal infection in patients with cirrhosis and ascites.

AIM

To review the known and changing bacteriology, risk factors, ascitic fluid interpretation, steps in performing paracentesis, treatment, prophylaxis and evolving perspectives related to SBP.

METHODS

Information was obtained from reviewing medical literature accessible on PubMed Central. The search term 'spontaneous bacterial peritonitis' was cross-referenced with 'bacteria', 'risk factors', 'ascites', 'paracentesis', 'ascitic fluid analysis', 'diagnosis', 'treatment', 'antibiotics', 'prophylaxis', 'liver transplantation' and 'nutrition'.

RESULTS

Gram-positive cocci (GPC) such as Staphylococcus, Enterococcus as well as multi-resistant bacteria have become common pathogens and have changed the conventional approach to treatment of SBP. Health care-associated and nosocomial SBP infections should prompt greater vigilance and consideration for alternative antibiotic coverage. Acid suppressive and beta-adrenergic antagonist therapies are strongly associated with SBP in at-risk individuals.

CONCLUSIONS

Third-generation, broad-spectrum cephalosporins remain a good initial choice for SBP treatment. Levofloxacin is an acceptable alternative for patients not receiving long-term flouroquinolone prophylaxis or for those with a penicillin allergy. For uncomplicated SBP, early oral switch therapy is reasonable. Alternative antibiotics such as pipercillin-tazobactam should be considered for patients with nosocomial SBP or for patients who fail to improve on traditional antibiotic regimens. Selective albumin supplementation remains an important adjunct in SBP treatment. Withholding acid suppressive medication deserves strong consideration, and discontinuing beta-adrenergic antagonist therapy in patients with end-stage liver disease and resistant ascites is standard care. Liver transplant evaluation should be undertaken for patients who develop SBP barring contraindications.

Clinical impression and ascites appearance do not rule out bacterial peritonitis

BACKGROUND

Previous research has demonstrated that physician clinical suspicion, determined without assessing fluid appearance, is not adequate to rule out spontaneous bacterial peritonitis (SBP) without fluid testing.

STUDY OBJECTIVE

To determine the sensitivity of physician clinical suspicion, including a bedside assessment of fluid appearance, in the detection of SBP in Emergency Department (ED) patients undergoing paracentesis.

METHODS

We conducted a prospective, observational study of ED patients with ascites undergoing paracentesis at three academic facilities. The enrolling physician recorded the clinical suspicion of SBP ("none," "low," "moderate," or "high"), and ascites appearance ("clear," "hazy," "cloudy," or "bloody"). SBP was defined as an absolute neutrophil count ≥ 250 cells/mm(3), or culture pathogen growth. We defined "clear" ascites fluid as negative for SBP, and "hazy," "cloudy," or "bloody" as positive. A physician clinical suspicion of "none" or "low" was considered negative for SBP, and an assessment of "moderate" or "high" was considered positive. The primary outcome measure was sensitivity of physician clinical impression and ascites appearance for SBP.

RESULTS

There were 348 cases enrolled, with SBP diagnosed in 43 (12%). Physician clinical suspicion had a sensitivity of 42% (95% confidence interval [CI] 29-55%) for the detection of SBP. Fluid appearance had a sensitivity of 72% (95% CI 58-83%).

CONCLUSION

Physician clinical impression, which included an assessment of fluid appearance, had poor sensitivity for the detection of SBP and cannot be used to exclude the diagnosis. Routine laboratory fluid analysis is indicated after ED paracentesis, even in patients considered to have a low degree of suspicion for SBP.

A new highly sensitive point of care screen for spontaneous bacterial peritonitis using the leukocyte esterase method

BACKGROUND & AIMS

Urine reagent strips measuring leukocyte esterase activity have been studied to screen spontaneous bacterial peritonitis (SBP) but are insensitive. We calibrated a strip specifically for ascitic fluid to achieve high sensitivity in this diagnosis.

METHODS

Experiments were conducted on ascitic fluid from patients with cirrhosis. Samples with SBP were diluted with native acellular ascitic fluid to achieve PMN counts below, above, and close to the diagnostic threshold of 250 PMN/microl. A model of SBP was created by spiking negative ascitic fluid samples (<250 PMN/microl) with activated PMN from blood of patients with sepsis, and diluted to achieve a range of PMN. Aliquots were tested at 2, 3, 4, and 10 min with the Periscreen leukocyte esterase strip. PMN/microl was correlated to timings and color scales: white defined negative (PMN <250/microl); and shades of brown, purple, and pink defined positive. Ascitic fluid samples were obtained from 58 patients. Negative ascitic fluid was used from 32 to generate the model SBP.

RESULTS

One thousand three hundred and four experiments were performed with a median PMN count of 492/microl (0-7510). After exclusion of uninterpretable colorimetric results, 1089 experiments were analyzed [PMN of 444/microl (0-7510)]. The best result was obtained at 3 min (n=299), with Se: 100%, Sp: 57.9%; NPV: 100%, PPV: 76.5%. The test was not interpretable in bloody, chylous or bilious ascitic fluid, or concurrent imipenem treatment.

CONCLUSIONS

This new leukocyte esterase strip calibrated to an ascitic fluid PMN count 250/microl is a robust screening tool when the strip turns any hue of tan/brown at 3 min.

Spontaneous bacterial peritonitis

Since its initial description in 1964, research has transformed spontaneous bacterial peritonitis (SBP) from a feared disease (with reported mortality of 90%) to a treatable complication of decompensated cirrhosis, albeit with steady prevalence and a high recurrence rate. Bacterial translocation, the key mechanism in the pathogenesis of SBP, is only possible because of the concurrent failure of defensive mechanisms in cirrhosis. Variants of SBP should be treated. Leucocyte esterase reagent strips have managed to shorten the ‘tap-to-shot’ time, while future studies should look into their combined use with ascitic fluid pH. Third generation cephalosporins are the antibiotic of choice because they have a number of advantages. Renal dysfunction has been shown to be an independent predictor of mortality in patients with SBP. Albumin is felt to reduce the risk of renal impairment by improving effective intravascular volume, and by helping to bind pro-inflammatory molecules. Following a single episode of SBP, patients should have long-term antibiotic prophylaxis and be considered for liver transplantation.

Physician clinical impression does not rule out spontaneous bacterial peritonitis in patients undergoing emergency department paracentesis

STUDY OBJECTIVE

We determine whether clinical characteristics and physician assessment are useful in the exclusion of spontaneous bacterial peritonitis in emergency department (ED) patients with ascites requiring paracentesis.

METHODS

We conducted a prospective, observational study of ED patients with ascites undergoing paracentesis. Predefined clinical characteristics including historical features and ED vital signs were recorded. Each patient was assessed by 2 separate, blinded physicians for severity of abdominal tenderness and overall clinical suspicion for spontaneous bacterial peritonitis. The primary outcome measures were sensitivity, specificity, and likelihood ratios (LR) of the individual clinical characteristics and the physician assessments. Spontaneous bacterial peritonitis was defined by absolute neutrophil count greater than 250 cells/mm(3) or positive fluid culture result.

RESULTS

There were 285 separate physician assessments in 144 patients enrolled with complete data. Spontaneous bacterial peritonitis was diagnosed in 17 (11.8%) patients. Physician clinical impression had a sensitivity of 76% (95% confidence interval [CI] 62% to 91%) and specificity of 34% (95% CI 28% to 40%) for the detection of spontaneous bacterial peritonitis. The lowest negative LR was associated with the presence of any abdominal pain or tenderness (negative LR=0.4); however, the presence of pain/tenderness was also observed in 85% of patients without spontaneous bacterial peritonitis. Six patients (4.2%) with spontaneous bacterial peritonitis had at least 1 physician assessment of little to no risk for spontaneous bacterial peritonitis, and 3 of the 6 subsequently died during their hospitalization.

CONCLUSION

Clinical characteristics and physician assessment were insufficient in the diagnosis or exclusion of spontaneous bacterial peritonitis in the ED patient undergoing diagnostic or therapeutic paracentesis. This finding supports routine laboratory fluid analysis after ED paracentesis.