Spontaneous bacterial peritonitis: Clinical sciences

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Introduction0:00–0:31

Spontaneous bacterial peritonitis refers to a bacterial infection of ascitic fluid without an identifiable source. It typically affects individuals with liver cirrhosis, and it’s thought to be due to a bacterial migration from the gut.
Based on ascitic fluid culture results, you can differentiate spontaneous bacterial peritonitis from secondary bacterial peritonitis, which is associated with an identifiable source of infection!When a patient presents with a chief concern suggesting spontaneous bacterial peritonitis, first you should perform an ABCDE assessment to determine if the patient is unstable or stable.

Unstable0:31–1:31

If unstable, stabilize the airway, breathing, and circulation, which means you may have to intubate the patient. Next, obtain IV access and put your patient on continuous vital sign monitoring, including heart rate, blood pressure, and pulse oximetry.
Finally, if needed, don’t forget to provide supplemental oxygen!Now, here’s a clinical pearl! Like any other infection, patients with spontaneous bacterial peritonitis can progress to septic shock.
In that case, broad spectrum antibiotics with carbapenems are essential, and remember to also look for other potential sources of infection.
In otherwise stable patients, a third generation cephalosporin is adequate.Okay, now let’s go back to the ABCDE assessment and focus on stable patients.

Focused H&P1:31–2:36

In this case, obtain a focused history and physical examination. Also, order labs including CBC, CMP, and serum albumin.
Finally, don't forget to order an abdominal ultrasound. Your patient will likely report systemic symptoms, such as fever and chills, as well as abdominal pain and progressive abdominal distention, as well as rigidity.
There might also be a history of cirrhosis, with or without prior episodes of ascites. The physical examination will reveal mild abdominal tenderness and signs of ascites, like bulging flanks, a palpable fluid wave, and shifting dullness.
In some cases, you might notice guarding as well. Finally, labs will usually show low serum albumin levels, and ultrasound will show free fluid in the peritoneal cavity.
With these findings, you should suspect peritonitis!Next, perform diagnostic paracentesis and send the ascitic fluid for analysis and cultures.

Diagnostic Paracentesis 2:36–3:33

Once the results of ascitic fluid analysis are available, calculate the Serum-Ascites Albumin Gradient, or SAAG for short.
To do so, subtract the ascitic fluid albumin value from the serum albumin value. Now, if the SAAG is less than 1.1 grams per deciliter, and the ascitic fluid polymorphonuclear, or PMN count, is less than 250 cells per cubic millimeter, you should consider an alternative diagnosis.Here’s a clinical pearl!
When calculating PMNs, it should be corrected for any RBCs present in the ascitic fluid sample. In fact, 1 PMN is subtracted from the absolute PMN count for every 250 red cells/mm3.Let’s go back to our SAAG!
Now, a SAAG of 1.1 or greater is indicative of portal hypertension. So, if you see this finding, and the ascitic fluid polymorphonuclear count is greater than 250 cells per cubic millimeters, suspect bacterial peritonitis.

SAAG ≥ 1.13:33–4:52

Next, start empiric antibiotics covering gram-negative and anaerobic organisms. For example, you can start a third-generation cephalosporin, like cefotaxime or ceftriaxone.Here’s a clinical pearl to keep in mind!
While not necessary for the diagnosis of spontaneous bacterial peritonitis, checking LDH, glucose, and total protein levels can provide valuable insights while waiting for culture results.
For example, an LDH level above the upper limit of normal, a glucose level below 50 milligrams per deciliter, and a total protein above 1 gram per deciliter may suggest secondary bacterial peritonitis as the most likely diagnosis.
On the flip side, a normal or slightly elevated LDH, a glucose level above 50 milligrams per deciliter, and a total protein below 1 gram per deciliter, point toward spontaneous bacterial peritonitis.Okay, now let’s assess the ascitic fluid culture results.
If the results reveal a positive monomicrobial culture, diagnose spontaneous bacterial peritonitis and tailor antibiotics based on culture results.

Positive Monomicrobial Culture4:52–6:32

The most commonly involved bacteria are gram-negative, such as Escherichia coli and Klebsiella. Once you tailor antibiotics, you should start cirrhosis management.
First, manage the underlying causes, which may include alcoholic liver disease or chronic viral infections, like hepatitis B or C.
Next, counsel your patient on lifestyle changes, like avoiding alcohol and hepatotoxic medications, such as acetaminophen.
You can let them know that patients with cirrhosis can still safely use up to 2 grams of acetaminophen a day for pain relief.
If applicable, offer vaccines against Hepatitis A and B and screen for esophageal varices. In severe cases, consult your surgery team for a liver transplantation!Here’s another clinical pearl!
Patients with spontaneous bacterial peritonitis, especially those with low serum albumin and effective arterial blood volume, are at an increased risk of developing acute renal failure, which is a major cause of death.
To address this risk, you might need to administer 25% albumin by IV infusion within 6 hours of a suspected diagnosis. This way you are going to improve the intravascular volume and subsequently renal perfusion.
Once renal failure has developed, treatment with a combination of octreotide and midodrine can be used.Now, let’s go back one last time and assess the ascitic fluid culture results!
If culture results are positive for a polymicrobial infection, diagnose secondary bacterial peritonitis. In most cases, secondary bacterial peritonitis occurs due to bowel perforation, appendicitis, cholecystitis, liver abscess, or necrotic bowel, so immediately consult your surgery team.

Positive Polymicrobial Culture6:32–7:55

Once you address the underlying cause of infection, proceed with cirrhosis management. Again, severe cases will need evaluation for a possible liver transplant!One last clinical pearl!
Occasionally, cultures might be negative despite having elevated ascitic PMNs. This condition is referred to as culture-negative neutrocytic ascites or CNNA for short.
To diagnose CNNA, specific criteria must be met. Your patient should have a negative ascitic culture, an ascitic fluid PMN count exceeding 500 cells per cubic millimeter, the absence of an intraabdominal source of infection, no antibiotic treatment within the past 30 days, and without evidence of pancreatitis.
Management is the same as bacterial peritonitis involving empiric antibiotics and the management of cirrhosis.Alright, as a quick recap...
Spontaneous bacterial peritonitis is a bacterial infection of ascitic fluid without an identifiable source, which occurs in the setting of hepatic cirrhosis.

Review7:55–8:54

If you suspect spontaneous bacterial peritonitis, perform diagnostic paracentesis and send the ascitic fluid for analysis and cultures.
If the SAAG is 1.1 grams per deciliter or greater, and the ascitic fluid polymorphonuclear count is greater than 250 cells per cubic millimeters, suspect bacterial peritonitis and start empiric antibiotics.
Next, assess the ascitic fluid culture results. If they reveal a monobacterial infection, diagnose spontaneous bacterial peritonitis and tailor antibiotics.
If the culture is positive and polymicrobial, diagnose secondary bacterial peritonitis and consult the surgical team. All patients with ascitic infections require cirrhosis management and, in severe cases, liver transplantation.
patients with acidic infections require