Peritonitis

As the name suggests, peritonitis is inflammation of the peritoneum.

Peritonitis may be generalised or it may become localised. With inflammation of an underlying organ (e.g. appendicitis) there is almost always some localised peritonitis (which will be resolved by treating the underlying organ).

Pathophysiology

We can have 2 main subtypes of peritonitis:

Infected peritonitis

Due to perforation of the GI tract (or reproductive system in women). It may be due to trauma, ulceration, or obstruction for example. The most common causative agent is E. coli.
Spontaneous bacterial peritonitis - occurring in kids and patients with ascites who rapidly deteriorates. Common causative agents are E. coli, klebsiella, streptococcus.

Non-infected peritonitis - due to leakage of sterile body fluids into the abdomen (e.g. blood, bile, urine) or due to Lupus.

😷 Presentation

⭐️ Sudden onset acute abdominal pain exacerbated by movement. It may be localised initially and then become generalised (due to activation of parietal nerve fibres)
Lying still
Signs of shock (tachycardia, fever, etc.)
Prostration (complete physical exhaustion)
Nausea + vomiting

📝

On examination we may notice:

Percussion/rebound tenderness
Guarding
Absent bowel sounds
Positive cough test - pain and flinching when asked to cough.
Washboard rigidity

🔍 Investigations

🩸

Bloods FBC, U&E, CRP, LFT etc. G&S is important as the patient may need an urgent laparotomy. Amylase is vital! It rules out pancreatitis (which does not require a laparotomy).

📷

Imaging CXR to assess for pneumoperitoneum 🏆 CT/US is used to confirm diagnosis

🧰 Management

Good initial management includes: patient being NBM, IV access analgesia antiemetics urine dip bloods, catheterisation (to assess urine output of patient).

IV fluids & electrolytes are required to resuscitate the patient and replenish the lost electrolytes.
IV antibiotics will be needed if it is infective in aetiology.

🔪

Surgical management: Laparotomy will be done after we have attained a good urine output. The aim would be to washout the peritoneal cavity, repair the perforation or underlying cause.

🚨 Complications

Abscesses are common
Sepsis
Fatal if untreated.

Ascites and spontaneous bacterial peritonitis

This is fluid collection on the peritoneal cavity. It occurs due to portal hypertension causing leakage of fluid out of the capillaries in the liver and into the peritoneal cavity. A reduction in the circulating volume causes reduced BP entering into the kidneys. This activates the RAAS to cause increased fluid retention. The ascitic fluid with cirrhosis is a transudative ascites (low-protein content).

🦠

Spontaneous bacterial peritonitis (SBP):

Happens in about 10% of patients with ascites that is secondary to cirrhosis. It has a high mortality of 10-20%. It is called spontaneous as the infection develops without any clear cause and not secondary to perforation or a drain.

😷 Presentation

Asymptomatic

Fever

Abdominal pain

Ileus

Hypotension

🦠 Causative agents
E. coli
K. pneumoniae
Staphylococcus spp.
Enterococcus spp.

🧰 Management

Low sodium diet
Spirinolactone - reduces aldosterone activity and decreases fluid retention as a result.
Paracentesis - an ascitic tap or ascitic drain.
Prophylactic antibiotics - to prevent spontaneous bacterial peritonitis in patients with a transudative ascites (<15g/litre of protein).

Ciprofloxacin or norfloxacin

TIPS or transplantation If refractory.