Peritonitis

Peritonitis is an inflammation of the peritoneum, the lining of the inner wall of the abdomen and the covering of abdominal organs. It can be either localised or generalised and is considered a medical emergency.

Signs and Symptoms

The main clinical manifestation of peritonitis is acute abdominal pain accompanied by tenderness and rigidity. Abdominal guarding and rigidity, particularly when exacerbated by movement such as coughing or flexing the hips, are common. The Blumberg's sign, where pressing on the abdomen elicits less pain than releasing the hand abruptly, is often used diagnostically.

Pain often starts as generalised and may become localised, depending on whether the peritonitis is localised (e.g., appendicitis) or generalised.

Other symptoms include diffuse abdominal rigidity, fever, sinus tachycardia, nausea, vomiting, and bloating due to paralytic ileus. Reduced or absent bowel sounds and passage of gas are also common.

Complications

Complications of peritonitis can be severe and include sequestration of fluids and electrolytes, leading to hypovolaemia, shock, and acute kidney failure. Peritoneal abscesses may form, and sepsis can develop, making blood cultures essential. In severe cases, multiple organs may be involved.

Causes

Infection

Infections leading to peritonitis often result from perforations in the gastrointestinal tract caused by conditions like Boerhaave syndrome, peptic ulcers, appendicitis, diverticulitis, inflammatory bowel disease, and colorectal carcinoma.

Other causes include abdominal trauma, ingestion of sharp foreign bodies, and surgical complications. Mixed bacteria, including Gram-negative bacilli and anaerobic bacteria, are commonly isolated.

Disruption of the peritoneum, even without perforation, can also cause infection, particularly in cases of trauma, surgical wounds, and peritoneal dialysis. Spontaneous bacterial peritonitis (SBP) occurs without an obvious source of infection and is common in people with ascites.

Non-infection

Non-infectious causes include leakage of sterile body fluids such as blood, gastric juice, bile, urine, and pancreatic juice into the peritoneum, which frequently become infected. Sterile abdominal surgery may cause localised peritonitis, and rare causes include familial Mediterranean fever and systemic lupus erythematosus.

Risk Factors

Risk factors for peritonitis include a previous history of the condition, alcoholism, liver disease, fluid accumulation in the abdomen, a weakened immune system, and pelvic inflammatory disease.

Diagnosis

Diagnosis is primarily clinical, with abdominal rigidity being a highly specific sign. In cases of focal peritonitis, further investigations are warranted, while diffuse peritonitis requires urgent surgical consultation. Blood tests may show leukocytosis, hypokalaemia, hypernatraemia, and acidosis.

Imaging like abdominal X-rays and CT scans can be helpful, and in people with ascites, paracentesis can be diagnostic if more than 250 polymorphonuclear cells per μL are found. Cultures of peritoneal fluid help determine the causative microorganism.

Pathology

The peritoneum normally appears greyish and glistening but becomes dull and turbid a few hours after the onset of peritonitis. The exudate initially appears serous but becomes purulent and may be spread throughout the peritoneum or walled off by the omentum and viscera. Inflammation involves infiltration by neutrophils with fibrino-purulent exudation.

Treatment

Management of peritonitis often involves broad-spectrum antibiotics administered intravenously or directly into the peritoneum, covering both Gram-positive and Gram-negative organisms. Common antibiotics include cefoxitin, cefotetan, ampicillin/sulbactam, piperacillin/tazobactam, carbapenems, and moxifloxacin.

Surgical intervention (laparotomy) is typically required to look at and lavage the peritoneum and correct any anatomical damage, except in cases of spontaneous bacterial peritonitis, which may be treated initially with antibiotics.

Prognosis

If treated promptly and effectively, the prognosis for peritonitis is generally good, with a mortality rate of less than 10% in otherwise healthy individuals. However, the mortality rate rises significantly in cases involving sepsis or underlying renal insufficiency.

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Self-assessment MCQs (single best answer)

What is the main clinical manifestation of peritonitis?

Which diagnostic sign involves less pain on pressing the abdomen and more pain on releasing the hand abruptly?

What can sequestration of fluids and electrolytes during peritonitis lead to?

Which of the following is a non-infectious cause of peritonitis?

What imaging techniques can be helpful in diagnosing peritonitis?

What is the initial appearance of the exudate in peritonitis?

Which antibiotic is commonly used in the treatment of peritonitis?

What is a possible complication of peritonitis that involves multiple organs?

What is a common risk factor for peritonitis?

What is the mortality rate for peritonitis in healthy individuals if treated promptly?