Peritonism

Peritonism is the set of signs produced by inflammation of the parietal peritoneum: localised tenderness with guarding or rigidity, rebound or percussion tenderness, and pain on coughing or movement. It usually means peritonitis, which in most patients is surgical disease or severe intra-abdominal sepsis.

Mechanism. The parietal peritoneum is supplied by somatic nerves, so inflammation causes sharp, well localised pain and reflex spasm of the overlying abdominal wall muscle. Visceral peritoneum is supplied by autonomic fibres and causes dull, poorly localised pain. Irritants include bacteria, gastric acid, bile, pancreatic enzymes, blood, urine and faeces.

Classification.

• By extent: localised (for example appendicitis, cholecystitis, diverticulitis) or generalised.
• By mechanism: primary or spontaneous (no visceral breach, such as spontaneous bacterial peritonitis in cirrhosis or peritoneal dialysis peritonitis), secondary (perforation, ischaemia, leak or inflammation of a viscus), and tertiary (persistent or recurrent after treated secondary peritonitis).
• By irritant: bacterial, chemical (gastric acid, bile, pancreatic enzymes), blood, urine.

Key distinctions. Rigidity is board-like, involuntary and persists when the patient is distracted. Voluntary guarding relaxes with distraction.

Percussion tenderness and pain on coughing are more reliable than rebound tenderness, which is painful and poorly specific.

Signs can be minimal or absent in older adults, immunosuppressed patients, those taking corticosteroids, diabetes, cirrhosis with ascites, pregnancy, paraplegia, sedation and young children, so a soft abdomen does not exclude peritonitis.

Generalised peritonitis with shock is an indication for theatre without waiting for imaging.

History.

• Onset and course: sudden severe pain (perforation), gradual migrating pain (appendicitis, from periumbilical to the right iliac fossa), colicky pain progressing to constant pain (obstruction with strangulation).
• Site, radiation (shoulder tip for diaphragmatic irritation, back for pancreatic or aortic pathology), vomiting, bowel habit and flatus, fever and rigors, urinary symptoms, haematemesis or melaena.
• Gynaecological: last menstrual period, contraception, vaginal discharge or bleeding, recent delivery, termination or instrumentation.
• Previous surgery, hernia, trauma, recent endoscopy or colonoscopy, ascites or cirrhosis, peritoneal dialysis, inflammatory bowel disease, diverticular disease, gallstones.
• Drugs: NSAIDs, corticosteroids, anticoagulants, immunosuppressants, opioids, recent antibiotics.
• Region specific points: typhoid fever in the second to third week of illness, tuberculosis, amoebic liver abscess, schistosomiasis with portal hypertension, travel.

Examination.

• General: lies still, shallow breathing, dry mucosa, temperature, heart rate, blood pressure, capillary refill, mottling, urine output, mental state, and shock index (heart rate divided by systolic pressure; over 1.0 is high risk).
• Abdomen: inspection for movement with respiration, distension and scars. Palpate gently, starting away from the pain. Test cough tenderness and percussion tenderness first, then rebound. Note rigidity, guarding, masses, bowel sounds (absent late), and hernial orifices. Rovsing, psoas and obturator signs, and Murphy sign, support localised causes.
• Rectal examination (tenderness, mass, blood, faecal impaction), pelvic examination in women, testes and groin, chest, spine and flanks.

Red flags.

• Rigidity, absent bowel sounds, fixed tenderness over a hernia, or rebound with systemic upset.
• Systolic pressure under 90 mmHg, heart rate over 120 beats/min, respiratory rate over 25 breaths/min, new confusion, temperature over 38.3 °C or under 36 °C, urine output under 0.5 mL/kg/hour.
• Lactate over 2 mmol/L (over 4 mmol/L is high risk), pain out of proportion to signs, blood in the stool or vomit, pulsatile mass.
• Pregnancy or recent delivery, neutropenia, anticoagulation, previous aortic graft.

Special groups.

• Pregnancy: the appendix is displaced upward, so pain may be higher or in the flank. Use ultrasound or MRI, and do not delay surgery for a surgical cause because maternal sepsis is the main threat to the foetus. Left lateral tilt after 20 weeks.
• Children: infants lie still and cry on examination. Appendicitis, intussusception and primary peritonitis are the main causes.
• Older adults and immunosuppressed patients: confusion or collapse may be the only presentation. Perforated diverticulitis and ischaemic bowel are common.
• Peritoneal dialysis: cloudy effluent with abdominal pain is peritonitis until proved otherwise.

Upper abdomen.

• Perforated peptic ulcer, gastric perforation from cancer, Boerhaave syndrome.
• Acute cholecystitis with perforation, ascending cholangitis, acute pancreatitis (chemical peritonitis), ruptured liver abscess, ruptured hepatocellular carcinoma, spontaneous splenic rupture.

Lower and generalised abdomen.

• Perforated appendicitis, perforated diverticulitis, perforated colorectal cancer, stercoral perforation, toxic megacolon.
• Mesenteric ischaemia with infarction, strangulated bowel obstruction, volvulus, strangulated hernia, Meckel diverticulitis, Crohn disease with perforation, anastomotic leak.
• Typhoid ileal perforation, tuberculous peritonitis, amoebic colitis with perforation, abdominal trauma.

Pelvic. Ruptured ectopic pregnancy, ovarian torsion, ruptured ovarian cyst, pelvic inflammatory disease with tubo-ovarian abscess, endometritis, septic abortion.

Vascular. Ruptured abdominal aortic aneurysm, aortic dissection, mesenteric venous thrombosis, ruptured visceral artery aneurysm.

Primary peritonitis. Spontaneous bacterial peritonitis, peritoneal dialysis peritonitis, primary peritonitis in nephrotic syndrome in children.

Mimics (abdominal wall rigidity or pain without peritoneal inflammation). Diabetic ketoacidosis, right lower lobe pneumonia, myocardial infarction, pulmonary embolism, herpes zoster, rectus sheath haematoma, acute porphyria, lead poisoning, sickle cell crisis, adrenal crisis, familial Mediterranean fever, black widow spider bite, acute urinary retention, renal colic.

Step 1. Decide whether the patient needs theatre at once. Generalised peritonitis with shock goes to theatre with resuscitation running, and imaging is skipped if it would delay surgery.

Step 2. First line tests:

• Venous blood gas with lactate, full blood count, CRP, urea, creatinine, electrolytes, glucose and liver tests.
• Lipase (over 3 times the upper limit of normal supports pancreatitis).
• Coagulation, group and crossmatch, blood cultures and urinalysis.
• Pregnancy test in women of reproductive age.
• ECG and troponin in older patients.
• Malaria testing in endemic or travel settings.

Step 3. Imaging.

• Erect chest radiograph (or left lateral decubitus film if the patient cannot stand) shows free gas in about 70 to 80% of upper gastrointestinal perforations, less in colonic and small bowel perforation. A normal film does not exclude perforation.
• CT abdomen and pelvis with intravenous contrast is the most sensitive test for cause (about 90 to 95%) and shows free gas, fat stranding, collections, bowel wall change, ischaemia and vascular catastrophe. Oral contrast is not needed.
• Ultrasound for appendicitis (children, pregnancy), gallbladder and biliary disease, pelvic pathology and free fluid. Extended focused assessment with sonography in trauma.
• Diagnostic laparoscopy when imaging is unclear and the patient is unwell.

Step 4. Peritoneal fluid.

• Ascites with abdominal pain, fever or deterioration: diagnostic paracentesis before antibiotics. Neutrophils 250 cells/mm3 or more supports spontaneous bacterial peritonitis. Culture in blood culture bottles at the bedside. A neutrophil count under 250 cells/mm3 with turbid fluid, or total protein over 10 g/L with a raised neutrophil count in a polymicrobial sample, suggests secondary peritonitis.
• Peritoneal dialysis effluent: white cells over 100 cells/mm3 after a dwell of at least 2 hours, with more than 50% neutrophils, plus culture.

Limitations. Lactate and white cell count can be normal early. CT contrast needs care in kidney impairment but should not be withheld from a patient with suspected catastrophe. Free gas can persist after recent laparoscopy or laparotomy. Opioid analgesia does not mask diagnosis when examination is repeated.

Resuscitation.

• Oxygen to saturation 94 to 98%, two large bore cannulae, continuous monitoring, urinary catheter, nil by mouth, and a nasogastric tube if vomiting or distended.
• Balanced crystalloid 500 mL boluses over 15 minutes, with reassessment after each bolus. Evidence for a fixed 30 mL/kg volume is limited.
• Noradrenaline 0.05 to 0.5 micrograms/kg/min IV titrated to a mean arterial pressure of 65 mmHg or more when hypotension persists after fluid; monitor arterial pressure and limb perfusion; doses over 0.5 micrograms/kg/min need critical care direction.
• Correct coagulopathy and give red cells for haemoglobin under 70 g/L (aim 70 to 90 g/L).

Analgesia and antiemetic (early analgesia does not obscure diagnosis).

• Paracetamol 1 g IV every 6 hours; maximum 4 g daily (3 g daily if weight under 50 kg, malnutrition, alcohol excess or liver disease); monitor liver tests with prolonged use.
• Morphine 0.05 to 0.1 mg/kg IV in 2 mg boluses every 5 minutes titrated to effect; maximum 10 mg before reassessment. Monitor respiratory rate and sedation with naloxone available.
• Reduce doses in older adults, shock and kidney impairment (use fentanyl 25 to 50 micrograms IV instead). Avoid NSAIDs.
• Ondansetron 4 mg IV slowly every 8 hours; maximum 16 mg daily (8 mg daily in severe liver impairment); check QTc and electrolytes.

Antimicrobials (within 1 hour in shock, otherwise within 3 hours of recognition). Take blood cultures first when this causes no more than 45 minutes of delay.

• Community acquired secondary peritonitis: ceftriaxone 2 g IV once daily (maximum 4 g daily) plus metronidazole 500 mg IV every 8 hours (maximum 1.5 g daily); monitor creatinine, liver tests and diarrhoea, and watch for neuropathy with prolonged metronidazole; reduce metronidazole in severe liver impairment.
• Hospital acquired, severe, or immunocompromised: piperacillin with tazobactam 4.5 g IV every 6 hours (maximum 18 g piperacillin daily).
• Reduce to 4.5 g every 8 hours for CrCl 20 to 40 mL/min and every 12 hours for CrCl under 20 mL/min. Monitor creatinine and full blood count.
• Risk of resistant organisms (previous extended spectrum beta lactamase isolation, recent broad spectrum antibiotics, prolonged admission): meropenem 1 g IV every 8 hours.
• Renal dosing: 1 g every 12 hours for CrCl 26 to 50 mL/min; 500 mg every 12 hours for CrCl 10 to 25 mL/min; 500 mg every 24 hours under 10 mL/min. Monitor seizures, creatinine and Clostridioides difficile infection.
• Severe penicillin allergy: ciprofloxacin 400 mg IV every 12 hours (maximum 1.2 g daily) plus metronidazole 500 mg IV every 8 hours (maximum 1.5 g daily); monitor QTc, tendon pain and glucose; reduce the dose in kidney impairment.
• Duration: after adequate source control, 4 days is usually enough (4 to 7 days); longer for undrained collections, ongoing sepsis or tertiary peritonitis, with cultures and imaging directing review.
• Typhoid perforation: ceftriaxone 2 g IV once daily (children 80 mg/kg once daily, maximum 4 g) plus metronidazole 500 mg IV every 8 hours for 10 to 14 days after surgical repair, adjusted to local resistance and culture.
• Spontaneous bacterial peritonitis: ceftriaxone 2 g IV once daily for 5 days (maximum 4 g daily), plus albumin 1.5 g/kg IV at diagnosis (maximum 100 g) and 1 g/kg IV (maximum 100 g) on day 3, which reduces kidney failure and mortality.
• Stop diuretics and NSAIDs during the episode. Monitor creatinine and repeat paracentesis at 48 hours (a fall in neutrophils of over 25% shows response).
• Secondary prophylaxis: ciprofloxacin 500 mg orally once daily long term. Monitor QTc, tendon pain and Clostridioides difficile infection. Reduce to 250 mg daily for CrCl under 30 mL/min.
• Peritoneal dialysis peritonitis: intraperitoneal antibiotics chosen by the renal unit, started after sending effluent for culture.

Source control. Laparotomy or laparoscopy within hours of resuscitation for generalised peritonitis, perforation, ischaemia, leak or necrosis. Percutaneous drainage for localised collections. Remove infected devices.

• Perforated peptic ulcer: omental patch repair or surgical closure, omeprazole 40 mg IV once daily then 40 mg orally once daily for 4 to 8 weeks (monitor magnesium and sodium with long courses), and Helicobacter pylori testing and eradication.
• Non-operative management (antibiotics, nil by mouth, nasogastric drainage, serial examination) is used only for selected localised conditions such as uncomplicated diverticular abscess under 4 cm, with surgical review every 4 to 6 hours.

Thromboprophylaxis. Enoxaparin 40 mg subcutaneously once daily from admission when bleeding risk allows (20 mg daily if CrCl 15 to 30 mL/min; unfractionated heparin 5000 units subcutaneously every 8 to 12 hours if CrCl under 15 mL/min).

Monitoring. Observations every 15 minutes at first, then hourly; hourly urine output; lactate every 2 hours until falling; creatinine, electrolytes and glucose every 6 hours; repeat abdominal examination every 4 to 6 hours; and daily CRP and white cell count.

Referral and escalation. General surgery at first recognition. Critical care for shock, lactate over 4 mmol/L or organ support. Interventional radiology for drainage. Gynaecology for pelvic causes. Hepatology for spontaneous bacterial peritonitis. Nephrology for peritoneal dialysis. Infectious diseases for resistant organisms or typhoid.

Admission criteria. All patients with peritonism are admitted under surgical care. Discharge is not appropriate until a surgical cause is excluded.

Discharge and safety netting. Discharge only after a surgical review, a clear diagnosis, pain controlled on oral treatment, eating and drinking, and a follow up plan. Patients are told to return for worsening pain, vomiting, fever, abdominal swelling, inability to pass stool or flatus, dizziness or black stool.