What does it feel like when the lining of your abdomen catches fire? Not from flame — from bacteria. From gut contents leaking into a space that was never meant to hold them. From a burst appendix. A torn ulcer. A leaking bowel. An infection that finds the one cavity where contamination turns fatal in hours. That is peritonitis. The abdomen is rigid. The pain is everywhere. And the clock is already running.

He was fifty-four. A stomach ulcer he had ignored for months finally ate through the wall of his duodenum. Acid, bile, and bacteria poured into the cavity. Like water through a cracked pipe. Two hours later, his abdomen was board-stiff. So rigid that the doctor could not press in at all. His heart rate was a hundred and thirty. His blood pressure was dropping. His temperature was spiking. Grey. Sweating. Screaming every time anyone touched his belly. Surgery started within the hour. Hole closed. Cavity washed out. He spent nine days in intensive care. He survived. Only because someone spotted peritonitis fast enough to cut before sepsis took hold.

This guide explains peritonitis with the urgency it demands. How the infection starts, what the body does when the peritoneum is breached, what the signs look like, how diagnosis works, and how the right clinical equipment supports the emergency response that peritonitis patients need to survive. Medigear supplies certified diagnostic and monitoring equipment to hospitals and clinics across the UK — because peritonitis caught in time is survivable. Caught late, it is not.

The Peritoneum

The peritoneum is a thin membrane that lines the inside of the abdominal wall and covers the organs within it. It is sterile. Not built to withstand bacteria, acid, bile, or faecal matter. When any of these get in — through a hole, a rupture, or a blood-borne seed — the response is massive. Vessels dilate. Fluid pours in. Immune cells flood. The body tips toward sepsis, organ failure, and death faster than almost any other belly emergency.

Types

Peritonitis is divided into two types. Primary — also called spontaneous bacterial peritonitis — occurs without a hole in the gut. Bacteria reach the cavity via the bloodstream, typically in patients with cirrhosis and fluid buildup. The infected fluid breeds more. Secondary peritonitis — the more common and more dangerous type — follows a breach. Burst appendix. Torn ulcer. Ruptured diverticulum. Leaking surgical joint. Stab wound. Burst gallbladder. Any hole that lets gut contents spill into a space built to stay clean.

Symptoms

The symptoms hit hard and fast. Pain hits first. Diffuse. Constant. Worse with any movement. Patients lie still. Shifting makes it unbearable. The abdomen becomes rigid — the muscles guarding against any pressure. Rebound tenderness — pain that spikes when the hand lifts off — is the classic sign. Fever, fast pulse, nausea, vomiting, and silence from a gut that has shut down. A patient with peritonitis does not look mildly unwell. They look like they are dying. Because they are.

Diagnosis

Diagnosis is clinical first. A rigid belly with rebound in a patient with ulcer history, recent surgery, or trauma points to peritonitis before any scan. Bloods show elevated white cell count, CRP, and lactate, with acidosis. An upright chest film may show free air under the diaphragm — gas that escaped from a hole in the gut. CT with contrast is the best scan, showing fluid, air, the hole, and any abscess. In a crashing patient, treatment starts before the scan finishes.

Linked Guides

For hospitals managing peritonitis emergencies alongside broader care, our guide to vital signs monitor features covers the continuous heart rate, blood pressure, and respiratory monitoring that peritonitis patients need from the moment of diagnosis through surgery and into ICU recovery. Our guide to portable vs stationary X-ray machines covers the chest and abdominal imaging that confirms perforation and guides surgical planning — because a portable X-ray in resus reaches the patient who is too unstable to travel to radiology.

Surgery

Surgery is the treatment for secondary peritonitis. Find the source. Close the hole. Remove the damage. Drain the abscess. Wash out the cavity with litres of warm saline. Not delicate. Urgent. Often dirty. Damage control, not perfection. A second look, one to two days later, checks for missed leaks and damage that the first wash could not see.

Antibiotics

Antibiotics start before surgery — broad-spectrum cover targeting gut organisms, including gram-negatives and anaerobes. The drugs narrow once cultures come back. But the first dose goes in the moment peritonitis is thought of. Delay raises death rates. Drug in the blood before the surgeon reaches the belly. That order matters.

Fluids

Fluid resuscitation runs alongside everything else. Peritonitis causes massive fluid shifts — litres of plasma leak into the peritoneal cavity, dropping blood volume and blood pressure. IV fluid pushed fast puts back what the cavity took. Too little dries the organs. Too much floods the lungs. Balancing it needs the same second-by-second watching as septic shock demands. Arterial lines. Urine tracking. Lactate trending.

Pain

Pain management in peritonitis is not optional — it is clinical. A patient in severe belly pain cannot breathe right, cannot cooperate, and cannot undergo the handling that surgery demands. Opioids — morphine or fentanyl — are first-line. The old rule that painkillers mask surgical signs is dead in every modern guideline. Treating pain does not hide peritonitis. Ignoring it hides the patient.

ICU

ICU care after peritonitis surgery can last days to weeks. Ventilation. Vasopressors. Antibiotics. Nutrition. Wound care. Repeat scans. Day after day. Abscess. Wound breakdown. Fistula. Gut shutdown. Organ failure. All possible. The patient who arrived with a rigid belly leaves with scars. On the skin and in the memory of hours that changed everything.

Spontaneous Bacterial Peritonitis

Spontaneous bacterial peritonitis in cirrhosis patients carries its own rules. No perforation. No surgery. Diagnosis is made by tapping the fluid and counting the white cells. Treatment is IV antibiotics and albumin. Long-term antibiotics in high-risk patients stop infection before it seeds. Less dramatic than the secondary type. But the death rate demands the same speed.

Prevention

Prevention of secondary peritonitis centres on treating the conditions that cause perforation. Managing ulcers with proton pump inhibitors. Removing an inflamed appendix before it bursts. Treating diverticulitis before it perforates. Ensuring surgical joins are built to heal. And recognising post-operative leak early — because a patient with rising heart rate, falling blood pressure, and new abdominal pain after bowel surgery has a leak until proven otherwise.

Post-Op Leak

Can your team recognise a post-operative leak before peritonitis sets in? A patient with rising pulse, falling pressure, increasing pain, and new fever after bowel surgery has a leak until proven otherwise. Waiting for the CT before acting wastes the hours that early return to the theatre would save. The clinical picture speaks louder than any scan — and the team that listens to it saves the patient; the scan would have been too late.

Emergency Readiness

Does your emergency department have the imaging and monitoring to manage peritonitis from door to theatre? Upright chest film for free air. CT for the perforation site. Multi-parameter monitoring for the crashing patient. Fluid running while the surgeon scrubs. Peritonitis does not allow gaps between departments. It demands a chain — assessment, imaging, drugs, and surgery — linked without a break.

Night Response

What does your facility do when peritonitis arrives at night? Fewer staff. Slower imaging. Longer waits for the theatre. The patient with peritonitis at 3 am needs the same speed as the one at 3pm. If your night pathway is slower, your night patients pay. Audit the out-of-hours response. Time it. Fix the gaps before the next rigid belly arrives in the dark.

Children

Children with peritonitis present differently and deteriorate faster. A child with a burst appendix may not show the rigid abdomen adults display — their abdominal wall is thinner and less muscular. Instead, the child refuses to move, draws up their knees, and cries with any touch. The paediatric version requires a lower imaging threshold and a faster track to surgery than adult protocols allow. A child who looks sick with a belly is a child who needs a scan now — not after the next blood result.

Elderly

Elderly patients with peritonitis carry the highest death rates because their symptoms are muted, their immune response is blunted, and their reserves are thin. A seventy-year-old with a perforated diverticulum may present with mild confusion and a soft abdomen — none of the drama that a younger patient shows. By the time the diagnosis is made, sepsis has already set in. Low threshold. High suspicion. Fast action. That is how elderly peritonitis patients survive — not by waiting for the classic signs that may never come.

Why Choose Medigear

Medigear supplies certified diagnostic and monitoring equipment — including vital signs monitors, multi-parameter monitors, and clinical accessories — to hospitals, emergency departments, and surgical units across the UK. Whether you are equipping a resuscitation bay, upgrading surgical monitoring, or building emergency readiness for abdominal emergencies, our team matches the right tools to your clinical need. Reach out to our team directly for guidance built around the patients whose abdomen is on fire — and the clinicians who race to put it out.

Conclusion

What does it feel like when the abdomen catches fire from the inside? Ask the patient lying rigid on the trolley with a pulse of a hundred and thirty and a belly nobody can press. Ask the surgeon washing litres of contaminated fluid from a cavity that was sterile six hours ago. Ask the ICU team managing the aftermath of a disease that went from stable to critical before the CT was reported. Peritonitis does not wait. It does not warn gently. It burns through the peritoneum and into the bloodstream with a speed that only faster hands can match. Medigear stands alongside surgical and emergency teams with certified monitoring equipment and the honest support that abdominal emergencies demand. Speak to our team today — because the rigid belly at 3am needs the same tools and the same speed as the one at 3pm.

⚠️ This post is for general information only. We do not sell medications or provide prescriptions — Medigear.uk is a medical equipment supplier only.