Etiology
- Pathologic intra-abdominal hypertension (>20mmHg) which leads to organ dysfunction, can be due to primary or secondary sources
Primary – Intra-abdominal disease or injury
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- Trauma
- Surgery – abdominal packing, post-operative haemoperitoneum
- Pancreatitis
- Ascites
- Pneumoperitoneum
- Ruptured abdominal aortic aneurysm (AAA)
Secondary – extra abdominal disease or injury
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- Splanchnic reperfusion after massive resuscitation
- Burns
- Sepsis
Pathophysiology
- Tissue fluid within the peritoneum and retroperitoneal space accumulates in such large volumes until the abdomen can no longer expand – leads to rise in intra-abdominal pressure
- Initially causes intra-abdominal hypertension (>12mmHg)
- ACS is defined as sustained intra-abdominal pressure above 20mmHg with new onset organ dysfunction
Pathology
- Underlying cause is due to increased in capillary permeability due to the systemic inflammatory response syndrome (SIRS) – causes fluid to leak out of capillary beds into the interstitial space
- Abdominal organs begin to collapse under the increased pressure – eventually causes compromise of the cardiovascular and respiratory systems
Clinical features
- Abdominal distension – may be tense and tender
- Difficulty breathing, wheezing, cyanosis
- Decreased urine output
Complications
- Renal failure – due to decreased renal perfusion
- Respiratory distress and failure
- Bowel ischemia
- Increased intracranial pressure
- Decreased cardiac output and decreased venous return
Investigations
- Bladder pressure – gold standard for measuring intra-abdominal pressure
- Measured with Foley’s catheter
- Lab studies – CBC, amylase, PT + aPTT, urinalysis, ABGs
- Abdominal CT
- Round belly sign – abdominal distension with an increased ratio of anteroposterior to transverse abdominal diameter (>0.8)
- Elevated diaphragm
- Flattened inferior vena cava
- Displacement of solid abdominal viscera
Treatment
- Removal of intraperitoneal collections and intraluminal bowel contents
- Paracentesis – for ascits or hemoperitoneum
- Gastric decompression
- Analgesia and sedation
- Optimise fluid status
- Surgical management
- Decompressive laparotomy – mortality is 70% if this is delayed