Abdominal compartment syndrome is a disease defined by the presence of new end-organ dysfunction secondary to elevated intra-abdominal pressure. Radiological diagnosis is difficult and usually suggested when a collection of imaging findings are present in the appropriate clinical setting or if the signs on sequential imaging studies are seen to progress. Diagnosis is usually clinically supported by elevated intravesicular pressure which closely parallels intra-abdominal compartment pressure.
On this page:
Terminology
Abdominal compartment syndrome is formally defined as a persistently elevated intra-abdominal pressure >20 mmHg with concomitant organ dysfunction or failure 10. Abdominal perfusion pressure (APP) is a supplementary measurement, with values of <60 mmHg concerning for compromised organ perfusion.
Pathologically elevated intra-abdominal compartment pressures >12 mmHg define intra-abdominal hypertension (IAH), which is further subdivided into four grades based on the degree of elevation.
Clinical presentation
Patients present with one or many organs failing due to the elevated pressure in the abdomen having direct or indirect effects on the major body systems. Most patients will have abdominal distension. Patients often have multifactorial diseases and injuries, and abdominal compartment syndrome is particularly associated with:
hypovolaemic shock
multiorgan dysfunction syndrome (MODS)
Typically, the severely ill patient is in the intensive care unit (ICU) and clinically presents with massive abdominal distension, anuria, or progressive oliguria despite adequate cardiac output and/or increasingly difficult mechanical ventilation.
Pathology
Aetiology
The elevated intra-abdominal pressure in abdominal compartment syndrome has numerous causes which can be subdivided accordingly:
-
primary (abdominopelvic disease or injury)
-
trauma
high-grade liver trauma
penetrating abdominopelvic trauma
-
surgery
abdominal surgery in obese patients
post-operative haemoperitoneum
abdominal packing for bleeding
-
-
secondary (disease or injury outside the abdomen and pelvis)
Radiographic features
The ratio of maximal anteroposterior to transverse abdominal diameter (>0.8) and the peritoneal to abdominal height ratio (PAR ≥0.52) in CT seem to be statistically associated with elevated intra-abdominal pressure in critically ill patients 6. Several other overlapping CT and sonographic signs may support the diagnosis, but none are considered sensitive or specific for abdominal compartment syndrome 2:
rounded appearance of the abdominal wall (round belly sign 4): a product of the ratios noted above
flattened inferior vena cava and renal veins
displacement of solid abdominal viscera
mosaic liver perfusion
increased bowel and gastric wall thickening and enhancement
gastric distension
pathological intra-abdominal fluids (e.g. ascites, haematoma, haemoperitoneum, pancreatic fluid collection) 6
increase in ascites over subsequent scans
bilateral inguinal herniation
pulmonary basal consolidation, collapse and/or pleural effusion
dense infiltration of the retroperitoneum out of proportion to peritoneal disease 5
Ultrasound
reduced diastolic flow in portal, hepatic, and/or renal veins
Treatment and prognosis
Mortality is high in abdominal compartment syndrome, in the range of 60-70% 2. Treatment of abdominal compartment syndrome requires restoration of the perfusion gradient across the abdomen, and broadly involves four approaches:
-
removal of intraperitoneal collections and intraluminal bowel contents 8
paracentesis of ascites or haemoperitoneum, if present
gastric decompression with an orogastric tube
-
addressing factors decreasing abdominal wall compliance
optimisation of analgesia and sedation
-
optimise fluid status
fluids, diuresis or dialysis to achieve euvolemia 9
surgical management with decompressive laparotomy
Complications
renal failure
respiratory failure causing hypercapnia and respiratory acidosis from reduced diaphragmatic efficiency and resulting compressive atelectasis
heart failure from reduced cardiac output and decreased venous return