What is Chilaidi sign, how can it be distinguished from pneumoperitoneum on imaging, and what is the recommended management?

Chilaiditi Sign: Definition, Imaging Differentiation, and Management

Definition and Clinical Presentation

Chilaiditi sign is a radiographic finding of bowel (colon or small intestine) interposed between the liver and right hemidiaphragm, appearing as radiolucency in the subdiaphragmatic space; when this anatomical variant becomes symptomatic with abdominal pain, nausea, vomiting, constipation, or bloating, it is termed Chilaiditi syndrome. 1, 2

• The prevalence is rare, accounting for only 0.25–0.28% of all abdominal imaging worldwide 1
• Most patients with Chilaiditi sign remain asymptomatic throughout their lifetime 3
• Predisposing factors include colonic elongation, laxity of colonic and hepatic suspensory ligaments, chronic constipation, and colonic dysmotility 2, 4

Critical Imaging Differentiation from Pneumoperitoneum

The key to distinguishing Chilaiditi sign from true pneumoperitoneum—which requires emergency surgical exploration—is identifying bowel wall markings (haustra) within the subdiaphragmatic lucency on plain radiographs or confirming colonic interposition on CT scan. 1, 2

Plain Radiograph Features

• Chilaiditi sign shows air-filled bowel with visible haustra or bowel wall markings between the liver and diaphragm 1
• True pneumoperitoneum presents as free air without bowel wall markings, typically outlining both sides of the bowel wall 5
• Upright or lateral decubitus chest radiographs can detect free air but have limited ability to characterize its source 5

CT Imaging—The Definitive Modality

Contrast-enhanced CT scan is the gold standard for differentiating Chilaiditi sign from pneumoperitoneum, providing >90% accuracy in identifying the anatomical relationship and excluding perforation. 6, 7

• CT definitively demonstrates colonic loop positioned between the right hemidiaphragm and liver, confirming pseudo-pneumoperitoneum 1, 2
• Absence of abdominal free fluid, peritoneal enhancement, or extraluminal air confirms isolated colonic interposition 1
• CT also identifies complications such as bowel obstruction, ischemia, or associated colonic pseudo-obstruction 8, 3

Clinical Assessment Algorithm

Immediate Evaluation

• Assess for peritonitis by checking for diffuse abdominal tenderness, guarding, rigidity, and rebound tenderness—these findings indicate surgical emergency regardless of imaging appearance 6
• Evaluate vital signs for fever, tachycardia, or hypotension suggesting perforation or ischemia 6
• Obtain laboratory markers including white blood cell count, lactate, C-reactive protein, and procalcitonin to assess for inflammatory response 6, 9

Imaging Pathway

• If hemodynamically unstable or peritonitis is present, proceed directly to emergency surgical exploration without awaiting CT imaging 6
• For stable patients without peritoneal signs, obtain contrast-enhanced CT abdomen/pelvis immediately to definitively characterize the subdiaphragmatic lucency 6, 7
• Plain radiographs alone are insufficient to exclude perforation or characterize the etiology of subdiaphragmatic air 6, 7

Management Recommendations

Conservative Management (First-Line for Chilaiditi Syndrome)

Conservative treatment is the treatment of choice for patients with Chilaiditi sign or Chilaiditi syndrome who are hemodynamically stable without peritonitis. 2, 8

• Bowel rest (NPO status), intravenous hydration, stool softeners, enemas, and laxatives constitute the standard conservative approach 8, 3
• Nasogastric decompression may be added if associated with colonic pseudo-obstruction or significant distension 8, 3
• Serial clinical examinations every 4–6 hours to monitor for deterioration 7
• Most patients improve clinically with resolution of symptoms and colonic distension 8, 3

Indications for Surgical Intervention

Surgical treatment is indicated when signs of bowel obstruction, ischemia, or perforation develop, or for recurrent symptomatic Chilaiditi syndrome refractory to conservative management. 2, 3

• Presence of peritonitis, hemodynamic instability, or free intraperitoneal air with fluid collections mandates immediate operative exploration 6, 9
• Progressive bowel obstruction with failure of conservative management after 48–72 hours requires surgical evaluation 7, 3
• Recurrent episodes causing significant morbidity may warrant elective surgical fixation 2

Critical Pitfalls to Avoid

• Misdiagnosing Chilaiditi sign as pneumoperitoneum leads to unnecessary exploratory laparotomies—thorough physical examination and CT imaging prevent this error 1, 2
• The presence of subdiaphragmatic air does not automatically mandate urgent surgery; management must be guided by clinical status 6
• Plain radiographs showing air under the diaphragm have a 92% positive predictive value for perforation during diagnostic procedures but only 45% during therapeutic procedures, emphasizing the need for clinical correlation 9
• Awareness of Chilaiditi syndrome reduces misdiagnosed surgical emergencies and avoids high-risk colonoscopies in patients with known colonic interposition 2
• Ultrasound can be useful for diagnosis and follow-up, showing an intestinal loop between the anterior liver surface and diaphragm 4