Slide 1: These two middle-aged patients are in the ER for abdominal pain. Which patient requires a surgical consult? Two CT scans are shown.

Slide 2: Which patient requires a surgical consult. Top CT scan. This patient has a left inguinal hernia with a loop of colon in the hernia sac. Notice the non-thickened appearance of those loops and lack of surrounding ascites. This was an uncomplicated left inguinal hernia. Bottom CT scan. This patients has a right inguinal hernia containing an unhappy looking small bowel loop. The bowel wall is thickened! This patient likely has a strangulated right inguinal hernia and needs a surgical consult.

Slide 3: What distinguishes an incarcerated and strangulated hernia? When a patient presents with a hernia, clinicians should try to reduce the hernia at the bedside. Hernia that cannot be reduced are incarcerated. Often, incarcerated hernias have normal perfusions and don’t require emergent surgery. Incarcerated hernia is clinical diagnosis!

Flow chart. Hernia. Yes. Uncomplicated versus reducible. No. reducible versus incarcerated. Incarcerated. Yes. Strangulated versus bowel ischemia. Strangulated. Yes. Consult surgery. Bowel ischemia. Yes. Pain/erythema, imaging findings: thickening, ascites, obstruction, pneumatosis. Lactic acidosis. Incarcerated. No. Not strangulated.

If blood flow is reduced to the herniated loop, resulting in bowel ischemia, this is called strangulation and is a surgical emergency! Incarcerated hernias are at higher risk for strangulation (2.6 to 4.5% compared to less than 1% for all hernias).

Slide 4: What are radiographic signs of hernia strangulation? Remember to order this CT with contrast to better visualize the appearance and enhancement of the bowel wall. As blood flow becomes restricted in strangulated bowel, you will see thickening of the bowel wall as the loop becomes inflamed. The hernia loop will often become obstructed, with thin transition points entering and exiting the hernia neck as the bowel is compressed at the entrance to the hernia sac. Notice the small waist of bowel as it enters the hernia sac between dilated loops.

Slide 5: Additional radiographic signs of hernia strangulation. Due to edema, and restricted venous outflow, there will often be ascites around the entrapped bowl loops. This can be one of the earliest signs of strangulation. As strangulation progresses, findings may include hypoattenuation of the entrapped bowel wall and pneumatosis as the bowel dies.

CT showing pneumatosis/hypoattenuation versus normal bowel. Note – the bowel in these two lower images is NOT herniated.

Slide 6: Let’s review! Signs of strangulation should prompt urgent surgical consultation. Outpatient repair. Physical exam. Reducible at bedside. CT scan. Nice thin wall. No ascites. No obstruction. Labs. Unremarkable. Urgent surgical consult. Any one finding is sufficient. Physical exam. Incarcerated plus significant tenderness and/or overlying erythema. CT scan. Thickened wall, ascites, pneumatosis, closed loop obstruction. Labs. Increased lactic acid. Poor prognostic marker but not sensitive.


  • Leubner KD, Chop WM Jr, Ewigman B, Loven B, Park MK. Clinical inquiries. What is the risk of bowel strangulation in an adult with an untreated inguinal hernia? J Fam Pract. 2007 Dec;56(12):1039-41. PMID 18053445.
  • Aguirre DA, Santosa AC, Casola G, Sirlin CB. Abdominal wall hernias: imaging features, complications, and diagnostic pitfalls at multi-detector row CT. Radiographics. 2005 Nov-Dec;25(6):1501-20. PMID 16284131.

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