Small Bowel Obstruction CT Reporting: Checklist and Examples

An obstruction report has to do more than say “ileus.” When mechanical obstruction is present, describe its level, degree, likely cause, and any findings that raise concern for a closed loop or impaired bowel-wall perfusion. This guide focuses on acute small bowel obstruction in adults. Neonatal obstruction is a different clinical population and should be assessed separately.

The ACR generally rates CT abdomen and pelvis with IV contrast as appropriate for suspected acute obstruction; oral contrast may not add diagnostic value in high-grade obstruction and can delay assessment. Report the protocol that was actually performed, and state when absent IV contrast limits evaluation of bowel-wall enhancement. The WSES Bologna guideline focuses on adhesive small bowel obstruction (ASBO); do not extend its cause-specific recommendations to every obstruction.

Clinical safety note: A closed-loop configuration, reduced bowel-wall enhancement, mesenteric edema or fluid, and other signs of ischemia may require urgent clinical assessment. Put these findings in the impression and document communication according to local policy.

Systematic review checklist

• Examination: Indication, surgery or hernia history, IV/oral contrast, coverage, and comparison
• Distribution: Are proximal small-bowel loops dilated with distal decompression? What is the calibre of the colon?
• Degree and level: Describe findings supporting low/high-grade or partial/complete obstruction; identify the transition point and anatomic level.
• Cause: Look for hernia, mass, inflammatory stricture, intussusception, volvulus, bezoar, or a likely adhesive cause after prior surgery. An adhesive band may not be directly visible.
• Closed loop: Describe the configuration, including two transition points, a U- or C-shaped loop, and crowded or twisted mesenteric vessels.
• Bowel wall and mesentery: Assess thickening, reduced enhancement, intramural hemorrhage, mesenteric edema/fluid, pneumatosis, and portal or mesenteric venous gas.
• Associated findings: Free fluid, free air, hernias, masses, stoma/anastomosis, and important alternatives
• Impression: Lead with the transition point, likely cause, and any complication that needs urgent attention.

Complete report framework

Examination: CT abdomen and pelvis [with IV contrast / without IV contrast].
Indication: [Abdominal pain, vomiting, distention; clinical question].
Comparison: [Date / none available].

Technique: [Phase, IV/oral contrast, coverage, and reconstructions]. [Limitation].

Findings: Small bowel loops are [not dilated / dilated; maximum calibre and distribution]. [No transition point / transition point at [anatomic level]]. Proximal bowel is [dilated]; distal bowel is [decompressed]. Appearance supports [partial/low-grade / high-grade / indeterminate] obstruction. Possible cause: [ ]. Closed-loop configuration [absent / describe]. Bowel-wall thickness and enhancement [ ]. Mesentery [ ]. Free fluid/air and associated findings [ ].

Impression:
1. [Small bowel obstruction with level and degree / no obstruction].
2. [Likely cause].
3. [Concern for ischemia, strangulation, closed loop, or perforation; include urgent communication documentation].

Example 1 — partial obstruction, likely adhesive

Fictional case. Adhesions are often not directly visible on CT; prior surgery and exclusion of other causes provide context.

Examination: CT abdomen and pelvis with IV contrast.
Indication: Abdominal pain and vomiting; prior laparotomy.
Comparison: None available.

Technique: Portal venous phase contrast-enhanced CT abdomen and pelvis; coronal and sagittal reformations reviewed.

Findings: Mid and distal small-bowel loops are dilated up to 3.4 cm. There is an abrupt transition point in the right lower quadrant near the prior operative bed, with dilated proximal loops and decompressed distal ileum and colon. No mass, hernia, or focal mural thickening at this level. Bowel-wall enhancement is preserved. No closed-loop configuration, pneumatosis, mesenteric venous gas, or free air. Small volume pelvic free fluid.

Impression:
1. Small bowel obstruction with a right lower quadrant transition point; the appearance and surgical history are compatible with an adhesive cause.
2. No definite CT finding of bowel ischemia or closed-loop obstruction.

Do not assign a partial degree from one sign alone; consider the transition point, distal gas, and luminal contents together. Describe an adhesive cause as likely rather than certain.

Example 2 — closed loop with concern for ischemia

Fictional case. Findings with urgent implications lead the impression.

Examination: CT abdomen and pelvis with IV contrast.
Indication: Worsening abdominal pain and vomiting.
Comparison: None available.

Technique: Portal venous phase contrast-enhanced CT abdomen and pelvis. Diagnostic image quality.

Findings: A fluid- and gas-distended U-shaped small-bowel loop is present in the left lower abdomen and pelvis. Two closely spaced transition points and twisting of the mesenteric vessels suggest closed-loop obstruction. The involved bowel wall shows heterogeneous and reduced enhancement, with mesenteric edema and a moderate volume of free fluid. No pneumatosis or portal venous gas.

Impression:
1. Closed-loop small bowel obstruction with reduced mural enhancement, mesenteric edema, and free fluid, concerning for ischemia/strangulation and requiring urgent clinical assessment.
2. Findings were communicated by telephone at [time] to [clinician/service].

Complete the bracketed communication fields according to institutional documentation policy. Do not leave concern for ischemia only in the findings section; record the critical-result communication and time in the report or designated system.

Limited examinations, uncertainty, and common errors

Without IV contrast, bowel-wall perfusion may be difficult to assess; state this limitation, especially when ischemia is a concern. Motion, lack of thin-section reconstructions, or diffuse fluid and edema may obscure the transition point. Intermittent or low-grade obstruction may not produce dilatation or a visible transition during the examination.

“Ileus” is not a synonym for mechanical obstruction. If there is no transition point or proximal-to-distal calibre change supporting mechanical obstruction, do not invent one. Free fluid alone does not diagnose ischemia; interpret it with enhancement, mesenteric findings, and clinical context. Prior surgery makes adhesions plausible, but does not remove the need to assess for hernia, mass, and other causes.

Quick pre-sign-off check

Is the obstruction mechanical? Are the transition point and bowel segment stated? Was a cause considered? Were a closed loop and bowel-wall perfusion assessed? Are urgent findings prominent in the impression and is communication documented?

References

• American College of Radiology. ACR Appropriateness Criteria®: Suspected Small-Bowel Obstruction (Revised 2019) — imaging approach for acute and low-grade obstruction. Guideline (opens in a new tab)
• ten Broek RPG, et al. Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the World Society of Emergency Surgery ASBO working group. World Journal of Emergency Surgery. 2018;13:24. Article (opens in a new tab)

Educational note: Cases are fictional and contain no patient data. This article does not replace clinical assessment, current protocols, or specialist radiology/surgical judgment.