Barium swallow X-ray in bowel obstruction

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Author: Mikael Häggström [notes 1]

Projectional radiography ("X-ray") with peroral intake of barium can determine whether a bowel obstruction is partial or incomplete, and may give clues to the cause.[1]



After a CT in abdominal pain indicates bowel obstruction, but otherwise inconclusive.[1]

Endpoint and chronology

Imaging is generally made until the contrast reaches the large colon (if small bowel obstruction is suspected). The first image may be taken at 2 hours after peroral contrast intake.



On abdominal X-rays, the small intestine is considered to be abnormally dilated when the diameter exceeds 3 cm.[2][3] This number accounts for an expected geometric magnification in radiography, where the projection on the detector becomes larger than the actual organ, with a factor that may be between 1.05 and 1.40.[4]

Distension on CT[5][6]
Mild 2.5–2.9 cm
Moderate 3-4 cm
Severe >4 cm

The exact geometric magnification of X-rays is generally not known, however, leaving the options:

  • If a previous CT has been made, adjust the sizes by fixed reference point such as the width of a lumbar vertebra:
    Actual width ≈ Width in X-ray / (Width of vertebra on X-ray) x (Width of same vertebra on CT)
Yet, this fully corrects the magnification only if the target structure and the reference point are at the same depth.
  • Reporting a "roughly estimated" diameter by dividing the measured intestinal diameter in the image and dividing it by a rather arbitrary factor of 1.2. However, this confers a false impression of certainty.
  • Reporting a qualitative diameter of the intestine, which may be on a mild-moderate-severe scale. However, the measured diameter still needs to be adjusted for geometric magnification in order to be compared to numbers in the table at right.
Transit time

Small intestinal transit time can generally be described as delayed if exceeding 6 hours from oral contrast intake to presence in the colon.[7]


Should include:

  • Time since intake of contrast.
  • Any distension of the intestines (see section above)
  • The most distal part reached by the contrast.

If contrast hasn't reached the large intestine already, a Swedish practice[8] is to also state when the next image will be taken unless otherwise decided by the referring clinician. The frequency of further imaging depends on the progress, interval until repeat images are often 4-8 and then 6-10 hours, possibly later if overnight.[8]

See also: General notes on reporting


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.


  1. 1.0 1.1 Thompson JS (2002). "Contrast radiography and intestinal obstruction. ". Ann Surg 236 (1): 7-8. PMID 12131079. PMC: 1422542. Archived from the original. . 
  2. Ali Nawaz Khan (2016-09-22). Small-Bowel Obstruction Imaging. Medscape. Retrieved on 2017-02-07.
  3. . Abdominal X-ray - Abnormal bowel gas pattern. Retrieved on 2017-02-07.
  4. Estimated from radiographs of the chest and lumbar vertebral colon: M Sandborg, D R Dance, and G Alm Carlsson. Implementation of unsharpness and noise into the model of the imaging system: Applications to chest and lumbar spine screen-film radiography. Faculty of Health Sciences, Linköping University. Report 90. Jan. 1999. ISRN: LIU-RAD-R-090
  5. Kuang, Lian-qin; Zhao, Da-wei; Cheng, Cheng; Wang, Yi (2016). "Prediction of Small Bowel Obstruction Caused by Bezoars Using Risk Factor Categories on Multidetector Computed Tomographic Findings ". BioMed Research International 2016: 1–9. doi:10.1155/2016/6569103. ISSN 2314-6133. 
  6. Jacobs, S.L.; Rozenblit, A.; Ricci, Z.; Roberts, J.; Milikow, D.; Chernyak, V.; Wolf, E. (2007). "Small bowel faeces sign in patients without small bowel obstruction ". Clinical Radiology 62 (4): 353–357. doi:10.1016/j.crad.2006.11.007. ISSN 00099260. 
  7. Szarka, Lawrence A.; Camilleri, Michael (2012). "Methods for the Assessment of Small-Bowel and Colonic Transit ". Seminars in Nuclear Medicine 42 (2): 113–123. doi:10.1053/j.semnuclmed.2011.10.004. ISSN 00012998. 
  8. 8.0 8.1 NU Hospital Group, Sweden