In the first image, we see the jejunum is dilated at 4.99cm. Normal small bowel thickness is 2.5cm or less. We can identify that this is jejunum by the presence of plicae circularis. Differentiating between large and small bowel on ultrasound can be a challenge, especially when there is pathology involved. Large bowel has haustra which look like creases in the bowel wall. Small bowel does not have haustra. In addition, jejunum can be differentiated from ileum by the presence of plicae circularis which look like fingers pointing into the lumen.

Another finding that is present, but not pictured directly, is thickened bowel wall. Normal bowel wall is made up of 5 layers that are visible on ultrasound: mucosa, muscularis mucosa, submucosa, muscularis propria, and serosa from inside to outside. The mucosa and serosa layers are not always visible. The layers are alternating black and white lines or concentric circles depending on the plane of the ultrasound. The muscularis layers are black, the others are white. Normal bowel wall is less than 4mm thick. This patient, although the measurement is not pictured, had bowel wall that was significantly thickened.

The video clips illustrate a finding called to-and-fro. This is bi-directional sloshing of the bowel contents that occurs because the peristalsis tries to propel the contents forward but is met with an opposite force. One of the clips only demonstrates unilateral flow. This is likely after the transition point in the bowel. This point was not able to be identified on this patient, however it is diagnostic for SBO. The transition point is where the obstruction ends and meets normal bowel. The wall and overall bowel will not be enlarged, and no to-and-fro sign will be noted past this point.

The last finding, which is also not pictured, is the tanga sign. This is triangular shaped anechoic region surrounding the bowel from free fluid and inflammation. The name originates from a triangular shaped bikini bottom.

Okay, so say you found all or some of these findings on ultrasound and the clinical picture sounds like SBO, what’s next?

For true obstruction, general surgery should be consulted to determine the need for operative vs medical management. The patient should be made NPO, and an NG tube should be placed to relieve the pressure in the stomach. 75% of the time, the patient can be managed medically. IV Fluids should be given for hydration. Often, CT abdomen pelvis with IV or oral contrast (if tolerated) can confirm diagnosis and provide more insight on the extent of the obstruction. For our case, the patient was told his diagnosis, but chose to leave against medical advice.

• The identification of haustra vs. plicae circularis helps to differentiate large from small bowel
• Normal small bowel diameter is <2.5cm
• Normal small bowel wall thickness is <4mm
• A sign of small bowel obstruction is to-and-fro movement of fluid. Also look to identify a transition point and tanga sign, although not always easily found.