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Stier et al. Mini-invasive Surg 2020;4:18 I http://dx.doi.org/10.20517/2574-1225.2019.75 Page 9 of 11

It remains undisputed that, in early perioperative complication management, with special regard to the
detection of leaks or stenosis, UGI is the first choice of diagnostic measures. While UE serves as a useful
routine examination in patients presenting with upper GI symptoms, 3D-CT allows additionally a more
detailed evaluation of post-procedural gastric anatomy and its adjacent structures, enabling easier detection
and differentiation of longer-term complications such as sleeve dilatation or thoracic migration [10-14] .
In sleeve dilatation, a tight sleeve diameter at the angulus fold may cause dysphagia, regurgitation and
vomiting after food intake comparable to the symptoms of a hiatal hernia with tight cardia. Thus, thoracic
migration is less frequently associated with pure oesophageal reflux symptoms and heartburn. Functional
SG stenosis may result in pre-stenotic dilatation of the proximal part of the sleeve. In both entities, 3D-
CT imaging is a very useful adjunctive diagnostic tool. It shows the functional anatomy that a highly
experienced bariatric endoscopist also might be able to notice, but 3D-CT represents the anatomy as
examiner-independent, objective imaging.

A further distinct advantage of 3D-CT is the clear depiction of implanted devices (e.g., bands), and their
precise anatomical position, which is not possible with UGI due to the lack of tissue extension during the
examination.

Additionally, in this study, we evaluated and compared the results of UE with those of 3D-CT for the
measurement of the pouch outlet. In contrast, 3D-CT is not the diagnostic tool of choice for that purpose.

In almost all cases, the diameter of the Pouch outlet during 3D-CT appeared smaller than was indicated by
direct measurement during endoscopy (P < 0.001). This may result from the different extension pressures
applied during the respective examinations: whereas, in 3D-CT, the foaming effervescent powder creates
enough pressure to gently distend the gastric wall, direct air inflation via endoscope, positioned directly
above the anastomosis, causes considerably greater distention. Remarkably, therefore, the pouch outlet after
RYGB was significantly underestimated in the examination with 3D-CT.

This is of particular significance in cases of dumping syndrome, a known long-term complication of
RYGB, which is often related to an enlarged pouch outlet. For planned outlet reduction procedures in these
[15]
patients, UE remains the diagnostic tool of choice .

From an economical point of view, the costs of 3D-CT are only slightly higher than those of UGI, with
current costs of 162.50 euro vs. 225 euro, as calculated by the state health insurance point system in
Germany. An additional contrast to the effervescent powder is not necessary for the examination.

3D-CT images reveal three-dimensional information, which is unattainable by alternative examination
methods, and allows precise location of the anatomical structures of the upper GI tract. While shape and
volume measurements of SG may be repeatedly assessed using this method, the optimal volume of SG or pouch
[9]
[10]
in RYGB remains as yet undefined, but Hanssen et al. recently showed the benefit of a volume ≤ 100 mL .
The patients in our SG group had an average volume of 174.41 ± 59.36 mL at a reported rate of weight regain of
78.20%. At least this seems to prove that a volume of 174.41 mL is too large to maintain the gastric restriction
and thus leads to a loss of satiety.

3D-CT scan offers a superior technique for the evaluation of volumetric questions, whereas two-dimensional
measurements, such as the objectively verifiable diameter of an anastomosis or stenosis, are obviously better
assessed by direct measurement with endoscopy.

3D-CT examination requires a bariatrically trained radiology team with a standardised protocol for best
results, as described above.