Use of Vernier caliper to measure diameter and anastomotic index of end‐to‐end jejunojejunostomy in horses

Dear Editor,

We read with interest the studies by Baldwin and Gillen ¹ and by Seitz‐Cherner and colleagues. ² The former evaluated different jejunal transection angles for end‐to‐end anastomosis in equine cadaveric tissue, whereas the latter assessed a suture pattern using both ex vivo and in vivo models. Although the topic is clinically relevant, we would like to raise concerns regarding certain aspects of the methodology and the interpretation of the results.

In both studies, luminal diameter measurements were obtained using Vernier calipers inserted into the intestinal lumen and opened until “resistance was encountered.” However, no standardization of the force applied to open the calipers was reported; consequently, the point at which resistance was perceived is subjective and likely dependent on the force applied by the operator. Moreover, this measurement technique is inherently subjective and prone to overestimation due to stretching of cadaveric tissue.

This concern is further substantiated by the figures provided in the manuscripts, which illustrate the technique used for luminal diameter assessment and allow a direct evaluation of the measurement approach.

By reproducing this methodology, we were able to stretch the small intestinal tissue by up to 20% relative to its resting diameter (Figures 1 and 2). This effect is even more pronounced and evident in Figure 3 of the study by Baldwin and Gillen (Figure 3), in which the intestine appears markedly distended and stretched to obtain a luminal diameter measurement, in contrast to figure in the studyby Seitz‐Cherner et al. (Figure 4).

FIGURE 1.

Measurement of anastomotic diameter with Vernier calipers “until resistance was encountered” made by one of the authors.

FIGURE 2.

Measurement of the anastomotic diameter of the same anastomosis as in Figure 1 made by another author “until resistance was encountered.” Note that in this cases the perceived resistance led to further stretching of the intestinal wall, causing an increase of 20% of the value.

FIGURE 3.

Figure 3 of reference ¹. Note the stretching caused by the measurement “until resistance was encountered,” which makes the width of the anastomosis unnaturally larger than the adjacent healthy intestine, even when accounting for the transection angle that would increase the diameter at the anastomotic site. Further notice the wrong application of the caliper. To measure the internal diameter of the anastomosis or intestine, the small, upper caliper jaws (red arrow) should have been used, instead of the large, beveled tips (yellow arrows). Note, in fact, that in the two images, the beveled shape of the caliper jaws causes the tissue to slide toward their tips. Consequently, the anastomosis is found at a different distance along these jaws, resulting in an incorrect measurement being obtained.

FIGURE 4.

Figure 1 from reference ². Note the correct placement of the caliper compared to Figure 3 and the less pronounced stretching of the anastomosis compared to the adjacent normal intestine.

When viewed collectively, these figures illustrate the substantial variability inherent to this measurement technique.

Furthermore, in the study by Seitz‐Cherner et al., the differences observed between ex vivo and in vivo measurements using this method may be explained by the resistance provided by the muscular tone of the intestinal wall in vivo, which can influence tissue compliance and affect the resistance encountered during caliper placement by the operator. In contrast, the authors conclude that the luminal diameter is narrower in vivo than ex vivo; however, we believe that such a conclusion cannot be reliably drawn using this measurement technique.

Furthermore, in the study by Baldwin et al., ¹ a more serious methodological flaw is evident, as illustrated in Figure 3, where the calipers appear to have been used incorrectly. When measuring internal diameters of hollow structures, the small, uppercaliper jaws should be used (red arrow) by placing the edges of the hollow structures on the outside of the jaws. In contrast, use of the large, beveled tips (yellow arrows) should be reserved to measure structures that are contained within the width of the internal surface of the same jaws. ³ Using the latter to measure hollow structures is wrong and introduces a substantial measurement error and compromises accuracy. If this technique was indeed employed, as suggested by the figures provided in the manuscript, the resulting measurements—and consequently the entire dataset—may be systematically biased.

To improve the reliability of luminal diameter assessment in future studies, measurement techniques should incorporate standardized and reproducible methods. These may include the application of a predefined and controlled force during caliper opening while using the external caliper jaws for internal diameter measurements, or the adoption of alternative approaches such as imaging‐based techniques or frozen section measures under pressure‐controlled distension. Such standardization would reduce operator‐dependent variability and allow more robust comparisons between experimental conditions.

The methodological limitations outlined above should be carefully considered when interpreting the reported findings and assessing their potential clinical implications.

FUNDING INFORMATION

No external funding was received for this work.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

DATA AVAILABILITY STATEMENT

Data sharing not applicable to this article as no datasets were generated or analysed during the current study.