Objective
Quantify the longitudinal shrinkage observed with resection and fixation of samples of canine small intestine and improve the objective interpretation of surgical margins reported after histopathological study of canine small intestinal tumors
Animals
Twelve clinically normal adult dogs of medium to large breed (weighing 12 to 40 kg) were included in the study.
Methods
The tissue to be excised was minimally handled and observed for a period of minimal peristaltic motion. The resection positions were marked with a sterile pen perpendicular to the antimesenteric border. The samples ranged from 80 to 280 mm in length, the measurement (M1) being taken, with a millimeter ruler, along the lateral serosal surface at mid-distance between its mesenteric and antimesenteric borders. The intestine was resected at the premeasured points. The lumen was occluded by means of clamps positioned perpendicular to the antimesenteric border adjacent to the resection lines. The intestine was sharply excised with a scalpel blade along the predrawn lines. The length of the excised jejunum, excluding the mucosal eversion, was measured 30 and 60 s after excision (measurement M2) with the same method. The samples were placed in 10% formalin for 24 h to allow adequate tissue fixation. The lengths of the formalin-fixed samples were then measured again (measurement M3). The measurements were made by a single observer, who recorded the average of 2 measurements, to the nearest 1 mm, at each time point. The samples were laid flat without stretching for measurement, with the aim of obtaining specimens representative of those obtained in a clinical setting.
Results
The resected specimens of small intestine showed a significant amount of longitudinal shrinkage and a marginal, but not statistically significant, increase in length between the end of the excision process and the end of the fixation period (M2–M3) (Table I). The mean reductions in length were 28.3% (P < 0. 0001) between the pre-excision and postexcision measurements (M1–M2) and 26.3% (P < 0.0001) between the pre-excision and postfixation measurements (M1–M3). The mean change in length from postexcision to postfixation (M2–M3) was −3.0% (P = 0.18). The 95% confidence intervals for the mean percentage changes in length were 32.9% to 23.7% (M1–M2), 31.4% to 21.2% (M1–M3), and 1.6% to −7.6% (M2–M3).
Summary
The aim of this study was to quantify the longitudinal shrinkage of canine small intestinal specimens after resection and fixation in 10% formalin. Samples were obtained from 12 clinically normal dogs of medium to large breed via ventral midline coeliotomy and enterectomy. The length of each sample was measured before excision, immediately after excision, and after 24 h in 10% formalin. The results were interpreted with the use of single-sample t-tests of the average changes; P-values of less than 0.01 were considered significant. The samples indicated a significant decrease in length after resection and fixation. The mean shrinkage from the pre-excision state was 28.3% immediately after excision (P < 0.0001) and 26.3% after 24 h of fixation (P < 0.0001). There was a small but not significant increase in the length of the specimens between the 2nd and 3rd measurement points. Quantification of the longitudinal shrinkage of resected intestinal specimens may improve interpretation of the distance of surgical margins from abnormal tissue in histopathology reports and allow investigation of the margins required for the clearance of specific tumors.
