Local and remote lesions in horses subjected to small colon distension and decompression

Abstract

The purpose of this study was to observe and characterize colonic and lung lesions in horses subjected to experimental distension and decompression of the small colon. Sixteen healthy adult horses were divided into 2 groups: 9 horses that were subjected to distension of the small colon by means of a latex balloon surgically implanted in the lumen and inflated to a pressure of 40 mm Hg for 4 h, and 7 horses in which the balloon was implanted but not inflated. Colonic biopsy specimens were collected before balloon implantation, at the end of the period of obstruction, and 1.5 and 12 h after decompression and were examined for hemorrhage, edema, and neutrophil infiltration; myeloperoxidase (MPO) activity and hemoglobin concentration were measured as well. At the end of the experiment, lung samples were also collected and examined for neutrophil accumulation and MPO activity. The mucosa was not affected by luminal distension; lesions were restricted to the seromuscular layer. Neutrophil accumulation and edema were observed in the samples from both groups of horses but were greater in those from the distension group, in which there was also hemorrhage, fibrin deposition, and increased MPO activity in the seromuscular layer. Similarly, there was greater accumulation of neutrophils in the lung samples from the distension group than in those from the sham-operated group, as determined by histologic evaluation and MPO assay. These findings provide new evidence of reperfusion injury and a systemic inflammatory response, followed by remote lesions, in horses with intestinal obstruction.

Figure 1

Lung sections from horses in the sham-operated group (left) and the distension group (right), showing few neutrophils in the former and many in the latter at the end of the experiment. Hematoxylineosin; original magnification ×400.

Figure 2

Seromuscular layer of equine small colon before intraluminal distension (A), during (B), and afterwards (C, D), demonstrating (B) hemorrhage (thin arrows) after 4 h of distension, (C) inflammatory cell infiltration, serosal edema (open arrow), and lymphatic vessel (LV) distension by 1.5 h after decompression, and (D) intense tissue infiltration of inflammatory cells and erythrocytes and fibrin deposition over the serosa (thick arrows) at 12 h after decompression. Hematoxylineosin; original magnification ×100.

Figure 3

Mean grades (and standard error) for serosal hemorrhage (A), fibrin deposition (B), and lymphatic vessel distension (C) in horses undergoing 4 h of colonic distension and then decompression (n = 9; dark bars) or a sham operation (n = 7; white bars). In all the figures, the asterisks indicate significant differences from the control segments of colon, and the number signs indicate a significant difference between the 2 groups of horses (P < 0.05).

Figure 4

Mean grades (and standard error) for neutrophil infiltration and edema in the muscular and serosal layers of the colon.

Figure 5

Means (and standard error) for neutrophil count in the serosa (A) and MPO activity (B) and hemoglobin concentration (C) in the seromuscular layer.

Figure 6

Mean grades (and standard error) for neutrophil accumulation (A) and MPO activity (B) in lung samples from the distension (n = 4) and sham-operated (n = 7) groups of horses.