The effects of intestinal ischemia on colonic motility in conscious rats

Healing of colonic anastomosis in rats under obstructive ileus conditions

BACKGROUND

The anastomosis leak in colon resections is a crucial post-operative complication with significant morbidity and mortality.  Methods: Forty (40) Wistar rats were allocated in two groups. In SHAM group only anastomosis was performed. In ILEUS group anastomosis was performed following one day of ileus. Animals in both groups were subdivided in two groups according to the day they were sacrificed, 4th or 8th post-operative day. A number of variables between the groups were estimated.

RESULTS

Body weight loss was higher following obstructive ileus on both days. Adhesion score in 4th and 8th post-operative day was higher in ILEUS1, ILEUS2 groups compared to SHAM1, SHAM2 groups respectively (p<0.001 for both). Neovascularization decreased following obstructive ileus compared to control on the 4th day (ILEUS1 vs. SHAM1, p=0.038). Bursting pressure was lower in ILEUS2 group than SHAM2 group (p<0.001). The number of fibroblasts decreased following obstructive ileus compared to control on the 4th and 8th day (ILEUS1 vs. SHAM1, p=0.001, ILEUS2 vs SHAM2, p=0.016). Hydroxyproline concentration was decreased in ILEUS2 group compared to SHAM2 group (p<0.001).

CONCLUSIONS

The balance of collagenolysis and collagenogenesis plays a decisive role in the healing of anastomoses following bowel obstruction. Under those circumstances, anastomosis' bursting pressure is reduced owning to decreased neovascularization, reduced fibroblast presence and lower hydroxyproline concertation. In our study, local inflammation, neocollagen concentration and collagenase activity were not associated with this adverse effect. However, further research should delineate the mechanisms of healing of colonic anastomoses and identify those factors that can improve our outcomes.

Surgical acquired aganglionosis: myth or reality?

PURPOSE

A number of patients operated on for Hirschsprung disease continue to have constipation and abdominal distension for years after surgery. Some authors have proposed that ischemia during surgery may induce secondary aganglionosis. The aim of the present study was to study the effects of ischemia on the enteric nervous system of sigmoid colon in an animal model.

METHODS

A surgical model of colonic ischemia was created. 34 adult Sprague-Dawley rats underwent a laparotomy where the marginal arterioles of the sigmoid colon were ligated. After that, a section in the middle segment of the sigmoid colon was performed followed by an anastomosis. The presence of ischemia was assessed by measurement of visible light spectroscopy tissue oximetry and histological examination. Colonic function was assessed by evaluation of stool weight. Rats were killed at 1, 8 and 12 weeks after the operation. 12 rats were sham-operated. Enteric nervous system was evaluated by means of immunohistochemistry with NGFR p75. Quantitative analysis of the number of ganglia and ganglion cells in the myenteric plexus was performed.

RESULTS

The surgical model of colonic ischemia significantly decreased tissue oxygenation (pre-surgical = 54.69 ± 7.32 %; post-surgical = 27.37 ± 9.2 %; p < 0.001). There was no disturbance in body-weight gaining in experimental groups and daily stool output did not vary after surgery (pre-surgical = 4.24 ± 0.94 g; post-surgical = 3.82 ± 1 g; p = 0.09). All experimental groups showed persistent ganglia. However, there was a significant decrease in the number of ganglia in all the experimental groups compared to control (1w: 45.91 ± 7.66; 8w: 44.17 ± 10.56; 12w: 36.17 ± 15.06 vs control: 56.88 ± 8.66; p < 0.01). The number of total ganglion cells was significantly reduced only in the experimental group killed at week 12 compared to control (1w: 539 ± 167.58; 8w: 488.58 ± 154.41; 12w: 343.94 ± 161.91 vs control: 513.96 ± 126.97; p < 0.01). The rate of ganglion cells per ganglia was significantly higher in the groups killed at week 1 and 8 versus control group (1w: 11.63 ± 2.53; 8w: 11.11 ± 2.56; 12w: 9.34 ± 1.16 vs control: 9.02 ± 1.81; p < 0.05).

CONCLUSION

Long-term follow-up after surgically induced colonic ischemia in the rat showed a decreased number of ganglion cells and ganglia. Nevertheless, it did not produce aganglionosis.

Review article: the pathophysiology and management of gastrointestinal symptoms during physical exercise, and the role of splanchnic blood flow

BACKGROUND

The prevalence of exercise-induced gastrointestinal (GI) symptoms has been reported up to 70%. The pathophysiology largely remains unknown.

AIM

To review the physiological and pathophysiological changes of the GI-tract during physical exercise and the management of the most common gastrointestinal symptoms.

METHODS

Search of the literature published in the English and Dutch languages using the Pubmed database to review the literature that focused on the relation between splanchnic blood flow (SBF), development of ischaemia, postischaemic endotoxinemia and motility.

RESULTS

During physical exercise, the increased activity of the sympathetic nervous system (SNS) redistributes blood flow from the splanchnic organs to the working muscles. With prolonged duration and/or intensity, the SBF may be decreased by 80% or more. Most studies point in the direction of increased SNS-activity as central driving force for reduction in SBF. A severely reduced SBF may frequently cause GI ischaemia. GI-ischaemia combined with reduced vagal activity probably triggers changes in GI-motility and GI absorption derangements. GI-symptoms during physical exercise may be prevented by lowering the exercise intensity, preventing dehydration and avoiding the ingestion of hypertonic fluids.

CONCLUSIONS

Literature on the pathophysiology of exercise-induced GI-symptoms is scarce. Increased sympathetic nervous system activity and decreased splanchnic blood flow during physical exercise seems to be the key factor in the pathogenesis of exercise-induced GI-symptoms, and this should be the target for symptom reduction.