No abstract

SUMMARY The paper considers the general principles of intestinal surgery in the horse and illustrates a theatre layout suitable for this purpose. The problems of locating and reducing obstructions of the small and large intestine are discussed, with particular emphasis on incarcerations of the small bowel and the techniques of jejunal and ileal re‐implantation after bowel resection. RÉSUMÉ Cet article expose les principes généraux de la chirurgie intestinale chez le cheval. Les difficultés de localisation et de réduction des obstructions grêles et coliques sont analysées en particulier le cas des incarcérations du grêle et les techniques de ré‐implantations jéjunales et iléales aprés resection d'un segment. ZUSAMMENFASSUNG Diese Arbeit betrachtet die allgemeinen Grundsätze der intestinalen Chirurgie beim Pferd und illustriert die geeignete Anlage eines Operationsraumes für diese Zwecke. Die Probleme des Auffindens und Behebens von Obstruktionen im Dünn‐ und Dickdarm werden diskutiert mit besonderem Gewicht auf den Inkarzerationen des Dünndarms und der Technik von Jejunum‐ und Ileum‐Reimplantation nach Resektion.

Summary In this study, the hypothesis that caecal smooth muscle layers would be thinner and the linear neuron density of myenteric plexus greater was tested in normal horses compared to those with chronic recurrent caecal impaction. Four normal horses and 18 horses with chronic recurrent caecal impaction were subjected to euthanasia and 7 tissue samples were collected from each horse at different regions of the caecum (apex, dorsal body, cranial base, dorsal base, caudal base, caudal body, ventral body). Twelve horses with chronic recurrent caecal impaction were treated surgically. Only one tissue sample of the cranial part of the caecal base close to the caecocolic orifice was taken during surgery. The thickness of the circular muscle layer of all caecal regions measured in killed horses with chronic recurrent caecal impaction was significantly increased compared to the equivalent caecal region of normal horses. On the other hand, the longitudinal muscle layer was significantly thicker only in the cranial and caudal caecal base and in the dorsal region of the caecal body. The linear neuron densities of all caecal base areas and 2 caecal body regions, the caudal body region and of the apex, of killed horses with chronic recurrent caecal impaction were significantly lower compared with those in clinically normal horses. The circular muscle layer of all caecal regions was thickened (hypertrophied) probably as a consequence of chronic uncoordinated hypercontractility due to neuron deficit in the myenteric plexus of the caecal base.

Summary Gastroduodenojejunitis is a catarrhal inflammation of the stomach and proximal portion of the small intestine. Secondary overloading of the stomach occurs so that affected horses rapidly enter a state of hypovolaemic shock which is further complicated by the presence of toxins. The condition can occur in a mild or severe form. In mild cases, conservative treatment comprising intravenous electrolyte therapy and repeated gastric decompression is indicated and is usually successful. In severe cases surgical treatment creating duodenocaecal anastomosis has given good results. This should be carried out if conservative treatment has shown no signs of improvement 24 h after the onset of the condition.

Summary Ninety‐six horses with chronic recurrent caecal impaction associated with hypertrophy of muscle layers in the caecal base or in the whole caecum were examined from 1990 to 1996. Enlargement of the caecocolic orifice was completed surgically in 58 horses. Of those horses having surgery, 50 were discharged from the hospital while 8 were subjected to euthanasia at the hospital due to complications. Twenty‐seven of the 50 horses discharged were normal at follow‐up while 23 died or were subjected to euthanasia due to acute or recurrent colic, recurrent impaction in the ascending or descending colon, complete caecal muscle layer hypertrophy, stomach rupture or lymphosarcoma. Approximately 50% of the cases were successfully treated by surgical enlargement of the caecocolic orifice. The results suggest, on the other hand, that enlargement of the caecocolic orifice was not successful in treating horses with hypertrophy of the caecal muscle layer in the whole caecum.

A retrospective study was performed on 342 horses with acute diarrhea (equine colitis). Clinical and laboratory data were obtained upon arrival at the equine hospital. The main focus of this study was to fi nd the difference between the clinical and laboratory variables of surviving and deceased acute colitis horses before the beginning of medical treatment, with the aim to provide a better guideline for determining the prognosis of survival.According to this retrospective study the lethality rate of acute equine colitis was 41.93 %. The time interval from the onset of acute diarrhea to the horse being taken to the clinic was signifi cantly longer in the case of horses which had not survived. The heart rate, hematocrit, blood pH, blood hydrogen carbonate concentration, base excess and HCT/TPP ratio were shown to be signifi cantly related to the survival of horses with colitis. Thus, the hematocrit, appeared to be the most relevant predictor of the outcome of acute equine colitis. Body temperature, respiration rate, total plasma protein and white blood cell count, did not show any prognostic signifi cance.

On clinical examination, a six-year-old Hassian gray gelding with a history of impaired performance, slight cough, colic, and edema of the ventral abdomen, prepuce and the legs had reduced skin turgor, pale mucous membranes, forced costoabdominal breathing, reduced venous return, enlarged lymph nodes, and splenomegaly. Hematologic findings revealed anemia, leukocytosis and a high percentage of monocytoid leukemic cells. Generalized lymphadenopathy, splenomegaly, ascites, hydrothorax, and a diffusely thickened gut wall were found at necropsy. Massive infiltration with monocytoid leukemic cells was detected in lymph nodes, spleen, bone marrow, liver, gut wall, kidneys, and choroid plexus. Incubation of living cells obtained from a leukocyte concentrate with latex particles revealed phagocytosis in the leukemic cells on light and electron microscopy. The leukemic cells also had a marked alpha-naphthyl-acetate and naphthol-AS-acetate esterase activity, but were only weakly positive to naphthol-AS-D-chloroacetate esterase. A very weak alkaline phosphatase activity only was demonstrated in a few leukemic cells. On scanning electron microscopy, the leukemic cells had prominent ruffles and ridge-like profiles. These features of the leukemic cells excluded lymphocytic and granulocytic leukemia, and monocytic leukemia was diagnosed.

An experimental study of duodenal obstruction was performed on four horses to determine the relation between the volume of accumulated fluid in the stomach and the degree of dehydration and acid-base disturbances. After a rapid increase, the production of fluid decreased slowly and ceased within 38 hours. The production averaged 0.3 I/ 100 kg body weight/hour. A continuing increase in packed cell volume was observed after the cessation of fluid production and the release of the obstruction. After the initial metabolic alkalosis, one horse had a metabolic acidosis, whereas two remained slightly alkalotic during the time of the duodenal obstruction. Acid-base values were within normal limits in one horse.