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Summary

The signalment, clinical and laboratory findings of surgical conditions, treatment, and outcome of 102 cases of descending colon disease in horses were reviewed. Abnormal conditions were categorized as enteroliths, impactions, strangulating lipomas, fecaliths, foreign body obstruction, volvulus, nephrosplenic entrapment, and other conditions. Eleven breed categories of horses were seen during this period. Arabians, ponies, and American miniature horses were more predisposed to descending colon disease than other breeds (P < 0.05). Female horses and animals >15 years old were more likely to be affected with descending colon disease, whereas horses <5 years old were less likely to be affected (P < 0.05). More specifically, Arabians, Quarter Horses, and Thoroughbreds >10 years old were breeds that were overrepresented when compared with the hospital population (P < 0.05). Enteroliths were most commonly seen in horses between 5 and 10 years old (P < 0.05) and were not seen in horses <2 years old. Enteroliths had a tendency to develop more commonly in Arabians and in female horses. Impactions affected horses >15 years old (P < 0.05) and had a greater tendency to affect ponies and American miniature horses. Female horses were more commonly affected by impaction than were males. Strangulating lipomas were commonly seen in horses >15 years old (P < 0.05) and more specifically female Quarter Horses (P < 0.05). Fecaliths tended to be a disease of horses <1 year old or >15years old and affected males more commonly than females. Ponies, American miniature horses, mixed-breed horses, and mustangs were the breeds most commonly affected. Surgical conditions were categorized as vascular (16%) or nonvascular (84%) conditions. Vascular conditions included strangulating lipomas (6%) and other conditions (10%). Nonvascular conditions included enteroliths (40%), impactions (25%), fecaliths (13%), and other conditions (6%). Horses with vascular lesions were older than horses with nonvascular conditions (P < 0.05). Peritoneal fluid values were high for all surgical conditions of the descending colon. Nucleated cell count and total protein concentration in peritoneal fluid retrieved from horses with vascular lesions were higher than in horses with nonvascular lesions (P < 0.01). Palpation per rectum revealed abnormal findings more commonly in horses with vascular compromise (P < 0.05). Of those horses taken to surgery, 91% were recovered from anesthesia and discharged; 90% of horses, for which the condition was monitored to at least 6 months after surgery, were alive. All horses that were medically treated were alive at least 6 months after discharge.

Free access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective

To compare the strength of the sutured linea alba, in vitro, using 2 suture patterns.

Animals

12 clinically normal llamas.

Procedure

2 incisions in the linea alba of 12 llamas were closed with a simple continuous or inverted cruciate pattern, and tissue was harvested after 10 days. In 6 llamas, the simple continuous line was intact; the inverted cruciate specimens contained 6 sutures. In 6 llamas, 1 knot was excised in the simple continuous pattern to simulate a failed line; the cruciate pattern contained 5 knots. Tissue sections were taken from cranial, between, and caudal to the linea alba incisions to compare fascial thickness. The sutured specimens were mounted in a mechanical testing system and tested to failure. A mixed-model ANOVA was used to evaluate the effects of suture pattern and incisional position on mechanical properties.

Results

Significant differences were not found between suture patterns or between location for yield force, failure force, or yield strain, whereas failure strain was lower for the intact simple continuous pattern than the inverted cruciate pattern (P = 0.003). From histomorphometric analysis, the caudal tissue specimens were significantly thinner than the middle tissue specimen cranial to the umbilicus (P = 0.006).

Conclusion

There was no significant difference in monotonic breaking strength of the linea alba sutured with the simple continuous or inverted cruciate pattern.

Clinical Relevance

These results justify the use of the simple continuous pattern over the cruciate pattern for ventral midline closure in llamas because of the ease of placement and speed. (Am J Vet Res 1996;57:938–942)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To provide an accurate and detailed description of the laparoscopic anatomy of the abdomen of horses positioned in dorsal recumbency and to compare those observations with laparoscopic anatomy of standing horses. The effects of laparoscopy and positional changes on arterial blood pressure and blood gas values also were investigated.

Design

Descriptive anatomic study.

Sample Population

Laparoscopy was performed on 6 horses (2 mares, 2 geldings, and 2 stallions) to record the normal laparoscopic anatomy of the abdomen in dorsal recumbency.

Procedure

Feed was withheld from all horses for 36 hours. Horses, under general anesthesia, were examined in horizontal and inclined positions (head-up and head-down). Intermittent positive-pressure ventilation was used, arterial blood pressure was continuously monitored, and samples for arterial blood gas measurements were taken at intervals.

Results

The main structures of diagnostic relevance observed in the caudal region of the abdomen were the urinary bladder, mesorchium and ductus deferens (left and right), left and right vaginal rings, insertion of the pre-pubic tendon, random segments of jejunum and descending colon, pelvic flexure of the ascending colon, body of the cecum, and cecocolic fold. The main structures observed in the cranial region of the abdomen were ventral surface of the diaphragm, falciform ligament and round ligaments of the liver, ventral portion of the left lateral, left medial, quadrate, and right lateral lobes of the liver, spleen, right and left ventral colons, sternal flexure of the ascending colon, apex of the cecum, and stomach.

Conclusions

Alterations in cardiovascular and respiratory function in response to pneumoperitoneum and various positional changes indicated the need for continuous and throrough anesthetic monitoring and support. Comparison of anatomic observations made in dorsally recumbent, inclined horses with those reported for standing horses should enable practitioners to make patient positioning decisions that best suit access to specific visceral structures. Development of special instrumentation for manipulation of the viscera in horses, particularly the intestinal tract, would increase the diagnostic and therapeutic capabilities of laparoscopy during dorsal recumbency. (Am J Vet Res 1996;57:923–931)

Free access
in American Journal of Veterinary Research

Summary

Medical records of 245 horses that had been evaluated by use of abdominal radiography between January 1990 and December 1992 were reviewed. One hundred forty-one horses subsequently had a postmortem examination or surgical exploration performed for definitive lesion diagnosis. The signalment, diagnosis, site, and number of enteroliths were obtained from the medical records. Radiographs were evaluated individually by 3 reviewers for the presence of enteroliths, preferred diagnostic view, evidence of large colon tympany, and film quality. Of the 141 cases reviewed, 66.7% (94/141) had confirmed enterolithiasis. Enteroliths were identified in the right dorsal colon of 59 horses, in the transverse colon of 28, in the small colon of 24, and in the ventral colon of 1 (enteroliths were detected in multiple sites in 12 horses). For the 3 reviewers, mean sensitivity was 76.9% and specificity was 94.4%. Mean positive-predictive value was 96.4%, and negative-predictive value was 67.5%. Cases involving only large colon enteroliths were correctly diagnosed 83.2% of the time, compared with 41.6% of the time for cases involving small colon enteroliths. Enteroliths were evident in 54.8% of the horses with radiographic signs of large colon distention. Fifteen horses had enteroliths in the small colon, 4 in the transverse colon, and 4 in the dorsal colon.

Radiographic quality was evaluated and scored as adequate (0), underexposed (−1), overexposed (1), or incomplete. Mean score was −0.5, and there were 21 (14.9%) incomplete studies. For the 75 cases correctly diagnosed via abdominal radiography, there were 14 (18.7%) incomplete studies and a mean score of −0.43. Of the 19 false-negative evaluations, there were 3 (15.8%) incomplete studies and a mean score of −0.69. The most common error leading to the missed diagnoses seemed to be inadequate penetration of the abdomen.

Free access
in Journal of the American Veterinary Medical Association

Summary

A review of medical records was used to identify 10 horses in which stringhalt developed subsequent to trauma to the dorsal metatarsus. Six horses developed stringhalt within 3 months after injury, 3 horses developed stringhalt > 3 months after injury, and time from injury to stringhalt was unknown for 1 horse. Horses were treated with exercise, including daily hand-walking with pasture turnout, followed by lunging; or surgically, using lateral digital extensor myotenectomy. Of the horses treated with exercise, 1 had resolution of stringhalt, 2 improved but had residual stringhalt, and 1 had no change. Two of the horses having lateral digital extensor myotenectomy had resolution of stringhalt. Two of the remaining 3 horses treated surgically had varying degrees of improvement, and in 1 horse there was no change. Stringhalt is a potential complication following trauma to the dorsal metatarsal region. Potential causes include tendon adhesions enhancing tarsocrural joint flexion or abnormalities in the myotatic reflex caused by tendon injury that result in abnormal flexion of the tarsocrural joint.

Free access
in Journal of the American Veterinary Medical Association

Summary

Intramural vascular patterns of the jejunum and colon were evaluated during ischemic strangulation obstruction (iso, 70 minutes) and subsequent reperfusion (60 minutes) in 7 adult anesthetized horses. Microvasculature of experimental and control segments was described by comparison of results from microangiography, light microscopy, and scanning electron microscopy of vascular replicas. Experimental and control segments with isolated vascular arcades were removed either immediately after the experimental period or after 60 minutes of reperfusion. Blood was flushed from the vascular system by use of isotonic NaCl, and the segments were divided. Half of each segment was perfused with a modified radiopaque medium for microangiographic evaluation, and half was perfused with dilute methylmethacrylate to create a vascular replica to be studied by scanning electron microscopy. Microangiographic section also were evaluated for histologic changes.

Microvasculature of jejunal control segments and all colon segments was similar to described normal microvasculature of the equine jejunum and ascending colon. In jejunal iso segments, intramural perfusion was redistributed away from the mucosa. In the villi, the central arteriole was short and convoluted and the subepithelial capillaries were not filled. The submucosal vessels and crypt capillaries were congested, compared with those of controls, and the serosal vessels were not filled in the ischemic segments. Histologic grade II-III mucosal lesion was seen in jejunal iso segments. Reperfused jejunal segments had a transmural hyperemic response, and previously unfilled capillaries were observed in all intestinal layers. After reperfusion, the mucosal lesion progressed to grade III-IV and a cellular infiltrate and edema formation were observed in the serosa.

The intramural vasculature of the ischemic and reperfused colon remain unchanged. Minimal histologic damage was observed in the colon after 70 minutes of iso or after 60 minutes of reperfusion.

Free access
in American Journal of Veterinary Research

Summary

Effects of intraluminal distention (25 cm of H2O, 120 minutes) and subsequent decompression (60 minutes) on intramural vascular patterns of the small intestine was evaluated in 7 anesthetized horses. Intraluminal distention (25 cm of H2O, 120 mintutes) was created in 2 jejunal segments in each horse. Experimental and control segments were removed either immediately after the experimental period or after 60 minutes of decompression. The vascular system of experimental and control jejunal segments was lavaged with NaCl, then was injected with a blue-colored radiopaque medium for microangiography or with a diluted methyl methacrylate for scanning electron microscopy of microcorrosion vascular casts. After angiographic evaluation, tissue sections were prepared for light microscopic evaluation to assess vascular filling and tissue morphology. The distended segments had short villi, which were separated by expanded crypts, and had mesothelial cell loss, neutrophil infiltration, and edema in the seromuscular layer. The number of perfused vessels was significantly (P < 0.05) decreased in the seromuscular layer and, to a lesser extent, in the mucosal layer of the distended segments, compared with controls. After decompression, the morphologic lesions progressed in mucosal and serosal layers and the number of observed vessels increased in all intramural layers; however, vascular density did not return to the predistention state. These results identify altered intramural vascular patterns in the equine jejunum during luminal distention and subsequent decompression.

Free access
in American Journal of Veterinary Research

SUMMARY

The ultrastructural injury that develops sequentially in the ascending colon during experimentally induced ischemia was examined in 6 halothane-anesthetized horses. Colonic ischemia was created by 2 types of vascular occlusion 24 cm proximal and distal to the pelvic flexure.

In all horses, transmural vascular compression was created. The colonic venous circulation was obstructed in 3 horses, whereas in the other 3 horses, arterial and venous circulation was obstructed. Two additional horses were anesthetized as controls for determination of any morphologic alterations associated with the experimental protocol.

Full-thickness colonic biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 1, 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, 4, 4.5, and 5 hours during occlusion, and were studied by light and transmission electron microscopy. Morphologic alterations did not develop in the colon of control horses. Mucosal congestion was observed by light microscopy in the colon of horses with experimentally induced ischemia, but congestion developed early in those with obstructed colonic venous circulation, compared with those having arterial and venous obstruction. Inter- and intracellular vacuolation and loss of staining initially resulted in groups of 3 to 5 superficial luminal epithelial cells. Alterations in the glandular epithelium lagged behind those in the superficial epithelium, but were observed in both groups by 2 hours of obstruction. These changes progressed to 100% sloughing of all epithelium by 4.5 to 5 hours.

The initial cellular alterations, which were observed by transmission electron microscopy, developed at 0.25 hour in horses with colonic venous obstruction and was characterized by inter- and intracellular edema. By 1 hour in horses with colonic venous obstruction, vacuoles were observed within the basal lamina and some vacuoles contained intracellular organelles. These cellular changes were followed by increases in the intercellular gap and breaks between degenerating and more normal-appearing superficial epithelium, which led to sloughing of the epithelium. Endocrine cells by 1 hour also had evidence of ischemic injury.

Injury to the vascular circulation, including congestion and platelet accumulations within the mucosal capillaries was apparent by 0.25 hour in horses with venous obstruction. By 1 to 1.5 hours in both groups of horses with experimentally induced ischemia, loss of vascular integrity and leukocyte migration frequently were observed. Platelets, proteinaceous material, and cellular debris continued to accumulate, and by 2.25 hour capillary plugging frequently was observed. These results indicated that the initial ultrastructural injury in the ischemic colon consisted of degenerative changes in epithelial cells, which led to sloughing of degenerating and necrotic cells. Although injury between the 2 types of vascular obstruction differed, end results were similar. Ischemic vascular injury may lead to further vascular thrombosis and necrosis, resulting in an irreversible injury or contribute to difficulty in medically managing horses with natural ischemia during the perioperative period.

Free access
in American Journal of Veterinary Research