Plasma lactate as a predictor of colonic viability and survival after 360 degrees volvulus of the ascending colon in horses

Objectives— To determine the relationship between plasma lactate concentration and colonic viability and survival in horses with ≥360° volvulus of the ascending colon.
Study Design— Retrospective study.
Animals— Horses (n=73) with ≥360° volvulus of the ascending colon.
Methods— Medical records (January 2000–November 2005) of all horses examined for colic at Michigan State University Veterinary Teaching Hospital were reviewed. Horses were included only if plasma lactate concentration was measured preoperatively and a diagnosis of ≥360° volvulus of the ascending colon was confirmed by surgery or necropsy. Non-survivors were only included if the ascending colon was evaluated histopathologically. Logistic regression analysis was used to model the relationship between lactate, colonic viability, and survival.
Results— Of 73 horses, 61 were discharged. Mean (±SD) plasma lactate concentration was significantly lower in survivors (2.98±2.53 mmol/L) compared with non-survivors (9.48±5.22 mmol/L; odds ratio [OR]=1.628, 95% confidence limit [CI]=1.259–2.105). Plasma lactate concentration was significantly lower in horses with a viable colon (3.30±2.85 mmol/L) compared with horses with a non-viable colon (9.1±6.09 mmol/L; OR=1.472, 95% CI=1.173–1.846). Plasma lactate concentration <6.0 mmol/L had a sensitivity of 84% and a specificity 83% for predicting horse survival.
Conclusions— Our results demonstrate a strong association between plasma lactate concentration at the time of hospital admission and outcome in horses with ≥360° volvulus of the ascending colon.
Clinical Relevance— Plasma lactate concentration may help predict colonic viability and horse survival after ascending colon volvulus in horses.     

Cecal volvulus in a dairy cow: partial resection of the proximal portion of the ascending colon

Cecal volvulus in a dairy cow with vascular compromise of the proximal portion of the ascending colon was corrected surgically with preservation of the ileocecocolic junction. Partial cecectomy was combined with resection of the proximal portion of the ascending colon and anastomosis of the remaining cecum to the distal portion of the ascending colon. The procedure was done with the use of mechanical suturing devices while the cow was standing. Previously, general anesthesia and relocation of the ileocecocolic junction had been suggested.     

Serosal injury in the equine jejunum and ascending colon after ischemia-reperfusion or intraluminal distention and decompression

OBJECTIVE: To document morphologic changes that occur in equine intestinal serosa after experimentally induced ischemia and subsequent reperfusion (jejunum, ascending colon) or after intraluminal distention and decompression (jejunum). STUDY DESIGN: Morphologic effects of ischemia-reperfusion or intraluminal distention-decompression determined on the serosal layer of the equine jejunum. The large colon serosa was evaluated after ischemia-reperfusion injury. ANIMALS OR SAMPLE POPULATION: Seven adult horses. METHODS: After induction of general anesthesia and ventral median celiotomy, ischemia was created by arteriovenous (AVO) and lumen occlusion of a 20-cm segment of jejunum and ascending colon for 70 minutes, followed by a 60-minute reperfusion period. Intraluminal distention (25 cm H2O) was created in a second 20-cm jejunal segment and maintained within the abdomen for 120 minutes, followed by a 120-minute decompression period. Seromuscular biopsies were obtained upon entering the abdomen and after the ischemic and reperfusion periods, and after the distention and decompression periods along with corresponding control seromuscular biopsies. Samples were processed and examined by light microscopy, transmission electron, and scanning electron microscopy. RESULTS: Ischemia and reperfusion, and intraluminal distention and decompression, resulted in severe morphologic changes in the seromuscular layer of equine jejunum. A similar period of ischemia-reperfusion caused minimal changes in the ascending colon serosa. CONCLUSION: Adult equine jejunum sustains more serosal damage than the ascending colon after similar periods of ischemia-reperfusion injury. Intraluminal distention and subsequent decompression causes serosal damage in the equine jejunum. CLINICAL RELEVANCE: The small intestine is more susceptible to seromuscular layer damage than the ascending colon.     

Observations on the macroscopic anatomy of the intestinal tract and its mesenteric folds in the pampas deer (Ozotoceros bezoarticus, Linnaeus 1758)

We described the macroscopic anatomy of the intestines and their peritoneal folds of five adult pampas deer ( Ozotoceros bezoarticus ), a cervid species considered to ingest a high proportion of grass in its natural diet. The mean (±SD) body weight was 17 (±2) kg. The small intestine and the caecocolon measured 495 (±37) cm and 237 (±24) cm in length, respectively, with an average ratio (small intestine:caecocolon) of 1.9 (±0.1). The ascending colon had two and a half centripetal gyri, a central flexure and two centrifugal gyri. The spiral ansa, which was similar to an ellipse, was fixed to the whole left face of the mesenterium. Apart from the peritoneal folds described in the Nomina Anatomica Veterinaria, three additional, hitherto not described folds were found: a fold that fixed the caecum to the proximal ansa of the ascending colon, one that joined the terminal part of the proximal ansa to the last centrifugal gyrus of the spiral ansa of the ascending colon, and one that linked the ascending duodenum to the proximal ansa of the ascending colon. When compared with published data from other cervids of different feeding niches, it appears that, among cervids, the ratio of small intestine to the caecocolon length does not reflect the natural diet.     

COMPUTED TOMOGRAPHIC PNEUMOCOLONOGRAPHY IN NORMAL DOGS

Objectives of this prospective study were to describe effects of varying technical components that may contribute to an optimal protocol for computed tomographic pneumocolonography (CTP) in dogs, and to develop a standardized methodology for CTP as a future potential diagnostic tool in canine clinical patients with large bowel disease. Eight purpose‐bred intact male hound cross‐research dogs were enrolled and randomized to groups based on variables of pressure/body position (n = 4) and insufflation time (n = 4). For each segment of large bowel (rectum, colorectal junction, descending colon, transverse colon, ascending colon), the adequacy of bowel preparation, % of bowel lumen filled with fecal material, and bowel tortuosity or folding were assessed. Measurements of bowel wall thickness (cm), cross‐sectional bowel lumen diameter (cm), and cross‐sectional bowel luminal area (cm²) were obtained at standardized locations within the large bowel. False discovery rates (FDR) were calculated to adjust for multiple testing. Values of FDR < 0.05 were considered significant. Differences in mean cross‐sectional area and diameter and bowel wall thickness under increasing pressure were not significant after adjusting for multiple testing; some had raw p values <0.05. Ascending colon diameter and ascending colon area significantly increased with insufflation time (FDR < 0.05). No other response variables showed a significant change with insufflation time. The optimal insufflation pressure for maintaining pneumocolon in this study was determined to be 20 mmHg. CTP is a feasible technique to provide consistent distension for imaging of the large bowel and further study on application of CTP in clinical patients is warranted.     

Obstruction of the Ascending Colon in Cattle: II. An Experimental Model of Partial Bypass of the Large Intestine

Four dairy calves were subjected to partial bypass of the large intestine by uniting the ileum to the distal centrifugal coil of the spiral loop of the ascending colon (spiral colon). Digesta bypassed the distal ileum, cecum, proximal loop of the ascending colon, and the centripetal coils of the spiral colon. The calves survived the surgical procedure and were healthy throughout the 4-week postoperative experimental period. Feces were loose immediately after bypass, but fecal dry matter (DM) gradually increased over the subsequent 2 weeks (P < 0.01), indicating adaptation of remaining bowel to absorb more water. There was no significant change in serum concentration of sodium or chloride. The calves continued to grow and gain weight at acceptable rates after bypass. Necropsy of 3 of the calves demonstrated a decrease in size of the bypassed bowel.     

Microvascular circulation of the ascending colon in horses

Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light microscopic observation, using standard histologic methods. In sections from 6 horses, injection replicas were made by perfusing the vessels with 2 types of plastics. The results of microangiography, light microscopy, and scanning electron microscopy of vascular replicas were correlated, providing a comprehensive documentation of the microvasculature of the ascending colon at the pelvic flexure. Arteries branched from mesenteric colic vessels approximately every 2 cm toward the colonic tissue. Immediately after branching, arterial vessels formed an anastomotic plexus, the colonic rete. However, each branch from the colic vessel eventually continued into the colonic tissue. A second set of vessels originated from the colonic tissue. A second set of vessels originated from the colonic rete and supplied the mesenteric lymph nodes. Arterial vessels penetrated the tunica muscularis into the submucosa 3 to 4 cm toward the antimesenteric border forming a submucosal vascular network. From the submucosal arterioles, branching took place at right angles to supply the mucosal capillaries. Capillaries surrounded the colonic glands and anastomosed at the luminal surface, forming a superficial luminal honeycomb-appearing vascular plexus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Retrograde intussusception of the descending colon secondary to multiple colonic hamartomas in a neonatal foal

A neonatal Thoroughbred filly presented with a 3-h history of abdominal pain and distention that failed to respond to medical treatment. Diagnostic evaluation, including abdominal ultrasound, barium enema and proctoscopy, was suggestive of atresia coli. Exploratory laparotomy revealed a pedunculated mass in the wall of the diaphragmatic flexure of the ascending colon. The mass, subsequently diagnosed as a hamartoma, was attached to a smaller hamartoma by a fibrous pedicle originating from the descending colon. The descending colon had intussuscepted retrograde into the ascending colon along the fibrous band. The filly was euthanised due to poor prognosis.     

Effects of age, sex, and post mortem interval on intestinal lengths of horses during development

Lengths of small intestine, caecum, ascending colon and descending colon were measured in intestinal tracts from 103 foetuses, foals and adult horses. Intestinal tracts from 21 of the horses were measured at varying intervals after death. Total intestinal length increased markedly from mid-gestation to one year of age, then showed little increment up to 35 years. Small intestinal length increased most rapidly in the first month of life. Caecal length increased most rapidly from one to six months and length of ascending colon increased most rapidly between one week and one year. Descending colon length increased gradually after birth. Periods of rapid increase in length of various intestinal segments and alterations in the percentage of total intestinal length were associated with periods of rapid body growth and changes in dietary composition. Sex and post mortem interval did not affect intestinal length significantly.     

Horseradish peroxidase study of the location of extrinsic efferent and afferent neurons innervating the colon of dogs

The abdominal portion of the colon of 13 clinically normal dogs was divided into 5 regions (ascending, transverse, left colic flexure, proximal descending, and distal descending), and each region was injected with 30 mg of horseradish peroxidase (HRP). The injected colonic region, brain stem, L7-Cd1 portion of the spinal cord, sympathetic trunk ganglia, celiacomesenteric ganglia, caudal mesenteric ganglion, pelvic plexi, distal vagal (nodose) ganglia, and L1-Cd1 spinal ganglia were obtained at post-injection hour 48, sectioned, and processed by use of the tetramethylbenzidine method. The entire length of the colon was found to be under extrinsic influence of the parasympathetic nucleus of cranial nerve X (PX), with the largest average number of labeled cells resulting from injection of the ascending colon. It was also indicated that the entire colon is under extrinsic influence of the sacral portion of the spinal cord because the pelvic ganglia (second-order neurons) of the pelvic plexi contained labeled cells for all colonic regions. The largest average number of labeled cells in pelvic ganglia was seen after injection of the distal portion of the descending colon. Only after injection of the distal portion of the descending colon were labeled cells found in the S1-S3 portion of the spinal cord. Labeled cells in the PX, spinal cord, and pelvic ganglia were found bilaterally. Although the entire abdominal portion of the colon appears to be influenced by cranial and sacral parasympathetic preganglionic (via pelvic ganglia) neurons, the relative importance of the 2 areas seems to be reversed between the ascending colon and distal portion of the descending colon.(ABSTRACT TRUNCATED AT 250 WORDS)     

Obstructive enterolith in an 11-month-old miniature horse.

An obstructive enterolith was diagnosed in an 11-month-old 68-kg miniature horse with a 24-hour history of mild, intermittent colic. Abdominal radiography revealed gas distention of the cecum and the right and left ascending colon, and a radiodense elliptical structure in the area of the left kidney. During exploratory laparotomy, the right dorsal colon was noticed to contain ecchymotic hemorrhage and generalized discoloration in the portion proximal to the location of the enterolith. While exteriorizing the ascending colon, it ruptured caudal to the diaphragmatic flexure in the right dorsal colon. Radiography of the enterolith did not reveal a metallic center, but division of the stone allowed identification of a canvas cloth, and chemical analysis determined the stone's composition to be ammonium magnesium phosphate. Although equine enteroliths were reported over 100 years ago and the factors involved in their formation were investigated, the reasons for their development have yet to be determined. The mean reported age of horses requiring abdominal surgery because of an obstructive enterolith is 10 years, with the youngest being 4 years. The time required for an enterolith to enlarge is unknown, although a true enterolith has not been reported in horses younger than 4 years of age.     

Chronic intestinal pseudo-obstruction in a horse: a case of myenteric ganglionitis

An 11-year-old Quarter horse mare was presented for recurrent episodes of colic. A chronic intestinal pseudo-obstruction was diagnosed. Medical treatment and surgical resection of the colon were performed but the condition did not improve and the horse was euthanized. Histopathological examination revealed a myenteric ganglionitis of the small intestine and ascending colon.     

Equine Large Intestinal Volvulus A Review of 124 Cases

The average age of 122 horses with ascending colon volvulus was 6.6 +/- 0.4 years. Gastric reflux was a presenting sign in 35% of the cases. Peritoneal fluid protein levels had a mean of 2.54 +/- 0.14 g/dl and 20 horses had grossly normal peritoneal fluid at the time of presentation. Ascending colon volvulus was most commonly found at the level of the cecocolic fold with the initial ventral colon movement in a dorsomedial direction about the ascending mesocolic axis. The overall survival rate was 34.7% with a recurrence rate of only 4.9%.     

Arterial supply to the rat colon

Rats are often used as animal models in studies such as on intestinal transplantation and anastomosis healing, which require colectomy. Although detailed information regarding arterial supply is important to establish accurate and reproducible experimental procedures, this has not been studied in the rat colon. Therefore, we analysed the detailed arterial distribution pattern and its individual variations in the colon of 34 rats. The rat colon received colic branches of the ileocolic artery, and the right, middle and left colic arteries. The single left colic artery constantly arose from the caudal mesenteric artery and was distributed to the descending colon, whereas the others showed variations in number and distribution. The ileocolic artery gave rise to one (12%) or two (88%) colic branches supplying the proximal ascending colon, and these branches formed rich, mesh-like anastomoses along the initial portion of the ascending colon. One (74%) or two (26%) right colic arteries originated from the cranial mesenteric artery and supplied the ascending colon and right colic flexure. Moreover, one (38%), two (56%) or three (6%) middle colic arteries emerged from the cranial mesenteric artery and were distributed to the transverse colon, left colic flexure and proximal descending colon. In total, we categorized the individual variations in arterial branching and anastomosis into 11 patterns. Arterial supply to the rat colon showed a specific pattern and frequent individual variations. These findings thus provide essential information for establishing reproducible models of rat colic surgery.     

The innervation of the hind gut of the domestic fowl

1. The intestinal nerve adjacent to the colon in the domestic fowl, contains motor fibres descending from the vagal and sympathetic thoracicolumbar outflows. 2. No electrophysiological or histological evidence for the existence of motor fibres ascending from the sacral part of the central nervous system could be obtained; ascending sensory fibres, however, were readily demonstrated.     

Inguinal Herniation of the Ascending Colon in a 6‐month‐old Standardbred Colt

Objective— To report inguinal herniation of the ascending colon in a Standardbred colt. Study Design— Case report. Animals— A 6‐month‐old Standardbred colt. Methods— The colt underwent surgical exploration of the hernia with large colon resection and anastomosis. Results— A successful large colon resection and anastomosis was completed, however, the colt was euthanatized at the end of surgery upon owner request. Conclusions and Clinical Relevance— Although uncommon, indirect inguinal herniation of the ascending colon can occur in young horses.     

Arterial Vascularization of the Gastrointestinal Tract of the Pampas Deer (Ozotoceros bezoarticus,Linnaeus, 1758)

Based on gross dissection of fifteen adult animals (11 females, 4 males), we described the arterial supply of the stomach and intestines of the pampas deer (Ozotoceros bezoarticus), a South American endangered species. The coeliac artery emitted the splenic, left gastric and hepatic arteries. The splenic artery directed towards the spleen, and the right ruminal artery, which is its only collateral directed towards the stomach, being the main artery of the rumen. The left gastric artery gave origin to the left ruminal, the reticular and the left gastroepiploic arteries. The left gastroepiploic artery originated the reticular accessory artery. Both arteries, gastric and left gastroepiploic, anastomosed their right counterparts derived from the hepatic artery on the curvatures of the abomasum. The cranial mesenteric artery irrigated the second half of the duodenum until the beginning of the descending colon. The thickest branch emitted by the cranial mesenteric artery was the ileocolic artery, which was destined to the ascending colon, caecum and ileum. The colic branches and the right colic arteries were irradiated on the right surface of the spiral loop of the ascending colon and distributed to both centripetal and centrifugal coils of the ascending colon; the colic branches were also anastomosed with the last jejunals and ileals and with the right colic arteries. There were no variations in the origin of any of the main branches derived from the coeliac and cranial mesenteric arteries. This species had a basic pattern of arterial distribution similar to small domestic ruminants.     

The topography and gross anatomy of the gastrointestinal tract of the Cape dune mole-rat (Bathyergus suillus)

The Cape dune mole-rat, Bathyergus suillus, is the largest truly subterranean rodent in the world and is restricted to sandy soil areas of the southern and South-western Cape Province. These animals are herbivorous, feeding mostly on the below ground portions of grass and geophytes. The present study was undertaken to explore whether there are any gross anatomical gastrointestinal adaptations associated with the herbivorous diet of the Cape dune mole-rat and to provide a basis for further investigations into the nutrition and ecology of this animal. The stomach was unilocular (simple) and the entire internal aspect displayed macroscopically visible glandular epithelium. The caecum was voluminous and arranged into a spiral of approximately one and a half turns. The tip of the caecum resembled a vermiform appendix and lay against the left lateral abdominal wall. The ascending colon consisted of proximal and distal portions, arranged in a large double loop and attached to each other by a fat-filled mesenteric fold. The looped, folded ascending colon filled the right side of the abdominal cavity, lying against the right dorsal, lateral and ventral abdominal wall. The internal structure of the ascending colon revealed a shallow groove, lined on either side by a row of papillae. The simple, glandular stomach in conjunction with a prominent caecum and a greatly enlarged ascending colon suggests that this animal is a hindgut fermenting herbivore, rather than a caecal fermenter, as is the case in most rodent species.     

Cisapride Stimulates Contraction of Idiopathic Megacolonic Smooth Muscle in Cats

We have previously shown that cisapride, a substituted piperidinyl benzamide, stimulates contraction of healthy feline colonic smooth muscle. The purpose of the present investigation was to determine the effect of cisapride on feline idiopathic megacolonic smooth muscle function. Longitudinal smooth muscle strips from ascending and descending colon were obtained from cats with idiopathic megacolon, suspended in a 1.5 mM Ca²⁺-HEPES buffer solution (37°C, 100% O₂, pH 7.4), attached to isometric force transducers, and stretched to optimal muscle length (L₀). Control responses were obtained at each muscle site with acetylcholine (10–⁸ to 10 ⁴ M), substance P (10–¹¹ to 10^-7 M), or potassium chloride (10 to 80 mM). Muscles were then stimulated with cumulative (10–⁹ to 10–⁶ M) doses of cisapride in the absence or presence of tetrodotoxin (10–⁶ M) and atropine (10–⁶ M), or in a 0 calcium HEPES buffer solution. In cats with idiopathic megacolon, cisapride stimulated contractions of longitudinal smooth muscle from both the ascending and the descending colon. Cisapride-induced contractions were similar in magnitude to those induced by substance P and acetylcholine in the ascending colon, but were less than those observed in the descending colon. Cisapride-induced contractions in megacolonic smooth muscle were only partially inhibited by tetrodotoxin and atropine, but were virtually abolished by removal of extracellular calcium. We concluded that cisapride-induced contractions of feline megacolonic smooth muscle are largely smooth muscle mediated and dependent on influx of extracellular calcium. Cisapride-induced contractions in megacolonic smooth muscle are only partially dependent on enteric cholinergic nerves. Thus, cisapride may be useful in the treatment of cats with idiopathic megacolon.