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Evaluation of gastrointestinal activity in healthy rabbits by means of duplex Doppler ultrasonography
Abstract
OBJECTIVE
To use duplex Doppler ultrasonography to compare gastrointestinal activity in healthy sedated versus nonsedated rabbits and to evaluate agreement between B-mode and pulsed-wave Doppler (PWD) ultrasonographic measurements.
ANIMALS
10 healthy client-owned rabbits brought for routine physical examination and 11 brought for routine ovariohysterectomy or castration.
PROCEDURES
Duplex Doppler ultrasonography of the gastrointestinal tract was performed once for the 10 rabbits that underwent physical examination and twice (before and after presurgical sedation) for the 11 rabbits that underwent routine ovariohysterectomy or castration. Mean number of peristaltic contractions during a 30-second period was determined for the stomach, duodenum, jejunum, cecum, and colon from B-mode and PWD ultrasonographic images that had been video recorded. Findings for the duodenum and jejunum were compared between B-mode and PWD ultrasonography and between sedated and nonsedated rabbits.
RESULTS
Duodenal and jejunal segments had measurable peristaltic waves; however, the stomach, cecum, and colon had no consistent measurable activity. B-mode and PWD ultrasonographic measurements for the duodenum and jejunum had high agreement. No significant difference was identified between nonsedated and sedated rabbits in mean number of peristaltic contractions of the duodenum or jejunum.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that both B-mode and PWD ultrasonography of the duodenum and jejunum may be suitable for noninvasive evaluation of small intestinal motility in rabbits and that the sedation protocol used in this study had no impact on measured peristaltic values. (Am J Vet Res 2019;80:657–662)
... Diagnostic imaging is an essential diagnostic tool for veterinarians working with exotic companion mammals [11,12,27,32]. Ultrasonographic evaluation of the GI tract in rabbits is challenging due to reverberation artifact caused by the normal large amount of gas and ingesta, mainly in the cecal region [11,[26][27][28][29][30]. Radiographic examination can be useful in the diagnosis of some GI diseases, but its use is limited when GI syndrome is suspected [1,7,8,14,32]. ...
Background
Gastrointestinal (GI) diseases are common in rabbits. Although diagnostic imaging studies can assist clinicians in selecting therapeutic approaches, there are few reports of advanced imaging findings in normal rabbits. Computed tomography (CT) is recognized as a useful tool in dogs and cats, but there are few reports of normal findings on multidetector computed tomography (MDTC) in rabbits. The goals of this study are to describe the CT anatomical imaging appearance of the GI tract and their normal variation in healthy pet rabbits and to obtain the normal wall thickness measurements of normal GI tract structures.
Methods
Twenty-three rabbits were scanned under general anesthesia and the CT abdominal images were analyzed by two experienced radiologists. Location and size of the major GI organs and structures were determined, and wall thickness of the stomach, small and large intestines were measured, including the interobserver agreement. Statistical analysis of quantitative and qualitative variables were performed.
Results
Wall thickness values were established for the different parts of the stomach (cardia: 3.4 ± 0.4mm; fundus: 1.4 ± 0.2mm; body: 1.4 ± 0.1mm; pylorus: 2.9 ± 0.5mm), small intestines (duodenum: 1.4 ± 0.1mm; jejunum: 1.2 ± 0.1mm; ileum: 1.4 ± 0.1mm), and large intestines (cecum: 1.2 ± 0.1mm; colon ascending: 1.4 ± 0.3 mm and descending: 1.3 ± 0.3mm). When distended the stomach did not extend beyond the caudal limits of the L2 vertebra. The cecum occupied the ventral abdominal region from T12/T13 to L7/S1, the sacculus rotundus was identified in 11 of the 23 rabbits. The sacculus rotundus and vermiform cecal appendix were identified only in rabbits with mild large intestinal distension.
Conclusions and clinical relevance
It was possible to use CT to evaluate the different portions of the GI tract that are not normally readily visible on radiographs and ultrasound (US). Normal wall thickness values of the different portion of the GI tract were stablished. These results provide new and important reference values for CT studies in normal pet rabbits and provide data for further studies in rabbits with GI diseases.
... In a recent study [20], ultrasonographic examination of intestinal and stomach contractions in rabbits were evaluated using ultrasonographic B mode and pulsed wave Doppler methods. It was concluded that the high agreement between the two methods at the duodenum and jejunum levels allows using B-mode instead of duplex Doppler to evaluate intestinal motility. ...
The aim of this study was to evaluate and compare the effects of single doses of butorphanol, morphine, and tramadol on gastrointestinal motility in rabbits (Oryctolagus cuniculus) using non-invasive imaging methods, such as radiographic barium follow through and ultrasonographic contraction counts. Time-lapse radiographic and ultrasound examinations were performed before and after a single intramuscular dose of 5 mg kg⁻¹ butorphanol, 10 mg kg⁻¹ morphine, or 10 mg kg⁻¹ tramadol. Pyloric and duodenal contraction counts by ultrasonography and radiographic repletion scores for the stomach and caecum were analysed using a mixed linear model. No significant effect was noted on ultrasound examinations of pyloric and duodenal contractions after administration of an opioid treatment. Morphine had a significant effect on the stomach and the caecum repletion scores, whereas butorphanol had a significant effect only on the caecum repletion score. Tramadol had no significant effect on the stomach or caecum repletion scores. The present findings suggest that a single dose of 5 mg kg⁻¹ butorphanol or 10 mg kg⁻¹ morphine temporarily slows gastrointestinal transit in healthy rabbits, preventing physiological progression of the alimentary bolus without the induction of ileus. In contrast, a single dose of 10 mg kg⁻¹ tramadol has no such effects.
... Diagnostic imaging is an essential diagnostic tool for veterinarians working with exotic companion mammals [11,12,27,32]. Ultrasonographic evaluation of the GI tract in rabbits is challenging due to reverberation artifact caused by the normal large amount of gas and ingesta, mainly in the cecal region [11,[26][27][28][29][30]. Radiographic examination can be useful in the diagnosis of some GI diseases, but its use is limited when GI syndrome is suspected [1,7,8,14,32]. ...
Background
There are few studies describing characteristics of the urinary tract in rabbits using multidetector computed tomography (CT). The aim of this study was to describe the CT appearance and main features of the urinary tract in healthy pet rabbits.
Methods
Twenty-three healthy rabbits underwent plain and contrast-enhanced CT scan under general anesthesia.
Results
Normal renal length was 3.27-3.43 cm. The ureters were identified in the pre-contrast phase, but better delineated in post-contrast phases. Some focal filling defects were observed in the middle and caudal third of the ureters in more than 50% of the animals on post-contrast exams. There was interobserver disagreement regarding the measurements of renal pelvis, ureters, and the exact position of the kidneys in relation to the lumbar vertebrae.
Conclusions and clinical relevance
This study provides a detailed anatomic description of the urinary tract in rabbits from CT imaging and reference values for further investigations.
... Recently, a method for quantitative analysis of small intestinal motility using ultrasonography has been developed in mice (Fig. 1), which enables noninvasive and rapid quantification of small intestinal motility [61]. Additionally, the usefulness of ultrasonography has been validated in animals other than mice [62][63][64]. Ultrasonography is an in vivo imaging modality that can be easily performed in both humans and animals and is expected to contribute to translational research. ...
In vivo assessment of murine gastrointestinal (GI) motility is useful for understanding GI diseases and developing effective therapies. The establishment of noninvasive measurement methods for mice will contribute to translational research bridging basic research and clinical practice, which can be a beneficial for maintaining quality of life in humans and animals. Recent advances in noninvasive diagnostic techniques have led to this update on the application and performance of available tests in mice. In vivo imaging techniques have been developed as noninvasive methods for the assessment of murine GI motility, and many of these methods have been applied to humans. Imaging techniques, including scintigraphy and ultrasonography, are frequently used in clinical practice. Basic data obtained using methods commonly used in clinical practice may be directly translated to clinical practice and are more attractive than those obtained using invasive methods. In this review, we provide recommended methods for noninvasively investigating gastric, small intestinal, and colonic motility in mice and detail the benefits of each test.
Exotic pets are presented to veterinary clinics with increasing frequency for routine, urgent, and emergency needs. With these increased visits, owners' expectations for high-quality veterinary care are also increasing. Many presenting complaints of reptiles, birds, and small mammals can benefit from the use of point of care ultrasound (POCUS) to establish a minimum database, aid in triage, and help guide further diagnostics, treatment, and prognostic discussions with the owner. Hospitalized exotic patients can also have their progress tracked and better assessed with the aid of POCUS.
Rabbits are a common companion animal and research subject and frequently require sedation to facilitate procedures. The objective of this study was to compare the effects of intramuscular butorphanol and midazolam combined with either alfaxalone or ketamine in rabbits. In a complete crossover study, healthy New Zealand white rabbits (n = 9; age, 6 mo) randomly received midazolam (1 mg/kg IM) and butorphanol (1 mg/kg IM) combined with either alfaxalone (2 mg/kg IM; ABM) or ketamine (5 mg/kg IM; KBM). Time to first effects, recumbency, and standing (recovery) were recorded. Every 5 min during recumbency, an investigator who was blind to treatment group collected serial physiologic parameters and sedation scores. At 5 min after rabbits became recumbent, manipulations were performed to mimic 2-view radiography and a cephalic intravenous catheter was placed. At 30 min after drug injection, flumazenil (0.05 mg/kg IM) was administered for reversal. Food consumption and fecal output were measured for 3 d after each study day. Time to standing and duration of recumbency differed significantly between groups. The median (range) of the total sedation score for ABM was 10 (8 to 10) and for KBM was 10 (6 to 10). Sham radiographs were successful in all rabbits in both groups. Physiologic parameters were not significantly different between groups over time. At 24 h after drug treatment, KBM-treated rabbits showed reduced food intake and both groups showed reduced fecal output. Total sedation scores decreased significantly over time in KBM rabbits (P < 0.001) but not in ABM rabbits (P = 1). The duration of recumbency was significantly longer in ABM rabbits than in KBM rabbits. Both protocols produced sufficient sedation for radiograph acquisition without clinically significant adverse effects.
Due to their effective analgesic properties, opioids are worthy of consideration for pain management in rabbits. However,this class of drugs causes undesirable effects including reduced gastrointestinal (GI) motility, reduced fecal output, and delays GI transit times and thus increases the risk of GI stasis. The risk of stasis discourages the use of opioids in rabbits, which could affect animal welfare. Gastroprokinetic agents such as cisapride are effective in promoting gastric emptying in many species, but whether this effect occurs in rabbits is unknown. This study assessed the efficacy of cisapride when administered as a single agent and in combination with buprenorphine in rabbits; efficacy was assessed by measuring GI transit times, fecal output, body weight, and food and water intake. Female New Zealand White rabbits (n = 10) were studied in a crossover,randomized design and received either vehicle and buprenorphine, cisapride and saline, cisapride and buprenorphine, or vehicle and saline (control) every 8 h for 2 d. Rabbits were anesthetized and administered radio-opaque, barium-filled spheres via orogastric tube. Feces was assessed via radiography for detection of the barium-spheres to determine GI transit time. GI transit time was significantly longer in buprenorphine groups than in control groups, regardless of the use of cisapride. Fecaloutput and food and water intake were lower for buprenorphine groups than control groups. Cisapride did not significantlyalter GI transit, fecal output, or food and water intake. In addition, treatment group did not significantly affect body weight. In conclusion, buprenorphine treatment (0.03 mg/kg TID) prolonged GI transit time and reduced fecal output and food andwater consumption in rabbits. Coadministration of buprenorphine and cisapride (0.5 mg/kg) did not ameliorate these effects,and the administration of cisapride at this dose did not appear to affect GI motility in female rabbits.
This study aimed to determine the ultrasonographic features and reference values of the
abdominal anatomy in mixed-breed dwarf rabbits. Complete abdominal ultrasonographic
examination was performed in 21 mixed-breed rabbits (12 males and 9 females) referred for
examination to the Department of Animal Medicine, Production and Health, University of
Padua, Italy. All animals were sedated during the procedure. The ultrasonographic anatomy of
the abdomen was determined, including measurement (mean±SD) of the right kidney (length
2.87±0.34 mm; width 1.62±0.17 mm; height 1.66±0.14 mm) and left kidney (length
2.86±0.33 mm; width 1.72±0.19; height 1.58±0.15 mm), left adrenal gland (width
0.38±0.11 mm; length 0.71±0.14), right adrenal gland (width 0.34±0.08 mm; length
0.73±0.15 mm) and thickness of the walls of the stomach (0.10±0.01 mm), pylorus
(0.28±0.04 mm), duodenum (0.19±0.04 mm), sacculus rotundus (0.22±0.06 mm), caecum
(0.08±0.01 mm), appendix (0.19±0.04 mm), spiral loop of the ascending colon
(0.14±0.04 mm) and distal colon (0.10±0.02 mm). A significant positive correlation between
bodyweight and kidney size, adrenal gland length, stomach wall and sacculus rotundus wall
was detected.
GASTROINTESTINAL stasis is a common syndrome in pet rabbits characterised by decreased or absent faecal output, decreased appetite, abdominal discomfort and lethargy (Harcourt-Brown 2002, 2007a, b, Oglesebee and Jenkins 2012, Varga 2014). Pathophysiological factors such as anorexia, pain, stress, dehydration, improper diet and trichobezoars can slow or inhibit gastrointestinal motility (Campbell-Ward 2012, Oglesebee and Jenkins 2012, Varga 2014). Clinical findings such as anorexia and lack of faecal production, in combination with radiographic findings of gaseous dilatation of the stomach, intestines and caecum, are well documented for diagnosing gastrointestinal stasis (Lichtenberger and Lennox 2010). However, there are very few data available in the literature about epidemiology of gastrointestinal stasis in pet rabbits.
This short communication describes a retrospective study about cases of gastrointestinal stasis diagnosed in pet rabbits presented to an exotic animal referral practice in England over a five-year period. Animals that were subsequently diagnosed with other diseases not directly related with the gastrointestinal tract were excluded from the study. Rabbits that underwent surgery within the month previous to the gastrointestinal episode were also excluded. The results were compared with a reference population that was constituted of all the rabbits presented for consultation over the same five-year period. Relative risk (RR) with 95% CIs was calculated and χ2 test were performed using a statistical software package (SPSS V.20.0, IBM).
Breeds, sex, age, date of occurrence and dental status at admission were systematically recorded. To examine the effect of phenotypic selection, the rabbits were classified …
Healthy adult horses were examined by using transabdominal ultrasonography to quantitatively and qualitatively evaluate activity of the jejunum, cecum, and colon with B mode and Doppler techniques. Doppler ultrasound was used to assess jejunal peristaltic activity. Examinations were performed on multiple occasions under imposed colic evaluation conditions, including fasting, nasogastric intubation, and xylazine sedation. In fasted horses, jejunal visibility was increased and jejunal, cecal, and colonic activity was decreased. The stomach was displaced ventrally and was visualized ventral to the costochondral junction. Xylazine sedation in fed horses had minimal effects; however, in fasted horses, xylazine significantly decreased jejunal and cecal activity. Nasogastric intubation in fasted horses had no observable effects on activity, but moved the stomach dorsally. B mode and Doppler jejunal activity were strongly correlated. Prior feeding and sedation status need to be considered when interpreting the results of equine abdominal ultrasound examinations. Doppler techniques may be useful for assessing jejunal activity.
Eighty-four incidents of gastric dilation (bloat) were investigated in 76 pet rabbits, and an intestinal obstruction was confirmed in 64 of them. In 49 the obstruction was due to pellets of compressed hair, in four to locust bean seeds, in five to neoplasia, in two to postspay adhesions, and in one case each to carpet fibre, tapeworm cysts, a strangulated hernia and diverticulosis. In all but four cases, the obstruction was in the small intestine. The condition affected a variety of breeds fed on a variety of diets. Radiography was a useful diagnostic tool because gas and/or fluid in the digestive tract outlined the dilated stomach and intestines. Twenty-nine of the rabbits died or were euthanased without treatment, and 40 underwent exploratory surgery; of these, 10 died during surgery, three were euthanased because of intestinal neoplasia, eight died postoperatively and 19 recovered. Fifteen rabbits in which radiography indicated that a foreign body had passed out of the small intestine did not undergo surgery; of these, 13 recovered and two died.
This article reviews diagnosis and management of gastrointestinal diseases in guinea pigs and rabbits. The review includes established causes of gastrointestinal disease in these species. The authors highlight syndromes that may be considered emerging or less-recognized causes of gastrointestinal stasis, including gastric dilation and volvulus in guinea pigs and lead toxicity, colonic entrapment, and liver torsion in rabbits. Practitioners should recommend initial diagnostics, including radiographs and blood work on guinea pigs and rabbits presenting with nonspecific signs of gastrointestinal stasis, to better determine possible cause and make the best treatment recommendations.
Gastrointestinal stasis is currently a vaguely defined term for decreased gastrointestinal motility. The term gastric stasis syndrome was previously proposed, but falls short of an accurate description, as in many cases portions of the gastrointestinal tract other than the stomach are affected. The term rabbit gastrointestinal syndrome (RGIS) defines a complex of clinical signs, symptoms, and concurrent pathologic conditions affecting the digestive apparatus of the rabbit. When ill rabbits present for examination it is important to determine if RGIS is present and if so, begin treatment and a diagnostic workup to determine underlying contributing factors. Identification of underlying cause is often difficult; many rabbits present with evidence of RGIS whereby attempts to identify an underlying cause are unfruitful. In many cases, these rabbits respond positively to supportive therapy including fluids, hand feeding, and motility-enhancing drugs.
Between September 1, 1982 and January 31, 1986, a study was undertaken in a total of 111 patients to assess the efficacy of ultrasonography in diagnosing intestinal obstruction and ileus. In 109 cases (98%), ultrasonography provided the correct diagnosis. In one case, obstruction was correctly suspected. In another case, the diagnosis was false negative. In 51 cases (46%), ultrasonography yielded the causative diagnosis. Ultrasonography was especially rewarding in the diagnosis of X-ray-negative intestinal obstruction, very high obstruction, clinically concealed incarcerated femoral hernias and in the differentiation of intestinal obstruction and ileus in the postoperative course. Ultrasonographic differential diagnosis was a reliable guideline for adequate treatment modalities in pertinent cases, thus contributing to therapeutic success.
Duplex-Doppler was used to visualize intestinal peristalsis in 30 patients with intestinal distension. The series included 12 patients with acute mechanical obstruction, 13 with long-standing mechanical obstruction, and five with paralytic ileus. The Duplex-Doppler recordings showed several patterns characterized by different degrees of intensity and frequency of the signals according to the type of obstruction, its duration, and the site of Doppler sampling relative to the obstructed segment. Duplex-Doppler evaluation provided both qualitative and quantitative data about intestinal peristalsis, allowing differentiation between mechanical and paralytic ileus. The visualization of intestinal segments having different degrees of peristaltic activity proved useful in localizing the site of mechanical obstruction.
Many techniques currently used to study motility of the small intestine are too complex for large-scale use; other techniques provide information that is nonspecific and nonquantitative. The aim of the present study was to verify whether intestinal peristalsis can be seen and quantitatively assessed by means of duplex Doppler sonography.
We prospectively studied 152 normal fasting subjects using sonography, duplex Doppler sonography, and stethoscopic auscultation or phonocardiographic registration of bowel sounds in three abdominal sites. In each subject, we positioned the sample volume near the intestinal wall and then recorded Doppler signals of different amplitude and duration that related to bowel motility. Studies were repeated after ingestion of water (n = 55) and after a standard test meal (n = 73). The number of peristaltic waves and the number of bowel sounds revealed by the different imaging techniques were compared and statistically evaluated by Student's t test.
Intestinal movements were classified as peristaltic or nonperistaltic (mixing movements) based on amplitude and duration of Doppler signals. The mean number of peristaltic waves revealed by Doppler sonography was three per minute in fasting subjects, with no significant increase after ingestion of water (3.78 per min) or the test meal (3.92 per min). The mean number of bowel sounds obtained with auscultation and phonocardiographic recordings was significantly higher in fasting subjects (8.7 per min) and after ingestion of water (9.55 per min) or the test meal (12 per min).
Intestinal contractions produce Doppler signals of different amplitudes and duration, thus potentially allowing differentiation between peristaltic and nonperistaltic movements. This differentiation is not possible with auscultation or phonocardiographic registration because similar bowel sounds are produced by nonprogressive, mixing movements as well as by true peristaltic movements. Duplex Doppler sonography allows graphic visualization of intestinal movements that can be subjected to qualitative and quantitative analysis and may be suitable for the noninvasive study of small-bowel motility.
The rabbit's gastrointestinal physiology is a complex system that centers around the separation of digestible and indigestible components of the diet in the proximal colon. The clinical importance of this system is the need for a consistent diet high in long particle length (> 0.5 mm) indigestible fiber to maintain the motility of the cecum and colon. Most of the common gastrointestinal problems seen in captive rabbits are related to inappropriate diets (low fiber; high protein; high carbohydrate) and infrequent feeding of treats to which the rabbit is not accustomed. Many of these problems can be avoided if captive rabbits are fed a diet consisting primarily of fibrous vegetation, such as grass, hay, and fibrous weeds. Feeding of fruits, grains, and carbohydrate or fat-based treats should be avoided. Pelleted feeds, although convenient, should be kept to a minimum, and where pellets are used those manufactured by an extrusion process, which retains the long particle length of the indigestible fiber, should be chosen.
The purpose of this study was to verify whether small intestinal peristalsis could be observed and quantitatively assessed using pulsed-Doppler ultrasound. Pulsed-Doppler ultrasound was used to evaluate small intestinal peristalsis after a meal in ten normal dogs and ten sedated dogs. The small intestinal peristalses were measured 0, 1, 3, 6, 9, 12, and 24 hours after a 24-hour fast and after feeding. The number of small intestinal peristalsis were 0.133/min, 0.100/min, 0.033/min, 0.167/min, 0.070/min, 0.067/min, and 0.100/min in the fasted dogs, and 1.667/ min, 0.933/min, 1.133/min, 1.234/min, 1.933/min, 1.533/ min, and 0.533/min in fed dogs, respectively. In the dogs sedated with xylazine HCl, the number of small intestinal peristalsis was significantly reduced (p<0.01). However, in the dogs treated with ketamine HCl and acepromazine, the number of small intestinal peristalsis remained unchanged. Therefore, it can be concluded that pulsed-Doppler ultrasound allows graphic visualization of the intestinal movements, which can be subjected to qualitative and quantitative analysis, and may be suitable for a non-invasive study of small intestinal motility.
A question frequently asked by clinicians who are treating small animals suspected of having gastrointestinal foreign bodies is whether one imaging test such as survey radiography or ultrasonography is sufficient to make the diagnosis. A study was undertaken to try and answer this question. Survey abdominal radiography and ultrasonography was performed on 16 small animals (11 dogs, five cats) with clinical signs of an obstruction because of a confirmed gastrointestinal foreign body. The majority of the foreign bodies (14/16) were confirmed by surgical removal and were located in the small intestine. A gastric foreign body was retrieved endoscopically and a colonic foreign body was passed in the feces. Radiographically identifiable foreign bodies were evident in nine animals. Small intestinal overdistension was present radiographically in seven animals. Ultrasonography detected a foreign body in all 16 animals. The foreign bodies were identified by their distal acoustic shadowing and variable degrees of surface reflection. An intestinal perforation was detected sonographically but not radiographically. The value of additional sonographic findings including thickening of the gastrointestinal wall and loss of layering, free peritoneal fluid, and lymphadenopathy in these animals is discussed. The findings in this series suggest that in a small animal with a gastrointestinal foreign body, ultrasonography alone could be used to make the diagnosis and may be a more appropriate choice than survey radiography.
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