Open Veterinary Journal, (2022), Vol. 12(2): 281–289 ISSN: 2226-4485 (Print) Original Research ISSN: 2218-6050 (Online) DOI: 10.5455/OVJ.2022.v12.i2.17 Submitted: 22/12/2021 Accepted: 30/03/2022 Published: 20/04/2022 Horizontal and vertical beam radiographs in vomiting dogs to diagnose mechanical gastrointestinal ileus: A diagnostic imaging comparative study Maria Frau Tascon1* , Hock Gan Heng2 , Rosa Novellas Torroja1 , Yvonne Espada Gerlach1 and Carlo Anselmi1,** 1 Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain 2 Veterinary Clinical Sciences, Purdue University College of Veterinary Medicine, West Lafayette, IN, USA ** Current address: Pride Veterinary Centre-Scarsdalevets, Derby, UK Abstract Background: The horizontal beam (HB) view has been used in the identification of pneumothorax, pleural effusion, and pneumoperitoneum in small animals. Based on the literature, there were no published data evaluating the utility of HB radiography in vomiting dogs to differentiate between patients with or without mechanical gastrointestinal ileus. Aim: The purpose of this prospective pilot study was to determine the utility of HB radiograph as an additional view in vomiting dogs to differentiate patients with or without mechanical gastrointestinal ileus; and describe if there are any radiographic image characteristics associated with the HB view for patients with mechanical gastrointestinal ileus. Methods: A prospective study was carried out on dogs presented with acute vomiting. For all dogs, four radiographic views [ventrodorsal (VD), right lateral, left lateral, and left-to-right lateral HB in sternal recumbency] of the abdomen and abdominal ultrasound were obtained. If a mechanical ileus was detected ultrasonographically, an exploratory laparotomy or endoscopy was performed, otherwise medical treatment was elected. Results: A total of 22 patients were recruited, 11 diagnosed with mechanical ileus and 11 without mechanical ileus. Three blinded reviewers independently assessed the radiographs in three sets: vertical beam (VB) views, HB view alone, and a combination of both views. No statistical difference was found in the differentiation between patients with or without mechanical gastrointestinal ileus between HB views alone or added to VB views. Conclusion: This study suggests that the HB view in sternal recumbency may be an alternative for patients who are not stable enough to be positioned in lateral or VD recumbency. Keywords: Canine, Radiographic projection, Gastrointestinal obstruction, Foreign body. Introduction intraluminal gas in the overlying bowel or peritoneal Horizontal beam (HB) radiography was first used in the free gas, patient weight, poor restraint, possible patient diagnosis of human pneumothorax in 1966 (Kurlander discomfort, and body conformation (Shanaman et al., and Helmen, 1966). Horizontal beam radiography has 2013; Garcia and Froes, 2014). been recommended as an useful additional view in the Abdominal radiography in horses is always performed in identification of pneumothorax, pleural effusion, and the standing position with HB because it is not feasible pneumoperitoneum in small animals, and it has been to perform VB studies due to the large size of these reported that HB was approximately twice as likely to patients (Butler et al., 2017). Vertical beam radiography identify concurrent free fluid and air as vertical beam is feasible in small size foals. Gas-capped fluid levels (VB) radiography (Lynch et al., 2012; Ng et al., 2019). in hollow organs can only be evaluated on radiographs Survey radiography and abdominal ultrasonography are obtained in the standing position with HB views (Gibbs the current preferred imaging modalities for evaluation and Pearson, 1973; Butler et al., 2017). Horizontal beam of acute vomiting in dogs, especially when foreign body views allow clinicians to take advantage of the physical ingestion is suspected and other systemic causes (e.g., nature of gas and fluid (Lynch et al., 2012). In the HB renal disease) have been ruled out. Multiple veterinary view, different levels of the gas-capped fluid lines in the studies have shown that abdominal ultrasonography same intestinal loop are commonly seen in the intestinal improves detection of gastrointestinal foreign bodies mechanical ileus, instead in paralytic ileus, gas-capped and has improved accuracy for diagnosing mechanical fluid lines tend to be at the same level in a given ileus when survey radiographic studies are equivocal U-shaped section of the intestine (Gibbs and Pearson, (Sharma et al., 2011; Ciasca et al., 2013). Abdominal 1973; Dennis et al., 2010; Geng et al., 2018). ultrasonography, however, has its limitations such as Although HB view is commonly practiced in equine being operator-dependent, possible interference/lack medicine, this technique has not been systematically of visibility of organs of interest due to presence of studied for small animal abdominal pathologies (Lynch *Corresponding Author: Maria Frau Tascon. Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, Carrer de l’Hospital s/n, 08193, Bellaterra, Barcelona, Spain. Email: frutascon@gmail.com 281 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 et al., 2012). The objectives of this study were to (1) ultrasonographically, an exploratory laparotomy or determine the diagnostic accuracy of HB radiograph endoscopy was performed, otherwise medical treatment as an additional view in vomiting dogs to differentiate was elected. For patients treated surgically, the location patients with or without mechanical gastrointestinal and type of foreign body were documented. For patients ileus; and (2) describe if there are any radiographic in the medically treated group, 2 weeks’ follow-up by image characteristics associated with the HB view for phone call or at the hospital was performed. According patients with mechanical gastrointestinal ileus. The to the outcome, the patients were classified into two authors hypothesized that the HB view, alone or added groups: dogs with mechanical ileus (group A) and to VB views in patients presented with a history of dogs without mechanical ileus (group B). Images were acute vomiting, would increase the diagnostic accuracy stored in the Digital Imaging and Communications in to differentiate patients with or without mechanical Medicine (DICOM) format to be reviewed later, in gastrointestinal ileus. individual review sessions using different workstation, by two board certified radiologists (H.G.H and R.N.T) Material and Methods and a senior professor veterinary radiology specialist This pilot study was a prospective, diagnostic case- (Y.E.G). All reviewers had more than 15 years of control study. Privately owned dogs were prospectively experience in film reading. The cases were reviewed recruited for an observational diagnostic accuracy in three sittings, the first sitting consisted of only VB study at the veterinary hospital (Fundació Hospital views, the second sitting consisted of only lateral HB Clínic Veterinari Universistat Autònoma de Barcelona) view and the third sitting consisted of a combination between January 2015 and June 2016. Written consent of VB and lateral HB views. The cases were randomly from each patient’s owner was obtained on admission. assigned a number using an open-source web-based Subject inclusion for the study was determined by one random integer generator (http://www.random.org) for of the authors (C.A. at that time, third-year diagnostic each sitting. The reviewers evaluated the three sets of imaging resident). Patients selected were those who images independently with at least 1 week apart from presented with signs of acute vomiting (less than 2 each sitting. The reviewers were only provided with weeks), without other gastrointestinal signs such as the history of acute vomiting and were blinded to the diarrhea and without any chronic disease identified at outcome of the cases. serum biochemistry and hematology (e.g., chronic renal The following criteria were examined by the disease). Patients were excluded if there were obvious reviewers: small intestinal distension and disposition, radiographic signs of mechanical gastrointestinal presence of gas-capped fluid lines, presence of sign of ileus caused by a large mineral or metallic opaque intussusception, presence of foreign bodies (number and foreign object(s) or an unequivocal obstruction pattern location), serosal margins visualization, and presence or due to linear-textile foreign body in the standard VB absence of peritoneal effusion and pneumoperitoneum. radiographic views. The reviewers were required to document the presence For all included dogs, four radiographic views of small-sized nonobstructive foreign material (e.g., (standard VB radiographic views [ventrodorsal (VD), pinpoint to millimetric mineral material/stones), even right lateral, and left lateral (LL)] and an additional if considered incidental. The reviewers had the option left-to-right lateral HB in the sternal recumbency of to add comments after the evaluation of each study. the abdomen were obtained (System: Premium Vet- Accuracy on the diagnosis of mechanical gastrointestinal variable focal distance, Sedecal, Madrid, Spain; X-ray ileus tube: Rotanode E7239X, Toshiba, Tokyo, Japan), The presence of a mechanical gastrointestinal ileus was using variables mAs and kVp determined by the considered when at least two of the following criteria thickness of each individual patient. For the HB view, were included by the reviewers: a focal distension a mobile antiscatter grid provided by the manufacture of the small intestine, stacked or plicated disposition of the X-ray machine was used. A radiolucent soft of the intestinal loops, and the suspected presence pad was placed between the table top and the patient of intraluminal foreign material. For the analysis in during the HB view: this was found to be important the detection of gastrointestinal mechanical ileus, to increase the distance between the patient and the patients with a small amount of pinpoint to millimetric table, allowing all the ventral portion of the patient’s small-sized gastric foreign material were considered abdomen to be included in the view. The image quality nonobstructive. of each study was evaluated and approved by C.A. Serosal margins visualization, peritoneal effusion, and After the radiographic study, all the patients included pneumoperitoneum underwent abdominal ultrasound (Mylab 70; Esaote, Reviewers were asked to differentiate if the serosal Genova, Italy) performed by C.A. The studies were margins visualization was normal or decreased, and performed in dorsal recumbency using microconvex to describe the presence or absence of peritoneal (CA 123; 3-9 MHz; Esaote) and linear (LA523, Esaote effusion and pneumoperitoneum. Ultrasonography 4-13) transducers. If a mechanical ileus was detected was used as a gold standard to confirm the presence 282 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 of diffuse or focal peritonitis, peritoneal effusion, and following day, and by resolution of the clinical signs. pneumoperitoneum. One case was finally diagnosed with gastrointestinal Small intestinal distension intoxication, secondary to mushroom ingestion, The small intestinal distension was determined if the confirmed by the history after the imaging studies small intestinal distension ratio was higher than 1.6 were performed. The remaining nine cases were times the height of the mid-vertebral body of L5. The presumptively diagnosed with gastroenteritis and/or distended intestine was then classified as diffuse or pancreatitis due to the resolution of the clinical signs focal. after the medical treatment. A total of 88 radiographs Presence of gas-capped fluid lines were available for review. A total of 198 answers from The presence or absence of different levels of the 3 reviewers were available for analysis. A total of 22 gas-capped fluid lines in the same intestinal loop was cases were evaluated by 3 reviewers to achieve 66 recorded by the reviewers. answers in each sitting. Small intestinal disposition Accuracy on the diagnosis of mechanical gastrointestinal The reviewers described the disposition of the small ileus intestine as normal, stacked, or plicated. The accuracy on the detection of mechanical ileus Statistical analyses in the three sittings was evaluated and there was no Statistical analyses were performed by a statistician, statistically significant increase in the accuracy of using commercially available software (SPSS v15.0, detection of mechanical ileus between VB views, HB SPSS Inc., III: Chicago, IL). Ultrasound was used as view, and the combination of VB and HB views (p = 0.24) the gold standard. Post-hoc analysis (G*Power 3.1) (Table 1). Hence, there was no statistical significance with a power analysis of 80% and α error of 0.05 was to support the authors’ hypothesis whereby the HB used to determine sample size, and approximately view, alone or added to VB views in patients presented 64 answers were needed. All results were classified with a history of acute vomiting, would increase the as categorical data and then comparisons between diagnostic accuracy on the diagnosis of gastrointestinal group A (with mechanical ileus) and group B (without mechanical ileus. Reviewers’ sensitivity and specificity mechanical ileus) were made for the radiographic views values for mechanical ileus with VB views were in and reviewers. Univariate analysis was performed the ranges of 64%–93% and 61%–91%, respectively, using Pearson’s χ2 or Fisher’s exact test for categorical and with both HB and VB views were 64%–93% and variables. Interobserver agreement for the accuracy 54%–86%, respectively. When HB view was evaluated on the diagnosis of mechanical gastrointestinal ileus alone, sensitivity and specificity were in the ranges of was tested with kappa statistic, defined as (observed 42%–77% and 57%–88%. The strength of agreement agreement-expected agreement)/(1-expected between the reviewers was 0.72 (good agreement). agreement). The level of agreement was classified as Interestingly, in one case diagnosed without mechanical poor (κ < 0.20), fair (κ between 0.21 and 0.4), moderate gastrointestinal ileus, all the reviewers classified it (κ between 0.41 and 0.6), good (κ between 0.61 and wrongly as mechanical ileus when evaluating the VB 0.80), and excellent (κ >0.80) (Landis and Koch 1977). views and correctly with only the HB view (Fig. 1). A value of p < 0.05 was considered as the critical level Serosal margins visualization, peritoneal effusion, and of significance. pneumoperitoneum Ethical approval The answers are summarized in Table 2. A statistically Not required for this study. significant difference was observed on the detection of abnormal serosal margins visualization (p = 0.05) Results between HB and VB views. No evidence of statistical A total of 22 dogs were included. The weight of the significance on the detection of peritoneal effusion (p = dogs ranged from of 3.0 to 34.2 kg (median = 15.3 0.98) or pneumoperitoneum was found comparing both kg). There were four Staffordshire Bull Terriers, two HB and VB views (p = 1). Labrador Retrievers, two Boxers, two Beagles, two Small intestinal distension Yorkshire Terriers, two Miniature Pinschers, three The diagnosis of diffuse small intestinal distension was mixed breeds, and one dog each of five other breeds. higher with the HB view (8/66) than with the VB views Of the 22 cases, 11 were included in group A and 11 (2/66). However, focal intestinal distension was higher were included in group B. In group A, two had a gastric with the VB views (24/66) than with the HB view foreign body obstruction, four had a linear foreign body (17/66). obstruction, three had jejunal foreign body obstruction, Presence of gas-capped fluid lines one had multiple foreign bodies obstruction located The presence of variable gas-capped fluid lines on the in the stomach and jejunum, and one had an intestinal HB view was positive in 36/66 cases, 78.8% (26/33) volvulus. In group B, one case was presented with from group A and 30.3% (10/33) from group B. multiple uncountable small nonobstructive mineral Small intestinal disposition gastrointestinal foreign bodies, which were passed, In the evaluation of the small intestinal disposition as confirmed by follow-up radiographic study the (classified as normal, plicated, or stacked), comparing 283 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 Table 1. Reviewers’ interpretations in 22 dogs. Reviewer Cases Correct diagnose VB views Mechanical ileus 9/11 1 No mechanical ileus 10/11 Mechanical ileus 10/11 2 No mechanical ileus 9/11 Mechanical ileus 8/11 3 No mechanical ileus 7/11 HB view Mechanical ileus 6/11 1 No mechanical ileus 10/11 Mechanical ileus 6/11 2 No mechanical ileus 9/11 Mechanical ileus 8/11 3 No mechanical ileus 6/11 VB + HB views Mechanical ileus 7/11 1 No mechanical ileus 9/11 Mechanical ileus 10/11 2 No mechanical ileus 10/11 Mechanical ileus 10/11 3 No mechanical ileus 5/11 VB: Vertical beam; HB: Horizontal beam. the different views, the results were as follows: 9/66 large animals. In this study, all the cases presented with cases presented a plicated disposition on the VB views acute vomiting of less than 2 weeks: 12 cases of 1-day and 6/66 on the HB view, and 14/66 were stacked on duration (5 from the group A and 7 from the group B; 8 the VB views versus 16/66 on the HB view (Table 3). cases of less than 7 days (3 from the group A and 5 from the group B); and 2 cases of less than 14 days (both Discussion from the group A). Accuracy on the diagnosis of gastrointestinal The sensitivity for detecting mechanical ileus was lower mechanical ileus using the HB view alone. In this view, a decreased The study failed to prove that the HB view, alone or serosal detail is more frequently described compared added to VB views in patients presented with a history of to the VB views, perhaps due to suboptimal technique acute vomiting, would increase the diagnostic accuracy of the HB view as the exposure techniques of VB to differentiate patients with or without mechanical views (e.g., exposure parameters, collimation, used of gastrointestinal ileus. We found no statistical difference antiscatter grid, and others) have been developed with in the detection of mechanical gastrointestinal ileus years of experience. However, the specificity using the between the HB view alone or added to VB views. HB view alone was slightly higher than using both the One of the reasons could be the absence of a control HB and VB views. This may be a type I error, due to the group in the study, which would have helped to identify subjective evaluation of each reviewer. The HB view normal radiographic findings in HB view, e.g., the is not a standard view to asses abdominal disorders in serosal margins visualization. Another possibility is dogs, thus the reviewers involved in the study have no the acuteness of the presenting clinical signs. In large prior experience interpreting the HB view. Secondary animals, patients tend to be presented after showing to this, the reviewers, when evaluating the VB and HB clinical signs for a longer period. In small animals, the in combination, were probably more prone to base their owners tend to easily observe if the patient is vomiting, final judgment on the standard VB views giving less as the animals are usually kept in door, as opposed to importance to the HB. In addition, the cases included in 284 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 Fig. 1. (A) Right lateral; (B) ventrodorsal; (C) left lateral; and (D) left-to-right lateral HB views of the abdomen of a dog presented with acute vomiting. In this case, the patient was correctly diagnosed as without mechanical ileus with the HB view and incorrectly diagnosed as mechanical ileus with the VB view by all reviewers. Abdominal ultrasound was unremarkable. Table 2. Comparison of decreased serosal margins visualization, pneumoperitoneum, and peritoneal effusion detection between views. VB HB VB+HB Decreased serosal margins visualization 25/66 (37.8%) 29/66 (43.9%) 20/66 (30.3%) Peritoneal effusion 15/66 (22.7%) 21/66 (31.8%) 18/66 (27.3%) Pneumoperitoneum 4/66 (6.1%) 7/66 (10.6%) 5/66 (7.6%) VB: Vertical beam; HB: Horizontal beam. 285 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 Table 3. Comparison of small intestinal disposition between with the HB view. We consider that it is possibly the different views. more difficult to visualize focal distension at the most dependent part of the abdomen with the HB view due Small intestinal disposition VB view HB view to fluid gravitation and a higher degree of crowding of Normal 43/66 44/66 the abdominal structures. Specific assessment of large Plicated 9/66 6/66 intestine identification in the different views was not Stacked 14/66 16/66 asked to the reviewers; authors hypothesized that the HB view did not supply more information to distinguish large from small intestines compared to VB views, thus this study were complicated, as the obvious mechanical colonography (positive or negative) is still needed. obstructions due to mineral or metal opaque foreign Presence of gas-capped fluid lines bodies and/or unequivocal linear foreign bodies were The presence of variable gas-capped fluid lines has excluded. This study focused on cases that are usually been reported as a radiographic sign of mechanical equivocal and where additional ultrasound or contrast gastrointestinal ileus in the HB view (Gibbs and studies are needed for further diagnostics. Pearson, 1973; Harlow et al., 1993). This study The results of this study shows that the HB view should confirms that 78.8% of the mechanical ileus cases not be used alone as the sensitivity and specificity exhibit this sign. However, this is not specific as 30.3% is low. The combination of VB view and HB view of the without mechanical ileus cases also have this together did not improve the sensitivity and specificity, similar radiographic sign (Fig. 2). Thus, the presence probably due to the minimal additional information of gas-capped fluid lines in the HB view needs to be gained with the HB view. Thus, it is not recommended interpreted carefully and it is not a pathognomonic to incorporate the HB view as a routinely abdominal sign for mechanical ileus. However, it may suggest view to diagnose mechanical ileus according to the mechanical ileus and need further investigation. ALARA/ALARP principles. In this study, specific timing between radiographic Serosal margins visualization, peritoneal effusion, and views was not recorded. The HB view was carried out pneumoperitoneum just after the VB views. The author (C.A.) personally We found statistical differences on the evaluation of involved in performing the radiographic studies found serosal margins visualization, being VB view superior that it was initially difficult to achieve the HB view to HB view. Based on our results, the HB view mainly due to lack of experience in this technique diagnosed more frequently a decrease in the serosal (collimation, different parameters, use of antiscatter margins visualization, and an increased presence of grid, superposition of hind limbs, and rotation/ peritoneal effusion compared with VB view. Since movement of the patient as no sedation was used), but there are no previous studies in healthy dogs describing the learning curve was fast (e.g., use of a radiolucent soft the serosal margins visualization using the HB view, we pad to increase the height of the patient from the table proposed that these findings could be artefactual due to and enhance comfort in sternal position, and stretching the position of the organs in the most dependent part caudally the hind limbs) and the HB view was usually because of the gravity effect and crowding. achievable in few minutes. There are no documented Pneumoperitoneum was more often visualized in the data specifying the time (minutes) of recumbency to HB view compared with the VB views in this study. This obtain a better visualization of the fluid-gas levels or was expected, as it is widely described in the literature redistribution of gas. More conspicuous amounts of gas that HB view has a higher accuracy in detecting small in the pylorus and duodenum are expected in the LL volumes of pneumoperitoneum (Thrall, 2013; Ng et al., view after prolonged LL recumbency (Vander Hart and 2019). In this study, there was no statistical difference Berry, 2015). detecting pneumoperitoneum between VB and HB Small intestinal disposition views, probably due to the low number of cases with It is reported that normal small intestinal loops are the presence of pneumoperitoneum. usually diffusely distributed in the abdominal cavity Small intestinal distension with a smooth round turn, appearing as continuously The authors did not find an explanation for the more curving tubes or as solid circles or rings (Thrall, frequent visualization of diffuse small intestinal 2013). In cases of mechanical ileus, the intestinal distension in the HB view. One of the hypotheses loops become progressively distended, the segments considered was that gas rises and fluid gravitates, thus become crowded into a relatively smaller space, often generalized gas-distended small intestines in the dorsal assuming a stacked appearance (Thrall, 2013). In aspect of the abdomen is easily identify, compared to this study, the use of the HB view did not affect the fluid filled intestines in the dependent (ventral) aspect visualization of small intestinal disposition compared of the abdomen. HB view thus allows the reviewers with the VB views, thus a different recumbency seems to visualize the diffuse small intestinal distension in not to alter the small intestinal disposition. However, the more dorsal aspect of the abdomen. However, the organs crowding at the ventral aspect of abdomen visualization of the small focal distension was lower make it difficult the evaluation of fluid/soft tissue filled 286 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 Fig. 2. Left-to-right lateral HB views in sternal recumbency of two different patients. (A) A dog with mechanical ileus due to a gastro-jejunal linear foreign body. Note the presence of different levels of the gas-capped fluid lines in the small intestine. Additionally, there is a curvilinear radiopaque structure in the stomach, which was not identified in the standard VB views but recognized on the HB view. (B) A dog diagnosed with gastrointestinal intoxication secondary to mushroom ingestion in group P. Note the presence of the different level of gas-capped fluid lines in the small intestines’ loops. intestines when there is concurrent peritoneal effusion be secondary to a partial mechanical obstruction, where due to border effacement of structures (Fig. 3). maybe the HB view could be beneficial. For future A potential limitation of this study is that reviewers are work, a larger number of dogs and a control group of not familiar interpreting the HB view in small animals, normal dogs may be helpful. as its use is not widespread and not all radiographic In summary, there was no statistical difference between equipment has this option. The time between viewing the HB view alone or in combination with VB views sessions could have affected the reviewer’s radiographic to differentiate dogs with or without mechanical evaluation, as they could remember the cases between gastrointestinal ileus. However, for patients who are each sitting. To avoid this limitation, a minimum of 1 not stable enough to be positioned in lateral or VD week time gap was established, although it might not be recumbency, the HB view in sternal recumbency may long enough. The order of viewing sessions had not been be valuable as an alternative radiographic view. randomized and could be considered a limiting factor. Conflict of interest An additional bias of the study is the exclusion of cases The authors declare that they have no conflict of with chronic (more than 2 weeks) vomiting, which can interest. 287 http://www.openveterinaryjournal.com M. F. Tascon et al. Open Veterinary Journal, (2022), Vol. 12(2): 281–289 Fig. 3. 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