Clinical Utility of Pneumogastrography in Dogs
Pneumogastrography utilizes negative contrast media such as air or carbonated beverages to improve visualization of luminal contents and mucosal surfaces within the stomach. Pneumogastrography as a diagnostic technique in cases of gastric disease has not been widely described in the veterinary literature and is a procedure that may yield additional information not obtained from survey radiographs. This technique is useful in the diagnosis of luminal and mucosal gastric diseases. In this article, the pneumogastrography technique and relevant literature are reviewed. Six case examples are included that demonstrate the utility of pneumogastrography in dogs with gastric disease.
Introduction
Radiography is a common initial diagnostic test when gastric disease is suspected, because it is noninvasive, inexpensive, and widely available. Gastrography is an excellent follow-up test when survey radiography is nondiagnostic or confirmation of a disease suspected on survey radiography is necessary.1–7 Specific indications for gastrography include suspicion of mural gastric disease; detection of luminal contents including radiolucent gastric foreign bodies; hematemesis; recurrent or nonresponsive vomiting; assessment of gastric size, shape, and location; and evaluation of motility.1,7 Evaluation of gastric motility can also be done under fluoroscopy.7,8
Pneumogastrography (i.e., negative contrast gastrography) utilizes air or carbonated beverages to improve visualization of the luminal contents and mucosal surfaces within the stomach. Grandage in 1974 first described the appearance of stomach gas in dogs and observed that gas provided an excellent contrast medium for outlining the gastric mucosa.2 Subsequent reports have confirmed that gas within the stomach outlines different regions, depending on patient positioning.1–4
Pneumogastrography has not been widely described in the veterinary literature as a diagnostic technique for use in cases of gastric disease.1,7 The procedure appears to be fast, safe, inexpensive, and may yield additional information not obtained from survey radiographs. The purposes of this paper are to describe the indications and technique for pneumogastrography and to provide clinical examples in which pneumogastrography assisted in the diagnosis of mural and luminal gastric disease.
Pneumogastrography Technique
Patient Preparation
Very little preparation is usually necessary. The stomach should be empty of ingesta; this may require that the animal be fasted for 12 to 24 hours. Fasting allows time for ingesta to leave the stomach and prevents superimposition of ingesta with other abdominal structures on the radiographs. However, it may be difficult to distinguish foreign material from normal ingesta. Survey radiographs are taken to determine the proper exposure technique and to ensure the stomach and colon are empty. If the animal resists passage of the orogastric tube, sedation of the animal may be indicated. A gastric hypomotility agent, such as glucagon, may be administered to induce gastric relaxation and improve visibility of the gastric mucosa and lumen.5 If the animal’s clinical status is deteriorating or if time is a factor in the animal’s treatment, fasting and administration of sedatives or hypomotility agents may be forgone.
Technique
Equipment required for pneumogastrography includes a mouth speculum, an orogastric tube, and lubricating jelly. The orogastric tube is measured from the dog’s nose to the last rib, and this point is marked with tape. Lubricating jelly is applied to the end of the orogastric tube. The orogastric tube is inserted through the mouth speculum and the oral cavity, down the esophagus, and into the stomach. A syringe is filled with room air at a dose of approximately 20 mL/kg, and the air is quickly administered through the tube to the point of palpable gastric distention. If the animal shows signs of discomfort during administration of the air, distention of the stomach is likely adequate and administration of air should cease. If administration of air by syringe does not result in adequate gastric distension, it may be necessary to physically blow into the tube to increase the volume of air in the stomach and prevent the escape of air from the orogastric tube. The tube is kinked and then rapidly removed to minimize the escape of air.
Left lateral and ventrodorsal radiographic views are immediately obtained, as these views are often the most diagnostic and are the most likely to reveal pyloric outflow obstructions. Other radiographic views such as the right lateral, dorsoventral, or lateral oblique views may also be taken. The exposure techniques used for pneumogastrography are identical to those used for the survey radiographs.
An alternative technique for pneumogastrography is the oral administration via syringe of approximately 60 mL of a carbonated beverage. This technique precludes the need to pass an orogastric tube. Occasionally, dogs may voluntarily drink the carbonated beverage from a bowl. Disadvantages of this latter technique include less gastric distension than with orogastric intubation and the addition of fluid that may obscure gastric structures.
Clinical Applications of Pneumogastrography
The following clinical cases demonstrate information that is gained from the use of pneumogastrography in dogs with gastric disease. Because of adequate animal cooperation, no sedatives were used in any of these dogs. None of the dogs were fasted or given gastric hypomotility agents because of the limited time that the animals were available for diagnostic imaging. Pneumogastrography was usually performed via orogastric intubation.
Case No. 1
A 13-year-old, spayed female Doberman pinscher was presented with a 2-day history of vomiting and possible foreign body ingestion. Plain abdominal radiographs demonstrated radiopaque material, fluid, and gas within the stomach and proximal duodenum [Figure 1A]. Pneumogastrography was performed, and a linear, opaque, soft-tissue structure was identified within the body and pylorus of the stomach that extended into the proximal duodenum [Figure 1B]. An exploratory celiotomy was performed, and a piece of carpet was removed from the stomach and duodenum.
Case No. 2
A 7-month-old, spayed female golden retriever was presented for vomiting of 2 days’ duration and possible foreign body ingestion. Survey abdominal radiographs showed a mildly distended stomach with mottled gas and soft-tissue opacities in the lumen. Multiple loops of small intestine containing mottled soft-tissue material and abnormal gas patterns were seen in the midventral abdomen [Figures 2A, 2B]. Pneumogastrography was performed, and soft-tissue material was outlined within the stomach and within portions of the small intestine [Figures 2C, 2D]. Radiographic findings were consistent with a gastric and proximal small-intestinal linear foreign body. A gastrotomy was performed via celiotomy, and grass and string were removed from the stomach. String was removed from the duodenum and jejunum via an enterotomy.
Case No. 3
An 8-year-old, spayed female, golden retriever/mixed-breed dog was presented with a history of vomiting and anorexia of 1 month’s duration that persisted despite medical therapy with cimetidine, metoclopramide, and amoxicillin. Survey abdominal radiographs were unremarkable [Figures 3A, 3B]. With pneumogastrography, a region of increased soft-tissue thickness was delineated at the lesser curvature of the stomach [Figures 3C, 3D], and a gastric mural mass was suspected based on the radiographic findings. Abdominal ultrasonography demonstrated gastric wall thickening with loss of normal wall layers. Exploratory celiotomy with duodenal and gastric biopsies revealed a gastric carcinoma.
Case No. 4
A 12-year-old, spayed female English setter was presented with a history of ptyalism, gagging, anorexia, and one episode of vomiting. Survey abdominal radiographs demonstrated a curvilinear, opaque structure within the pylorus [Figure 4A] that became more obvious with pneumogastrography [Figure 4B]. Endoscopy was performed, and a Brazil nut was removed from the stomach.
Case No. 5
A 12-year-old, miniature pinscher was presented with a history of hematemesis. Survey abdominal radiographs demonstrated increased soft-tissue opacity within the stomach [Figure 5A]. Pneumogastrography revealed the presence of a multilobulated mural mass at the cardia of the stomach [Figure 5B]. The final diagnosis was gastric leiomyoma, which was obtained by endoscopy and biopsy of the gastric mass.
Case No. 6
A 10-year-old, spayed female Siberian husky was presented for vomiting of 1 day’s duration, with a prior history of foreign body ingestion. Survey radiographs revealed a moderately distended gastric pylorus containing gas and a soft-tissue opacity. On the left lateral survey radiograph, a tubular, soft-tissue opacity with a lucent center was present within the pylorus; streaky, mottled gas and soft-tissue material were seen within the small intestine of the midabdomen [Figures 6A, 6B]. Pneumogastrography was performed via administration of approximately 45 mL of a carbonated beverage per os, which caused moderate gas distention of the stomach and proximal duodenum. On the left lateral radiograph, a linear structure was delineated within the pylorus and the proximal duodenum. The duodenum was mildly plicated around the soft-tissue structure [Figures 6C, 6D]. Endoscopy was performed, and a sock was removed.
Discussion
When mural and/or luminal gastric disease is suspected, several diagnostic options are available, including survey radiography, gastrography, ultrasonography, endoscopy, and exploratory laparotomy.1,7–9 Advantages and disadvantages of each option are listed in the Table.
Pneumogastrography utilizes the principle that negative contrast within the stomach provides improved visualization of the gastric lumen and mucosa, because it creates an air/soft-tissue interface, as well as gastric distension. Gas within the stomach can outline specific anatomical regions of the stomach, depending on the positioning of the animal and the quantity of gas versus fluid present. Gas rises to the nondependent portions of the stomach; thus, in the left lateral view, gas lies within the pylorus, and in the right lateral view, gas outlines the fundus. On the ventrodorsal view, gas is usually in the pylorus and the body; and on the dorsoventral view, gas outlines the fundus.1–4 The left lateral and ventrodorsal views are usually performed first with pneumogastrography, because these views allow visualization of the pylorus. Visualization of the pylorus more commonly reveals foreign bodies and mural masses associated with pyloric outflow obstructions.1,4,7
Gastric hypomotility agents were not utilized in the cases discussed in this report; however, such agents have been used for double contrast gastrography in the normal dog and cat.5,6 Glucagon is a hypomotility agent that produces gastric relaxation and may improve visualization of the gastric mucosa.5 Glucagon was not used in the cases discussed in this study because of adequate visibility of the gastric lumen and mucosa (without the drug) and the lack of availability of glucagon. Glucagon is contraindicated in animals with pheochromocytoma and diabetes mellitus because of glucagon-mediated release of catecholamine and glucose, respectively.5
No complications or side effects associated with pneumogastrography have been noted in previous reports or in the cases presented here.1,5 To the authors’ knowledge, gastric dilatation-volvulus has not been reported following this procedure; however, it has been recommended that double contrast gastrography should not be performed in animals with a prior history of gastric torsion.7 Trauma to the oropharynx, esophagus, or stomach may occur during passage of the orogastric tube if the animal resists passage of the gastric tube or if the tube is passed forcefully. The orogastric tube may fold onto itself within the stomach if the tube length is too long.
An advantage of pneumogastrography is that it does not impede visualization of gastric mucosa or gastric contents during subsequent endoscopy. In comparison, the use of barium in upper gastrointestinal studies requires that endoscopy be delayed for 12 to 24 hours.10 One disadvantage of pneumogastrography is that the additional air instilled within the stomach acts as a barrier to the transmission of ultrasound beams and prevents visualization of deeper structures in the abdomen. Therefore, pneumogastrography should not be performed prior to ultrasonography if ultrasonography is to be performed on the same day.
Pneumogastrography provides more detailed information on gastric mural and luminal diseases, which may facilitate diagnosis and allow a more accurate prognosis. Although the cases presented in this report only included dogs, the authors have also performed pneumogastrography in cats with gastric disease. In case nos. 1, 2, 4, and 6, pneumogastrography allowed prompt and detailed visualization of gastric and proximal small intestinal foreign bodies. In case nos. 3 and 5, pneumogastrography increased the visualization of gastric mural masses when survey radiographic findings were of questionable significance. Pneumogastrography was a fast, noninvasive, inexpensive diagnostic test that delineated intraluminal and mural gastric diseases. Pneumogastrography does not replace other diagnostic tests such as ultrasonography, endoscopy, and exploratory celiotomy; however, it may be useful when such diagnostic tests are unavailable or unaffordable.
Conclusion
Pneumogastrography is clinically useful in the diagnosis of luminal and mural gastric diseases. The additional gas administered in pneumogastrography creates more contrast with the surrounding soft tissues of the stomach and also distends the stomach, which increases the visualization of abnormal structures. The technique appears to be fast, safe, and inexpensive, thereby providing an additional diagnostic option for certain gastric diseases.
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Citation: Journal of the American Animal Hospital Association 41, 3; 10.5326/0410171
Survey left lateral (A) abdominal radiograph of a Doberman pinscher (case no. 1) with a 2-day history of vomiting. Radiopaque material surrounded by gas and fluid was present within the stomach (single arrow) and proximal duodenum (arrowheads). Pneumogastrography was performed, and the left lateral (B) abdominal radiograph revealed an opaque, soft-tissue structure within the gastric body and pylorus that extended into the proximal duodenum (arrows). The appearance of the structure was consistent with a linear foreign body.
Survey left lateral (A) and ventrodorsal (B) abdominal radiographs of a golden retriever (case no. 2) with a 2-day history of vomiting. The radiographs revealed mild distention of the stomach with mottled gas and soft-tissue opacities (arrows). Multiple loops of small intestine also contained abnormally shaped gas patterns and mottled soft-tissue opacities (arrowheads). Left lateral (C) and ventrodorsal (D) abdominal radiographs obtained with pneumogastrography indicated a soft-tissue opacity within the stomach and proximal duodenum (white arrows) that was consistent with a foreign body.
Survey right lateral (A) and ventrodorsal (B) abdominal radiographs of a golden retriever (case no. 3) with vomiting and anorexia of 1 month’s duration. Pneumogastrography revealed an increased soft-tissue opacity at the lesser curvature of the stomach (arrows) on both left lateral (C) and ventrodorsal (D) radiographs. The gastric wall was also grossly thickened adjacent to the lesion. A gastric mural mass was suspected, and gastric carcinoma was confirmed at celiotomy.
Survey right lateral (A) abdominal radiograph of an English setter (case no. 4) with ptyalism, gagging, anorexia, and vomiting. A curvilinear, opaque structure was present within the pylorus (black arrow). A left lateral radiograph (B) after pneumogastrography, showing improved visualization of the pyloric foreign body (white arrows). The foreign body was a Brazil nut.
Survey ventrodorsal (A) abdominal radiograph of a miniature pinscher (case no. 5) with hematemesis, indicating increased soft-tissue opacity within the stomach (black arrows). Ventrodorsal radiograph (B) after pneumogastrography, revealing a multilobulated gastric mural mass at the cardia (white arrows). The final diagnosis was gastric leiomyoma.
Survey left lateral (A) and ventrodorsal (B) abdominal radiographs of a Siberian husky (case no. 6) with vomiting of 1 day’s duration. A tubular, soft-tissue structure is visible within the pylorus (black arrows), and mottled gas and soft-tissue material are seen within the small intestine (white arrows) on the lateral view (A). Pneumogastrography improved visualization of the linear structure within the pylorus and the proximal duodenum (black arrows) on both the left lateral (C) and ventrodorsal (D) radiographs. The duodenum was mildly plicated. A sock was retrieved via endoscopy.
