The left lateral projection is comparable to horizontal beam radiography for identifying experimental small volume pneumoperitoneum in the canine abdomen

Abstract

Nontraumatic spontaneous pneumoperitoneum suggests the presence of gastrointestinal perforation; early detection can be lifesaving. Horizontal beam projections have been reported to be more sensitive than standard radiographic views for detecting small volumes of free peritoneal gas. This prospective, experimental, analytical study compared both left lateral (LL) and ventrodorsal (VD) standard views to horizontal beam projections for detecting small volumes of artificially induced pneumoperitoneum in live dogs. The effect of radiology training on accurate detection of small amounts of free peritoneal air was also assessed. Fourteen dogs had four radiographic projections taken after injection of 0, 2.5, 5, and 10 mL of cumulative air into their abdominal cavities. Radiographs were interpreted individually by three American College of Veterinary Radiology‐certified radiologists and three small animal internship‐trained veterinarians who were blinded to the air volume injected. At 2.5 and 10 mL of air injected, the LL projection had highest odds of an accurate response (odds ratio [OR] = 2.4 and 99.0 when compared to VD horizontal and VD projections, respectively). At 5 mL of air injected, the lateral horizontal (LH) projection had the highest odds of an accurate response (OR = 3.2 compared to VD horizontal). The LL projection was not significantly different from the LH projection at all volumes of air injected. Board certification led to higher odds of accurate responses at volumes of 5 (OR = 2.2) and 10 mL (OR = 3.6), as compared to nonspecialist veterinarians. Overall, LH and standard LL appeared to be the most useful radiographic projections for detection of small amounts of free peritoneal gas.

Accuracy of radiographic diagnosis of pneumoperitoneum secondary to gastrointestinal perforation in dogs and cats

“…The lateral view with a horizontally directed x‐ray beam has historically been suggested as the most sensitive view for detecting small volume pneumoperitoneum 27,28 . Recently, however, a study comparing horizontal beam radiography to standard left lateral projections found that evaluation of standard left lateral views were not significantly different from the lateral horizontal projection for all volumes of air tested 9 . Another study evaluating right lateral projections, left lateral horizontal beam and ventrodorsal projections found free gas was more likely to be detected on lateral computed radiography images than other projections 29 .…”

“…This does, however, raise the question if inexperience may lead to overdiagnosis of free gas in practice, and therefore unnecessary surgery. A recent paper also demonstrated that experience in radiology increased the odds of achieving an accurate response, although this was when examining patients with iatrogenic pneumoperitoneum 9 …”

“…In a recent paper, patient signalment was found to affect accuracy of detection of canine pneumoperitoneum 9 . This was thought to be most likely due to patients' body habitus affecting the inherent contrast from abdominal fat and gastrointestinal luminal gas 9 .…”

“…Recently, one study investigating the detection of small amounts of free peritoneal gas in experimental healthy dogs found observers with board certification had higher odds of accurate diagnoses with increasing volume of injected air 9 . However, having board certification was not significantly associated with an accurate diagnosis for volumes of air less than 5 ml when compared to small animal veterinarians without advanced training in radiology 9 …”

“…[1][2][3][4][5][6][7] In dogs, the most common cause of pneumoperitoneum is gastrointestinal perforation, which when identified, is considered a medical emergency and can be life threatening. 1,4,8,9 When presented to the clinic, patients with gastrointestinal perforation can sometimes be difficult to immediately diagnose. Clinical history often varies depending on the chronicity, severity and inciting cause.…”