Comparative Imaging In The Canine Acute Abdomen: Survey Radiography, Contrast-Enhanced Ultrasound, And Contrast- Enhanced Multi-Detector Helical Ct

Shanaman MM, Schwarz T, Gal A, et al.

American College of Veterinary Radiologists 2012:86.

Introduction/Purpose: Contrast-enhanced multi-detector computed tomography (CE- MDCT) is the current modality of choice in evaluating the human emergency patient with acute abdominal pain. The primary purpose of this study is to compare the diagnostic potential and agreement of survey radiography, combined B-Mode/contrast- enhanced ultrasound (CEUS) and CE-MDCT in evaluation of canine patients presenting with acute abdominal signs. We hypothesized that CE-MDCT would provide the most accurate staging and diagnosis of disease reliably differentiating surgical versus medical underlying conditions.

Methods: Nineteen dogs with acute abdominal signs were prospectively enrolled. All patients underwent routine abdominal radiography, B-mode and CEUS (the latter limited to identified lesion(s) with questionable perfusion) and dual-phase CE-MDCT. B-mode and CEUS images were evaluated prospectively by the primary author. Survey radiographic and CT images were evaluated retrospectively in a randomized blinded fashion by three independent reviewers (MMS, TS, RTO). Consensus was achieved for specific imaging findings.

Results: Eleven dogs were diagnosed with a condition requiring surgical intervention including hepatic abscessation (2), splenic abscess (sarcoma) with rupture (1), gastric perforation (B-cell lymphoma) (1), traumatic diaphragmatic hernia (1), and small intestinal mechanical ileus secondary to foreign body (6). CE-MDCT was the only modality to correctly identify all conditions requiring immediate surgical intervention. All small intestinal foreign bodies were visible on CT, 4 of which were linear in nature and each revealing a distinct and accurate zone of transition (confirmed by exploratory laparotomy). Spontaneous pneumoperitoneum was detected by both survey radiography and CT in two cases where routine ultrasound failed to do so. Routine ultrasound was most sensitive for detection of free fluid. CEUS provided improved sensitivity for detection of gastrointestinal hypoperfusion relative to CE-MDCT, although restricted field of view and patient motion were significant limitations.

Discussion/Conclusion: Survey radiography and routine B-mode ultrasound have inherent limitations including, but not limited to, superimposition of abdominal organs, non-specific findings, patient stress induced by manual restraint, duration of image acquisition and variable operator skill. We propose that CE-MDCT may effectively replace combined survey radiography and B-mode ultrasound in screening dogs with acute abdominal signs. A CT finding termed “mesenteric fat stranding” will be described for the first time in the veterinary literature and may prove beneficial in future studies as an estimation of severity of bowel ischemia. CEUS may be beneficial in evaluating lesions with questionable perfusion deficits following preliminary CE-MDCT evaluation.