Should you recommend abdominal rads on top of abdominal CT for staging of dogs with cancer?

Radiographs are of limited use and low cost-effectiveness when combined with ultrasound for abdominal restaging in dogs with solid, soft tissue tumours

T. J. Bevelock, O. T. Skinner, R. M. Baumgardner, L. Dean, J. S. Matheson, M. A. Mickelson, L. L. Donnelly, K. D. Hutcheson

Background
Abdominal imaging is a key component in restaging solid, soft tissue tumors in dogs. While ultrasound is widely used due to its superior resolution for soft tissues, abdominal radiographs are often included despite limited evidence of their additional benefit. This study aimed to assess the frequency of clinically relevant findings (CRFs) detected by radiographs versus ultrasound during abdominal restaging and to evaluate the cost-effectiveness of each modality.

Methods
A retrospective review of 223 restaging episodes across 159 dogs with solid, soft tissue tumors was conducted. Eligible cases involved concurrent use of abdominal radiographs (AXR) and ultrasound (AUS) for restaging. CRFs, defined as imaging findings that influenced diagnosis, prognosis, or treatment, were documented. The cost per CRF was calculated for both modalities based on institutional pricing. Statistical analyses compared the diagnostic yields and costs between AXR and AUS.

Results
Diagnostic Yield:
-AUS detected 92 CRFs (58.2% of total CRFs) as a standalone modality, while AXR alone detected just 1 unique CRF (0.6%).
-Combined use of AXR and AUS yielded 65 CRFs.
-AUS was significantly more effective in detecting CRFs than AXR (p < 0.001).

Cost-Effectiveness:
-The cost per CRF was $495 for AXR compared to $323 for AUS, with a cost ratio of 1:1.52.
-Including AXR added minimal diagnostic value while increasing costs and resource usage.

Clinical Findings: The single CRF detected by AXR alone (a sublumbar soft tissue opacity) was ultimately deemed a false positive upon subsequent imaging.

Limitations
The retrospective design introduced variability in imaging interpretation and lacked a gold-standard diagnostic comparator. The study also excluded certain tumor types (e.g., lymphoma) and relied on institutional cost data, which may limit generalizability. Limited restaging adherence reduced the sample size for follow-up evaluations.

Conclusions
Ultrasound was significantly more effective than radiographs in detecting CRFs during abdominal restaging of dogs with soft tissue tumors. The minimal diagnostic yield of radiographs, combined with higher costs and radiation exposure, does not support their routine use alongside ultrasound in this context. Eliminating radiographs could reduce costs and improve resource efficiency without compromising diagnostic outcomes.

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