Small animal practices now have a 20-year national comparison point for reviewing post-operative outcomes after neutering procedures.
RCVS Knowledge has published the 20th anniversary National Audit for Small Animal Neutering (NASAN) benchmark report, bringing together data from 90,363 dog, cat and rabbit neutering procedures carried out between 2005 and 2025 across the UK and Republic of Ireland. Of these, 76,222 cases had known outcomes and were included in the benchmark calculations.
What the report covers
NASAN is a voluntary audit designed to help veterinary teams track short-term post-operative outcomes after small animal neutering. Practices can submit their own data, which is then cleaned, collated and analysed by RCVS Knowledge.
For 2025, the report introduces species- and procedure-specific benchmarks, rather than presenting neutering outcomes as a broad combined dataset. This means practices can compare dog spays with dog spays, cat castrates with cat castrates, and so on.
Outcomes are grouped using categories based on the Clavien-Dindo classification for surgical complications. These range from “no abnormality present” through to abnormal healing requiring medical or surgical treatment, and fatality.
Key benchmark figures
Across the full 2005 to 2025 dataset, the benchmark for “no abnormality present” after spay procedures was 75.5% in dogs, 86.3% in cats and 80.8% in rabbits.
For castrates, the equivalent figures were 75.4% in dogs, 95.2% in cats and 77.9% in rabbits.
The 2025-only data included 9,854 procedures, of which 7,559 had known outcomes. In that year, “no abnormality present” was recorded for 80.5% of dog spays, 86.9% of cat spays and 79.3% of rabbit spays. For castrates, the figures were 72.6% in dogs, 94.6% in cats and 81.2% in rabbits.
Why follow-up matters
The report also highlights the effect of missing outcome data. Cases lost to follow up were excluded from the benchmark calculations because the final clinical outcome was unknown.
Across the full benchmark period, 12% of spays and 20% of castrates were lost to follow up. The highest loss to follow up was seen in cat castrates, at 37%.
For practice teams, this is a useful reminder that audit findings are only as strong as the data behind them. Improving post-operative check attendance, recording telephone follow-up consistently, and capturing outcomes in a structured way can all make local audit data more meaningful.
Interpreting the data with care
RCVS Knowledge notes that case mix, patient factors and surgical techniques are likely to have changed over the 20-year period. Age, weight, breed type, cryptorchid status and surgical approach may all influence complication rates, so direct comparisons should be interpreted cautiously.
Rabbit benchmarks should also be treated with particular care, as rabbit data has only been collected from 2024 onwards and the dataset is much smaller than for dogs and cats.
The takeaway for practice teams
The NASAN report is not a pass-or-fail measure for neutering outcomes. Its main value is as a practical quality improvement tool.
Practices can use the data to compare their own audit findings with national benchmarks, discuss variation within the team, review follow-up processes and identify realistic areas for improvement over time.
Source / full details: RCVS Knowledge, National Audit for Small Animal Neutering Report 2025, published June 2026.
