Sources & References

Every tool on this site is built on published veterinary work rather than on general web writing. This page lists what that work is, so you can check it yourself. Where a page reports a figure from a study, the study is named on that page too — this is the consolidated list.

If you find something here that is out of date or that we have represented inaccurately, please tell us. Corrections are made and dated.

About These Citations

Where we have a DOI we have verified, it is linked. Where we have the journal, volume and page reference but have not independently confirmed a persistent identifier, we give the full reference without a link rather than guessing at one — a wrong DOI is worse than no DOI, because it sends you somewhere that is not the paper. Every reference here is complete enough to find through PubMed or your library.

Clinical Instruments We Implement

Several tools are interactive implementations of screening instruments developed and validated by veterinary researchers. In each case the tool follows the published scoring rule rather than a version of our own.

• Feline Musculoskeletal Pain Screening Checklist — Enomoto M, Lascelles BDX, Gruen ME. Development of a checklist for the detection of degenerative joint disease-associated pain in cats. Journal of Feline Medicine and Surgery, 2020;22(12):1137–1147. doi:10.1177/1098612X20907424
  Implemented in: Cat Arthritis Screening Tool. The six questions and the "any single no prompts further evaluation" rule are the authors'.
• Owner-assessed pruritus visual analog scale (pVAS) — Hill PB, Lau P, Rybníček J. Development of an owner-assessed scale to measure the severity of pruritus in dogs. Veterinary Dermatology, 2007;18(5):301–308. Further validated in Rybníček J, Lau-Gillard PJ, Harvey R, Hill PB, Veterinary Dermatology, 2009;20(2):115–122.
  Implemented in: Pet Itch Score Tracker. The 2009 paper's finding that visible numerical markings distort owner scoring is why our slider hides the number until after you place it.
• HHHHHMM Quality of Life Scale — Villalobos AE. Quality of life scale for pets in palliative and hospice care.
  Implemented in: Dog Quality of Life Calculator and Cat Quality of Life Calculator.
• Tufts Animal Care and Condition (TACC) weather safety scale — Patronek GJ, Tufts Center for Animals and Public Policy, 1997.
  Adapted in: Dog Cold Weather Safety Calculator. That page states plainly that TACC was built as a neglect-screening instrument for investigators rather than as an owner walk planner, and that we are adapting it.

Studies We Report Figures From

• Huang L, Coradini M, Rand J, Morton J, Albrecht K, Wasson B, Robertson D. Search Methods Used to Locate Missing Cats and Locations Where Missing Cats Are Found. Animals, 2018;8(1):5. doi:10.3390/ani8010005
  Used in: Lost Pet Search Plan — the 500 m recovery radius, the 50 m median for indoor-only cats, and the recovery-rate timeline. That page also notes that the study's physical-searching finding reached only p = 0.073, short of conventional significance, because the figure is widely repeated online as settled.
• Krontveit RI, Nødtvedt A, Sævik BK, Ropstad E, Trangerud C. Housing- and exercise-related risk factors associated with the development of hip dysplasia as determined by radiographic evaluation in a prospective cohort of Newfoundlands, Labrador Retrievers, Leonbergers, and Irish Wolfhounds in Norway. American Journal of Veterinary Research, 2012;73(6):838–846. doi:10.2460/ajvr.73.6.838
  Used in: How Much Exercise Does a Puppy Need? — stairs before three months associated with higher hip dysplasia risk; off-lead exercise on soft uneven ground associated with lower risk. The page notes this is an observational study of four large breeds and should not be stretched to toy breeds.
• Sallander MH, Hedhammar Å, Trogen ME. Diet, exercise, and weight as risk factors in hip dysplasia and elbow arthrosis in Labrador Retrievers. Journal of Nutrition, 2006;136(7):2050S–2052S.
  Used in: How Much Exercise Does a Puppy Need? — free-choice feeding associated with hip and elbow conditions.
• Quimby J, Gowland S, Carney HC, DePorter T, Plummer P, Westropp J. 2021 AAHA/AAFP Feline Life Stage Guidelines. Journal of Feline Medicine and Surgery, 2021. doi:10.1177/1098612X21993657
  Used in: Cat Age Calculator — the four age-based life stages (kitten to 1 year, young adult 1–6, mature adult 7–10, senior over 10) and the note that older six-stage charts use different labels.
• Buffington CAT, Westropp JL, Chew DJ, Bolus RR. Clinical evaluation of multimodal environmental modification (MEMO) in the management of cats with idiopathic cystitis. Journal of Feline Medicine and Surgery, 2006;8(4):261–268.
  Used in: Cat Urinary Health Checklist.
• Olivry T, Mueller RS, Prélaud P. Critically appraised topic on adverse food reactions of companion animals (1): duration of elimination diets. BMC Veterinary Research, 2015;11:225.
  Used in: Elimination Diet Trial Planner — trial duration.
• AAFP / ISFM feline environmental needs guidelines — Journal of Feline Medicine and Surgery, 2013;15(3):219–230.
  Used in: Cat Urinary Health Checklist — the five pillars framework.

Veterinary Associations & Reference Works

For clinical framing, prevalence and standard-of-care statements we work from association guidance and established veterinary references rather than from consumer blogs:

• American Veterinary Medical Association (AVMA) — feline lower urinary tract disease, including that straining in the litter box is more often urethral obstruction than constipation.
• American Association of Feline Practitioners (AAFP) — feline life-stage and environmental guidelines.
• WSAVA — body condition scoring, nutritional assessment.
• Merck Veterinary Manual — otitis externa, the primary/secondary/predisposing/perpetuating framework.
• Today's Veterinary Practice and dvm360 — clinical review articles, including the share of canine otitis externa attributable to atopic dermatitis.
• US Food and Drug Administration (FDA), Center for Veterinary Medicine — product approvals and label safety information, including the isoxazoline neurologic warning and the 2025 approval of the first once-yearly injectable canine flea and tick preventive.
• American Heartworm Society (AHS) — heartworm testing guidance: the roughly six-to-seven-month lag before an infection can be detected, testing schedules for puppies and after missed doses, annual testing on year-round prevention, pairing antigen with microfilaria testing, and antigen-plus-antibody screening in cats. Also its position on the melarsomine protocol versus "slow kill", which it describes as a salvage procedure rather than a treatment of choice. Used in Heartworm Test Cost and Heartworm Treatment Cost.
• Itemized US cost reporting — PetMD (veterinarian-reviewed) for line-by-line heartworm treatment prices, and MetLife Pet Insurance's published figures for surgical-removal cases. Used only for price ranges in Heartworm Treatment Cost, which shows the arithmetic behind its total.
• Manufacturer guarantee terms — the published Zoetis ProHeart satisfaction guarantee, cited only for what its conditions require (testing, purchase and administration by a veterinary practice) and what it covers. It is not a product recommendation.
• Association for Pet Obesity Prevention — weight and body condition data.
• Shelter medicine and neonatal rescue guidance — University of Wisconsin-Madison Shelter Medicine Program, Maddie's Fund, ASPCApro and the National Kitten Coalition, for neonatal warming, feeding volumes and stomach capacity.

What We Deliberately Do Not Use

This matters as much as the list above. During research we repeatedly encounter figures that are presented as if they came from studies but cannot be traced to one — content-marketing pages citing non-existent papers, or statistics that appear only on sites selling something. We exclude those, even when they would have made a page look more authoritative.

Two concrete examples of figures we found circulating and chose not to use: a specific daily water-intake threshold for cats attributed to a study we could not locate, and recurrence percentages for feline idiopathic cystitis attributed to a case series with no verifiable source. Where we could not verify a number, the page either omits it or says plainly that the evidence is weaker than it is usually presented to be.

How to Read Our Numbers

• Ranges, not targets. Weight charts and cost figures are bands because healthy animals and real invoices vary. We say where the variation comes from.
• Costs are US estimates and move with region and clinic type. We say so on cost pages and give the drivers rather than a single number.
• Screening is not diagnosis. Our screening tools indicate whether something is worth a veterinary conversation. None of them diagnoses, and several are deliberately built to err toward sending you to a vet.
• We name disagreement where it exists. Veterinary guidance is not always settled — the question of whether to withhold food from a pet with diarrhoea is a live example, and our page on it presents both positions rather than picking one silently.

See also our editorial policy for how pages are written, reviewed and corrected.