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WSAVA guidelines for the control of reproduction in dogs and cats

2024; Wiley; Volume: 65; Issue: 7 Linguagem: Inglês

10.1111/jsap.13724

1748-5827

Stefano Romagnoli, Natali Krekeler, Kerry Cramer, Michelle Anne Kutzler, Robert J. McCarthy, S. Schaefer‐Somi,

Human-Animal Interaction Studies

1. Introduction 5 1.1. Use of this document 6 2. Surgical sterilisation in dogs and cats 7 2.1. Surgical methods of sterilisation in dogs and cats associated with loss of gonadal hormones 7 2.1.1. Female dogs 7 2.1.1.1. Ovariectomy, subtotal ovariohysterectomy and ovariohysterectomy 7 2.1.1.1.1. Ventral midline laparotomy for ovariectomy in dogs 9 2.1.1.1.2. Ventral midline laparotomy for subtotal ovariohysterectomy in dogs 14 2.1.1.1.3. Ventral midline laparotomy for ovariohysterectomy in dogs 14 2.1.1.1.4. Flank laparotomy for ovariectomy and subtotal ovariohysterectomy in dogs 17 2.1.1.1.5. Laparoscopic ovariectomy, subtotal ovariohysterectomy and ovariohysterectomy in dogs 17 2.1.1.1.6. Ventral midline laparotomy for surgical sterilization of the periparturient female dog21 2.1.1.1.6.1. Hysterotomy and concurrent subtotal ovariohysterectomy 22 2.1.1.1.6.2. En-bloc subtotal ovariohysterectomy 25 2.1.1.1.7. Prevention and treatment of complications associated with ovariectomy, subtotal ovariohysterectomy and ovariohysterectomy. 26 2.1.2. Female cats 30 2.1.2.1. Ovariectomy, subtotal ovariohysterectomy and ovariohysterectomy 30 2.1.2.1.1. Ventral midline laparotomy for ovariectomy in cats 31 2.1.2.1.2. Ventral midline laparotomy for subtotal ovariohysterectomy and ovariohysterectomy in cats 33 2.1.2.1.3. Flank laparotomy for ovariectomy and subtotal ovariohysterectomy in cats 33 2.1.2.1.4. Laparoscopic ovariectomy, subtotal ovariohysterectomy and ovariohysterectomy in cats33 2.1.3. Male dogs 33 2.1.3.1. Orchiectomy in dogs with descended testes 33 2.1.3.1.1. Prescrotal orchiectomy in dogs 33 2.1.3.1.2. Prevention and treatment of complications associated with prescrotal orchiectomy in dogs 37 2.1.3.1.3. Scrotal orchiectomy in dogs 37 2.1.3.1.4. Orchiectomy in dogs with scrotal ablation 37 2.1.3.2. Orchiectomy in dogs with cryptorchid testes 37 2.1.3.2.1. Cryptorchidectomy of an extra-inguinal testis 40 2.1.3.2.2. Cryptorchidectomy of an inguinal testis 40 2.1.3.2.3. Ventral midline laparotomy for cryptorchidectomy of an intra-abdominal testis 40 2.1.3.2.4. Laparoscopic cryptorchidectomy in dogs 41 2.1.4. Male cats 41 2.1.4.1. Orchiectomy in cats with descended testes 41 2.1.4.1.1. Scrotal orchiectomy in cats 41 2.1.4.2. Orchiectomy in cats with cryptorchid testes 43 2.1.4.2.1. Cryptorchidectomy of an extra-inguinal testis 43 2.1.4.2.2. Cryptorchidectomy of an inguinal testis 43 2.1.4.2.3. Ventral midline laparotomy for cryptorchidectomy of an intra-abdominal testis 45 2.2. Surgical sterilisation of dogs and cats with preservation of gonadal hormones 45 2.2.1. Female dogs 45 2.2.1.1. Hysterectomy 45 2.2.1.1.1. Ventral midline laparotomy for hysterectomy in dogs 46 2.2.1.1.2. Flank laparotomy for hysterectomy in dogs 48 2.2.1.1.3. Laparoscopic hysterectomy in dogs 48 2.2.1.2. Salpingectomy 48 2.2.1.3. Ovarian tissue implant50 2.2.2. Female cats 51 2.2.2.1. Hysterectomy 51 2.2.2.1.1. Ventral midline laparotomy for hysterectomy in cats 51 2.2.3. Male dogs 51 2.2.3.1. Vasectomy 51 2.2.3.1.1. Prescrotal vasectomy in dogs 52 2.2.3.1.2. Laparoscopic vasectomy in dogs 52 2.2.4. Male cats 54 2.2.4.1. Vasectomy 54 2.2.4.1.1. Bilateral inguinal vasectomy in cats 54 2.2.4.1.2. Prescrotal vasectomy in cats 54 2.2.4.1.3. Ventral midline laparotomy for vasectomy in cats 55 2.2.4.1.4. Laparoscopic vasectomy in male cats 55 2.2.4.2. Epididymectomy in male cats 55 2.3. Antimicrobial use for surgical sterilisation 55 2.4. Surgical sterilisation and pain control 59 3. Non-surgical sterilisation in dogs and cats 59 3.1. Hormonal downregulation 59 3.1.1. GnRH agonists and antagonists 59 3.1.1.1. GnRH agonist: Deslorelin 60 3.1.1.1.1. Male dogs 60 3.1.1.1.2. Female dogs 60 3.1.1.1.3. Male cats 61 3.1.1.1.4. Female cats 61 3.1.1.2. GnRH antagonists: acyline and antide 61 3.1.1.2.1. Female dogs 61 3.1.1.2.2. Cats 61 3.1.2. Progestogens 62 3.1.2.1. Megestrol acetate 62 3.1.2.1.1. Female dogs 62 3.1.2.1.2. Female cats 62 3.1.2.1.3. Male dogs 62 3.1.2.2. Medroxyprogesterone acetate 63 3.1.2.2.1. Female dogs 63 3.1.2.2.2. Female cats 63 3.1.2.2.3. Male dogs 63 3.1.3. Androgens 63 3.1.3.1. Mibolerone 63 3.1.3.1.1. Female dogs 63 3.1.3.1.2. Female cats 64 3.1.3.2. Other androgens 64 3.1.4. Melatonin 64 3.1.4.1. Female cats 64 3.1.4.2. Male cats 64 3.2. Immunocontraceptives 64 3.2.1. Immunisation against gonadotropin-releasing hormone 64 3.2.1.1. GnRH-conjugated to keyhole limpet haemocyanin 65 3.2.1.1.1. Male dogs 65 3.2.1.1.2. Female dogs 65 3.2.1.1.3. Male cats 65 3.2.1.1.4. Female cats 65 3.2.1.2. GnRH-conjugated to diphtheria toxin 65 3.2.2. Immunisation against zona pellucida 65 3.2.2.1. Female dogs 66 3.2.2.2. Female cats 66 3.2.3. Immunisation against GnRH and ZP 66 3.3. Chemical castration 66 3.3.1. Intratesticular injection 66 3.3.1.1. Calcium chloride 66 3.3.1.1.1. Male dogs 66 3.3.1.1.2. Male cats 67 3.3.1.2. Zinc gluconate 67 3.3.1.2.1. Male dogs 68 3.3.1.2.2. Male cats 68 3.3.1.3. Glycerol 68 3.3.1.3.1. Male dogs 68 3.3.1.3.2. Male cats 68 3.3.2. Intra-epididymal injections 68 3.3.2.1. Male dogs 68 3.3.2.2. Male cats 69 3.4. Mechanical methods 69 3.4.1. Intrauterine devices 69 3.4.2. Therapeutic ultrasonography 69 3.5. Gene therapy 69 3.5.1. Gene silencing 69 3.5.2. Gene overexpression 70 4. Health benefits of sterilisation with loss of gonadal steroid hormones 70 4.1. Female dogs 70 4.1.1. Reproductive tract diseases 70 4.1.1.1. Ovarian diseases 70 4.1.1.2. Uterine diseases and unwanted pregnancies 72 4.1.1.3. Reproductive tubular tract neoplasia 72 4.1.1.4. Mammary tumours 73 4.1.1.5. Transmissible venereal tumour 75 4.1.1.6. Vaginal hyperplasia and vaginal prolapse 76 4.1.1.7. Disorders of sexual development 77 4.1.2. Progestogen dependent diabetes mellitus 77 4.1.3. Behavioural issues 78 4.1.4. Life expectancy 78 4.2. Male dogs 81 4.2.1. Reproductive tract diseases 81 4.2.1.1. Testicular diseases 81 4.2.1.2. Prostate gland diseases 82 4.2.1.2.1. Benign prostatic hyperplasia 82 4.2.1.2.2. Prostatitis 83 4.2.1.2.3. Prostatic neoplasia 84 4.2.2. Perianal gland tumours 84 4.2.3. Transmissible venereal tumour. 84 4.2.4. Urethral prolapse 85 4.2.5. Perineal hernia 86 4.2.6. Behavioural concerns 86 4.2.7. Life expectancy 88 4.3. Cats 88 4.3.1. Reproductive tract diseases 88 4.3.1.1. Inflammatory mammary diseases in female cats 90 4.3.1.2. Proliferative diseases of the mammary gland in cats 90 4.3.1.2.1. Mammary fibroadenomatosis in cats 90 4.3.1.2.2. Mammary tumours 91 4.3.2. Infections and diseases of the immune system 92 4.3.3. Behavioural issues 92 4.3.4. Life expectancy 92 5. Health detriments of sterilisation with loss of reproductive hormones 92 5.1. Female dogs 93 5.1.1. Tumours 93 5.1.1.1. Mast cell tumours 93 5.1.1.2. Transitional cell carcinomas 94 5.1.1.3. Osteosarcoma 94 5.1.1.4. Lymphomas 95 5.1.1.5. Haemangiosarcomas 96 5.1.2. Urethral sphincter mechanism incompetence 96 5.1.3. Orthopaedic diseases 98 5.1.4. Metabolic and endocrine disorders 99 5.1.5. Immune disorders 100 5.1.6. Behavioural concerns 101 5.1.7. Paediatric gonadectomy 102 5.2. Male dogs 102 5.2.1. Tumours 102 5.2.1.1. Prostate gland tumours 102 5.2.1.2. Mast cell tumours 105 5.2.1.3. Transitional cell carcinomas 105 5.2.1.4. Osteosarcomas 105 5.2.1.5. Lymphomas 105 5.2.1.6. Haemangiosarcomas 105 5.2.2. Urethral sphincter mechanism incompetence (USMI) 106 5.2.3. Orthopaedic diseases 106 5.2.4. Metabolic and endocrine disorders 107 5.2.5. Immune disorders 107 5.2.6. Behavioural concerns 108 5.2.7. Paediatric gonadectomy 109 5.3. Cats 109 5.3.1. Effects on metabolism 109 5.3.2. Orthopaedic diseases 110 5.3.3. Tumours 110 5.3.4. Lower urinary tract diseases 110 5.3.5. Paediatric gonadectomy 110 6. Ethics of Reproduction Control in dogs and cats 111 6.1. Introduction 111 6.2. Overpopulation and shelter intake 111 6.3. Trap, neuter, return programmes 111 6.4. Responsible pet ownership 112 6.5. Variation of spaying and neutering rates 113 6.6. Early age spaying and neutering 113 6.7. Ethical implications of sterilisation of dogs and cats 113 6.8. Mandatory spay and neuter laws 114 6.9. Recommendations on reproduction control of dogs and cats in different settings 114 6.10. Position of Reproduction Control Committee on prosthetic testicular implants 117 7. References 118 During the second half of the last century, dogs and cats have gained an important place in many households and their numbers have increased remarkably in many countries. While there are anecdotal estimates of pet ownership by country provided on websites and in the lay literature, there is a lack of peer-reviewed data on the actual world population of dogs and cats, both owned and unowned. These animals may easily reproduce once they achieve puberty if not constantly under control. Therefore, veterinarians are continuously presented with requests to contain or eliminate reproductive behaviour or fertility as a whole in owned dogs and cats. The increased presence of small animals in our homes has been paralleled by an increase in dog and cat populations in suburban areas where free-roaming stray or unsupervised animals reproduce uncontrolled, causing public health concerns. Animal shelters in many areas are overcrowded by dogs and cats. Proactive rehoming, adoption and sterilisation policies are being promoted in many parts of the world. However, shelter populations seem to have remained stable and have, despite all these efforts, increased in some countries/areas/municipalities (Crawford et al., 2019). Therefore, controlling dog and cat reproduction has always been a key issue for veterinarians working in animal welfare organisations and for small animal practitioners alike. The historical approach to controlling dog and cat reproduction has been through surgical gonadectomy. For males, multiple surgical methods, approaches and means of haemostasis have been utilised with success and precise technique is generally based on surgeon experience and preference. For females, removal of all (ovariohysterectomy, OHE) or part (subtotal ovariohysterectomy; SOHE) of the uterus may be performed concomitantly with removal of the gonads. While many veterinary textbooks describe the OHE procedure with ligatures placed and subsequent transection made at the level of the uterine body, it is important to recognise that this is both anatomically and physiologically incorrect. Some portion of the uterus will inevitably remain in the patient and therefore what is being performed, is a SOHE (Mejia et al., 2020). SOHE should be avoided as it exposes the female to the risk of developing a uterine stump condition should an ovarian remnant be present, or a progestogen treatment administered at a later date. Ovariectomy (OE) alone is quicker, uses a smaller incision and is associated with less potential complications (Okkens et al., 1997). Consequently, in the absence of uterine pathology, and if lack of gonadal hormones is both predicted and desired, these guidelines recommend OE as the preferred surgical procedure for sterilisation of female dogs and cats. Laparoscopic sterilisation is less painful and provides better visualisation of all pertinent structures, especially in small breed dogs. Owner familiarity with minimally invasive surgery in humans is producing a large demand for its use in pets (Buote, 2022). Surgical sterilisation techniques that maintain gonadal hormones such as vasectomy and hysterectomy have also been proposed as effective and safe means of inhibiting reproduction in pets (Kutzler, 2020b; McCarthy, 2019; Zink et al., 2023). Alternatives to the surgical removal of gonads for dogs and cats have existed since the second half of last century. The first drugs commercially available for the control of reproduction in small animals were synthetic analogues of progesterone (progestogens) that block the action of the hypothalamic–pituitary–gonadal (HPG) axis. Unfortunately, improper use in dogs and cats has led to several case reports of side effects from overdosing (Romagnoli & Ferre-Dolcet, 2022; Romagnoli & Lopate, 2017). After careful patient selection, progestogen use at the appropriate dose and duration can be a safe and effective method for reproduction control. Earlier this century a new category of active principles, long-acting preparations of gonadotropin-releasing hormone (GnRH) agonists became available as veterinary drugs in some countries allowing for prolonged duration of reproduction control (Fontaine & Fontbonne, 2011; Goericke-Pesch et al., 2013; Romagnoli et al., 2009; Trigg et al., 2006). The effect of a single administration of a long-acting GnRH agonist implant varies from 6 to 12 months (depending on dosage) in dogs and is much longer in cats. Repeated administration is effective and appears to be safe based on the limited data available (Brändli et al., 2021; Romagnoli et al., 2023). Therefore, its use in bitches for which surgery is not an option may be considered. Long-acting GnRH agonists are approved in some countries for use in male dogs and cats and in prepuberal bitches; their off-label use is proving effective and safe in queens while more data is needed to warrant its use in postpubertal bitches. Male dogs and cats may also be rendered sterile by local administration of chemical agents (Oliveira et al., 2013). Approaches such as vaccination against GnRH or, more recently, gene therapy causing overexpression of Mullerian inhibiting substance are promising, particularly for females (Levy et al., 2005, 2011; Ochoa et al., 2023; Vansandt et al., 2023; Vargas-Pino et al., 2013). The remarkable extent of current knowledge on this topic makes it increasingly challenging for veterinarians to advise clients and stakeholders on the best approach to reproduction control for small animals. This is particularly true for small animal practitioners given the emotional value clients usually place on pets. Reproduction control as a presenting request has gone from the very simple "I would like my pet to be spayed/neutered" to a very elaborate set of questions the most intriguing of which are "how and at what age should it be done" and more recently and importantly "should we do it or not"? As a consequence of the more important role dogs and cats are playing in our lives, shelter conditions have also been receiving increased attention from the public and social media. Once in a shelter, rescued or captured animals are invariably gonadectomised, a practice which continues around the world using a standard surgical approach. Reproduction of shelter animals needs to be blocked permanently as this prevents further reproduction and increases their chances of being adopted. Therefore, surgical sterilization remains a valid solution in certain situations because of its ease and cost-effectiveness. However, evidence is accumulating in favour of the efficacy of newer surgical techniques which, in spite of maintaining reproductive behaviour, may offer the option of adopting healthier animals. Small animal practitioners need to acquaint themselves with current knowledge regarding reproductive control offering a host of novel approaches replacing the potentially harmful practice of routine gonadectomy of young dogs and cats. The best options for reproduction control in dogs and cats are the ones that have the least long-term health concerns which may be more pronounced particularly in large and giant breed dogs (Benka et al., 2023). For owned pets, such a decision should be made on a case-by-case basis in consultation with the owner with due consideration of species, sex, breed, purpose and lifestyle of the pet as well as financial constraints. Albeit less ideal for the individual pet, methods for reproduction control in the shelter environment may differ to that of owned animals. Effective strategies to curb reproduction of stray dogs and cats are lacking, may be cost- and labour-intensive and are often regarded as controversial (Read et al., 2020; Wolf et al., 2019). Shelter policy makers will only agree to the selection of permanent sterilisation options that are affordable and they oppose alternative options which maintain sexual behaviour in pets as that may lessen the probability of adoption and increase pet abandonment. Veterinarians are in a key position to educate policy makers and the pet-adopting public about alternative approaches with less long-term health concerns. Their action may in time lead to acceptance of reproduction control options that better align with the health concerns of individual pets. The purpose of this document is to assist veterinarians best apply current knowledge on surgical and medical reproduction control methods in dogs and cats with animal welfare as the first and foremost priority. Animal welfare is an elaborate concept, which requires sound scientific knowledge as well as applying common sense amidst the diverse settings of small animal practice. The risk of long-term health concerns associated with routine gonadectomy may no longer be acceptable for all owned pets. The concerns of shelter policy makers should be acknowledged. Cats and smaller breed dogs may be continued to be gonadectomised by traditional gonadectomy at traditional ages. Conversely, vasectomy and ovary-sparing surgery should be offered as an alternative option to gonadectomy following proper consultation with the prospective owners of large and giant breed dogs at risk. There is not a single technique which is ideal in all situations or one which should never be used. Every approach to reproduction control has advantages and disadvantages depending on the practical/financial situation of the owner, genetics of the animal, age, health, lifestyle and purpose for which the animal is kept. Over the last few decades evidence of long-term health concerns associated with surgical gonadectomy such as orthopaedic, behavioural, endocrine and neoplastic conditions is continuing to emerge. As a consequence, the development of alternative reproduction control methods for animals at risk ensued. As more data becomes available on age of gonadectomy and individual breed risk, the choice of best reproduction control option based on individual case by case in consultation with pet owners will improve. Although surgical gonadectomy may remain a valid option for cats of both sexes and small and medium-sized female dogs, in large male and female dogs potential health concerns associated with gonadectomy may make alternative options more appropriate and should be considered both in client- as well as shelter-owned animals. The body of evidence regarding detriments and benefits of gonadectomy is complex, sometimes conflicting and differs depending on sex, species, age of gonadectomy and breed. Arriving at the best possible decision for the individual pet requires wide and intensive consultation with the pet owner. Considering the complex nature of this decision-making process and the multitude of factors to consider, the reproduction control guidelines are intended to provide a tool for small animal practitioners and policy makers to reach informed, consensual decisions while meeting the welfare interest of the animals, expectations of the pet owners and avoiding possible litigation. Whilst there is a general expectation that guidelines should be concise and consistent, this is not achievable with the reproduction control guidelines. This is because there is a complex network of variables and circumstances that impact on the decisions of, should I or should I not neuter and if so, at what age and what method should I use. Therefore, standard routine recommendations suited as "best practice" for all animals cannot be made. What has become clear, however, is that the decision to routinely neuter all animals not intended for breeding can no longer be supported for all categories of animals. Harmonising risk/benefit assessment with client preferences, shelter requirements and most importantly, ultimate long-term welfare of the individual animal requires a thorough understanding of the confounding elements involved. These include age at gonadectomy, species, sex, breed, animal lifestyle, purpose of animal and whether the animal is owned and whether there is responsible pet ownership. In cases where there is responsible pet ownership, best practice may be to leave the animals unaltered unless there is a medical necessity to intervene. This had been advocated for decades in some parts of the world. In cases where permanent sterility is non-negotiable, hysterectomy may be suggested as an option. Routine OE and OHE should be reserved for those animals at lower risk or for those animals where the elimination of both reproduction and reproductive behaviour is necessitated. Sterilisation of dogs and cats is the most common surgical procedure performed by small animal practitioners worldwide (Greenfield et al., 2004). Numerous methods are employed successfully and can be divided into those that remove the source of gonadal hormones and those that preserve them. The role of gonadal hormones on long term health is debated, and this issue is discussed in detail later in this document. Gonadectomy by removal of the ovaries alone (OE), or with concomitant partial (SOHE) or complete (OHE) removal of the uterus are the most common methods of surgical sterilisation of female dogs (Fig 1). Preventing cystic-endometrial-hyperplasia-pyometra complex has been touted as a reason for performing OHE but this condition will not occur without the presence of remnant ovarian tissue or an exogenous source of progesterone (DeTora & McCarthy, 2011; Noakes et al., 2001). Uterine tumours can be prevented by removal of the entire uterus, but the incidence of these is quite low and many are benign (Brodey, 1970; Saba & Lawrence, 2020). In addition, to our knowledge uterine neoplasia has not been reported in a dog or cat that has had OE alone before 2 years of age (DeTora & McCarthy, 2011). The incidence of uterine neoplasia if OE or SOHE is performed after 2 years of age is unknown and warrants investigation. Advantages of OE over the alternate procedures include a smaller incision and therefore possibly less pain, shorter surgical times, fewer sites for potential haemorrhage, less likely inadvertent ureter ligation and easier access to the ovarian pedicles (DeTora & McCarthy, 2011; Okkens et al., 1997; Van Goethem et al., 2006). For these reasons, in the absence of uterine pathology or pregnancy, OE is the preferred procedure for routine surgical sterilisation of female dogs if loss of gonadal hormones is desired. OE, SOHE and OHE can each be performed by either laparotomy or laparoscopy. With the exception of OHE, the incision can be either on ventral midline or flank. Potential advantages of midline laparotomy include increased familiarity of regional anatomy for most surgeons and ability to simultaneously explore the abdomen for other reasons if necessary. Potential advantages of the flank laparotomy include less damage to mammary gland tissue if these glands are enlarged and easier visualisation of the incision after surgery in shelter or feral population situations (McGrath et al., 2004). No significant difference in ease of surgical procedure, rate of complications or pain has been consistently demonstrated between the laparotomy approaches, so choice is one of personal preference and training (Griffin et al., 2016; Looney et al., 2008). Laparoscopic surgery is less painful than laparotomy and provides improved visualisation and safety, especially in large breed dogs (Culp et al., 2009; Devitt et al., 2005; Fransson & Mayhew, 2015; Hancock et al., 2005). Wound complications are less frequent after laparoscopic procedures (Charlesworth & Sanchez, 2019). Owner familiarity with minimally invasive surgery in humans has produced a large demand for performing sterilisation procedures with this method (Buote, 2022; Hsueh et al., 2018). Each of the laparotomy procedures can be performed in paediatric (6- to 16-week-old) patients, provided several precautions are taken (Faggella & Aronsohn, 1994; Kustritz, 2002; Looney et al., 2008; Oliveira-Martins et al., 2023; Olson et al., 2001; Porters et al., 2015; Kustritz, 2002). Patients should be healthy, properly immunised for their age and have normal hydration status. A complete pre-anaesthetic physical exam should be performed, and a warm preoperative and postoperative environment provided. While traditional recommendation has been to avoid fasting greater than 4 hours to avoid hypoglycaemia, recent data suggests that hypoglycaemia does not occur in paediatric puppies ≥0.9 kg fasted for longer durations (Fudge et al., 2022). Puppies should be provided food after surgery as soon as the patient is able to stand (Griffin et al., 2016). Tissue dissection must be meticulous to avoid damage to delicate vital structures. All animals surgically sterilised should be identified by tattoo, or other easily identified external means to avoid inadvertent reoperation at a later date (Looney et al., 2008; Mielo et al., 2022). Microchips are gaining popularity for pet identification, but inaccuracy of owner data, added expense and required access to an appropriate microchip reader limit their usefulness for identification of sterilisation status (Brent, 2019). A green linear tattoo applied to the ventral aspect of the abdomen either on or immediately lateral to the ventral midline is recommended for both female and male dogs (Griffin et al., 2016). If a flank approach is used for sterilisation of a female patient, the tattoo should be placed where a ventral midline incision would have been. Tattoo ink or paste can be applied directly to the surgical incision after intradermal closure, placed in a separate cutaneous incision or injected intradermally (Bushby, 2013; Griffin et al., 2016; Welborn et al., 2011). A recent survey-based study including all USA and Canadian veterinary schools indicated that curricula included discussion of sterilisation identifiers in only 31% of lecture-based training, 75% of spay/neuter laboratory training and 38% of clinical practice-based training. The same study found that while 80% of shelters and 72% of spay/neuter clinics tattooed all owned animals, and 84% of shelters and 70% of spay/neuter clinics tattooed all unowned animals, private practices identified sterilisation status after surgery in only 5% of patients (Mielo et al., 2022). Enhanced training and implementation of sterilisation identifiers are needed throughout the veterinary industry (Mielo et al., 2022). Location of the initial skin incision is often calculated by dividing the distance between the umbilicus and pubis into thirds and making the incision the length of the cranial third. The length of the incision depends on the dog's size, amount of abdominal fat and surgical experience of the operator. The incision should not be longer than needed but should always allow adequate exposure to safely perform the procedure. Inadequate exposure increases the risk of haemorrhage from both the ovarian and uterine arteries, as well as incomplete removal of all ovarian tissue [ovarian remnant syndrome (ORS)]. While cold instrument incision with a scalpel blade is most frequently used, electroincision with an electrosurgery device reduces complications such as blood loss, incision redness and wound discharge without affecting clinical wound healing (Meakin et al., 2017). A sharp or blunt dissection of the subcutaneous tissue along the midline is made with a scalpel blade or Metzenbaum scissors, respectively. Once the linea alba is clearly identified it is elevated with a thumb forceps and punctured with a scalpel blade sharp side facing up. The incision is extended towards both ends by cutting with a scissor or by using a blade with a tissue forceps or grooved director as a guide (Fig 2). The uterus is located dorsal to the bladder and ventral to the descending colon by advancing the hand into the abdomen between the internal aspect of the abdominal wall (towards the palm of the hand) and the viscera (towards the dorsal aspect of the hand). Spay hooks (Fig 3) are commonly used and may be helpful in locating the first uterine horn; however, they must be used with great care, especially in very young animals, where potential risk of inadvertently damaging delicate intra-abdominal structures is increased. Either the left or right uterine horn can be identified first based on personal preference. The spay hook is positioned so that the hook points towards the body wall and is swept down the body wall to the inside fold of the ipsilateral rear leg. The point of the hook is then rotated 180° and swept slightly towards the midline incision. If the uterine horn is engaged, tension will be felt on the hook. Too much tension indicates that a ureter has likely been engaged. If so, the hook is disengaged, and another attempt made to engage the uterine horn (Valdez, 2022). If repeated attempts fail to isolate the uterine horn the abdominal incision should be enlarged, or an alternate method, such as direct palpation caudal to the kidney should be utilised. After the uterine horn is identified it is gently retracted and followed cranially until the ovary is located. Application of local anaesthetic to the ovary at this point improves intraoperative analgesia (Cicirelli et al., 2022). Forceps are placed on the proper ligament to use for retraction and the suspensory ligament is broken or stretched with digital pressure. Performing this manoeuvre as close as possible to the diaphragm avoids inadvertent damage to the ovarian vessels. Sharp transection is faster and may cause less pain (Shivley et al., 2019). Releasing the suspensory ligament may not be required in all dogs, especially dogs who have previously given birth as there is increased laxity of the reproductive structures in these animals. A window is made in the mesovarium immediately caudal to th