Gonadectomy (ie, ovariohysterectomy [OHE] or neutering) is one of the most commonly performed veterinary surgical procedures.^1-6 Gonadectomy reduces pet overpopulation and euthanasia in animal shelters and decreases the risk for gonadal tumors, mammary neoplasia and pyometra in dams and queens, and perianal adenomas and benign prostatic hyperplasia in male dogs.⁷ It may also increase longevity and reduce hormonally driven behavior.⁷

Although gonadectomy is considered a routine procedure, complications can arise. Following are 5 of the most common complications of gonadectomy according to the author.

Incisional inflammation is an expected effect of any surgery and typically resolves without treatment⁸; incisional complications, however, occur less frequently¹ and are likely underreported, as clinicians may not closely evaluate the incision line after anesthetic recovery or may not record findings they consider expected, minor, or self-limiting. Incisional complications associated with gonadectomy can include incisional and/or scrotal swelling, pain, redness, seromas, hernias, peri-incisional dermatitis, and skin bruising and generally occur more frequently in dogs >50 lb (22.7 kg) and in cats.^4,9-11

Incision location may affect complication rates. For example, in a study of kittens undergoing OHE, incisional complications occurred more commonly with a midline approach as compared with a flank approach.¹² In a study of dogs, prescrotal neuters resulted in a higher rate of self-trauma than did scrotal neuters,¹¹ which may be attributed to scrotal neuters being performed without suture closure, thus lessening the amount of tissue handling.^10,11

Surgical-site infections and other serious wound complications that are suggestive of infection (eg, wound pain and swelling, dehiscence, drainage; Figure 1) have been reported in 0.1% to 3% of elective gonadectomies.^1,2,4,13 This rate is similar to the infection rates reported for clean, elective procedures in general (2.3%-5.7%).¹⁴ Infection rates can be reduced by decreasing surgery duration and using appropriate surgical technique (eg, gentle tissue handling, closure of dead space).^14,15

Intraoperative hemorrhage is noted in 1.1% to 11% of dogs and cats undergoing gonadectomy and is most common in dogs >50 lb (22.7 kg) or when the surgery is performed by students.^1,4,16 Postoperative abdominal hemorrhage is noted in ≤2.8% of patients undergoing gonadectomy.⁴ Rough tissue handling, poor ligation technique, inexperience, and inadequate exposure may play a role in intra-abdominal hemorrhage.

Cats undergoing gonadectomy are less likely to experience intra-abdominal hemorrhage than are dogs, even if ligatures are not used for ovarian pedicle hemostasis, as feline ovarian pedicles are generally small, less vascular, and more mobile as compared with canine ovarian pedicles. In a study of 2136 cats undergoing pedicle tie OHE, 0.28% of cats experienced intra-abdominal hemorrhage¹⁷; most cases were recognized and corrected during the procedure. In that study, uterine pedicle hemorrhage was noted in 0.14% of cats, and suspensory ligament hemorrhage was noted in 0.05% of cats.

Another source of intra-abdominal hemorrhage is splenic laceration, which can be caused by laparoscopic equipment or excessive spay hook use.¹⁸

Fatal abdominal hemorrhage from OHE or ovariectomy is rare, as most hemorrhaging is noted and addressed prior to closure.^1,4,16,17 Patients with significant postoperative hemorrhage may have nonspecific signs (eg, slow anesthetic recovery, tachycardia, hypothermia, pale mucous membranes). Diagnosis is made via abdominal ultrasonography and abdominocentesis. In clinics without ultrasonography equipment, 4-quadrant abdominocentesis can be performed if the falciform ligament, which will block the needle, and spleen are avoided. Nonclotting blood on abdominocentesis confirms the diagnosis of hemoabdomen.¹⁹ If significant abdominal hemorrhage is detected, coagulation tests should be considered. The clinician must decide whether to treat the patient conservatively (eg, abdominal bandaging, sedation, monitoring, judicious use of fluids) or perform exploratory surgery. If surgery is chosen, the incision should be extended to provide adequate exposure, and the ovarian pedicles, suspensory ligaments, uterine stump, and other organs should be closely evaluated. If bleeding is identified, the tissue in question should be gently elevated from underlying structures with thumb forceps before the vessels are clamped and ligated. Transected ovarian pedicles commonly retract caudomedial to the kidneys and may rest immediately over the ureters. In cats, the distal ureters lie close to the uterine stump. Regardless of location, the ureters can be inadvertently ligated. If no active hemorrhage is observed during surgery, all pedicles should be ligated again, as anesthetic hypotension may mask vessel leakage.

Serious hemorrhage from gonadectomy is rare, but bleeding can occur from the incision or, in dogs undergoing prescrotal neutering, in the scrotum. In one study of scrotal and prescrotal neutering in 437 dogs >6 months of age, hemorrhage was observed in 16% of all dogs.¹¹ Bleeding occurred more commonly in larger dogs, and surgical approach was not a factor in its occurrence.¹¹ In another study of scrotal neutering with sutureless pedicle ties in dogs <6 months of age, no postoperative hemorrhage was noted.¹⁰ Hemorrhage after neutering is often related to bleeding from the tunics or SC tissue and is usually self-limiting.¹⁴ Affected patients can be treated with local pressure (dogs, scrotum; cats, scrotum or inguinal ring), cold packs, sedation, and exercise restriction and monitored for significant changes in hematocrit. Dogs with severe scrotal hematomas may develop abscessation or scrotal necrosis necessitating scrotal ablation. In rare cases, testicular vessels can retract through the inguinal ring into the peritoneal cavity, resulting in intra-abdominal hemorrhage. In these patients, clinical signs and treatment are similar to those in patients with postoperative hemorrhage after OHE.

Some clinicians consider postoperative pain a normal effect of surgery. In one study, ≤12% of clinicians did not administer any postoperative analgesics to their patients, and many others relied on butorphanol, which may provide insufficient analgesia.³ Most retrospective studies of elective gonadectomy do not list pain as a potential surgical complication, and dogs undergoing routine gonadectomy are less likely to be prescribed postoperative analgesics than those undergoing other surgeries.^1,2,9,12,20

Inadequate treatment of postoperative pain may be due to generational or gender differences among clinicians, cost or regulatory concerns, lack of access to appropriate drugs, and/or insufficient knowledge of pharmacology or pain detection in various species. For example, pain in cats tends to be undertreated because cats rarely show signs of pain after elective procedures.²¹ However, when mechanical nociceptor threshold (scrotal pressure tolerance) was measured in a study of cats after neutering, cats often reacted for ≥8 hours after surgery.²¹ In another study, cats exhibited decreased tolerance to abdominal palpation 18 hours after OHE but appeared pain free on visual assessment.²²

Prolonged pain has also been noted in gonadectomized dogs. In one study, abdominal palpation and pain scores had not returned to normal by 72 hours after OHE.⁸ In another study, when pain was closely monitored after neutering, ≈50% of dogs required rescue analgesia within 3 to 4 hours of receiving preoperative morphine.²³ Owners may note patient discomfort in dogs in the form of lethargy, restlessness, vocalization, and/or decreased appetite 1 to 3 days after gonadectomy.^20,24

Clinicians should consider pre-emptive analgesics (eg, local or regional nerve blocks) and administer rescue opioids while the patient is being monitored in the clinical setting.^3,25 Analgesics should also be prescribed for several days after the procedure.

Reported surgical errors include incomplete ovariectomy, pedicle granulomas and fistulas from use of nonabsorbable multifilament suture or nylon cable ties, inadvertent ureteral ligation, incisional hernias, retained surgical sponges or other foreign bodies (ie, gossypibomas), and inadvertent prostatectomy during cryptorchidectomy.^1,14 The author has also seen uterine horns inadvertently tied together around the colon or urethra, resulting in stricture or obstruction. The exact incidence of surgical errors during elective gonadectomy is unknown. As with intra-abdominal hemorrhage, surgical errors can occur from inexperience or lack of sufficient anatomic exposure.

Ovarian remnant syndrome (ORS) occurs when functional ovarian tissue is inadvertently left in the patient (Figure 2).¹⁴ Patients with ovarian remnants are often overweight or have been spayed through a small incision, both of which can interfere with ovary visualization and appropriate clamp or ligature placement.¹ Affected patients may display signs of estrus (eg, mammary or vulvar enlargement, behavior changes, vulvar discharge) or become clinically ill due to stump pyometra. Diagnosis of ORS is based on elevated concentrations of anti-Müllerian hormone and progesterone in peripheral blood.²⁶ Treatment includes exploratory celiotomy, ovariectomy, and/or, if stump pyometra is present, removal of the uterus. Retained ovarian remnants are easier to locate when the patient is showing signs of estrus, as associated vessels will be enlarged and cystic follicles may be present in retained tissue.¹⁴

Inadvertent prostatectomy during removal of a cryptorchid testicle can also result from inadequate exposure, in which the clinician incorrectly identifies the almond-shaped prostate as a retained intra-abdominal testicle without noting the attached bladder and urethra. The author has witnessed students inadvertently expose the prostate through an abdominal incision when using a spay hook in attempt to locate a retained testicle. Dogs that have undergone inadvertent prostatectomy will have azotemia and anuria from urethral transection and ligation; subsequent bladder necrosis from overdistension can result in uroabdomen. Some dogs will regain urinary continence with surgical reanastomosis of the urethra.²⁷

Retained surgical sponges can become walled off and cause no clinical signs for years; alternatively, affected patients may develop clinical signs as a result of adhesions, mass effect, fistulas or sinus tracts, vessel or visceral erosion, infection, or neoplastic transformation.^28,29 Diagnosis can be difficult if a radiopaque marker is not present in the sponge, although the mass is usually evident on ultrasonography or CT. Treatment entails surgical removal of the sponge, in which careful dissection is required to prevent damage to local structures.²⁹ Institution of sponge counts before and after each abdominal surgery can help decrease the risk for gossypibomas.

Ventral midline hernias occur in <1% of patients undergoing OHE.^1,2,13,14 If the hernia is present within the first week after surgery, it is likely the result of technical error (eg, missed external rectus fascia, inappropriate suture size, suture bites that are too small or too far apart, knot failure).^1,14

Gonadectomy is common in the United States due to its value in surgical sterilization and preventing or reducing reproductive diseases (eg, benign prostatic hyperplasia, testicular tumors, pyometra, mammary neoplasia) and sexually driven behaviors.⁷ Adoption rates of shelter dogs are often increased with preadoption gonadectomy; however, evidence of its potential negative effects has been accumulating.^7,30-40

Gonadectomy has been correlated with obesity in dogs and cats,^30-32 which may result from changes in fasting metabolic rate (as has been noted in female cats), increased food intake, and/or decreased activity.^31,32 Obesity may increase the risk for or exacerbate osteoarthritis and/or other systemic illnesses. Owners should be instructed on how to adjust activity levels and food intake to maintain their pet’s ideal body condition.

Another condition associated with neuter status is urinary incontinence in female dogs.³³ Urinary incontinence is rare in intact bitches (0%-1%) but reportedly occurs in 5% to 20% of spayed female dogs.^7,33,39,40 The risk appears to be greatest in dogs >33 lb (15 kg).⁴⁰ Some studies have reported correlations with the dog’s age at the time of OHE, whereas others have found no significant effects.^39-41 Signs of urinary incontinence can manifest as early as 4 weeks postoperation or may be delayed for 3 to 10 years.^24,33 The pathophysiology of this acquired sphincter mechanism incompetence is unclear. Small-breed female dogs may have a greater risk for pyometra and mammary tumors than urinary incontinence; thus, the benefits of OHE before the first or second heat may outweigh the likelihood of complications.

Large- and giant-breed dogs, particularly golden retrievers, German shepherd dogs, and rottweilers, may be at greater risk for morbidity and mortality from joint disease, neoplasia, and urinary incontinence resulting from gonadectomy at a young age. Gonadectomy has been shown to increase the incidence of joint disorders in large-breed dogs by 2 to 5 times that of intact dogs, especially when performed in dogs <6 months of age.^7,34,35 For example, in one study, the incidence of joint disorders was 5% in intact adult male golden retrievers as compared with 27% in those neutered before 6 months of age.³⁴ In another study, joint disorders were diagnosed in 21% and 16% of male and female German shepherd dogs, respectively, gonadectomized at <1 year of age as compared with 7% and 5% of intact male and female German shepherd dogs, respectively.³⁵

Gonadectomy may also be associated with an increased risk for certain cancers in large-breed dogs, although controlled studies are lacking. In one study of 683 rottweilers, bone sarcoma was diagnosed in 12.6% of dogs³⁶; the risk for development of bone sarcomas was >3 times greater in dogs gonadectomized before 1 year of age. In other breeds, cancer-related deaths may be increased because gonadectomized animals live longer.⁷ Delaying gonadectomy until physical maturity (eg, >12 months of age) may be beneficial for large-breed dogs, although delaying surgery increases the risk for wound complications and surgical errors, likelihood of greater costs due to increased surgical time and anesthesia, and potential for unwanted litters before sterilization.

Because cats do not appear to experience many long-term ill effects from gonadectomy, other than the potential for obesity, prepubertal gonadectomy is usually considered acceptable for this species.³⁷ However, gonadectomy in animals <7 months of age will delay physeal closure, which could increase the risk for physeal fractures in male cats, particularly if they become obese.⁴²

Clinicians must weigh the risks and benefits of gonadectomy with the pet owner and determine the most appropriate age to neuter different breeds and species.

During examination, patients should be approached in a calm, gentle manner and minimal physical force should be applied. Staff should wear gloves, as some animals may carry zoonotic pathogens.^1-3 Chemical immobilization with injectable sedatives or inhalant anesthesia should be considered in patients that are extremely fractious and/or painful and for invasive and/or prolonged procedures.

The following can serve as a general guide for handling select small mammals commonly evaluated in the clinical setting.

In human medicine, the average rate of patient adherence is ≈50%.² In veterinary medicine, study results indicate that compliance and adherence are similarly low; in studies of dogs receiving short-term antimicrobial therapy, 56% to 59% of owners administered the incorrect number of doses per day, with most underdosing their pet.^3,4 Adherence failure and lack of compliance can result in lack of patient improvement, disease progression, or even death of the patient. Lack of compliance can also have more subtle adverse effects; for example, incomplete treatment of infection can promote antimicrobial resistance.³ Withdrawal signs can occur with abrupt discontinuation of some drugs, and overdosing can result in toxicity or extra costs. Decisions regarding treatment efficacy can be adversely influenced by unidentified poor compliance, and lack of improvement can increase the frustration of the pet owner and/or veterinary staff.^1,3

Factors that affect adherence to and compliance with therapeutic regimens include cost and accessibility of medications, number of drugs administered, frequency and duration of drug administration, complexity of the treatment regimen, and abilities of those administering the drug (eg, able to administer eye drops to pets, able to administer oral medications to cats).^2,3,5,6 Patient behavior and owner lifestyle (eg, long working hours or travel) can also preclude drug administration that is required more than once a day.

Some therapeutic regimens are inherently complex. For example, a 5-minute interval between eye drops is typically advised to prevent washout of the previous medication and, in some cases, to increase the combined effects of the drugs.⁷ A longer interval may be necessary between oral administration of some drugs (eg, oral sucralfate suspension administration is delayed for 2 hours after doxycycline administration) to decrease negative effects on bioavailability.⁸ Such necessary but complex instructions are likely to reduce pet owner compliance.

Simplifying dose regimens can help improve owner compliance.⁹ In a study of canine otitis externa, owner compliance with the therapeutic regimen increased from 21% to 79% when the topical medication was only administered once a day rather than twice a day and as a single volume rather than as multiple drops.¹⁰ Similar findings were noted in another study when antibiotics were prescribed for once- or twice-daily administration rather than every 8 hours.⁹

Clinicians can also improve pet owner compliance with complex therapeutic regimens by building a relationship with the owner, eliciting the owner’s perspective on treatment, demonstrating empathy, and investing the owner in the outcome by sharing information regarding the condition and treatment options and involving the owner in the decision-making process.¹ Follow-up telephone calls and coaching from staff can also be helpful.¹¹ Some owners may be hesitant to discuss technical difficulties with clinicians; however, if staff provide demonstrations and observe treatments, owners may be more confident in the treatment plan and therefore more compliant.^1,2,5,12

Compliance can be verified by examining the amount of medication that remains during a follow-up visit.^2,13 If residual medication counts are unexpectedly high or low, the staff should determine the cause and ways to assist the owner in improving compliance.

Tools for improving compliance include written instructions, videos, charts, checklists, calendars, and special packaging that explain, organize, and streamline treatments.^1,2,5,12

In human medicine, division of daily or weekly doses into a multicompartment pill box can help increase patient compliance.² However, such a technique is usually not possible with topical or oral liquid medications. In addition, removing medications from labeled containers may be risky if the medications appear similar, as in the case of omeprazole and cyclophosphamide capsules, acepromazine and chlorpheniramine tablets, and grapiprant and metronidazole caplets.

A safer method may be the use of a compartmentalized tray that can be labeled with times and medications (eg, name, color, number) and hold the medication containers (Figure 1). The owner can place the medications in a row at the beginning of the day and move each drug to the next row once administered; this allows the person administering a complex medication regimen to keep track of the drugs that have been administered. Additional labels can be added to indicate which medications should be stored in the refrigerator.

Examples of medication logs are available (see Suggested Reading). Clinicians and staff may be able to devise medication sheets that are more readily adaptable to the patient or type of treatment (Figures 2 and 3).

Checklists should be adjusted for each patient. Rows can be added for headings or special instructions (eg, rest periods between treatments); these headings can later be filled in with treatment times once the best scheduling options have been discussed with the owner. Medications should be entered on the checklist in the order of administration, and rows should be left empty as needed for additional instructions between treatments. Maintaining a document of pretyped instructions with blank spaces to add the dose, frequency, or other medication directions can be beneficial. The details of each medication should be entered after each instruction is added to the checklist to tailor the treatment to the patient. Including a box for additional instructions or information (eg, next appointment time or clinician signature line) at the bottom of the document can also be helpful. To improve visual recognition, color-coding each treatment and placing a sticker of similar color on the checklist may help the owner adhere to the schedule.

The medication checklist can be copied and printed for daily use; as a more environmentally sound practice, the checklist can be laminated or placed in a clear plastic document folder. The owner can use an erasable marker to check off each medication once administered.

If a medication must be refrigerated between each administration, medication management options should be discussed with the owner. Some owners may prefer to leave an empty container in the appropriate compartment as a reminder, whereas others may wish to retrieve the medication from the refrigerator immediately before administration and place it in the appropriate compartment. If several medications must be refrigerated, incorporating a separate compartmentalized organizer that fits on a refrigerator shelf may be helpful.

Successful resolution of some veterinary conditions may rely on complex treatment regimens. Owner compliance with these regimens can be improved by simplifying the dose schedule and providing clear, concise written instructions, charts, or checklists. Use of compartmentalized, labeled medication trays or color-coded medication containers and instructions can provide additional visual cues to help the owner deliver the treatments appropriately.

Following are differential diagnoses for patients presented with hypercalcemia.*

• Artifactual hypercalcemia
  • Severe lipemia or icterus
• Physiologic hypercalcemia (mild hypercalcemia due to bone growth in young animals)
• Increased protein binding
  • Hemoconcentration (ie, hyperalbuminemia)
  • Hyperproteinemia (ie, paraproteinemia)
• Malignant hypercalcemia (most common cause in dogs)
  • Lymphoma
  • Anal sac apocrine gland adenocarcinoma
  • Other carcinomas (eg, mammary, thyroid, lung, clitoral), particularly if metastatic to bone
  • Thymoma
  • Multiple myeloma
  • Osteosarcoma or other primary bone tumor
  • Melanoma
• Hypoadrenocorticism
• Idiopathic hypercalcemia (most common cause in cats)
• Primary hyperparathyroidism
• Chronic kidney disease (less commonly, acute kidney injury)
• Raisin/grape toxicity
• Hypervitaminosis D
  • Cholecalciferol toxicity
  • Calcipotriene/calcipotriol (eg, antipsoriasis creams) ingestion
  • Calcitriol or vitamin D overdose (eg, due to inappropriate dietary supplementation)
  • Plant (eg, day-blooming jessamine) ingestion
• Drug-induced effect
  • Thiazide diuretics
  • Excessive calcium (eg, calcium carbonate) supplementation
  • Aluminum-based phosphate binders
  • Dimethyl sulfoxide when used extra-label in the treatment of calcinosis cutis
• Localized osteolysis
• Osteomyelitis
• Hypertrophic osteodystrophy
• Disuse osteoporosis
• Granulomatous disease
  • Blastomycosis
  • Histoplasmosis
  • Hepatozoonosis
  • Schistosomiasis
  • Pythiosis
  • Angiostrongylus vasorum infection
  • Heterobilharzia americana infection
  • Secondary to biologic implants
• Benign humoral hypercalcemia
  • Benign mixed mammary tumors
  • Benign renal angiomyxoma
  • Benign esophageal/vaginal leiomyoma
• Hypervitaminosis A
• Retained fetus (dogs)

Ultrasonography is a valuable, noninvasive tool for evaluating the parathyroid gland in dogs, but very little information on the evaluation of parathyroid glands in cats is available. This study sought to ultrasonographically characterize the size, location, and appearance of parathyroid glands in cat cadavers and compared the results with histologic findings. The study also sought to ultrasonographically assess the thyroid lobes in living healthy cats that did not have clinically detectable kidney, parathyroid, or thyroid disease. The authors hypothesized that ultrasonography would detect 2 parathyroid glands in each thyroid lobe (ie, 4 total), with the glands appearing as hypoechoic nodules associated with the thyroid lobes. In addition, the authors hypothesized that a reference range for parathyroid gland size would be determined for healthy normocalcemic cats.

In the 6 cat cadavers, ultrasonography revealed 28 hypoechoic nodules in 12 thyroid lobes. On histology, 33 separate nodules were observed in the 12 thyroid lobes; 25 of these were characterized as parathyroid tissue and the remaining were characterized as being of thyroid origin. Of the 28 nodules identified on ultrasonography, only 6 could be confidently associated with nodules seen on histology.

In the 20 living healthy cats, thyroid glands were identified via ultrasonography in all cats, with only the right thyroid lobe not being evaluated in one cat due to poor compliance. This study demonstrated obtaining parathyroid gland measurements in nonsedated cats to be difficult, as generally only one measurement could be reliably obtained in each cat. Hypoechoic nodules frequently did not correspond to parathyroid tissue on ultrasonography, proving ultrasonography was not a reliable method for evaluating parathyroid tissue in healthy cats; this is important to note, as any hypoechoic nodule in thyroid glands is generally considered to be parathyroid tissue. Because ultrasonography could not differentiate normal parathyroid glands from thyroid tissue, no reference ranges were provided.

Although this study demonstrated normal parathyroid tissue to be ultrasonographically similar to thyroid tissue, evaluating the ultrasonographic appearance of the parathyroid glands in cats with suspected parathyroid disease and validating thyroid gland size in cats with known hyperthyroidism is necessary to determine the clinical applicability of ultrasonography when evaluating the thyroid and parathyroid glands in cats.

Key pearls to put into practice:

Obtaining parathyroid gland measurements in clinically normal cats through ultrasonography can be difficult without sedation.

Although this study found no benefit in performing ultrasonography to evaluate the parathyroid glands in normal cats, performing ultrasonography on parathyroid glands in cats with hypercalcemia may be beneficial.

Further studies on hypercalcemic cats may find that abnormal parathyroid tissue is easier to differentiate from thyroid tissue, but in normal cats, the parathyroid glands are not reliably visible.

Multiple outbreaks of canine influenza virus (CIV) caused by avian-origin H3N2 influenza A virus have been reported in the United States since 2015 and in Canada since 2017. This virus was a new introduction to North America, and these outbreaks were due to multiple virus introductions associated with the importation of rescue dogs from Asia.¹ 

This study illustrated several important points in the Canadian outbreak, most notably the use of contact tracing and longitudinal sampling. Use of contact tracing effectively identified other at-risk dogs for testing, whereby the actual nidus of infection for several of the outbreaks was identified. Contact tracing confirmed previously identified risk factors for CIV, including exposure to rescue dogs from Asia, use of boarding and grooming facilities, and, in one case, use of a public trail. In addition, longitudinal sampling confirmed the efficacy of a 28-day quarantine period, especially when combined with 2 sequential negative PCR tests, a requirement for releasing animals from quarantine.

Overall mortality observed in the H3N2 CIV cases in this study was 2%, which is similar to previous observations.² The 2 fatalities that occurred were in older dogs; this observation reinforces the need to vaccinate and revaccinate older dogs, particularly when other risk factors are present (eg, boarding, grooming). The need for initial vaccination to be administered twice, 14 to 28 days apart, limits the overall utility of vaccination during an outbreak, supporting the need for proactive vaccination.

In addition, although virus survival times tend to be longer in colder temperatures, the spread of CIV in this study appears to have been limited. This was presumed to be due to decreased outdoor activity, potentially limiting exposure. In contrast, during the summer of 2018, multiple CIV cases occurred at the height of summer travel season on the US east coast, presumably due to increased movement of shedding dogs and/or time spent in boarding facilities, despite the relatively short survival time of the virus during summer months.

CIV remains an ongoing threat to dog populations; however, a combination of diagnostics, contact tracing, and quarantine can be used to limit the extent of an outbreak. Appropriate initial vaccination in conjunction with annual revaccination of at-risk dogs with a licensed H3N2 CIV vaccine remains the best option to prevent severe clinical signs and mortality, especially in older dogs.

Key pearls to put into practice:

Appropriate diagnostic testing of suspected CIV cases, in conjunction with contact tracing and testing and 28-day isolation periods, is critical to contain outbreaks of CIV.

PCR testing on nasal/oropharyngeal swabs and influenza serology may be necessary to trace CIV cases. A PCR-negative unvaccinated dog with a hemagglutinin inhibition titer >1:16 indicates likely exposure to H3N2.

Lack of known exposure to another dog exhibiting clinical signs should not rule out CIV infection, as demonstrated in this study in which one case had no known exposure other than using a public walking path.

Gallbladder mucoceles (GBMs) have become a clinically important cause of extrahepatic biliary disease in dogs, particularly in older patients and certain predisposed breeds. The reported percentage of positive bacterial cultures in cases of GBMs, however, has been variable. This study investigated the use of fluorescence in situ hybridization, a culture-independent technique, for detecting bacteria in GBMs. Fluorescence in situ hybridization was found to be more sensitive than bile culture for detecting bacteria. Of the 25 dogs with GBMs in this study, 68% were also found to have concurrent cholecystitis, a higher percentage than has been reported previously in dogs with GBMs (ie, 17%-40%). The relationship among bacteria, cholecystitis, and the etiology and progression of GBMs remains to be determined.

Bite wounds are a common type of trauma in cats and can involve deep tissue, muscles, and internal organs, even when the surface wounds appear small. The animal trauma triage (ATT) score measures injury severity by assessing perfusion, cardiac, respiratory, eye/muscle/integument, skeletal, and neurologic status; ATT score has been significantly associated with outcome in dogs and cats. This retrospective study sought to document the clinical and clinicopathologic changes in 43 cats presented with dog-bite trauma and identify significant clinicopathologic changes associated with ATT. Low venous blood pH, high plasma lactate concentration, and low ionized calcium were significantly associated with higher ATT scores on presentation. Early recognition of these changes may help identify bite wound patients with more severe injuries.

The growing crisis of the abuse of illicit and prescription opioids in humans has led to accidental exposures in pets and working dogs.^1-4 In humans, a commercial intranasal naloxone hydrochloride atomizer is available to treat opioid overdoses and may be purchased without a prescription.⁵ There is a growing interest in the use of such atomizers in veterinary patients, particularly for emergency stabilization prior to transporting a patient to a veterinary facility for care.^3,4

This study compared IV naloxone with intranasal naloxone delivered by a commercially available atomizer in healthy dogs. Time to reach peak plasma levels, maximum concentration, and naloxone half-life were measured and calculated. The intranasal route rapidly achieved clinically useful plasma levels in healthy medium-sized dogs. Naloxone was detectable in plasma 2.3 ± 1.4 minutes after intranasal administration; mean time to maximum concentration in plasma was 22.5 ± 8.2 minutes. Naloxone half-life was similar for both routes of administration (IV, 37 ± 6.7 minutes; intranasal, 47.4 ± 6.7 minutes). It is unclear if nasal conformation (eg, brachycephaly, dolichocephaly) affects intranasal absorption.

Reported adverse effects of naloxone include excitability, vomiting, and tachycardia; however, there were no notable changes in behavior, heart rate, or respiratory rate following naloxone administration by either route in this study.

Key pearls to put into practice:

Naloxone has a shorter half-life as compared with many opiates.^5-8 Therefore, it should be stressed to pet owners that, in the event of an accidental opioid overdose, veterinary attention should be sought immediately even if naloxone has been administered and the pet has responded well, as the pet will likely require further care.

The commercially available naloxone atomizer delivers a single 4-mg dose. The relative body size will likely affect the dose achieved in plasma. Smaller dogs should theoretically achieve higher plasma levels, whereas large- or giant-breed dogs may achieve lower plasma levels.

Because of their gentle character when habituated properly by their owner, rats (Rattus norvegicus) have become common household pets.¹ Little preventive care is required for these animals that have relatively short lifespans (ie, 2-3 years), and rats can withstand the problems that come with reduced supervision and suboptimal veterinary care often seen with caged companion mammals relatively well.

In this retrospective review of records from 2 veterinary medical centers, dermatologic conditions seen in pet rats presented for health evaluation were characterized. The study found that skin diseases can make up a large portion (first center, 39%; second center, 47%) of the cases presented for clinical examination and therefore should be added to the list of common conditions seen in pet rats (eg, respiratory infections, mammary gland neoplasia).

Dermatologic diseases in pet rodents have been reported.^2-5 Because pruritus is one of the most common clinical signs associated with dermatopathies in pet rodents, timely diagnosis and treatment is required for resolution. In this study, nodules, alopecia, and crusts were also commonly noted. Pododermatitis was also frequently observed, and obesity, poor diet, wire-bottom caging, and excessive use of running wheels were identified as risk factors for this condition.

Many health issues in pet rats result from suboptimal husbandry (ie, environment, diet). A thorough review of husbandry is required for successful diagnosis and treatment of rat dermatoses. Any husbandry deficiencies, once identified, should be addressed and environmental treatments implemented to prevent recurrence and control parasitic infections.²

A detailed dermatologic examination is necessary in all rats presented with skin disease, and the methods described in this study are all commonly used in other companion mammals. However, some owners may decline to perform a wide array of tests, so empiric treatments may be required for presumptive diagnoses; the data from this study suggest that this practice should be discouraged. Furthermore, empiric treatments based on assumptions of what is “common” should be discouraged, as disease occurrence can differ based on geography. Basic diagnostic testing can help ensure accurate and timely diagnosis and resolution for affected patients.

Key pearls to put into practice:

Fecal testing of both clinical and subclinical patients can often reveal the presence of ecto- and endoparasites and should be performed routinely in all rat patients.

If owners decline skin testing or if other tests fail to provide a diagnosis, a full-thickness punch biopsy can be the most helpful test to perform. For example, a 2-mm punch biopsy can be collected with brief anesthesia and a local anesthetic block and the skin later closed with a drop of surgical glue.

Clinicians should be aware that rats are particularly sensitive to repeat intradermal injections, especially when potentially irritating substances (eg, enrofloxacin, ketamine) are administered.

Heinz bodies can occur at low levels in RBCs in clinically healthy cats.¹ Exposure to oxidizing agents (eg, acetaminophen, onion-containing foods) or presence of certain underlying diseases (eg, diabetes mellitus, hyperthyroidism) can increase the frequency of Heinz body occurrence, sometimes affecting >50% of cells (Figure). The presence of these structures on erythrocytes can interfere with automated CBC analysis, resulting in erroneous interpretations without careful inspection.

This retrospective study sought to determine whether examination of hematology analyzer graphs and data raised suspicion for presence of Heinz bodies and to document changes over time in patients with Heinz bodies. Data from 32 cats were obtained through a flow-cytometry–based automated hematology analyzer and results of microscopic examination of blood smears. Results showed that the presence of Heinz bodies on >36% of erythrocytes resulted in artifacts that impacted the ability of the automated analyzer to accurately determine WBC count. This was detected as an abnormality on the graphs produced by the analyzer and confirmed on blood smear examination. As cats recovered and the percentage of inclusion-containing erythrocytes declined, the interference with obtaining a proper WBC count became minimal.

The effect of Heinz bodies on the measurement of hemoglobin variables has been described.² Inclusions result in increased optical density of the affected erythrocytes, which increases mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration as detected by a laser. RBCs cannot contain additional hemoglobin above physiologic amounts, so increases in these variables should always raise suspicion for artifacts.

Although the hematology instrument used in this study is not commonly used in general practice, other hematology analyzers could also produce interference, as reported in this study. Any clinic that maintains hematology laboratory equipment should have procedures in place to assure quality and accuracy of results to prevent erroneous interpretation of data when interferences such as Heinz bodies are present in a blood sample. Blood smear examination is crucial in any ill patient that has hematologic abnormalities.

Key pearls to put into practice:

Feline blood samples in which >36% of erythrocytes contain Heinz bodies may cause analytic errors with certain hematology instruments.

Heinz body interferences most commonly impact certain hemoglobin measurements and may also result in overestimation of WBC count.

If laboratory results do not correlate with clinical signs or make physiologic sense, the possibility of analytic error should be pursued.

Repurposing existing drugs and using a topical antimicrobial as a first-line treatment option for superficial pyoderma can help promote good antimicrobial stewardship, protect the efficacy of newer systemic antimicrobial classes, and limit use of newer antimicrobial classes. The aim of this study was to provide proof-of-concept for repurposing the drug oxyclozanide, a salicylanilide anthelmintic used primarily in humans and ruminants, as a topical treatment option for superficial pyoderma in small animals. Results showed promising in vitro activity against both methicillin-sensitive and methicillin-resistant Staphylococcus pseudintermedius canine isolates. Pilot data from this study may help guide clinical studies of topical application of oxyclozanide.

Pulmonary hypertension is a common respiratory disorder in dogs and can be caused by various disorders with different pathophysiologic mechanisms. In clinical practice, the most common causes of pulmonary hypertension include left-sided heart disease and pulmonary arterial hypertension associated with respiratory disease and/or hypoxemia (RD/H). Despite the seemingly high prevalence of RD/H-associated pulmonary hypertension, little is known about its clinical presentation, diagnostic characteristics, prognostic variables, therapeutic responsiveness, and/or long-term outcome.

This retrospective study evaluated patients that had RD/H-associated pulmonary hypertension documented on echocardiogram. The mechanism of each patient’s respiratory disease was characterized based on available diagnostic testing. The population was diverse and included both obstructive and restrictive disease processes.

The authors suggested a correlation between the severity of estimated pulmonary arterial pressures and patient outcome. Furthermore, intervention with phosphodiesterase-5 (PDE5) inhibitors was demonstrated to improve survival time. Although this information is preliminary and represents cumulative information of a diverse population, it shows that patients with RD/H-associated pulmonary hypertension could benefit from PDE5 inhibitors and that echocardiogram could potentially provide prognostic information.

This study provides a basis for additional studies. It demonstrates the variability in associated underlying etiologies and can help guide clinicians in identification of patients at risk for pulmonary hypertension. Additional studies evaluating therapy in subset groups will be necessary to optimize therapy and establish a better understanding of long-term outcome and progression.

Key pearls to put into practice:

Estimated systolic pulmonary arterial pressure (sPAP) is negatively correlated with survival. A sPAP ≥47 mm Hg has a sensitivity of 78% and a specificity of 63% for nonsurvival; a sPAP >95 mm Hg has a specificity of 95% and a sensitivity of 17% for nonsurvival.

Treatment with a PDE5 inhibitor (ie, tadalafil, sildenafil) may help improve survival, as observed in this study. Patients that received PDE5 inhibitors (ie, tadalafil [median dose, 2 mg/kg PO every 24 hours; range, 0.9-2 mg/kg], sildenafil [median dose, 0.5 mg/kg PO every 8 hours; range, 0.5-3.3 mg/kg]) were 4 times more likely to survive as compared with patients that did not receive PDE5 inhibitors.

RD/H-associated pulmonary hypertension represents a diverse population of respiratory conditions, including restrictive and obstructive disorders (eg, conducting airways [ie, nasal/nasopharyngeal, laryngeal, trachea and mainstem bronchi], large airway obstruction [ie, bronchi], small airways [ie, bronchioles]).

Sam, a 12-year-old retriever, was presented for owner-observed signs of pain while eating (ie, moving food in his mouth to chew, occasional vocalization). His owners reported that he also exhibited other signs, including aggressively chewing on multiple objects.

On physical examination, recent, unilateral, mild hemorrhage of the lip commissure was identified. An uncomplicated crown fracture of the right maxillary fourth premolar (with the fragment extending into the gum) was presumptively diagnosed. The tooth fragment was removed with the patient under general anesthesia. Because the pulp was apparently not directly exposed, no further treatment was performed. Dental radiography was not performed.

Sam was presented again a few months later for swelling below his right eye. An abscess from the right maxillary fourth premolar was presumptively diagnosed, and the tooth was sectioned and removed with a closed extraction technique. Dental radiography, again, was not performed.

After several months, the oral wound had not healed appropriately, and the patient demonstrated apparent continued discomfort, especially while eating. He was referred to a specialist for further treatment. Oral examination on referral revealed that the extraction site of the right maxillary fourth premolar was unhealed, with a root fragment extending from the inflamed gingiva (Figure 1).

A full physical examination with preoperative testing (ie, CBC, serum chemistry profile, urinalysis) revealed no significant abnormalities. A complete oral examination and full-mouth radiography were performed with the patient under general anesthesia.

Oral examination confirmed an unhealed extraction site of the right maxillary fourth premolar with a root fragment protruding into the oral cavity. Periodontal disease of the left maxillary fourth premolar (Figure 2) and a complicated crown fracture of the right maxillary canine (Figure 3) were also identified.

Dental radiographs confirmed the root fragment of the right maxillary fourth premolar had been retained (Figure 4). Periapical rarefaction (ie, periapical lucency) and periodontal disease of the right maxillary canine were also confirmed on radiographs; comparison with the contralateral left maxillary canine revealed that the canine tooth had been nonvital for several months, as the pulp cavity of the right maxillary canine had failed to narrow (Figures 5 and 6).¹ Dental radiographs of the left maxillary fourth premolar revealed fractures of the mesiobuccal and mesiopalatinal roots in addition to advanced periodontal disease of the distal root (Figure 7).

After the remaining teeth were cleaned, maxillary nerve blocks were performed and IV analgesia administered as part of a multimodal analgesia approach. Surgical extractions—which included removal of the mucogingival flaps and buccal bones and closure of the surgical sites—of the maxillary fourth premolars and the right maxillary canine were performed.²

Sam was discharged the same day on an oral NSAID to be administered daily for the next 4 days. His recovery was uneventful, and he started eating soft food the day after surgery.

Tooth fractures are common in dogs and cats and are typically incidental findings. In a study, fractured teeth were diagnosed in ≈50% of companion animals.³

Tooth fractures can be classified based on the amount of tooth structure (ie, enamel, dentin, cementum) exposed and whether the dental pulp tissue is directly exposed. An injury that does not expose the pulp is considered uncomplicated; direct pulp exposure is considered complicated.⁴

All vital teeth with direct pulp exposure are painful.⁵ The exposed pulp may become infected by oral bacteria, which can lead to pulpitis and pulp necrosis.

Special attention should be paid to uncomplicated crown fractures, as progressive clinical implications are typically underestimated. Dentinal tubules are exposed in almost all cases of uncomplicated crown fractures and can have several consequences:

• Pain can be felt due to dentinal sensitivity.⁶
• Bacteria can penetrate the tubules and infect the pulp without direct exposure of the pulp, resulting in pulpitis and pulp necrosis.⁷ Infection can extend through the apical delta and affect the periapical bone (ie, periapical rarefaction; Figure 8), which has been reported to occur in 24.3% of uncomplicated fractures of maxillary fourth premolars.⁸ If not recognized, the disease may end in abscessation with typical swelling (Figure 9) or in a fistula.
• The rough surface of a fractured tooth enables faster plaque and calculus accumulation, which can hasten the onset of periodontal disease.

Because the appearance of the crown does not always correlate with what is happening below the gumline, dental exploration and radiography are necessary for thorough examination of a fractured tooth. Uncomplicated crown fractures that appear harmless can have severe endodontic consequences seen on dental radiographs (Figure 8).⁹ Treatment options are directly related to the type and degree of damage, as well as the presence or absence of endodontic disease.¹⁰ Any complicated fracture (ie, involving direct pulp exposure) should be treated via extraction or root canal therapy. If a therapeutic delay is necessary, pain management should be provided until surgery can be performed; antibiotics are typically not indicated in these cases.¹¹

Treatment for dentin exposure (ie, uncomplicated fracture) is recommended to reduce sensitivity, block the pathway for infection, and smooth out the tooth, which should decrease periodontal disease.¹²

Dental radiography should be performed prior to treatment to ensure there is no existing endodontic disease. If evidence of endodontic inflammation and/or infection is noted on dental radiographs, root canal therapy or extraction is typically required.

Animals rarely show signs of oral pain, despite their nociceptive pathways functioning similarly to those of humans.¹³ Clinicians are responsible for recognizing when an animal is in pain and reacting accordingly. The intense pain from pulp exposure and the long duration required for an infection to develop outward clinical signs are of great animal welfare relevance. Animal welfare is gaining in importance, and neglecting guidelines may lead to future consequences.

Sam’s case demonstrates the importance of quickly performing a full dental examination, including dental radiography, with the patient under general anesthesia. Clinicians should have the minimum equipment and expertise needed if dental procedures are expected to be performed. Referral should be considered if the clinician is not properly equipped to handle these dental conditions.