Diagnosis of traumatic urethral stricture in a canine patient with contrast-enhanced voiding urosonography : A case report.

A 5-year-old intact male mixed-breed dog presented with a 3-day history of stranguria and dysuria. Results of physical examination, plain radiographs, and ultrasonography were consistent with a traumatic urethral stricture in the prescrotal urethra just under the previous trauma region, resulting in partial obstruction of urine outflow. Contrast-enhanced voiding urosonography (CE-VUS) was performed, and a urethral stricture was confirmed. The dog underwent surgery. A scrotal urethrostomy was performed. After 3 days of hospitalization, the dog was discharged from the Clinic. Based on an extensive literature review, this is the first report using CE-VUS to evaluate urethral pathology in a canine patient.

Influence of age on resistance to distraction after tracheal anastomoses in dogs: An ex vivo study.

OBJECTIVE: To determine the influence of age on the ability of tracheal anastomoses to sustain distraction in dogs. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Cadaveric canine tracheae (n = 16). METHODS: Tracheae were harvested from the cadavers of 8 immature and 8 adult dogs. Each trachea underwent end-to-end annular ligament anastomosis with a simple continuous pattern with 2-0 polypropylene on a taper cut needle. The constructs were tested to failure in distraction, with a tensiometer set at a drop head speed of 50 mm/min, as determined by preliminary testing. Failure was defined by tissue pullthrough or suture material failure. The force and elongation at failure were compared between age groups. RESULTS: The median age was 5.5 months (4-7.5 months) in immature dogs and 8.25 years in adult dogs (2-18 years) Tracheal anastomoses failed at lower forces (44.91 ± 59.03 N) but sustained more elongation (39.75 ± 5.45%) in immature dogs than in adult dogs (149.31 ± 45.36 N, P = .007 and 30.57 ± 7.19%, P = .0012, respectively). Tissue apposition was not achieved in 4 specimens each in immature and adult dogs, respectively. CONCLUSIONS: The technique used for tracheal anastomoses in this study failed at lower loads but sustained more elongation when performed in immature dogs. CLINICAL SIGNIFICANCE: Immature dogs may be able to withstand longer tracheal resection than adult dogs but reinforcement techniques seem mandatory to improve resistance to tension. Alternative anastomosis techniques should be considered to improve tissue apposition.

The Benefits of Expert Instruction in Microsurgery Courses.

BACKGROUND: Microsurgery requires repeated practice and training to achieve proficiency, and there are a variety of curriculums available. This study aims to determine the importance of an expert instructor to guide students through procedures. We compared student proficiency across two microsurgery courses: one with (Columbia University, United States [CU] cohort) and one without a dedicated microsurgery instructor (University of Thessaloniki, Greece [UT] cohort). METHODS: Students were divided into two cohorts of 22 students (UT cohort) and 25 students (CU cohort). Student progress was evaluated by examining patency (lift-up and milking tests), anastomotic timing, and quality (Anastomosis Lapse Index [ALI]) of end-to-end arterial and venous anastomoses on day 1 and again on day 5. Chi-squared tests evaluated patency immediately and 30 minutes postoperation. t-Tests evaluated anastomotic timing and ALI scores. p-Values < 0.05 were considered significant. RESULTS: We evaluated progress within and between each cohort. Within the CU cohort, the quality of the arterial and venous anastomosis improved, respectively (by 54%, p = 0.0059 and by 43%, p = 0.0027), the patency of both the arterial and venous anastomosis improved, respectively (by 44%, p = 0.0002 and by 40%, p = 0.0019), and timing of arterial and venous anastomosis reduced respectively (by 36%, p = 0.0002 and by 33%, p = 0.0010). The UT cohort improved the quality of their arterial anastomoses (by 29%, p = 0.0312). The UT cohort did not demonstrate significant improvement in the other above-mentioned parameters. The CU cohort improved materially over the UT cohort across categories of quality, patency, and timing. CONCLUSION: There are clear benefits of an expert instructor when examining the rate of progress and proficiency level attained at the conclusion of the course. We suggest students who are seeking to maximize proficiency in microsurgical procedures enroll in courses with an expert instructor.

Contrast enhanced computed tomography assessment of superficial inguinal lymph node metastasis in canine mammary gland tumors.

Mammary gland neoplasms are predominant in dogs. However, sentinel lymph node (SLN) status assessment criteria have not been established for these cases. In this retrospective, secondary analysis, diagnostic case control study, CT images of 65 superficial inguinal SLNs were obtained before and 1, 3, 5, and 10 min after intravenous administration of contrast agent (iopamidol 370 mgI/mL). The presence and degree of postcontrast enhancement were assessed, by means of the median absolute density value and the maximum absolute density value at any time point in the center and in the periphery of each SLN measured in Hounsfield units (HU), before and after contrast agent administration. These values were compared with histopathological findings postsurgical excision. Receiver operating characteristic analysis was conducted. The absolute density values ranged widely at each time point and within each group of nodes (negative, positive, control group). At all time points, the median density value in the center and in the periphery was significantly higher in metastatic than in non-metastatic SLNs (P ≤ .014). Among the parameters tested, the median absolute density value measured in the periphery of the SLN 3 min after injection showed the highest sensitivity, specificity, and accuracy (AUC) (87.5%, 82.1%, and 92.1% respectively), with a cutoff value of 50.9 HU. The maximum absolute density value at any time point in the center and periphery of the SLNs was also significantly higher in metastatic SLNs compared to non-metastatic (P ≤ .001). With a cutoff value of 59.5 HU, the maximum absolute density value in the periphery of the SLN displayed high sensitivity and specificity (87.5% and 89.3%, respectively). The results of this study support the hypothesis that contrast enhanced CT imaging may aid in the assessment of SLN metastasis in dogs with mammary gland neoplasms.

Transdiaphragmatic Gastrotomy for the Extraction of Distal Esophageal Foreign Bodies in 13 Dogs (1997-2016).

The records of 13 dogs with distal esophageal foreign body obstruction not amenable to endoscopic management that had transdiaphragmatic gastrotomy (TG) for the foreign body extraction were reviewed. West Highland white terriers were over-represented. Mean age of the dogs at presentation was 38.6 mo, and mean duration of clinical signs associated with esophageal foreign bodies was 5.8 days. A TG was performed via an eighth or ninth left intercostal thoracotomy, and clinical results were successful in 12 dogs. In 1 dog, gastrotomy failed to retrieve a foreign body and esophagotomy was performed. Foreign bodies that were removed included 3 fishhooks and 10 animal bones. Postoperatively, all dogs developed esophagitis, 1 dog showed esophageal stricture, and 1 dog died of pyothorax associated with esophageal perforation 1 day postsurgery. Overall, 12 dogs survived and were free of clinical signs after a median follow-up time of 17 mo. TG is an effective surgical technique for the retrieval of distal esophageal foreign bodies.

Contrast-enhanced voiding urosonography: A new, radiation-free, alternative method for imaging of urinary bladder and urethra in healthy dogs.

Contrast-enhanced voiding urosonography (CE-VUS) has been generally considered as a promising tool to diagnose vesicoureteral reflux and abnormalities in lower urinary tract in human patients, especially in children. The purpose of this prospective study is to evaluate the quality of images of the urinary bladder and urethra obtained by CE-VUS using a second-generation ultrasound contrast agent (SonoVue®) in healthy dogs and to investigate the safety profile of SonoVue® after intravesical administration. Eighty-four CE-VUS examinations with SonoVue® were successfully performed in both unsedated (39/84) and sedated (45/84) dogs. Contrast-enhanced voiding urosonography examination of urinary bladder was technically successful in all (84/84) dogs. The image quality was not considered adequate in five (5/84) dogs including three dogs in whom layering of contrast media during filling phase was observed and two dogs with premature destruction of microbubbles. In these five dogs, the problem was readily recognized and corrected such that the procedure was still successfully undertaken. The assessment of the urethra during spontaneous micturition was successfully performed in all (84/84) dogs in whom voiding was elicited during the examination. No side effects were observed after intravesical application of SonoVue®. This study demonstrates that CE-VUS is a feasible and valuable technique to evaluate low urinary tract morphology and function in dogs. Based on our review of the literature, there are no published reports about the use of this method in dogs.

Comparison of maximum force to failure of 4 thoracostomy tube connecting devices.

OBJECTIVE: To compare the maximum force and displacement to failure of 4 different types of thoracostomy tube connecting devices. STUDY DESIGN: Experimental in vitro study. STUDY POPULATION: Four types of thoracostomy tube connecting devices (n = 10 each). METHODS: Four different connecting device configurations (10 constructs each) were tested by maximum distraction to failure using a dynamometer: (1) CTTWW-a 3-way connector with a male luer slip attached to a thoracostomy tube by a Christmas tree adapter and secured to the tube with 21 gauge orthopedic wire; (2) CTTWRCW-a 3-way connector with a male luer lock with a rotating collar attached to a tube by a Christmas tree adapter and secured to the tube with 21 gauge orthopedic wire; (3) LVSBC-a Lopez valve attached to a tube with its short-barbed connector; and (4) LVLBC-a Lopez valve attached to a tube with its long-barbed connector. RESULTS: The maximum distraction force to failure was significantly greater for CTTWRCW (250.9 N; range 143.7-293.6) than CTTWW (132.9 N; range 84.2-224.1), LVLBC (90.8 N; range 74.0-123.4), and LVSBC (54.6 N; range 39.6-164.2). The median displacement to failure of CTTWRCW (150 mm; range 54-190) was significantly longer than that of CTTWW (34.5 mm; range 22-70), LVLBC (32.5 mm; range 24-57), and LVSBC (16 mm; range 11-69). CONCLUSION: The CTTWRCW group required greater force to create failure and had a longer displacement to failure, making it a more secure choice for connection to thoracostomy tubes.

ASSESSMENT OF SENTINEL LYMPH NODE METASTASIS IN CANINE MAMMARY GLAND TUMORS USING COMPUTED TOMOGRAPHIC INDIRECT LYMPHOGRAPHY.

In the staging process of the breast cancer, demonstrating metastasis of the sentinel lymph node (SLN) has an important prognostic value, in both humans and animals. The aim of this prospective case-control study was to determine the diagnostic value of computed tomographic indirect lymphography (CT-LG) for detecting SLN metastasis in dogs with mammary cancer. Thirty-three female dogs with tumors in the abdominal and inguinal mammary glands were prospectively selected and subjected to CT-LG, 1 and 5 min after injection of 1 ml of contrast agent (iopamidol) in the subareolar tissue of the neoplastic and the contralateral normal mammary glands. The pattern of postcontrast opacification, degree of postcontrast enhancement, and size and shape were assessed in 65 SLNs in total and were correlated with histopathological findings. The absence of opacification or heterogeneous opacification 1 min after contrast medium injection showed the highest sensitivity, specificity, and accuracy (93%, 100%, and 98.4%, respectively). In images taken 1 min after injection, an absolute density value lower than 444 Hounsfield units (HU) in the center of the SLN also provided significant sensitivity and specificity (93.8% and 75%, respectively). The size and shape of the SLN (maximum and minimum diameter, maximum/minimum diameter ratio, maximum diameter/height of fifth thoracic vertebral body ratio) showed the lowest sensitivity and specificity. Results of this study support the hypothesis that CT-LG could help in the assessment of SLN metastasis in cases of mammary gland tumors in dogs.

Successful management of jejunojejunal anastomosis dehiscence by extra-abdominal exteriorization and bandaging in a cat with septic peritonitis.

Duodenal and jejunal resections were performed in a cat with septic peritonitis due to small intestinal perforations by a linear foreign body. Three days later jejunal resection and anastomosis were repeated due to dehiscence of the anastomosis site. This segment of intestine was exteriorized through the body wall and managed with bandages for 5 days before it was surgically replaced into the abdomen. The cat made a full recovery.

Gestion réussie d'une déhiscence d'une anastomose jéjunojéjunale par l'extériorisation extraabdominale et des pansements chez un chat atteint de péritonite septique. Des résections duodénale et jéjunale ont été réalisées chez un chat atteint de péritonite septique en raison de petites perforations intestinales par un corps étranger linéaire. Trois jours plus tard, la résection jéjunale et l'anastomose ont été répétées en raison d'une déhiscence du site de l'anastomose. Ce segment de l'intestin était extériorisé au travers de la paroi du corps et il a été géré à l'aide de pansements pendant 5 jours jusqu'à ce qu'il soit replacé dans l'abdomen par une chirurgie. Le chat s'est complètement rétabli.(Traduit par Isabelle Vallières).

Saline volume required to achieve peristaltic intraluminal pressure during leak testing of canine colotomies, using two methods of luminal occlusion.

Background: No studies have appeared in the literature evaluating the intraluminal volume of injected saline in the canine colon for performing leak tests in colotomy incisions. Aim: To determine the volume of the injected intraluminal saline necessary to achieve an intraluminal pressure of 17.3 cm H2O in 10 cm colonic segments containing a closed colotomy occluded with intestinal forceps or by digital pressure. Methods: Fresh colon was obtained from 8 canine cadavers and divided into 10 cm segments. A 3 cm antimesenteric colonic incision was performed at each intestinal segment which was closed using a 3-0 polydioxanone suture in a simple continuous pattern. Each colonic construct was occluded with Doyen intestinal forceps or by digital pressure and a leak test was performed by saline infusion. The saline volume needed to achieve a predetermined intraluminal pressure of 17.3 cm H2O, following occlusion was recorded. Results: The mean volume of injected saline with the Doyen intestinal forceps occlusion (20.4 ± 8.2 ml) was significantly larger than that of the digital occlusion technique (17.5 ± 6.8 ml) [p = 0.021]. Conclusion: For 10 cm canine colonic constructs containing a closed colotomy, saline volumes of 20.4 ml with Doyen occlusion and 17.5 ml with digital occlusion can be utilized to achieve intraluminal pressures of 17.3 cm H2O.

Surgical management of squamous cell carcinoma of the canine male external genitalia: 15 cases (1994-2020).

Fifteen male dogs with squamous cell carcinoma of the external genitalia were admitted for further investigation and surgical management between 1994 and 2020. The dogs belonged to various breeds. Thirteen dogs were intact and two were castrated with a median age of 8 years and a median weight of 28 kg. Seven dogs were white-coated and eight nonwhite coated. Scrotal ablation and orchiectomy were performed in four dogs, partial penile amputation in two, partial penile amputation plus partial preputial ablation in one, penile amputation, and scrotal urethrostomy in seven, and local preputial excision in one dog. Postoperative complications included hemorrhage in 10 dogs, bruising at the urethrostomy site in seven, and urethrostomy dehiscence in one dog. Tumor recurrence was recorded in six dogs. Dogs with poorly differentiated tumors that had tumor recurrence had shorter survival and worse prognosis compared to those with well and moderately differentiated tumors. The mean survival time was 48.132 months. After a median follow-up of 23 months (range: 8 to 72 months), eight dogs were alive, five were euthanized and two dogs died from unrelated causes. Surgical excision seems to be a treatment option for dogs with squamous cell carcinoma of the external genitalia.

Cutaneous Canine Mast Cell Tumor: The Use of Proliferative Markers (Ki-67 and Ki-67 × AgNOR) in Cytological Samples for Diagnosis and Prognosis.

A cytological grading system for canine mast cell tumors (MCTs) has been developed, but its integration into clinical routine has been hindered due to its diagnostic limitations. The aim of this study was to assess the prognostic value of Ki-67 and argyrophilic nucleolar organizing region (AgNOR) markers in cytological MCT samples and to determine cut-off values for these markers in correlation with histopathological grading. Cytological samples were collected prior to surgical excision, and histopathological samples were obtained postsurgery from 45 dogs diagnosed with cutaneous mast cell tumors (MCTs). The cytological specimens were classified using a two-tier grading system, and their Ki-67 (average immunopositive nuclei per 100 cells) and AgNOR (average AgNOR counts per 100 nuclei) signaling was assessed. Through receiver operating characteristic (ROC) analysis, cut-off values for Ki-67 and Ki-67 × AgNOR were determined to better align with histopathological grading (classified as low or high grade according to Kiupel's scoring system). Without the inclusion of proliferative markers, there was a 73% agreement between cytological and histopathological grading. The prediction of histopathological grade was slightly more accurate when assessing Ki-67 and Ki-67 × AgNOR signaling in cytological specimens (75% and 80%, respectively) compared to the initial cytological grading. The cytological assessment of canine MCTs proves beneficial for the initial evaluation, and the incorporation of the evaluation of Ki-67 and AgNOR markers may assist in identifying diagnostically highly malignant MCTs.

Scrotal flap for closure of perineal skin defects in dogs.

OBJECTIVE: To describe the use of a scrotal flap for covering perineal skin defects in dogs. STUDY DESIGN: Experimental study. ANIMALS: Male Beagles (n = 5). METHODS: A scrotal flap was created by making a U-shaped incision around the scrotum, with the base of the flap at its rostral border. Orchiectomy was performed through this incision and the scrotum was undermined from the underlying tissue. A small median longitudinal incision in the caudal aspect of the scrotum eliminated its curvature. A skin defect, comparable to the size of the scrotal flap, was created in the perineum extending from the caudal side of the scrotum toward the anus. The scrotal flap covered the defect and was sutured in place. RESULTS: By 5-7 days, all flaps had ∼27% necrosis on their caudal border. The necrotic area was surgically excised and the defect was covered completely again by the remaining healthy flap. One year after surgery, wound healing was normal and flap survival was complete, providing full coverage of the perineal skin defect. CONCLUSION: A scrotal flap can be used to reconstruct perineal skin defects ventral to the anus.

Surgical Anatomy of the Gastrointestinal Tract in Cats.

In cats, the gastrointestinal tract is one of the regions in which surgical procedures are most frequently performed by veterinary surgeons; therefore, knowledge of the surgical anatomy of the feline gastrointestinal tract is of high importance. The main surgical procedures performed include gastrotomy, gastrectomy, enterotomy, and enterectomy, as well as procedures in the liver and pancreas. There are also anatomical differences between dogs and cats, increasing the need for deep knowledge of the anatomy treated in the different surgical approaches. The aim of the present review is to describe in detail the anatomy of the gastrointestinal tract in cats highlighting the anatomical regions of significant importance in different surgical procedures.

Congenital Portosystemic Shunts in Dogs and Cats: Classification, Pathophysiology, Clinical Presentation and Diagnosis.

Congenital portosystemic shunts (CPSS) are abnormal vascular communications between the portal and the systemic circulation, bypassing the hepatic parenchyma and resulting in liver hypoplasia and hepatic insufficiency. Such connections develop in utero and persist postnatally. CPSS are among the two most common congenital vascular anomalies of the liver in small animals, along with primary hypoplasia of the portal vein without portal hypertension (PHPV without PH). CPSS can be extrahepatic (ECPSS), most commonly diagnosed in small and toy breed dogs and cats, or intrahepatic (ICPSS), most commonly seen in large breed dogs. Single ECPSS is the most common type encountered in both dogs and cats. Clinical signs of CPSS are non-specific and may wax and wane, while laboratory findings can raise clinical suspicion for CPSS, but they are also not specific. Definitive diagnosis will be established by evaluation of liver function tests, such as determination of fasting plasma ammonia (FA) levels, and pre- and postprandial serum bile acids concentrations, and diagnostic imaging. The purpose of this article is to review the definition, classification, pathogenesis, clinical presentation, and diagnosis of CPSS in dogs and cats, highlighted by the authors' clinical experience.

Evaluation of Survival of Subdermal Plexus Skin Flaps in 8 Cats After Injection of Platelet Rich Plasma.

The aim of the present study was to evaluate the effect of platelet-rich plasma injection on the survival of experimentally developed subdermal plexus skin flaps in cats. Two flaps, 2 cm wide and 6 cm long were created bilaterally in the dorsal midline in 8 cats. Each flap was randomized to 1 of 2 groups: platelet-rich plasma injection and control. After flap development, the flaps were immediately placed back on the recipient bed. Then 1.8 mL of platelet-rich plasma was equally injected into 6 different parts of the treatment flap. All flaps were evaluated macroscopically daily and on days 0, 7, 14, and 25 by planimetry, Laser Doppler flowmetry, and histology. Mean flap survival on day 14 was 80.437 % (±22.745) for the treatment group and 66.516 % (±24,12) for the control group with no statistically significant difference between the 2 groups (P = .158). Histologically, a significant difference was found between the base of the PRP and the control flap in edema score on day 25 (P = .034). In conclusion, there is no evidence to support the use of platelet-rich plasma in subdermal plexus flaps in cats. However, the use of platelet-rich plasma may aid in reducing edema of subdermal plexus flaps.

Congenital Portosystemic Shunts in Dogs and Cats: Treatment, Complications and Prognosis.

Congenital portosystemic shunts (CPSS) are a common vascular anomaly of the liver in dogs and cats. Clinical signs of CPSS are non-specific and may wax and wane, while laboratory findings can raise the clinical suspicion for CPSS, but they are also not specific. Definitive diagnosis will be established by evaluation of liver function tests and diagnostic imaging. The aim of this article is to review the management, both medical and surgical, complications, and prognosis of CPSS in dogs and cats. Attenuation of the CPSS is the treatment of choice and may be performed by open surgical intervention using ameroid ring constrictors, thin film banding, and partial or complete suture ligation or by percutaneous transvenous coil embolization. There is no strong evidence to recommend one surgical technique over another. Medical treatment strategies include administration of non-absorbable disaccharides (i.e., lactulose), antibiotics, and dietary changes, and are indicated for pre-surgical stabilization or when surgical intervention is not feasible. After CPSS attenuation, short- and long-term post-surgical complications may be seen, such as post-operative seizures and recurrence of clinical signs, respectively. Prognosis after surgical attenuation of CPSS is generally favorable for dogs and fair for cats.

Evaluation of the Effectiveness of Medical-Grade Honey and Hypericum Perforatum Ointment on Second-Intention Healing of Full-Thickness Skin Wounds in Cats.

This study aimed to determine the effects of two topical treatments on second-intention wound healing in cats. Eight 2 × 2 cm full-thickness wounds were created, four on each side of the dorsal midline of eight laboratory cats, to receive either medical-grade honey ointment (MGH) and its control (HC), or Hypericum-based ointment (HP) and its control (HPC). MGH or HP ointment was applied to four wounds on the same side, while the remaining four were used as controls, chosen at random. Planimetry, laser Doppler flowmetry, daily physical examinations, and histologic examinations on days 0, 7, 14, and 25 were used to assess the healing of wounds. Tissue perfusion was better in the MGH-treated (2.14 ± 0.18 mm/s) and HP-treated wounds (2.02 ± 0.13 mm/s) than in the untreated controls HC (1.59 ± 0.11 mm/s) and HPC (1.60 ± 0.05 mm/s), respectively (p = 0.001). Histopathology revealed that the median edema score was lower in the MGH-treated (2; range 1-4) compared to the HC-treated wounds (3; range 2-4) on day 7 (p < 0.05). The median angiogenesis score was higher on day 7 in the MGH-treated (2; range 1-3) compared to the HP-treated wounds (2; range 1-2) (p = 0.046). The fibroblast concentration was increased in the MGH-treated wounds (3.5; range 3-4) compared to the HP-treated wounds (3; range 2-4) on day 25 (p = 0.046). MGH and HP increased tissue perfusion compared to the untreated controls. The MGH-treated wounds had histologic parameters superior to the HP-treated wounds regarding angiogenesis and fibroblast concentration in cutaneous wound healing in cats. Topical application of MGH and HP did not accelerate the healing process of feline cutaneous wounds.

Anesthesia and perioperative management of a pneumonectomized dog.

Although left- or right-sided pneumonectomy is tolerated by normal dogs, complications impacting the respiratory, cardiovascular, and gastrointestinal systems are not uncommon. Pneumonectomy in dogs results in secondary changes in the remaining lung, which include: decreased compliance and vital capacity; and increased pulmonary vascular resistance potentially leading to right ventricular hypertrophy. Such alterations make the anesthetic management of an animal with one lung particularly challenging. This report describes a dog with a history of left pneumonectomy due to Aspergillus fumigatus pneumonia 3 yr before presentation. The dog presented with a vaginal wall prolapse, and surgical resection of the protruding vaginal wall, ovariectomy, and prophylactic gastropexy were performed. Anesthesia was induced with midazolam, fentanyl, and propofol and was maintained with isoflurane using intermittent positive pressure ventilation and a constant rate infusion of fentanyl. Epidural anesthesia was also used. Recovery and postoperative management were uncomplicated. Intensive hemodynamic and respiratory monitoring and appropriate response and treatment of any detected abnormalities, taking into consideration the pathophysiologic alterations occurring in a pneumonectomized animal, are required for successful perianesthetic management.

Τhe Effect of Opioid Administration on Cytologic and Histopathologic Diagnosis of Canine Cutaneous Mast Cell Tumors Treated by Surgical Excision.

Mast cell tumor (MCT) is a frequent cutaneous tumor in dogs, with a variable biological behavior. Studies correlate cytologic and histopathologic features of MCTs with their biological behavior, prognosis, and response to treatment. The use of preoperative opioids is common in canine patients undergoing surgical removal of these tumors. Certain opioids can induce or downregulate mast cell degranulation and influence cancer progression. The aim of the present study was to investigate whether the administration of morphine or butorphanol during surgical excision of canine cutaneous MCTs affects their cytologic and histopathologic appearance, thus influencing cytologic and histopathologic grading. This was a prospective, blinded, randomized, cohort clinical study. Forty-five dogs with cutaneous MCTs were randomly allocated into three groups according to preanaesthetic medication: dexmedetomidine combined with morphine (group M) or butorphanol (group B) or normal saline (group C). Cytologic specimens and histopathologic samples were obtained both prior to and after surgery. Samples were graded according to Kiupel's and Patnaik's systems, examined immunohistochemically for Ki-67 protein (Ki-67) and c-kit proto-oncogene product (KIT) expression, and histochemically for argyrophilic nucleolar organizing regions (AgNORs). Based on both Kiupel's and Patnaik's systems, no statistically significant differences were noted concerning the number of cases with grading discrepancies in grades allocated prior to versus after surgery among the groups. The same applied for cytological grading and immunohistochemical and histochemical evaluation. It seems that administration of morphine or butorphanol as part of the preanesthetic medication for surgical removal of canine cutaneous mast cell tumors does not influence histopathologic and cytologic grading of MCTs.