Evaluation of prostate-specific antigen levels via clinical and ultrasonographic examination in healthy dogsABSTRACT
While there are many diagnostic methods in human medicine for diseases of the prostate gland, which forms a significant part of the seminal plasma with the secretions it produces in dogs and prevents sperm from being affected by the acidic environment in the vagina, what can be done to diagnose them in veterinary medicine is much more limited. Anamnesis, clinical examination, ultrasonographic findings/dimensions of the prostate and prostate specific antigen (PSA) levels are very important in the diagnosis of prostate gland diseases in dogs. In this study, prostate dimensions, volumes and PSA levels were determined in 35 healthy dogs of different breeds, ages, body weights and neutering statuses, and it was aimed to establish a standard for use in clinical practice in line with the obtained data. As a result of ultrasonographic examinations, the mean prostate length, width and height of the dogs were determined to be 1.76cm, 2.73cm and 1.43cm, respectively. The average prostate volume of dogs was found to be 6.19cm3 and the average PSA level was found to be 1.434ng/mL. This study determined that demographic factors such as age, breed, body weight and castration status did not affect PSA and prostate volume at a statistically significant level in healthy dogs. In conclusion, this study provided a general understanding of the mean prostate volumes and serum PSA levels of healthy dogs, providing simple reference values and contributing to the literature.
Key words:
dog; prostate; prostate volume; PSA; ultrasonography
RESUMO
Embora existam muitos métodos de diagnóstico na medicina humana para doenças da próstata, que constitui uma parte significativa do plasma seminal com as secreções que produz em cães e que protege os espermatozoides do ambiente ácido da vagina, as opções para diagnosticá-las na medicina veterinária são muito mais limitadas. Anamnese, exame clínico, achados/dimensões ultrassonográficas da próstata e níveis de antígeno prostático específico (PSA) são muito importantes no diagnóstico de doenças da próstata em cães. Neste estudo, as dimensões, os volumes e os níveis de PSA da próstata foram determinados em 35 cães saudáveis de diferentes raças, idades, pesos corporais e estados reprodutivos, com o objetivo de estabelecer um padrão para uso na prática clínica, de acordo com os dados obtidos. Como resultado dos exames ultrassonográficos, o comprimento, a largura e a altura médios da próstata dos cães foram determinados em 1,76cm, 2,73cm e 1,43cm, respectivamente. O volume prostático médio dos cães foi de 6,19cm³ e o nível médio de PSA foi de 1,434ng/mL. Este estudo determinou que fatores demográficos, como idade, raça, peso corporal e estado de castração, não afetaram o PSA e o volume prostático de forma estatisticamente significativa em cães saudáveis. Em conclusão, este estudo proporcionou uma compreensão geral dos volumes prostáticos médios e dos níveis séricos de PSA em cães saudáveis, fornecendo valores de referência simples e contribuindo para a literatura científica.
Palavras-chave:
cão; próstata; volume da próstata; PSA; ultrassonografia
INTRODUCTION
The prostate is a sexual gland in dogs that has two lobes and is located between the caudal part of the bladder and the proximal part of the urethra. The prostate gland, which produces an alkaline secretion that constitutes a significant portion of seminal plasma, protects sperm from the acidic environment of the vagina (Davidson, 2017, Cunto et al., 2019, Polat, 2021). Factors such as age, breed and body weight can affect the size of the prostate gland. The prostate gland, which continues to grow in dogs until the age of two, is located in the pelvic cavity until sexual maturity, but with age it descends into the abdominal cavity (Polat, 2021).
Prostate gland diseases are more common in dogs than in cats. Benign prostatic hyperplasia (BPH), squamous metaplasia, paraprostatic cysts, infectious prostatitis, and prostate neoplasms are the most common prostate gland diseases in dogs (Polat, 2021). These diseases can cause many different clinical and ultrasonographic findings. For example, prostatomegaly occurs in cases of BPH and acute prostatitis, while the prostate is often normal in size in cases of chronic prostatitis (Polat, 2021). In BPH cases, mild or moderate hyperechoic areas are observed in prostate ultrasonography; whereas in prostate neoplasia cases, widespread hyperechoic areas are seen. One of the important markers of prostate gland disease is the Canine Prostatic Specific Esterase (CPSE), also known as Prostate Specific Antigen (PSA) value. Except for pathological conditions, certain physiological conditions (such as age) can cause increases in both prostate gland volume and PSA levels (Atalan et al., 1999, Alpay and Civelek, 2022). In some studies conducted on healthy dogs, the average prostate volume was reported as 18.9±15.5cm³ (Ruel et al., 1998), 12.3cm³ (Atalan et al., 1999), and 16.77±11.77cm³ (Kamolpatana et al., 2000), respectively. Although studies on serum PSA levels in dogs are limited, some studies report this level to be approximately 0.005ng/dL (Amorim et al., 2004, Golchin-Rad et al., 2019), while some studies report the reference range as 0.000-4.000ng/mL (Alpay and Civelek, 2022).
This study aimed to establish a basic standard value by evaluating clinical and ultrasonographic examinations of the prostate gland and serum PSA values in healthy dogs. Additionally, in this study, data such as prostate volume and PSA levels were compared with factors like age, weight, neutering status, breed, and size to determine their relationships and average values, aiming to contribute to the literature.
ETHICAL ASPECTS
Ethical approval for this study was obtained from the Fırat University Local Ethics Committee for Animal Experiments in accordance with the decision of the meeting dated 05 April 2024 and numbered 23594.
MATERIALS AND METHODS
Study Materials and Anamnesis Phase. During the study, before beginning the prostate examination of 35 male dogs brought to the Firat University Animal Hospital and whose owners gave consent, information was obtained from the owners regarding whether their dogs had any past or ongoing problems such as difficulty urinating or hematuria. In addition, characteristics such as age, breed, castration status and body weight of the dogs were recorded in the anamnesis.
Collection of Blood Samples. In order to prevent the serum PSA levels from being affected by the procedures performed during the clinical and ultrasonographic examinations of the dogs included in the study, blood samples were taken before the examination. Blood samples were collected into yellow-capped gel vacuum blood collection tubes and then centrifuged at 4,000 rpm for 5 minutes to obtain serum. The serum samples obtained were stored under appropriate conditions (-80°C) until the time when PSA levels would be determined.
Clinical and Ultrasonographic Examination. No medication was administered prior to the prostate examination, and no sedation was performed. In the clinical examination of the dogs, rectal examination was performed to evaluate the size, shape, contours, consistency of the prostate gland, whether it caused sensitivity in the animal, and whether it pressed on the rectum. Thus, a preliminary opinion was reached about the prostate gland. Then, each dog underwent transabdominal prostate gland ultrasonography using a convex probe with a frequency range of 3.5-7.5mHz. As a result of ultrasonography, findings such as length, width and height of the prostate gland were determined (Figure 1). Based on all these data, prostate volume (PV) was calculated using the ellipsoid formula recommended by Ruel et al. (1998) according to the formula in Table 1.
Measurements of Prostate Specific Antigen (PSA) Values. In order to determine the prostate-specific antigen levels from the serum samples obtained after centrifugation, measurements were made in accordance with the protocol that came with the commercially available ELISA kit (Catalog No: 201-15-0105 and Sensitivity: 0.048ng/mL, Canine Spesific).
Statistical Analysis. All statistical analyses were performed using the SPSS statistical software package (version 20.0; IBM Corp., Armonk, NY, USA). Descriptive statistics were expressed as mean ± standard error (SE). A multifactorial analysis of variance (ANOVA) was performed within the General Linear Model (GLM) procedure to evaluate the effects of race, age, body weight, and castration status on prostate volume and PSA levels. The model included the main effects of these factors as well as their two-way and higher-order interactions. Because there were insufficient observations for some factor combinations, the relevant interaction terms could not be tested and were therefore removed from the analysis. Statistical significance was set at p<0.05.
RESULTS
In the study, clinical examinations of all 35 dogs that underwent prostate examination revealed that the prostate glands were of normal size, symmetrical, had normal consistency, and showed no abnormal sensitivity upon palpation. The dogs included in the study were determined to have an average age of 3.8 years and an average weight of 27.69kg. Based on the ultrasonographic examinations performed on healthy dogs that were found to have no prostate-related disease during clinical evaluations, the average prostate length, width, and height were calculated as 1.76cm, 2.73cm, and 1.43cm, respectively. In addition, the average prostate volume of these 35 healthy dogs was determined as 6.19cm3. The mean PSA value of the dogs was determined as 1.434ng/mL. Additionally, the mean prostate volumes and PSA levels according to breed, age, body weight, and castration status of the dogs in the study are presented in Table 2.
Mean (±SE) values of prostate volume and PSA levels in dogs grouped by breed, age, body weight, and castration status
When the relationship with breed size was evaluated, it was found that the average prostate volume was lower in medium-sized dog breeds than in large and small breed dogs. It was observed that most medium-sized dog breeds included in the study were less than 1 year old. When the relationship between breed size and PSA value was examined, it was found that the average was lower in medium-sized dog breeds than in large and small dog breeds.
When the relationship with age was evaluated, it was observed that prostate volume increased with increasing age. However, when the relationship between age and PSA was evaluated, it was determined that the average PSA in dogs from one to five years old was higher than in dogs over five years old.
When the relationship between body weight and prostate volume was evaluated, it was determined that prostate volume was greater in dogs weighing 16-35kg compared to those over 35kg, and greater in dogs over 35kg compared to those weighing 15kg or less. It was found that PSA levels were higher on average in dogs weighing over 35kg compared to other dogs.
When the relationship with castration was evaluated, it was determined that the mean prostate volume and PSA were higher in castrated dogs than in non-castrated dogs. It was also determined that the majority of castrated dogs were over five years old.
Statistical analysis showed that breed, age, body weight and castration status had no significant effect on prostate volume or PSA levels (p>0.05 for all). Similarly, no statistical differences were detected in any of the two-way interactions tested (Breed × Age, Breed × Body weight, Age × Body weight). In interactions involving castration status (Breed × Castration, Age × Castration, Body weight × Castration, and four-way interaction), observations could not be tested due to missing data in some factor combinations (Table 3).
DISCUSSION
The prostate, an important part of the male reproductive system in dogs, is a two-lobed glandular organ surrounding the urethra (Evans and Christensen, 1979, Polat, 2021, Alpay and Civelek, 2022). Prostate secretions constitute a significant portion of seminal plasma and are important fluids that provide protection and nutrition for sperm (Davidson, 2017, Cunto et al., 2019, Polat, 2021, Alpay and Civelek, 2022). The prostate gland, which is located in the pelvic cavity until sexual maturity, can descend into the abdominal cavity with age (Polat, 2021). In this study, the ultrasonographic findings of the prostate gland-an organ with important reproductive functions-and the PSA levels in healthy dogs were evaluated in relation to demographic factors. Based on these findings, the study aimed to establish baseline reference values and provide a fundamental standard. In addition, findings from previous studies on prostate diseases involving both healthy and diseased animals were reviewed and compared with the results of this study, and the reliability of the obtained reference values was evaluated.
Ruel et al. (1998) reported that in a study conducted on 100 healthy male dogs with a mean age of 5.1±3.4 years and a mean body weight of 18±11.8kg, the average prostate length was 3.4±1.1cm, the average width was 3.3±0.9cm, and the average height was 2.8±0.8 cm. In the same study, the mean prostate volume obtained using these data was found to be 18.9±15.5cm³. Atalan et al. (1999) reported in their study conducted on 154 adult, healthy, and intact male dogs-aged from one to 14 years (median 4.3 years) and weighing from 4.5 to 65kg (median 17.8kg)-that the mean prostate length was 2.9cm, and the mean prostate width was 2.5cm. In the same study, they reported that the average prostate volume of dogs was 12.3cm3. Atalan et al. (1999) reported in their study that factors such as age and live weight had no significant effect on prostate volume. Cazzuli et al. (2025) reported in their study that the mean prostate volume in healthy male dogs was 22 ± 15cm3. Kamolpatana et al. (2000) reported in their study, which examined the prostate ultrasonography of 12 intact male dogs under 5 years of age with an average body weight of 21.8kg, that the mean prostate volume was 16.77±11.77cm³. In this study, it was determined that the average prostate length of 35 dogs with an average age of 3.8 years and an average weight of 27.69kg was 1.76cm, the average prostate width was 2.73cm and the average prostate height was 1.43cm. The average prostate volume obtained from these data was observed to be 6.19cm3. In this study, similar to the study by Atalan et al. (1999), it was determined that age and body weight had no significant effect on prostate volume. Although the effect of age on prostate volume was not significant, it was determined that the group with the highest prostate volume was dogs over five years old (9.288±2.954cm3).
The most common prostate gland diseases in dogs are benign prostatic hyperplasia (BPH), squamous metaplasia, paraprostatic cyst, infectious prostatitis and prostate neoplasms (Krawiec and Heflin, 1992, Polat, 2021, Alpay and Civelek, 2022). BPH is a disease that mostly occurs due to aging and is associated with prostatomegaly, encountered in approximately 80% of dogs over the age of five (Korodi et al., 2008, Lévy et al., 2014, Alpay and Civelek, 2022). Similar to BPH cases, prostatomegaly is observed in acute prostatitis cases, while prostate size appears normal in chronic prostatitis cases (Polat, 2021). Cazzuli et al. (2025) reported in their study that the average prostate volume in dogs with BPH was 81±41cm³. Dearakhshandeh et al. (2020) induced BPH in 25 intact dogs aged one-three years by administering testosterone enanthate and estradiol benzoate injections. They reported that the prostate volume, which was 9.66±4.81cm³ on day 0, increased significantly to 20.59±6.83cm³ by day 63. Alpay and Civelek, (2022) reported in their study in which they performed ultrasonographic evaluation of 24 male dogs in which they detected BPH and other prostate gland diseases, that the average prostate length was 4.88±0.15cm, the average prostate width was 3.98±0.11cm and the average prostate height was 3.46±0.13cm. They found that the mean prostate volume of the 24 dogs in the study was 35.18±2.01cm3. Pasikowska et al. (2015) reported in their study that the mean prostate length in dogs diagnosed with BPH was 43.87±11mm, the mean prostate width was 48.95±8.76mm, and the mean prostate height was 44.9±9.48mm. In this study, the mean prostate volume was determined as 6.19cm³ as a result of ultrasonographic examinations of 35 healthy dogs with an average age of 3.8 years. Additionally, in this study, it was determined that the average prostate length was 1.76cm, the average prostate width was 2.73cm, and the average prostate height was 1.43cm. The fact that all these obtained measurement values largely overlap with previous studies related to prostate diseases accompanied by prostatomegaly in dogs demonstrates that the results are quite consistent with the accepted reference values. Additionally, the study reported the average prostate volume results by age group as follows: 2.814±2.772cm³ (≤ one year), 6.515±2.772cm³ (one-five years), and 9.288±2.954cm³ (≥ five years), which supports the age-related increase in prostate volume reported in the literature.
Canine Prostatic Specific Esterase (CPSE) or PSA is a biomarker produced by the prostatic epithelium that helps in diagnosis by showing increased serum levels in prostate gland diseases causing disruption of the blood-glandular barrier of the prostate (Roehrborn et al., 1999, Alpay and Civelek, 2022). Amorim et al. (2004) reported that the mean PSA level was 0.005 ng/dL in their study in which they measured the serum PSA values of healthy dogs with a human kit. Again, in some studies (Alpay and Civelek, 2022), it is stated that the reference value ranges specified by laboratories are 0.000-4.000ng/mL. Alpay and Civelek (2022) reported that PSA values measured with the help of a human kit in 24 dogs with prostate gland disease were lower than 0.006ng/mL in all dogs. In this study, the average PSA value measured with the dog-specific ELISA kit was determined to be 1.434ng/mL. Additionally, the findings from this study showed that PSA levels were higher in small breed dogs compared to medium and large breeds; in dogs aged one-five years compared to other age groups; and in neutered dogs compared to intact dogs. However, these differences were not found to be statistically significant.
CONCLUSION
As a result, it was determined that demographic factors such as breed, age, body weight, and castration status had no significant effect on prostate volume or PSA levels. However, this study contributed to the literature by providing a general consensus on the average prostate volumes and serum PSA levels of healthy dogs, establishing basic reference values. Additionally, determining prostate volume and serum PSA levels based on different demographic groupings is an important aspect that can be used as a reference in clinical practice. However, it has been demonstrated that studies targeting variables such as breed, age, live weight, and castration status need to be designed in a more specific manner.
REFERENCES
- ALPAY, Ö.C.; CIVELEK, T. Comparative evaluation of PSA and USG results in the diagnosis of prostate hyperplasia in geriatric dogs. Kocatepe Vet. J, v.15, p.189-193, 2022.
- AMORIM, R.L.; MOURA, V.M.B.D.; DI SANTIS, G.W. et al Serum and urinary measurements of prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA) in dogs. Arq. Bras. Med. Vet. Zootec, v.56, p.320-324, 2004.
- ATALAN, G.; HOLT, P.E.; BARR, F.J. Ultrasonographic estimation of prostate size in normal dogs and relationship to bodyweight and age. J. Small Anim. Pract, v.40, p.119-122, 1999.
- CAZZULI, G.; DAMIAN, J.P.; PESSINA, P. et al Development of a model for predicting enlarged prostate size in noncastrated dogs through B-mode ultrasound. Vet. Med. Int, v.2025, p.9593213, 2025.
- CUNTO, M.; MARIAN, E.; GUIDO, E.A. et al Clinical approach to prostatic diseases in the dog. Reprod. Dom. Anim, v.54, p.815-822, 2019.
- DAVIDSON A.P. Management of prostatic diseases. In: ELLIOTT, J.; GRAVER, F.G.; WESTROPP, J.L. BSAVA Manual of Canine and Feline Nephrology and Urology 3.ed. Gloucester: BSAVA, 2017. p.291-303.
- DEARAKHSHANDEH, N.; MOGHEISEH, A.; NAZIFI, S. et al Treatment of experimentally induced benign prostatic hyperplasia with tadalafil and castration in dogs. Theriogenology, v.142, p.236-245, 2020.
- EVANS, H.E.; CHRISTENSEN, G.C. The urogenital system. In: EVANS, H.E.; MILLER, M.E. Miller’s Anatomy of the Dog 3.ed. Philadelphia: WB Saunders, 1979. p.514-516.
- GOLCHIN-RAD, K.; ASGHAR, M.; NAZIFI, S. et al Changes in specific serum biomarkers during the induction of prostatic hyperplasia in dogs. BMC Vet. Res, v.15, p.1-11, 2019.
- KAMOLPATANA, K.; JOHNSTON, G.R.; JOHNSTON, S.D. Determination of canine prostatic volume using transabdominal ultrasonography. Vet. Radiol. Ultrasound, v.41, p.73-77, 2000.
- KORODI, G.; IGNA, V.; CERNESCU, H. et al Canine prostate pathology. Lucr. Științ. Med. Vet, v.41, p.187-194, 2008.
- KRAWIEC, D.; HEFLIN, D. Study of prostatic disease in dogs: 177 cases (1981-1986). J. Am. Vet. Med. Assoc, v.200, p.1119-1122, 1992.
- LÉVY, X.; NIŻAŃSKI, W.; VON HEIMENDAHL, A. et al Diagnosis of common prostatic conditions in dogs: an update. Reprod. Domest. Anim, v.49, p.50-57, 2014.
- PASIKOWSKA, J.; HEBEL, M.; NIZANSKI, W. et al Computed tomography of the prostate gland in healthy intact dogs and dogs with benign prostatic hyperplasia. Reprod. Domest. Anim, v.50, p.776-783, 2015.
- POLAT, E. Management of prostate diseases process in dogs. In: INTERNATIONAL ACADEMIC STUDIES CONFERENCE, 5., 2021, Ankara. Proceedings... Ankara: Academic Studies Publishing, 2021. p.427-434.
- ROEHRBORN, C.G.; BOYLE, P.; GOULD, A.L. Serum prostate-specific antigen as a predictor of prostate volume in men with benign prostatic hyperplasia. Urology, v.53, p.581-589, 1999.
- RUEL, Y.; BARTHEZ, P.Y.; MAILLES, A. Ultrasonographic evaluation of the prostate in healthy intact dogs. Vet. Radiol. Ultrasound, v.39, p.212-216, 1998.
