Aging of the prostate in dogs : part I: appearance of abnormal ultrasonographic findings

Introduction and aim. Age related changes of the canine prostate have been well documented (1,2,3). The prostate gland may develop benign prostatic hyperplasia (BPH) in dogs over 5 years (4), and in aged dogs pathological findings such as prostatic cysts, paraprostatic cysts or other focal lesions, as mineralization or alterations of the normal echotexture and/or echogenicity (5,6), might be revealed by ultrasonographic exam. The purpose of the present study was to estimate the most suitable age for a preventive ultrasonographic examination of the prostate in dogs. Materials and methods. Intact male dogs (n=612) of different breed, age (1-18 years) and bodyweight (2-55 kg), irrespective of the reason of clinical examination, underwent ultrasonographic evaluation of the prostate. Prostatic abnormal findings were recorded, and the size was estimated as small, normal or big, according to the literature (3). The age of each dog was considered as the percentage of the maximum age (age ratio) expected for the breed (7,8). The cutoff age ratio with the best balance between sensitivity and specificity (maximum proportion of true positives and negatives) in order to detect a finding at prostatic level was determined by a receiving-operating characteristic curve (ROC). The area under the curve was calculated, and a z-test was performed to determine the significance of the area (H0- area>0.5). The positive predictive value (PPV) was calculated for the cutoff age ratio and other age ratios > cutoff. Results. The prostate of 46.3% (279/612) of dogs showed at least one abnormal finding detailed in Table 1. The ROC curve (Figure 1) allowed the definition of a significant (p<0.001) cutoff age ratio at 40.9% with a PPV of 0.662. The third-grade interpolation of different PPV at several age ratio was calculated as follows: 0.7 at 55%, 0.8 at 75%, and 0.9 at 89% of maximum age of the breed. Conclusions. Results suggest that for a preventive control of the prostate conditions, an ultrasonographic examination when the dog reaches approximately 40% of the maximum age of its breed, is advisable. References. 1) Atalan et al., Res Vet Sci 1999;67:7-15. 2) O’Shea, J Comp Pathol 1962;72:321-31. 3) Ruel et al., Vet Radiol Ultrasound 1998;39:212-6. 4) Johnston et al., Anim Reprod Sci 2000;60-61:405-15. 5) Smith, Theriogenology 2008;70:375-83. 6) Levy et al., Reprod Dom Anim 2014;49(Suppl.2):50-7. 7) Adams et al., JSAP 2010;51:512-24. 8) O'Neill et al., Vet J 2013;198:638-43.