**1. Introduction**

The prostate gland is the only accessory sexual gland in the male dog. Some authors in addition name the ampullae ductus deferentes. The canine prostate secretion is a transport medium among others for passive transportation of the spermatozoa into the uterus during ejaculation. The prostate secretions furthermore influence the motility and function of the semen cells; the exact composition and many functions are not yet known and vary dependent on the laboratory and the analysis method used [1]. The composition of mineral nutrients, as well as the amount of cholesterol, albumin [2], zinc-binding proteins [3], fertility-associated proteins like osteopontin [4], the antioxidative capacity [5], and many more have been examined. A new study investigated the composition of the seminal plasma by use of massspectrometry [6].

Diseases of the prostate gland frequently occur in aging dogs [7, 8]; the incidence increases with age: 6.2% in intact males with ≤ 4 years, 17.5% in 4–7 years old dogs,

32.8% in 7–10-years old dogs, and 43.5% in male dogs >10 years of age [9, 10]. Diseases of the prostate gland can be infectious or noninfectious. In aging dogs, the noninfectious benign prostate gland hyperplasia (BPH) is the most frequent disease, occurring in 80% of all intact male dogs older than 5 years and in >95% of male dogs older than 9 years [11, 12]. The BPH can be easily treated; however, the disease will become chronical with regular rezidives and only castration will finally cure the dog. Inflammatory diseases may be chronical or acute; the acute prostatitis is mostly caused by bacterial infections, either ascending via the urethra or via the bloodstream. The chronical prostatitis develops from a BPH or an acute prostatitis if treated with wrong antibiotics or for a too short period of time [7]. Highly effective antibiotics applicated for a sufficient period are essential for the successful treatment of the prostatitis.

The squamous metaplasia develops due to hyperestrogenism occurring because of endocrine testicular tumors; however, may also be caused by estrogen applications [8].

Prostate tumors are relatively rare in dogs, the incidence is on average 0.43% [13], they mainly occur in older dogs and more frequently in castrated than in intact dogs; the growth is not androgen-dependent [14–16]. In this chapter, modern diagnostics and therapeutical methods are discussed.

The aim of each treatment must be, to hinder the development of chronical diseases, for prevention of the long-term use of antibiotics that are needed for special infections [17]. Regular examinations, best starting when the dog reached 40% of life expectancy, will help to reach this goal [18].

This article provides an overview of diagnostical and therapeutical measures in different prostate gland diseases and insights into at present most actual developments.
