Effects of intratesticular vs intraepididymal calcium chloride sterilant on testicular morphology and fertility in dogs

Background: Both stray and free-roaming owned dogs contribute to the serious global dog overpopulation problem. Many dog owners are unwilling to have their pet castrated for various reasons, including a reluctance to have their dog's behavior changed. A non-surgical method of sterilizing both stray and owned dogs would help to prevent unwanted litters. Previous studies have shown that intratesticular injection of calcium chloride dihydrate (CaCl 2 ) in alcohol is a promising and cost-effective alternative to surgery for stray dogs, with testosterone significantly decreased and sexual activity eliminated. The aim of this study was to compare the use of a solution of 20% CaCl 2 in 95% ethanol injected into the testicles or into the head of the epididymis. Methods: A total of 148 dogs divided into 4 groups (2 experimental and 2 control) were respectively injected with CaCl 2 or saline solution into the testicle or epididymal head (ultrasound-guided). The animals were examined at 0, 3, 6, and 9 months for sperm quality, concentration of testosterone in serum, and side effects; at 0 and 5 months with contrast-enhanced ultrasound (CEUS) to enhance the morphological aspects/alteration of the testicular parenchyma or epididymis; and at 9 months when all were castrated for histological examination. Results: All dogs treated with CaCl 2 became sterile with azoospermia achieved over the 9-month study. The concentration of testosterone in serum significantly decreased following intratesticular treatment with CaCl 2 . No adverse effects were noted. Conclusions: A single, bilateral intratesticular injection of 20% CaCl 2 in 95% ethanol was confirmed to be a reliable method for induction of sterilization in male dogs. The approach showed long-term efficacy and may reduce sexual behavior, with the additional benefits of low-cost and ease of use, making this nonsurgical method appropriate for use in stray dogs. Sterility was also achieved if injected in the head of the epididymis but no significant decrease in serum concentration of testosterone occurred. Moreover, performing the intraepididymal injection into the epididymal head was as time consuming as orchiectomy. This approach may be optimal for use in owned dogs where anatomical integrity and testosterone maintenance is preferred by the owner.