REPRODUCTION
terone assays can be used to determine whether she is currently in dioestrus and the owner missed the previous signs of oestrus or whether a luteal cyst is present whereby progesterone concentrations will persist beyond the 70-90 day lifespan of a normal CL . 16 An ultrasonographic examination of the reproductive tract should also be performed with special attention paid to the ovaries to check for cystic structures . In a pregnant bitch , progesterone levels drop to below 5 nmol / L about 24-48h prior to partus and can be used to determine readiness for whelping . A decrease in plasma progesterone to less than 3 nmol / L in pregnant bitches may indicate impending abortion . 17 Recent work by De Cramer et al will assist us in more accurately determining the optimum day for elective caesarian sections in dogs .
Relaxin
In dogs and cats , the hormone relaxin is secreted by the placenta and a qualitative relaxin assay ( WITNESS ® available on request from Zoetis South Africa ) can be used to diagnose pregnancy from about , 16-22 days after the first day of cytological dioestrous in dogs ( D1 ) or 22-28 days after ovulation and about 31 days after mating in cats . In dogs , prior to establishment of the placenta , a false-negative result may be obtained
Testosterone
Testosterone can be used in the diagnosis of bilateral cryptorchidism in the dog or in unilateral cryptorchidism where only the descended testis has been removed . In “ castrated ” male dogs with unknown backgrounds , that are exhibiting intact male characteristics such as urine marking , aggression and interest in females , various diagnostic options are available . The undescended testis may be present anywhere from the caudal pole of the kidney to the inguinal canal and a dedicated ultrasonographic abdominal examination may be instrumental in identifying the cryptorchid testis . Cryptorchid testes remain hormonally active but lose spermatogenic capability and are therefore more likely to undergo neoplastic change with sertoli cell tumours having the higher incidence in cryptorchid testes .
Due to the episodic release of LH and therefore testosterone , as well as the low systemic concentration of testosterone , a hCG or GnRH -stimulation test with subsequent measurement of testosterone will give a better indication of whether or not testicular tissue is present . The baseline value will be more than double if testicular tissue is present . 18 Owing to the overlap of resting ranges between cryptorchid and neutered males , LH is not accurate for the identification of castrated males
In the future , Anti-Mullerian Hormone ( AMH ) assays may be more accurate for the diagnosis of crytorchidism in dogs and are already being used in the diagnosis of cryptorchid stallions . AMH is secreted by the sertoli cells and the granulosa cells in the ovary and a measurable concentration of AMH indicates the presence of testicular or ovarian tissue . 19 An AMH test would therefore also be useful to determine the reproductive status of dogs or bitches . The test is currently available at the Veterinary Population Management Laboratory at Onderstepoort , however , it is very costly at this stage .
In cats , the presence of spines on the penis indicates the presence of testosterone-secreting tissue . These spines atrophy about 6 weeks post castration and provide a very convenient means of determining the presence of cryptorchid testis / es in the tomcat prior to the use of hormone assays or ultrasonography .
Ovarian remnant syndrome
Ovarian Remnant Syndrome ( ORS ), is defined as functional ovarian tissue present in a previously ovariectomized patient . ORS is an iatrogenic condition that results from failure to remove all ovarian tissue during ovariohysterectomy . This is most often due to surgical error such as incomplete ovary removal or auto-transplantation of dropped ovarian tissue . It has been shown that ovarian tissue placed free in the abdomen can become re-vascularized and functional , In the majority of reports of ORS , residual ovarian tissue is found located in the region of the ovarian pedicle so incomplete ovary removal is suspected in most cases . 20 , 21 Another reported explanation for ORS is the presence of extra-ovarian tissue such as ectopic ovarian tissue or an accessory ovary that is not identified at the time of surgery . Accessory ovaries have been reported in cows , women and cats and in most reports , located in the proper ligament . 22 Accessory ovaries have not been reported in dogs .
Clinical signs of ORS are consistent with pro-oestrus or oestrus and include vulvar discharge ( serosanguinous or purulent ), vulvar swelling , mammary gland enlargement , behavioural signs such as attracting males and postural behaviour in cats . 23 Polyuria and polydipsia , weight loss , alopecia and poor coat have also reported with most animals having more than one clinical sign . 24 The time to clinical signs after OHE can vary greatly . One study had a range of one month to ten years with a median time to diagnosis of 17 months . Animals with neoplastic ovarian tissue , such as granulosa cell tumours , take longer to present with clinical signs with a reported median interval of 96 months . 24 Dogs with ORS have been shown to develop ovarian neoplasms ( 23.8 %) more frequently than intact dogs ( 6.25 %). 24-26
Diagnosis of ORS can be difficult because the ovarian tissue may be very small . There are several tests to diagnose ovarian remnants in a patient with clinical signs . By far the easiest and least costly is to perform vaginal cytology during signs of oestrus and look for vet360
Issue 04 | AUGUST 2017 | 10