I thought I would talk about cystic ovaries since elective neutering has been a contentious issue.
It is not yet routine in the UK to neuter female guinea pigs. However, cystic ovaries occur in around 80% of adult females (over 4 years if age). Cystic ovaries may or may not produce hormones. Those that do will cause clinical signs such as increased sexual or aggressive behaviour, hair-loss, sometimes mild weightloss and blood in the urine. Those that are non-hormone producing, if small, may have no clinical signs. If they become very large (5cm or more in diameter) they may cause gut motility issues and increased respiratory effort, due to pressure on the diaphragm.
Treatments that have been attempted include drainage of the cyst, hormone treatment or surgical removal.
Drainage is via a needle inserted through the skin in a conscious or mildly sedated animal. Risks include leakage of fluid into the abdomen which can result in adhesions forming between organs, affecting gut motility. It would not improve symptoms if the cyst was hormone producing.
Hormone treatment involves the use of a medication called chorulon (human chorionic gonadotrophin) but it's efficacy is probably only 50% and it is expensive.
The treatment of choice is surgical removal of the ovaries. Ideally this is performed via a surgery called a bilateral flank ovariectomy. Where the ovaries only are removed through 2 small incisions. This type of surgery has much lower impact on gut motility post operatively than a midline spey.
So why don't vets routinely remove ovaries pre-emptively as in dogs and cats?
The surgery in guinea pigs is technically more challenging with risks of post-op gut stasis. In addition, general anaesthetic in guinea pigs still carries greater risks than in dogs and cats. Some studies suggest anaesthetic deaths in otherwise healthy guinea pigs averages 1 in 75. So there is a weigh up between the anaesthetic risk and the prevention of possible future symptoms resulting from cystic ovaries. The debate over the right decision to make will likely continue for some time.