What's this growth on my male guinea pig's bum near his testicles?

Thanks for reaching out about Toby and including photos. Dermal cysts, skin abscesses and benign tumors (trichofolliculoma) are very common in guinea pigs. A veterinary visit is recommended, but these are rarely emergencies. But is the abscess, cyst or tumor ruptures, secondary problems can develop. Good luck.

Thanks for reaching out about Meeko and including pictures. This appears to be benign growth called a trichofolliculoma. These are tumors of the skin with very low likelihood of metastasis but likely to recur if not surgically removed. Hair should be gently clipped around the mass in an attempt to decrease bacterial contamination. Clean cotton tipped applicators can be used to gently remove the debris from inside the lesion. Gentle flushing with sterile saline can help irrigate the lesion, then allow to heal on its own. As previously stated, these are likely to recur. Do not apply any topical antibiotics such as Neosporin or triple antibiotics since guinea pig gastrointestinal tracts are very sensitive to antibiotics. Good luck.

Thanks for reaching out about Sprou and including pictures. By the history and pictures, the most likely answer is a dermal (sebaceous) cyst. This condition is very common in middle aged guinea pigs. Keeping it clean as you did, is a good start. Clipping the hair around the edges to prevent further contamination is important. Ideally a veterinarian should be seen to have the cyst surgically removed, else it is likely to come back, over and over. Secondary infections of the open wound are also possible. Good luck.

Thank you for your question, and thank you for the photos - they are very helpful. The area in the photo is a normal structure, and it is a nipple on your guinea pig's belly. There should be one on the other side if you part the hair. These will be present on both sexes of guinea pigs (males and females), and there should be two of them. In the photo that you provided, the nipple and surrounding area do not look inflammed or irritated, and the skin appears very comfortable. I saw that you mentioned that your guinea pig had been itching - mites and lice are very common in guinea pigs, and these could be potential sources of the itchiness that you are seeing. If the itching continues, I would recommend seeking out a veterinarian to evaluate for parasites. If they find them, s/he can prescribe an anti-parasitic medication to treat your guinea pigs. Please do not give your guinea pigs any human medications at home, as many of them can be harmful to our furry friends. I hope that helps, and thank you again for including photos!

It is hard to tell from the photo but the swelling may just be his testicles they can retract them, so sometimes you won't see them. If there are 2 swellings then it will be tested, if not or you are unsure best to have it checked at the vets.

Thank you for reaching out about Piglet - that is a very cute name. I didn't see how old he was? The reason that I ask is that it is common for older guinea pigs, including males, to have problems occur with their nipples. This can include trauma, masses, and crusting. This can be due to hormonal changes, other systemic disease processes, and cancer. I would recommend one of two courses of action - you can continue to monitor the masses for changes (if this occurs, please take Piglet to a veterinarian) or you can take him to a veterinarian for evaluation now, and get additional recommendations based on the exam that s/he performs. I hope that gives you a place to start, and thank you for using Petco Pet Education Center, formerly Petcoach.

Have him examined by your veterinarian or a vet experienced in treating pocket pets. A fine needle aspirate can be done to collect a sample for pathology. This may lead to a diagnosis. In the meantime, make sure he is eating, drinking and eliminating normally.