For veterinary professionals
October 2026
A sow comes in squeaking when she urinates, with blood in the litter, and the plan almost writes itself: urinalysis, a radiograph to look for stones, and an empiric antibiotic. Sometimes the only complaint is that she's stopped eating. These are presentations we see constantly, and a new retrospective study in JAVMA suggests that our empiric choice may be wrong more often than we'd like. Here's a summary, plus the options I'd consider.
Urinary disease is among the most common problems in pet guinea pigs. A separate retrospective study of 600 guinea pigs from a Budapest exotic-animal clinic, published this quarter, ranked urinary tract disease second only to molar malocclusion (Keszeli et al.).
Bacterial cystitis frequently coexists with urolithiasis. Sows are predisposed by a short urethra and the proximity of the vulva to the anus. In boars, ascending bacteria after ejaculation are suspected to play a role.
Martinson and Mans reviewed 112 bacterial isolates from 63 clinically ill pet guinea pigs cultured between 2004 and 2023. Across all sites, Streptococcus, Corynebacterium and Prevotella were the most common genera, and Corynebacterium renale was the most common species.
Urine told a more specific story. Corynebacterium made up about half of urinary isolates. It was usually susceptible to doxycycline and azithromycin, less consistently to enrofloxacin and TMS. Across all urinary isolates, only about half were TMS-susceptible, and not many more were enrofloxacin-susceptible.
TMS and enrofloxacin are the go-to empiric antibiotics for many of us, partly because they're familiar and well tolerated. These data suggest they may miss a meaningful share of guinea pig urinary infections. It's a single-center retrospective dataset, so local patterns may differ, but it gives us a few options to think about.
Culture early, ideally by cystocentesis. That's especially true for recurrent cases, sows with repeated hematuria, and patients that haven't responded to a first antibiotic. In sows, confirm the blood is truly urinary and not vulvar or uterine.
Think about Corynebacterium when you must start empirically. If treatment can't wait for results, these susceptibility patterns are worth weighing, and doxycycline and azithromycin covered Corynebacterium well in this dataset.
Keep fluoroquinolones in reserve. I don't consider empiric fluoroquinolones appropriate in guinea pigs without sepsis, because of the risk of driving multidrug resistance, and the modest enrofloxacin susceptibility here is one more reason. When cases relapse, re-culture rather than switching blindly between drug classes.
Radiograph the entire perineum, because distal urethral stones are easy to cut off the film. Add ultrasound when localization is unclear, whether that's a ureter, a kidney or a boar's seminal vesicles, and remember ovarian cysts in intact sows. Most guinea pig uroliths are calcium-based, and recurrence after cystotomy is common, so families should hear about it up front.
Bloodwork earns its place too. Reduced PCV, low phosphorus and high creatinine have been associated with urolithiasis (Rooney et al.), and a biochemistry panel screens for the chronic interstitial nephritis that's common at necropsy in older guinea pigs.
NSAIDs and fluids are part of managing cystitis, not an afterthought. Meloxicam pharmacokinetics in guinea pigs support 1.5 mg/kg PO every 12 hours, although long-term safety data are lacking, so monitor bloodwork. And any antibiotic in a hindgut fermenter needs the usual attention to appetite, fecal output and supportive feeding.
Martinson A, Mans C. Corynebacterium species and Streptococcus species are the most commonly isolated bacteria from clinically ill pet guinea pigs. J Am Vet Med Assoc. 2026;264(11):1-6. doi:10.2460/javma.25.12.0875
Keszeli AA, Sátorhelyi T, Lang Z, et al. Diseases of pet guinea pigs (Cavia porcellus) presented to a specialist exotic-animal clinic: a retrospective study. Animals (Basel). 2026;16(19). doi:10.3390/ani16193026
Rooney TA, Eshar D, Wong AD, Gardhouse S, Beaufrère H. The association between bloodwork, signalment, and urolithiasis in guinea pigs (Cavia porcellus). J Exot Pet Med. 2021;38:26-31.
Moeremans I, Devreese M, De Baere S, Croubels S, Hermans K. Pharmacokinetics and absolute oral bioavailability of meloxicam in guinea pigs (Cavia porcellus). Vet Anaesth Analg. 2019;46(4):548-555.
If you have a guinea pig with recurrent urinary signs, bladder stones or a culture result you'd like to talk through, reach out to Nashville's guinea pig specialist. Dr. Logan Kopp, DABVP (Exotic Companion Mammal Practice), sees referrals at Priest Lake Veterinary Hospital, (615) 361-4646. Referral details are on the referring veterinarians page.
This content is for educational purposes for veterinary professionals. It doesn't establish a VCPR or replace clinical judgment for an individual patient. Drug use and doses should be checked against current references and adjusted for each case.