Have you treated a female cat for recurrent bacterial cystitis? Was it an overweight to obese cat? If both are true, you may have noted severe dermatitis was present in the perivulvar and perianal areas (Figure 1). This group of findings is typical when an obese female cat has perivulvar skin fold disease.
As weight gain occurs, a vertically oriented skin fold develops on each side of the vulvar opening (Figure 2). It will cover the vulvar opening, so it is no longer visible (Figure 3). When the cat urinates, urine is trapped in these skin folds. Chronic, moist skin folds invite bacteria to multiply. The most common is Staphylococcus; other normal skin residents may also be present. The dermatitis becomes more severe as fecal bacteria, especially E. coli, are added to the mix. Long-haired cats are at increased risk.
Frequently, these bacteria ascend the urethra and cause bacterial cystitis. The cat shows dysuria, hematuria, and periuria. These are the signs first noted by the owner and usually the reason the owner seeks your care. You do a cystocentesis to collect urine, often not noting or appreciating the skin folds and the dermatitis. You treat with antibiotics for the cystitis and often correct the dermatitis at the same time. However, the cat is predisposed for the next event, which may be only a few weeks away.
The cystitis and dermatitis must be corrected, but the skin folds need to be removed surgically.
Two vertically oriented elliptical-shaped incisions are made on each side of the vulva (Figure 4). They need to be wide enough to remove all of the skin folds. Medially, they need to be 1 to 2 mm from the lateral aspects of the vulva; enough skin should be left for suturing.
The first two sutures are placed next to the vulva, which will probably be in the dorsal one-third of the incisions (Figure 5). The incisions are closed with simple interrupted sutures 1 to 2 mm apart (Figure 6). My preferred suture material is 4-0 PDS.
When suturing is completed, the vulvar opening will be held open by the first two sutures. This confirms you have removed the skin folds and made the incisions wide enough. Over the next two to three weeks the skin will stretch, so the vulva is in a normal (closed) position.
The second key to long-term success is to prevent reformation of the skin folds. If the cat gains weight, they will reform, and the sequence will start again. The dermatitis and cystitis will return, so a second surgery may be needed (Figure 7).
Gary D. Norsworthy, DVM, DABVP (feline) is the owner of Alamo Feline Health Center in San Antonio, Texas. He has been in private practice for 50 years, including 25 in feline-only practice. Dr. Norsworthy lectures frequently on feline diseases and is the editor and major author of seven feline textbooks. He is a board-certified feline specialist (one of only two in South Texas) and an adjunct professor at the College of Veterinary Medicine, Mississippi State University and the Western University of Health Sciences. He received the 2020 Distinguished Career Achievement Award from the Texas Veterinary Medical Association.