Testing for Retained Testicular Tissue in Neutered Cats with Urine Marking

My patient is a 5-year-old neutered, male DLH that presented for inappropriate urination. He was not neutered until almost a year of age. He primarily urinates on vertical surfaces, the bed, and laundry piles; however, he does generally urinate in his litter box as well. There is one litter box in the house for 2 cats.

On my physical examination, nothing significant was detected. I was able to extrude his penis, and I did not find any penile barbs. I did a baseline testosterone level, which came back as less than 5 nmol/L, normal for a neutered male cat according to the laboratory.

My gut says this cat shows all the signs of behavioral spraying, although the only medical workup for the inappropriate urination has been a routine urinalysis (which was normal). That minimal workup was 11 months ago, and he has continued his occasional spraying ever since, with no progression of signs such as hematuria or or apparent pollakiurua. I did recommend that we do another complete urinalysis with culture, as well as abdominal radiographs to rule out stones etc. That said, I did explain to the owner (the wife) that a behavior problem sounded most likely in this cat. The owner was willing to start him on clomipramine, so I started him on 5.0 mg, PO once daily, warning her it may take 4 weeks to exhibit efficacy, if it is going to work at all.

I'm just wondering what your take would be on usefulness of single testosterone determination? I've read that it is pretty useless, given the natural fluctuations in hormone secretion and that even an intact male cat could normally have a low value. Do you agree?

Do I need a gonadotrophin-releasing hormone (GnRH) stimulation test to ensure that this cat doesn't have retained testicular tissue, which could be contributing to the problem?

My Response:

Basal testosterone determinations generally are not very useful in evaluating dogs and cats with retained testicular tissue. You certainly could do a GnRH stimulation test, which is much more useful than baseline measurements, at least in male dogs (1).  To perform a GnRH stimulation test in a cat, one protocol is to collect a serum sample for testosterone measurement before and 60 minutes after the intramuscular administration of 25 µg of GnRH (Cystorelin; Merial). A 2-fold rise in basal testosterone after GnRH stimulation indicates that functional testosterone tissue (e.g., retained testicle) is present.

Penile barbs in cat

However, we don't generally need to perform basal testosterone measurements or do provocative GnRH stimulation tests on male cats. A intact male cat's penis has a band of about 120–150 backwards-pointing spines, which are about one millimeter long (2).

As you have already reported in this cat, castrated cats will loose their penile barbs. In other words, if there are barbs on the penis, the cat has testosterone in their circulation—if there are no barbs, there is no testosterone. Cats are great that way!

Inappropriate urination is a common problem in male cats, with a prevalence of approximately 10% in neutered males. I'd definitely recommend a workup to exclude lower urinary tract disease (3) but I would also continue to try to convince the owners to add at least one more litter box. In addition, litter box hygiene has been proven to be an important part in treating feline urine marking (4-6). You should also discuss things like identifying triggers and preventing exposure to them (e.g., block access to windows where they may see other cats) and provide more environmental stimulation (7,8).

Flouxetine and clomipramine are of roughly equal efficacy (6,9). With both drugs, it's not uncommon to see noticeable clinical improvement within the first couple of weeks if the drug is going to work. I personally prefer fluoxetine, since it is associated with less side effects.

Bottom Line

Because the finding of spines on a cat's penis indicate the presence of testosterone in the cat's body, these penile spines act as a bioassay for testosterone.

There are other tests we can do (i.e., GnRH or hCG stimulation tests) but in cats, I don't do these —I check the penis. This bioassay is the cheapest and best kind of assay for circulating testosterone in cats.

References:

1. de Gier J, Buijtels JJ, Albers-Wolthers CH, et al. Effects of gonadotropin-releasing hormone administration on the pituitary-gonadal axis in male and female dogs before and after gonadectomy. Theriogenology 2012;77:967-978. 
2. Aronson LR, Cooper ML. Penile spines of the domestic cat: their endocrine-behavior relations. Anat Rec 1967;157:71–78.
3. Tynes VV, Hart BL, Pryor PA, et al. Evaluation of the role of lower urinary tract disease in cats with urine-marking behavior. J Am Vet Med Assoc 2003;223:457-461. 
4. Pryor PA, Hart BL, Bain MJ, et al. Causes of urine marking in cats and effects of environmental management on frequency of marking. J Am Vet Med Assoc 2001;219:1709-1713. 
5. Neilson JC. House soiling by cats In: Horwitz DF, Mills DS, eds. BSAVA Manual of Canine and Feline Behavioural Medicine Second ed. Gloucester: British Small Animal Veterinary Association;, 2009;117–126.
6. Mills DS, Redgate SE, Landsberg GM. A meta-analysis of studies of treatments for feline urine spraying. PLoS One 2011;6:e18448. 
7. Herron ME, Buffington CA. Environmental enrichment for indoor cats: implementing enrichment. Compend Contin Educ Vet 2012;34:E3. 
8. Ellis SL, Rodan I, Carney HC, et al. AAFP and ISFM feline environmental needs guidelines. J Feline Med Surg 2013;15:219-230. 
9. Hart BL, Cliff KD, Tynes VV, et al. Control of urine marking by use of long-term treatment with fluoxetine or clomipramine in cats. J Am Vet Med Assoc 2005;226:378-382.