Managing Urinary Incontinence in Dogs Treated for Addison's Disease

I am the owner of Abbie, a 55 pound (25 kg) female spayed dog with Addison’s disease. She was diagnosed in January of this year; Abbie has been treated with daily prednisone (1.5 mg/day), as well as an intramuscular injection of Desoxycorticosterone pivalate (DOCP; Percorten-V, Novartis) given every 3 weeks (1.8 mg/kg).

All of Abbie's clinical signs have resolved but our problem is that she now has an ongoing issue with urinary incontinence. I just do not know whether this is due to too much or not enough prednisone or DOCP. We have tried increasing the prednisone dose for a day but it doesn't appear to help. Her routine serum chemistry panel done this week was normal with a sodium:potassium ratio of 35 (serum sodium, 149 mEq/L; serum potassium, 4.2 mEq/L).

This has been a rough ride for Abbie and us. There is not a lot of literature I can find. I would appreciate ANY helpful suggestions you may have.

My Response:

You don't mention if Abbie is drinking and urinating more or if she is only showing urinary incontinence.  Many dogs treated for Addison's disease will develop polyuria and polydipsia (increased thirst and urination) secondary to the drug they receive (1-3). Some of those dogs will develop an overflow incontinence (i.e., the bladder overfills and the dogs will leak urine, especially overnight when they haven't been walked for a few hours).

Why do dogs treated for Addison's disease develop a increased thirst and urination?
In dogs, treatment with any form of glucocorticoid (e.g., prednisone, prednisolone, methyprednisonlone, cortisone, dexamethasone) can lead to a form of nephrogenic diabetes insipidus (3). In simple terms, this means that the kidneys loose the ability to concentrate the urine, and this can result in large volumes of urine being produced.

To avoid this complication, it's very important not to give too much of any of these glucocorticoids — for prednisone or prednisolone, the maintenance dosage to replace the missing glucocorticoid hormones is about 0.1 mg/kg/day (or about 2.5 mg/day in Abbie) (1).  So, for Abbie, her dosage of 1.5 mg per day is not at all high, in fact, you might think that raising it could help — unfortunately, it could make her feel better if she is deficient, but giving more glucocorticoid will never help polyuria or urinary incontinence.

Treatment or control of polyuria, polydipsia or incontinence in dogs treated for Addison's disease
Unfortunately, some dogs (like Abbie) are simply overly sensitive to the "correct" dosages of glucocorticoid which are being given. Management of these dogs can be complicated, but may include one or more of the following steps (3):

1. Stopping all salt supplementation (if the dog is receiving any NaCl supplementation).

2.  Reducing the glucocorticoid dosage or stopping administration completely, if possible. Many dogs will do fine getting prednisone every 2 or 3 days. In some dogs, glucocorticoids can be discontinued without any ill effects and mineralocorticoid replacement alone will adequately control signs of hypoadrenocorticism.

3.  If glucocorticoid is required to prevent signs of hypoadrenocorticism, the glucocorticoid can be switched from prednisone or prednisolone to either cortisone acetate or methyprednisonolone (Medrol).

Cortisone acetate is a synthetic steroid that has equipotent glucocorticoid and mineralocorticoid activity (1,4). Therefore, it will provide more mineralocorticoid activity than other synthetic glucocorticoids, such as prednisone or prednisolone. In addition, its shorter half-life and lower overall activity means it is less likely to create polyuria or polydipsia. Generally, a daily dose of approximately 1.0 mg/kg provides adequate glucocorticoid coverage (1).

Methyprednisonolone (Medrol), the 6-methyl derivative of prednisolone, is also associated with less polyuria than that seen with prednisone or prednisolone (3). The daily maintenance dosage for this glucocorticoid is similar to prednisolone (0.2 mg/kg).

4. If all of the above fails, one can reduce the monthly dosage of DOCP and evaluate the effect.

5. Finally, if on Florinef instead of DOCP, then a switch to Percorten-V may solve the problem (obviously, this is not the case for Abbie).

Urinary incontinence without any increase in thirst
If Abbie's thirst is completely normal, however, it certainly is possible that she has estrogen-responsive incontinence (not uncommon in spayed female dogs) or a urinary tract infection (5,6). If you haven't already done so, I'd recommend that your veterinarian do a complete urinalysis and urine culture. If an infection is found, administration of an appropriate antibiotic may cure the incontinence.

References and Suggested Reading:

1. Church DB. Canine hypoadrenocorticism In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;156-166.
2. Kintzer PP, Peterson ME. Treatment and long-term follow-up of 205 dogs with hypoadrenocorticism. J Vet Intern Med 1997;11:43-49.
3. Nichols R, Peterson ME. Investigation of polyuria and polydipsia In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;215-220.
4. Plumbs DC. Plumb's Veterinary Drug Handbook. Seventh edition. Wiley-Blackwell; 2011.
5. Forsee KM, Davis GJ, Mouat EE, et al. Evaluation of the prevalence of urinary incontinence in spayed female dogs: 566 cases (2003-2008). J Am Vet Med Assoc. 2013;242(7):959-962.  
6. Stöcklin-Gautschi NM, Hässig M, Reichler IM, et al. The relationship of urinary incontinence to early spaying in bitches. J Reprod Fertil (Suppl) 2001;57:233-236.