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Feline Urology Update
Western Veterinary Conference 2002
India F. Lane, DVM, MS The University of Tennessee College of Veterinary Medicine
Knoxville, TN, USA
Objectives
To present information presented regarding lower urinary tract disease in the last few years.
To present suggested diagnostic approaches to first time and recurrent lower urinary tract (LUT) signs in cats.
To review proposed treatments for idiopathic lower urinary tract disease (LUTD) in cats.
To update the major principles of managing calcium oxalate urolithiasis in cats.
Key Points
Whats new in the literature?
The relative decrease in struvite urolithiasis and increase in calcium oxalate urolithiasis continues.
Struvite crystals continue to be the most common crystal observed in urethral plugs.
The number of perineal urethrostomies performed at veterinary institutions has decreased markedly since 1980.
The frustrating condition of idiopathic, nonobstructive lower urinary tract disease continues to appear in cats.
The severity and frequency of LUTD may decrease as cats get older.
A higher incidence of LUTD has not been associated with FIV infection.
Cats fed moist food have less frequent recurrences of idiopathic LUTD than cats fed a comparable dry food.
Despite advances in isolation techniques, viruses still do not appear to be a consistent finding in feline LUTD.
Some features of idiopathic LUTD in cats are similar to those found in people with interstitial cystitis.
Use of amitriptyline in acute non-obstructive LUTD may decrease the duration of pollakiuria but may lead to urine retention and bacterial UTI.
A high placebo effect makes it difficult to detect the true effect of pharmacologic treatments on feline LUTD.
What have I learned in the last few years about cats with lower urinary tract disease?
Water intake and lifestyle changes are as important as drug treatments for cats with LUTD.
Keep looking for small uroliths in cats with persistent or recurrent LUT signs.
A small subpopulation of cats with idiopathic LUT will exhibit persistent, chronic signs as opposed to the typical waxing and waning nature of the disorder.
Some cats with idiopathic disease will respond temporally to antimicrobial agents, which may be due to anti-inflammatory properties of the drug.
I have seen an increasing number of dogs with highly resistant UTI after receiving multiple or prolonged antimicrobial treatment, and expect this trend to develop in cats treated indiscriminately with multiple antimicrobial agents.
A thorough diagnostic approach is warranted in cats that have persistent signs or frequent recurrences.
Some cats may be helped by short-term analgesic treatment during acute flare-ups.
Some cats will have prolonged improvement with glycosaminoglycan supplementation.
For obstructed cats, tincture of time and urinary bladder management will ultimately restore voiding function. Prazosin may be useful in reducing urethral outlet resistance post-obstruction.
Mildly azotemic, hypercalcemic cats with calcium oxalate urolithiasis may do better on diets formulated to prevent calcium oxalate formation than on typical renal failure diets.
Key Clinical Diagnostic Points
Survey radiographs and a urinalysis are recommended for evaluation of the initial episode.
With rare episodes, repeat radiographs, urinalysis and urine culture are indicated.
In cats with radioopaque uroliths, a guesstimation of the stone type can be made.
Previous diet
Size and appearance
Location (lower tract only or upper and lower)
Urine pH
Crystals, if observed
Minimum data base findings (hypercalcemia)
Investigation for hypercalcemic disorders is indicated in some cats with calcium oxalate urolithiasis, although most are considered idiopathic.
For frequent recurrences in cats without radioopaque stones a full evaluation is required to rule out any unexpected disorder:
Minimum data base with feline leukemia and FIV testing
Urinalysis and urine culture
Survey radiographs
Abdominal ultrasound examination
Contrast radiography
+/- Cystoscopy
Key Etiologic and Pathophysiologic Points
The most common causes of LUTD in young cats are
Idiopathic sterile inflammation (with or without urethral plugs)
Calcium oxalate or stuvite cystouroliths
The most common causes of LUTD in older cats are:
Idiopathic disease
Bacterial UTI
Neoplasia
Other, less common causes include
Anatomical defects
Behavioral
Neoplasia
Bacterial UTI
Foreign bodies (e.g., catheter remnants)
Potential etiologies of the sterile inflammatory component include
Lifestyle factors including obesity, indoor environment or winter weather, water intake and urine voiding frequency, diet changes other stressors, inactivity.
Enhanced sensory nerve activity and/or bladder wall defect leading to interstitial inflammation
Increased inflammatory reactants (e.g., mast cells)
Unidentified infectious agent?
Factors influencing the development of crystals and uroliths include:
Diet mineral, protein and moisture composition
Urine pH
Urine concentration
Metabolic derangements leading to supersaturation of minerals in urine
Risk factors for the development of calcium oxalate uroliths include
Breed (Himalayan, Persian, Burmese)
Diet (low magnesium, low protein, low calcium, acidifying)
Urine retention or highly concentrated urine
Furosemide administration
Metabolic acidosis
Bacterial and viral infections are RARELY documented as initial causes of LUTD in young to middle-aged cats.
Key Therapeutic Points
Most episodes of idiopathic LUTD are self-limiting within 57 days.
Dietary strategies for idiopathic LUTD
Moist or canned food is preferred
Moderate protein and magnesium reduction
Formulated to produce increased volume of urine
Formulated to produce neutral to acidic urine (pH 6.87.0)
Meal feeding may be preferred to minimize degree of alkaline tide
Minimize changes in diet
Options for frequently recurrent idiopathic cases include
Amitriptyline
Anti-anxiety, anticholinergic, antihistaminic and analgesic effects
Prolonged treatment course (612 months or indefinitely
Adverse effects include sedation, urine retention, poor grooming, weight gain, increased liver enzymes, hematological aberrations
Conflicting reports regarding long term control of recurrences
Pentosan polysulfate sodium (Elmiron, Baker pharmaceuticals)
Oral glycosaminoglycan supplement
Promotes protective glycosaminoglycan layer along bladder mucosa
Results of multi-center study unavailable
Corticosteroids or non-steroidal anti-inflammatory agents?
Perhaps short term in cats with chronic, persistent LUT signs
Ineffective compared to placebo in short-term, acute LUT
Avoid when indwelling catheter is in place
Other anti-anxiety medications or other glycosaminoglycan preparations?
Principles of management of calcium oxalate uroliths
Feed moist food and encourage water intake
Choose a diet formulated for calcium oxalate prevention: avoid excess protein, calcium and oxalate precursors, but provide adequate calcium, magnesium and phosphorus intake, provide adequate but not excess sodium and potassium, provide adequate vitamin B6
Consider added fiber for hypercalcemic cats
Strive for urine pH 6.87.0 and urine specific gravity < 1.025
Consider meal feeding
Consider potassium citrate supplementation
Avoid excess vitamin C or vitamin D
Avoid corticosteroids
Principles of management for struvite uroliths:
Control UTI if documented
Feed moist diet formulated to moderately restrict protein, magnesium and phosphorus content and to moderately alkalinize urine (pH 6.87.0)
Encourage water intake and promote urine specific gravity < 1.030
Monitor stone dissolution and prevention strategies by periodic urinalyses and radiographs
Key Drugs, Dosages and Indications
Key Drug
Drug Class
Dose Range
Frequency
Route
Indications
Amitriptyline
Tricyclic antidepressant
2.512.5 mg/cat
q 24 hrs
PO
Frequently recurrent idiopathic LUTD
Pentosan polysulfate
Glycosamino-glycan
8 mg/kg
q12 hrs
PO
Frequently recurrent idiopathic LUTD
Hydroxyzine
Antihistamine
510 mg/cat
q12 hrs
PO
Frequently recurrent idiopathic LUTD
Prazosin
Alpha antagonist
0.250.5 mg/cat
q 24 hrs
PO
Urethrospasm
Diazepam
Skeletal muscle relaxant
12.5 mg/cat
q 824 hrs
PO
Urethrospasm (short-term)
Butorphanol
Analgesic
11.25 mg/cat
q 6 hrs prn
PO
Acute idiopathic LUTD (painful)
Oxybutynin
Anticholinergic
0.51.25 mg/cat
q 812 hrs
PO
Acute nonobstructive LUTD (severe pollakiuria)
Key Prognostic Points
Idiopathic LUTD in most cats is self-limiting.
Frequency of recurrence can be minimized by increasing water intake and making lifestyle changes.
Lower tract uroliths in cats can be removed and preventive strategies initiated to prevent recurrence.
Summary
Urolithiasis and idiopathic disease are the most common LUT disorders in cats
An appropriate diagnostic workup is indicated in all cats with LUT and should be repeated with most recurrent episodes to detect unusual causes of LUT.
Dietary strategies are useful for the management of most cats with LUTD.
Pharmacological agents may be useful in some severely affected or frequently recurring cases with idiopathic LUTD.
No pharmacological agent has proven significantly more effective than placebo in controlled studies.
References
1. Multiple chapters in Osborne, Kruger and Lulich, eds. Disorders of the Feline Lower Urinary Tract I and II. Vet Clinics North Am; Small Anim Pract 1996; 26 (2 and 3).
2. Kalkstein TS, Kruger JM, Osborne CA. Feline idiopathic lower urinary tract disease. Part I. Potential causes. Comp Cont Ed Pract Vet 1999;21:148-154.
3. Kalkstein TS, Kruger JM, Osborne CA. Feline idiopathic lower urinary tract disease. Part IV. Therapeutic options. Comp Cont Ed Pract Vet 1999;21:497-509.
4. Bartges JW, Barsanti JA. Bacterial urinary tract infections in cats. In Bonagura, ed. Kirks Current Veterinary Therapy XIII; Small Animal Practice. Philadelphia: WB Saunders, 2000; pp 880-882.
5. Buffington CAT, Chew DJ. CVT update: Idiopathic (interstitial) cystitis in cats. In Bonagura J, ed. Kirks Current Veterinary Therapy XIII; Small Animal Practice. Philadelphia: WB Saunders, 2000,pp 894-895.
6. Chew DJ, Buffington CAT, Kendall MS, et al. Amitriptyline treatment for severe recurrent idiopathic cystitis in cats. J Am Vet Med Assoc 1998;213:1282-1285.
7. Osborne CA et al. Feline calcium oxalate uroliths. In: Bonagura, ed. Kirk's Current Veterinary Therapy XII; Small Animal Practice. Philadelphia: WB Saunders, 1995, p.989-992.