z.-perros.-enfermedad felina del tracto urinario bajo 2

8/3/2019 Z.-perros.-enfermedad Felina Del Tracto Urinario Bajo 2

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U - Nephrology & UrologyFELINE LOWER URINARY TRACT DISEASE

David Senior

Professor and Head, Veterinary

Clinical Sciences, Louisiana StateUniversity.Department of Veterinary ClinicalSciencesSchool of Veterinary MedicineLouisiana State UniversityBaton Rouge, LA 70803USA

ETIOLOGYFeline lower urinary tract disease (FLUTD)includes inflammatory diseases of the lowerurinary tract and non-inflammatory conditions

that cause urination in inappropriate places. Bothmale and female cats are affected but mostlyonly male cats develop urethral obstruction.Typical signs in non-obstructed cats include

pollakiuria, stranguria, hematuria and urinationin inappropriate places. FLUTD is one of mostcommon reasons for cats to be presented toveterinary hospitals. In various surveys, the

incidence of the syndrome has usually beenabout 0.6% in the cat population and 3-13 % ofcats presented for veterinary care.

Table 1: Diagnoses in cats with FLUTD

1981-19851 1993-19952

(Number of cases) (47) (43) (47) (62)

Male Female Male Female

No urethral obstruction % % % %

Idiopathic 79 58 64 65

Urolith 17 40 9 19

Anatomical defect - - 11 10

Behavioral problem - - 13 6.5

Urolith and UTI 0 2 0 0

UTI 0.04 0 0.02 0

Neoplasia 0 0 4 0

Data from:1. Osborne CA et al. Feline lower urinary tract disorders. Definition of terms and concepts. Vet ClinNorth Am Small Anim Pract. 1996 Mar; 26(2): 169-79.

2. Buffington CA et al. Clinical evaluation of cats with nonobstructive urinary tract diseases. J Am VetMed Assoc. 1997 Jan 1; 210(1): 46-50.

The etiology of FLUTD was investigated prospectively in two studies a decade apart (Table 1). These

data suggest that non-obstructive FLUTD ismost likely to be idiopathic. Identifiable causesof non-obstructive FLUTD included urolithiasis,anatomical defects and behavioral problems.Urinary tract infection and neoplasia were rare.Urolithiasis is one of the major identifiable causesof FLUTD. The composition of bladder urolithssubmitted for analysis has recently changed from

predominantly struvite to mostly calcium oxalate.The reason for this change appears to be relatedto reformulation of commercial diets to preventstruvite crystalluria. Reduced magnesium and

phosphorus content and urine acidification caused by these diets may predispose to formation ofcalcium oxalate uroliths.Cats with FLUTD tend to urinate in inappropriateplaces. However, this sign could be an indicationof a behavioral abnormality. Marking or sprayingis a normal territorial behavior response in cats,so urination outside the litter box can be confused

with FLUTD.Vesicourachal diverticula visible on contrastcystography have been reported in 25 % of catswith signs of hematuria, dysuria and urethral

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obstruction. Clinical evidence suggests thatdiseases that induce increased intravesicularpressure can cause potential diverticula to openup. Once the underlying condition causingincreased pressure is resolved, the diverticuladisappear. As such, vesicourachal diverticula

appear to be a consequence rather than a causeof FLUTD.In most surveys of cats with FLUTD, the incidenceof urinary tract infection is very low, around 3-4 %. This low incidence may be related to veryeffective host defense mechanisms and the highconcentration of urea in cat urine may be a majorcontributing factor to resistance. The incidenceof urinary tract infection increases with ageabove 10 years. This may be due to loss of urineconcentrating capacity but other factors may beinvolved. Also, cats with a perineal urethrostomy

are prone to urinary tract infection.Bladder cancer is relatively rare in the cat.Almost all affected animals are older than 5 years,about 80% are malignant and about 30% aretransitional cell carcinomas.Many possible etiologies have been proposedfor idiopathic FLUTD including viral infection,Mycoplasma spp. infection, food allergy, the presence of toxic metabolites in urine, and adefect in the protective glycosaminoglycan(GAG) layer which covers the uroepithelium ofthe bladder, mast cell abnormalities, and visceral

pain syndrome.The discovery of viral particles in the mucus ofurethral plugs is intriguing but the significance isnot yet clear. Several attempts have been madeto implicate mycoplasmas in FLUTD but theevidence is strongly against their involvement asa causative agent.Food allergy has been proposed as a causeof FLUTD on the basis that elimination dietsappeared to reduce signs in some clinicalsituations. Unfortunately, no controlled studieshave been performed to support or deny this

possibility.There has been no work performed to confirmor deny the contention that a toxic metabolitein urine causes uroepithelial irritation andinflammation.Idiopathic FLUTD bears some similarity to thesyndrome in humans called interstitial cystitis.Both humans and cats demonstrate chronicongoing sterile inflammation of the lowerurinary tract, submucosal hemorrhages visible oncystoscopy after mild bladder distention, reducedexcretion of glycosaminoglycans, increased

bladder mucosal permeability, and infiltration ofmast cells.Unfortunately the causes of interstitial cystitisin humans are not known and there is suspicion

that the abnormalities observed in both speciesmay be non-specific stereotypic responses ofthe lower urinary tract to a variety of insults.Proposed causes of interstitial cystitis in humanshave been as fanciful as proposed causes ofFLUTD. Suggestions have included viruses,

fastidious bacteria, deficient protective GAGlayer and psychosomatic. Some veterinarianshave associated episodes of idiopathic FLUTDwith stress. Interesting comparative researchcontinues on this line of investigation.

CLINICAL SIGNSCats with nonobstructive FLUTD have periodicepisodes of urgency, dysuria, urination outside thelitter box, pollakiuria and hematuria. Urinationmay be sufficiently painful for cats to vocalizeduring urination. The episodes can last for one to

ten days separated by days to weeks of apparentnormalcy.On physical examination the bladder may bethickened and sensitive to direct palpation.Uroliths can be difficult to detect in the bladderof cats particularly if they are solitary becausecrepitus will not be present.DIAGNOSISThe history should be carefully assessedto determine the possibility of behavioralabnormalities. Careful bladder palpation should

be performed to detect the presence of crepitusand masses, which may indicate stones ortumors. The thickness of the bladder wall canalso be assessed.A problem specific database includes urinalysis,urine culture, radiographs, ultrasound, cystoscopy,biopsy, and urolith and crystal analysis.Urinalysis and culture and sensitivity should be performed on urine obtained by cystocentesis.Urine can be collected by caging the cat withouta litter for 2-3 hours, then sedation with ketaminegiven at 1-3 mg intravenously. Once the cat is

sedated, an assistant can grasp the urethrawhile a cystocentesis is performed. Attempts atcystocentesis in the fully conscious cat usuallyresult in reflex micturition as soon as the bladderis manipulated and collection by cystocentesisbecomes impossible.Radiographs including double contrastcystography should be performed to investigatethe possibility of uroliths, tumors and diverticula.Ultrasound examination can be used instead.Although not available in many practicesettings, cystoscopy can allow visualizationof submucosal hemorrhages, uroliths, tumorsand diverticula. Biopsy can also be performedthrough the cystoscope. Histologic examinationof bladder biopsies can reveal inflammation andmast cell infiltration.

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Mineral analysis of crystals and uroliths shouldbe performed as appropriate.

MANAGEMENTThe management of urolithiasis and urinary tractinfection is discussed in other sections. Little

is known about treatment of bladder tumors incats because they are so rare. Management ofbehavioral abnormalities is beyond the scope ofhis chapter.The development of effective managementstrategies for idiopathic FLUTD has beenconfounded by not knowing the etiology (oretiologies) and a paucity of controlled studies.Unfortunately, the waxing and waning nature ofclinical signs leads investigators to conclude thatcertain treatments are successful when, in fact, aplacebo would have been just as effective.Feeding canned food instead of dry food seemsto reduce recurrence of idiopathic FLUTD.Investigators postulated that this effect could be due increased urine volume associated witha canned food diet that would dilute toxicmetabolites in urine.Anticholinergic agents have been suggestedto reduce bladder spasticity and increase thetime between urination in cats with FLUTD.Propantheline given at 0.2-0.4 mg/kg po sid orbid has been suggested but controlled studies todetermine efficacy are lacking.Antiinflammatory agents such as corticosteroids

have been proposed to reduce inflammationassociated with idiopathic FLUTD. A short-termstudy indicated that predisolone given at 1 mg/kg po bid failed to reduce the magnitude andduration of clinical signs faster than in controlcats. However, long-term studies have not been

performed to see if glucocorticoids have apreventive effect.Intravesicular dimethyl sulfoxide (DMSO) isestablished as a treatment of interstitial cystitisin humans. Although intravesicular instillationof 10-20 mL of 10 % DMSO has been reportedto reduce clinical signs in cats with FLUTD, nocontrolled studies have been performed.In humans with interstitial cystitis, GAGs have been reported to alleviate clinical signs. The proposed mechanism of action is to set up abarrier between potentially irritating urine and the

uroepithelium. There is evidence that the normalGAG layer is deficient in humans with interstitialcystitis and similar evidence exists in cats.Pentosan polysulfate is used in humans. Safetyand efficacy need to be established in cats.The tricyclic antidepressant, amitriptyline, actsas an anticholinergic, anxiolytic and analgesic. Ina study of cats severely affected with idiopathicFLUTD, amitriptyline seemed to reduce clinicalsigns for up to a year when given at 5-10 mg posid at night. The drug is in popular use at presentand further studies are needed.

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Distension of the bladder associated withcystoscopy is thought to give humans affectedwith interstitial cystitis a prolonged symptom-free period. The proposed mechanisms of actioninclude dissipation of inflammatory mediatorsfrom nerve fibers in the submucosa of the bladderand die back of sensory nerves. Whether thisprocedure has a beneficial effect in FLUTD hasnot been established.

PREVENTIONFeeding canned food rather than dry food mayprevent recurrence in some forms of idiopathicFLUTD. Reduction of stress is thought by manyto reduce clinical signs in many affected cats.

REFERENCESAvailable on request.

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