Randi, I guess my concern would be the impact on his ability to control the urine. My guess is that they are removing any wall or barrier that my build up blockage. I got this from the net. Hope it helps you understand.
Lower Urinary Tract Disorders of the Cat
Katherine James -- April, 1998
Lecture 7
Terminology
The signs of lower urinary tract disease in the cat are hematuria, stranguria and pollakiuria. Several different conditions of the feline lower tract can result in theses signs. In many cases, no clearly defined cause is found. For many years, these cats were classified as having “feline urologic syndrome” (FUS). This term has now fallen out of favor because clinicians tended to equate feline lower urinary tract signs with FUS, in part because of how common the syndrome is in young cats. However, many disease conditions cause lower urinary tract signs and a diagnostic evaluation is warranted. Thus, the poorly understood syndrome known as FUS has been renamed as idiopathic feline lower urinary tract disease (IFLUTD). There is an inflammatory bladder disease in humans termed interstitial cystitis (IC). Its cause is similarly unknown. There are similarities between IFLUTD and IC. Thus, some people may refer to IFLUTD as IC. This is probably premature until more evidence is available to substantiate that these conditions are in fact the same. It is appropriate to refer to IFLUTD as “idiopathic sterile cystitis.”
Clinical signs of lower urinary tract disease include hematuria, dysuria, pollakiuria, stranguria, and/or partial or complete urinary tract obstruction. Some cats with lower urinary tract disease may urinate outside the litterbox, although this sign is not specific for lower urinary tract disease and is also seen with behavioral disorders. Veterinary urologists also frequently divide IFLUTD into obstructive and non-obstructive disease. This is useful as the management strategies and outcomes are often significantly different in the short term.
Causes of Feline Lower Urinary Tract Disease
Bacterial Infections
Bacterial urinary tract infections in cats are uncommon. They account for approximately 1-3% of cases of feline lower urinary tract disease (FLUTD). Feline bacterial urinary tract infections (UTIs) usually result from compromised local defenses and, therefore, are more likely to be secondary to other disorders, rather than a primary problem. The high osmolarity and high concentrations of urea and organic acids in feline urine inhibit bacterial growth. Bacterial UTIs are relatively common in cats after placement of urinary catheters, or in cats with perineal urethrostomies. This suggests that the urethra itself is an important defense against bacterial UTI in the cat.
Diagnosis of bacterial UTI in a cat should prompt a search for an underlying cause. Contrast radiography should be used to evaluate the patient for underlying anatomical defects, urolithiasis or neoplasia. Cats with dilute urine are at higher risk for UTI. Metabolic diseases such as diabetes mellitus or chronic renal failure may also predispose the feline patient to bacterial UTI.
Diagnosis of bacterial UTI requires a urine culture. Therapy will be dictated by the results of culture and sensitivity testing. E. coli and gram-positive cocci are the most common isolates. Proteus, Klebsiella, Pasteurella, Enterobacter, and Pseudomonas are occasionally seen. Antibiotics are routinely prescribed for cats with FLUTD. In many cases this constitutes inappropriate therapy because the vast majority of FLUTD patients do NOT have bacterial UTI.
Miscellaneous Infectious Agents
Mycoplasma and Ureaplasma species have been suggested to play a role in FLUTD. However, there is currently no evidence that they act as primary pathogens.
Fungal urinary tract infections have been reported in cats, although they are rare. Fungal infections are also likely to result from impaired urinary tract defenses. The diagnosis is based on examination of urine sediment, but urine culture should be performed. Causes include Candida albicans and Aspergillus fumigatus. Fluconazole is the preferred therapy for candida infections.
Capillaria felis cati is a nematode parasite that has been associated with FLUTD.
Urethral Plugs, Urolithiasis, and Crystalluria
Although the urinary system is designed to dispose of wastes in liquid form, some components of urine may precipitate to form crystals. These crystals may be simply carried out of the urinary tract with the flow of urine; however, if they are retained, they may grow in size, or combine with organic matrix, to become large enough to be clinically significant.
Urethral Plugs
Plugs are objects of any composition that obstruct passageways or ducts. Feline urethral plugs are usually composed of large quantities of matrix (protein) mixed with minerals. Some urethral plugs are predominantly composed of matrix, some may contain tissue fragments, blood cells and cellular debris, and a few may be composed primarily of crystalline minerals. The description of urethral plugs should reflect their mineral and matrix composition, if known.
Minerals identified in feline urethral plugs include ammonium urate, calcium oxalate, calcium phosphate, and magnesium ammonium phosphate (struvite). Struvite plugs are the most common. Risk factors for the formation of these crystals in urethral plugs are probably similar to those associated with mineral formation in urolithiasis.
The components of feline urethral plug matrix have not been fully elucidated. One candidate is Tamm-Horsfall glycoprotein (THP), which is present in higher concentration in the urine of male cats with urethral plugs, compared to normal cats. THP has also been identified in human and ovine uroliths. THP is a 100 kD glycoprotein produced by the cells lining the thick ascending limb of the loop of Henle. It is the most abundant protein in normal human urine, however its function is unknown. It has been hypothesized to play a role in urine concentration, immunoregulation, and resistance to bacterial colonization of the urinary tract. Other non-crystalline components of feline urethral plugs include red and white blood cells, epithelial cells, spermatozoa, virus-like particles, and bacteria.
Osborne and coworkers have hypothesized that the formation of matrix-crystalline urethral plugs is the result of two concomitant, but etiologically distinct, disorders. These disorders are lower urinary tract inflammation (idiopathic or infectious) and crystalluria. Urinary tract inflammation alone may lead to accumulation of mucoprotein and inflammatory reactants which are readily voided through the urethra. Affected cats show signs of dysuria or hematuria, but urethral obstruction is unlikely. In the presence of conditions promoting crystal formation and growth, without inflammation, classical urolithiasis may result. The concomitant occurrence of urinary tract inflammation and crystalluria may lead to the formation of matrix-crystalline plugs (“fruit jello” hypothesis), which may lead to obstruction.
Urolithiasis
Urolithiasis accounts for approximately 20- 25% of cases presented for FLUTD. Uroliths are macroscopic polycrystalline concretions composed primarily of minerals (organic and inorganic crystalloids) and small amounts of matrix. They may be named according to location; e.g. nephrolith, urocystolith. (lithos = stone; sabulous = sand; calculus = pebble).
Over the last decade, there has been a significant change in the prevalence of struvite and calcium oxalate uroliths in cats (and dogs). This is at least partly due to the use of calculolytic diets to dissolve struvite uroliths, along with the use of modified maintenance and prevention diets. The latter have reduced the prevalence of struvite urolithiasis, while calcium oxalate uroliths have become considerably more common. Both magnesium restriction, and urine acidification, which are used to control struvite urolithiasis, may predispose cats to the development of calcium oxalate urolithiasis.
Struvite Urolithiasis
Struvite is magnesium ammonium phosphate hexahydrate. The majority (90%) of feline struvite uroliths are sterile, however a small percentage result from urinary tract infection with urease-producing bacteria (especially staphylococci). Struvite can also be a significant component of feline urethral matrix-mineral plugs.
Risk factors for struvite include dietary factors and possibly obesity. Initially, the ash content of diets was thought to influence the formation of struvite, however subsequent studies focused on the role of dietary magnesium. Cats fed diets with a high (0.45%) content of MgO developed struvite urolithiasis. However, MgO is an alkalinizing salt, and it was later demonstrated that a high magnesium (0.5%) diet in which the magnesium was present as MgCl2, did not result in the formation of struvite. MgCl2 is an acidifying salt and can therefore actually prevent struvite urolithiasis.
Sterile struvite uroliths can be medically dissolved by feeding a diet which promotes a urine pH of 6.3 or less, which is restricted in magnesium, and which is supplemented with NaCl. The latter stimulates thirst and promotes dieresis. There are some risks associated with the use of diets designed for dissolution of struvite. Chronic use of acidifying diets leads to metabolic acidosis, which can lead to decreased bone formation and detrimental effects on calcium, phosphorus, potassium, and magnesium balance. Potassium depletion, hypokalemia, and chronic renal failure can result from feeding acidifying diets which have a marginal potassium content. The use of acidifying diets is also contraindicated in cats with chronic renal failure as these animals are often already acidotic. The use of diets high in NaCl should also be avoided in animals with congestive cardiac failure. Finally, as indicated above, the use of diets designed to dissolve struvite may lead to a higher risk of calcium oxalate urolithiasis.
Infection-induced struvite uroliths should be managed with anti-microbials in addition to dietary therapy. Antibiotics should continue for as long as struvite uroliths are present, as microbes can persist in the inner layers of the uroliths, and are released as they dissolve.
Calcium Oxalate Urolithiasis
Risk factors include the use of acidifying diets. Magnesium restriction and NaCl supplementation may also play a role. Persians, Himalayan, and Burmese cats are over-represented. Hypercalcemia should always be ruled out in these patients.
Management is by surgical removal of large stones, if clinically indicated, or voiding urohydropropulsion of smaller stones. However, calcium oxalate uroliths are often clinically silent. If they are not causing lower urinary tract signs they may be left in place in the bladder; a risk of later obstruction, especially in male cats, persists. Strategies for prevention include feeding non-acidifying diets that are protein-restricted (lower in calcium and oxalic acid) and high in moisture.
Ammonium Urate Urolithiasis
These are usually idiopathic, however portovascular anomalies and a renal tubular defect have been implicated in some cases. Risk factors include a diet high in purine precursors (especially liver), highly acidic and highly concentrated urine. Preventive diets should therefore avoid these risk factors. Medical dissolution of urate uroliths has not been fully developed for the cat. Naturally occurring xanthine urolithiasis had also been reported in at least one cat.
Calcium Phosphate Urolithiasis
These account for approximately 1% of feline uroliths. Potential risk factors include hypercalciuria and hyperphosphaturia. There are no medical protocols for dissolution of these uroliths. Diets avoiding excessive protein, sodium, calcium, and vitamin D may be useful in reducing the risk of calcium phosphate urolithiasis. Increased water consumption may also be beneficial.
Cystine Urolithiasis
This results from aminoaciduria due to a tubular defect
Crystalluria
Crystals form in urine that is supersaturated with respect to crystallogenic substances. Therefore crystalluria is a risk factor for urolithiasis and the formation of matrix-mineral urethral plugs. Detection of crystalluria does not necessarily predict the formation of stones or the development of urethral plugs. Evaluation of crystals can be useful in detection of disorders predisposing to urolithiasis or plug formation (for example, cystine or ammonium urate crystals). It can also be used to estimate the composition of uroliths or plugs, and can be used to monitor the effectiveness of medical dissolution or prevention of urolithiasis. Frequent detection of large aggregates of crystals may also be significant It is important to remember that crystals can form, or dissolve, in urine after voiding.
There is no currently available evidence to suggest that crystalluria alone is a cause of FLUTD.
Miscellaneous Structural Causes
Other causes of FLUTD include congenital and hereditary defects, acquired anatomical defects, neoplasia, trauma, and iatrogenic disorders.
Idiopathic Feline Lower Urinary Tract Disease (Idiopathic Cystitis)
A recent prospective case series of 109 cats with nonobstructive urinary tract disease identified 70 cats (64%) which had stranguria, hematuria, pollakiuria or inappropriate urination with no evidence of anatomical defects, neoplasia, UTI, or urolithiasis. These cats had bladder lesions compatible with inflammation identified during radiographic or cystoscopic examination. Therefore, their clinical signs were attributed to idiopathic cystitis. Radiographic changes included diffuse or focal thickening of the bladder wall, or dissection of contrast into the bladder wall. All the cats examined by cystoscopy (21) had multiple submucosal petechial hemorrhages. Hematuria was present in 46% of the cats with idiopathic cystitis. Pyuria was rare (3%). In 20% of cats with idiopathic cystitis, inappropriate urination was the only clinical sign. These cats had no signs of hematuria, stranguria, or pollakiuria, and had normal urinalyses. These cats all had radiographic or cystoscopic abnormalities. Almost all the cats with idiopathic cystitis showed urination in inappropriate places. This case series showed a significant association between idiopathic cystitis and the feeding of a dry diet.
The natural history of IFLUTD is one of cyclic episodes of lower urinary tract signs lasting 3 days to 2 weeks (occasionally longer). The episodes of active clinical signs may be precipitated by stress. Most cats with IFLUTD develop the condition at a young age (2-3 yrs) and they will cease to have episodes in middle age. IFLUTD is not a steroid-responsive or antibiotic-responsive disease.
Viral Infections
For many years veterinarians have hunted for viral cause of IFLUTD. Viruses isolated from urine and tissues of cats with IFLUTD include BHV-4, FCV, and SFV. BHV-4 is bovine herpesvirus 4, which was initially termed CAHV (cell-associated herpesvirus). Members of this group are distinct from feline rhinotracheitis virus (FHV-1) and other bovine herpes viruses; they are able to replicate in a wide variety of experimental hosts. While there is some experimental evidence to suggest a role for BHV-4 in IFLUTD, strong clinical evidence has not been presented.
Feline syncytia-forming virus (SFV) has been isolated from cats with naturally occurring FLUTD, however there is no experimental evidence for a causal role for this virus. Feline calicivirus (FCV) has been suggested to cause FLUTD in experimental cats, but has not been isolated from naturally occurring cases.
There does not appear to be a significant relationship between FLUTD and seropositivity to FIV.
Interstitial Cystitis (IC)
Interstitial cystitis is a lower urinary tract disorder of humans that shows some similar features to FLUTD. This disorder is most common in women of 20 to 40 years of age; and it is characterized by difficult, painful, and frequent urination, with no discernable cause. The diagnosis of IC requires the presence of the appropriate symptoms, sterile and cytologically negative urine, and characteristic cystoscopic findings. These must be present without any other diagnosable cause. The characteristic cystoscopic findings are submucosal petechial hemorrhages (glomerulations) after hydrodistension of the bladder to 80 cm water pressure.
Comparison Between IC and IFLUTD (idiopathic cystitis)
Clearly the signs of dysuria, stranguria and pollakiuria are similar in IC and IFLUTD. In addition, the signs can be of variable severity, with a waxing and waning course, and the possibility of spontaneous remissions. In both IC and IFLUTD, the urine is sterile and cytologically unremarkable. Microscopic hematuria is more common in the feline disease, however this may be partly due to the frequent use of cystocentesis for urine collection in the cat. Radiography is more commonly used to evaluate cats for the presence of IFLUTD, as cystoscopy is less readily available. However, in the all the cats examined by cystoscopy in the Buffington study, lesions were seen that correspond to the glomerulations seen in human IC. These lesions have not been detected in normal cats.
Histopathology in human IC patients shows a relatively normal epithelium and muscularis, with submucosal edema, and vasodilation. Mast cells may also be present, but there is relatively little inflammatory infiltrate. Similar changes have been described in IFLUTD.
Increased sensory nerve fiber density occurs in the bladders of patients with IC. This suggests a role for neurogenic inflammation in the pathogenesis of IC. Substance-P containing nerve fibers are increased in the submucosa of some cats with IFLUTD, and some humans with IC. Bladder epithelial permeability is also increased in human and feline patients with IFLUTD. This could be an effect of substance-P.
One of the most consistent findings in human patients with IC is that the natural coating of glycosaminoglycans (GAGs) that lines the bladder uroepithelium is defective in some patients. A functional deficit in this protective layer exposes the underlying epithelium to the damaging effects of irritating urine components. A defect in the GAG layer may also be responsible for the increased bladder epithelial permeability seen in IC and IFLUTD. In both human patients with IC and IFLUTD, urinary GAG excretion is reduced, which has been attributed to increased binding of GAG to the urinary epithelium.
Although comparisons between IC and IFLUTD are fascinating, and may direct us towards new therapies for IFLUTD, it is important to bear in mind that these are both idiopathic disorders. Any similarities between the two disorders may be coincidental, or they may reflect the limited ways in which the lower urinary tract responds to a variety of insults.
Treatment of Feline Idiopathic Cystitis
The finding of a defective GAG layer in human patients with IC has lead to the use of a semi-synthetic mucopolysaccharide for treatment of this condition. Pentosan polysulfate sodium (ElmironÒ - Baker Norton) has been shown to be beneficial in relieving symptoms of IC. Pentosan is poorly absorbed from the GI tract, but 4-11% of the oral dose is excreted in the urine, where it is believed to act by adhering to the luminal aspect of the bladder mucosa, thus maintaining the permeability barrier. Pentosan is also effective when administered by the intravesicular route. It has been used in a limited number of cats with anecdotally good results. Clinical trials are ongoing.
Amitriptyline is potentially beneficial in the management of IFLUTD, for a number of reasons. This tricyclic antidepressant inhibits the reuptake of neurotransmitters, such as norepinephrine and serotonin, and has potent anticholinergic activity. In the management of IFLUTD, amitriptyline may act as an analgesic and a stabilizer of mast cell membranes. The anticholinergic effects may reduce frequency of urination. The dose for cats is 2.5 to 12.5 mg once daily. It is usual to start at the low end of the dose range, and increase if necessary because side effects are possible. The tablets taste extremely bitter and should be placed in gel-caps if possible. They can not be hidden in food. Mild sedation may be seen, and therefore cats are best dosed at night time. Controlled safety and efficacy studies are not available, therefore serum liver enzymes should be regularly evaluated in patients receiving amitriptyline.
Dietary management was previously considered important for the prevention of episodes of IFLUTD. This now appears to be of questionable benefit. Acidifying diets to minimize the formation of struvite crystals may reduce the risk of obstruction in male cats with IFLUTD. Some people have theorized that an acid urine might irritate the inflammed bladder wall and lengthen episodes of IFLUTD.
Antibiotics and corticosteroids are not useful in the management of IFLUTD. As this disorder can go into spontaneous remission, some “cures” are falsely attributed to medical therapy. Propantheline bromide can be considered for cats with severe detrusor hypercontractility. The dose is 7.5 mg once. The tablets are extremely bitter and can be placed in gel caps.
Other useful management strategies include minimizing stress and feeding a diet with a high water content. Stress is highly significant in inducing a “flare” of symptoms in human IC. Similarly in cats, signs of FLUTD often follow severe weather or climatic changes, or other stressors such departure of an owner, moving to a new home, or other changes in the household. Stress in cats may be reduced by providing places to hide, and opportunities to climb, play, and “hunt”.
Evaluation of the Feline Patient with Signs of Lower Urinary Tract Disease
Urinalysis
If the urine sample can not be evaluated immediately, it should be refrigerated.
pH can be affected by a recent meal, and by stress. A stressed cat may hyperventilate, leading to alkalosis and urinary alkalinization.
Hematuria may be induced by cystocentesis.
Crystals can form, or dissolve, after voiding.
Culture is necessary to document bacterial UTI.
Imaging
Plain and contrast radiographs
Ultrasound
Cystoscopy: can be difficult in the male cat.
The results of the Buffington study indicate that imaging of the lower urinary tract is necessary to rule out IFLUTD, before signs of inappropriate urination can be attributed to behavioral disorders.
Biochemistry and Hematology
These may be useful in addressing underlying diseases, such as causes of hypercalcemia, diabetes mellitus, and liver disease.
Stone or Plug Analysis
Stones and urethral plugs should always be submitted for analysis, so that preventive measures can be introduced, if possible. Methods of analysis can be qualitative or quantitative. The latter is strongly preferred, and includes optical crystallography, infrared spectroscopy, and x-ray diffraction. Qualitative testing uses chemical tests to identify chemical radicals and ions, and is not recommended.
note: much of the content of this handout was provided by Katharine Lunn
Bibliography
Consultations in Feline Internal Medicine (3) (August) Chapters 46 (Osborne et al) and 47 (Buffington and Chew).
Veterinary Clinics of North America: Small Animal Practice 26 (2) and (3). Disorders of the Feline Lower Urinary Tract I and II. March and May, 1996.
Osborne et al., JAVMA 196 (7) 1053-1063, 1990. Medical dissolution of feline struvite urocystoliths.
Buffington, J. Nutrition 124 2643S-2651S, 1994. Lower urinary tract disease in cats - new problems, new paradigms.
Buffington et al., JAVMA 205 (11) 1524-1527, 1994. Lower urinary tract disease in cats: Is diet still a cause?
Buffington et al., JAVMA 210 (1) 46-50, 1997. Clinical evaluation of cats with nonobstructive urinary tract diseases.
Hanno, Urology 49 (Suppl 5A) 93-99, 1997. Analysis of long term Elmiron therapy for interstitial cystitis.
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