Feline matrix-crystalline urethral plugs: A unifying hypothesis of causes

Causes of lower urinary tract disease in Czech cat population

This study was done to investigate epidemiological data and to report causes of lower urinary tract disease in a population of cats presented at the Small Animal Clinic of the University of Veterinary and Pharmaceutical Sciences Brno. Cats presented with lower urinary tract disease signs that had undergone a thorough physical examination and urinalysis (dipstick, urine specific gravity, urine sediment and dipslide urine culture) were included in the study. Urine samples were collected only by cystocentesis or sterile catheterization. Bloodwork, abdominal ultrasound, and abdominal radiographs were performed in 118 (66%), 170 (96%) and 9 (5%) patients, respectively. Cats that were treated with antibiotics or glucocorticoids during an episode of feline lower urinary tract disease (FLUTD) or during the foregoing month and which had undergone perineal urethrostomy or catheterization in private practice, were excluded. The study population consisted of 177 cats. Forty-one (23%) cats were diagnosed with a urethral plug, 26 cats (14%) with a urinary tract infection (UTI), 9 cats (5%) with urolithiasis and 101 cats (57%) with feline idiopathic cystitis (FIC). The cats diagnosed with UTI were significantly older than the cats with FIC, urethral plugs and urolithiasis. Urinary tract infection was diagnosed significantly more often in patients older than 10 years, and in female cats. The diagnosis of urethral plug was made significantly more often in males. Feline idiopathic cystitis and urethral plugs are the most common causes of FLUTD, and the causes are significantly age and sex-related.

An imaging investigation of in situ uroliths in hospitalized cats in New Zealand and in the United States

The submission rates of feline uroliths to laboratories and the composition of uroliths have been reported in studies. The prevalence of uroliths reported on imaging findings has not been published. The objective of this retrospective study was to use imaging data to investigate the anatomical location and the prevalence of macroscopic in situ uroliths in cats. Radiographs, sonograms and imaging reports from two cohorts of cats (from New Zealand (n = 497) and the United States (n = 693)) from 2004‐2013 were reviewed for the presence of in situ uroliths. Uroliths were categorized by their location in the lower or upper urinary tract. Radiographic studies were performed on 43% (212/497) of the cats from New Zealand and 50% (349/693) of the cats from the USA. Sonographic studies were performed on 57% (285/497) of the cats from New Zealand and 50% (344/693) of the cats from the USA. The total prevalence of uroliths was 3% in the New Zealand cohort and 13% in the USA cohort. Lower tract urolith prevalence in the New Zealand cohort was 2.4% (5/212) in cats ≤ 6y and 1.1% (3/285) in cats >6y. Upper tract urolith prevalence in the New Zealand cohort was 0.5% (1/212) in cats ≤ 6y and 1.8% (5/285) in cats >6y. Lower tract urolith prevalence in the United States cohort was 6.0% (11/183) in cats ≤ 6y and 2.9% (15/510) in cats >6y. Upper tract urolith prevalence in the United States cohort was 2.7% (5/183) in cats ≤ 6y and 10.2% (52/510) in cats >6y. The prevalence of uroliths in the upper tract or lower tract was low in the New Zealand cohort compared to that of cats in the USA cohort, irrespective of age category. Geographical location may be important when evaluating risk factors for feline urolithiasis.

Companion Animals Symposium: dietary management of feline lower urinary tract symptoms

Experimental and clinical investigations have confirmed the importance of dietary modifications in medical protocols designed to treat and prevent feline lower urinary tract signs (LUTS). The objective of this review is to discuss common medical conditions contributing to feline LUTS and to present currently used and potential preventative dietary modifications. Feline LUTS are a set of clinical conditions with similar symptoms related to inappropriate urine elimination due to a combination of genetics, stress and frustration reactions, environment, and medical condition or conditions, for example, idiopathic cystitis, urolithiasis, urethral obstruction, and urinary tract infection. The main goals of dietary modifications to prevent LUTS are 1) promote large dilute volumes of urine, 2) decrease the relative supersaturation of urine for specific stone types, and 3) promote healthy bacterial populations in the gastrointestinal and urogenital tracts. The impact of dietary composition, including dietary moisture, protein concentration and digestibility, mineral concentrations (i.e., Na, Cl, Ca, P, and Mg), inclusion of acidifiers and alkalinizing agents, inclusion of vitamin B6, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and γ-linolenic acid, fiber concentration and characteristics, and oxalate degrading probiotics, on these outcomes is discussed, and dietary guidelines for cats are provided. Because of the complex interaction of diet composition, environment, and animal physiology, there is a need for clinical research linking current recommendations or dietary options for the treatment and prevention of LUTS with physiological outcomes (i.e., decreased relative supersaturation and LUTS recurrence). Additionally, for many recommendations (e.g., probiotic administration, EPA, DHA), extrapolation from other species was necessary. Research is needed in feline patients with LUTS on these dietary components.

Risk factors and clinical presentation of cats with feline idiopathic cystitis

Feline idiopathic cystitis (FIC) is the most common cause of feline lower urinary tract disease (FLUTD). This retrospective, case-controlled study evaluated possible risk factors associated with FIC and compared different clinical presentations in 64 cats with FIC. Several risk factors known to be involved in FLUTD were identified as playing a role in FIC. Of the stressful situations considered, most did not occur with increased frequency in cats with FIC compared to controls, except for a house move. The presence of pyuria, haematuria and an increased urine protein:creatinine ratio were significantly higher in obstructed males compared with non-obstructed males. An obstruction was significantly more likely in cats with struvite crystalluria compared with cats without struvite crystalluria. These findings suggest that urethral plugs might be an important cause or contributing factor of obstruction in FIC. Episodes of FIC seem to occur mainly in susceptible cats in combination with a deficient environment.

Analysis of 451,891 canine uroliths, feline uroliths, and feline urethral plugs from 1981 to 2007: perspectives from the Minnesota Urolith Center

Urolithiasis is a general term referring to the causes and effects of stones anywhere in the urinary tract. Urolithiasis should not be viewed conceptually as a single disease with a single cause, but rather as a sequela of multiple interacting underlying abnormalities. Thus, the syndrome of urolithiasis may be defined as the occurrence of familial, congenital, or acquired pathophysiologic factors that, in combination, progressively increase the risk of precipitation of excretory metabolites in urine to form stones (ie, uroliths). The following epidemiologic discussion is based on quantitative analysis of 350,803 canine uroliths, 94,778 feline uroliths, and 6310 feline urethral plugs submitted to the Minnesota Urolith Center from 1981 to 2007.

Effects of a high-protein diet versus dietary supplementation with ammonium chloride on struvite crystal formation in urine of clinically normal cats

OBJECTIVE

To evaluate the effects of a high-protein diet versus dietary supplementation with ammonium chloride (NH4Cl) on struvite crystal formation in the urine of clinically normal cats by measuring the urine concentration of hydrochloric acid (HCl)-insoluble sediment, urine pH, struvite activity product (SAP), number of struvite crystals in urine, and urine volume.

ANIMALS

23 healthy adult cats.

PROCEDURE

Urine was fractionated by centrifugation with subsequent extraction of the sediment with 1 N HCl (study 1). Diets containing either 29% crude protein or 55% crude protein were fed to cats in a crossover trial of 3 weeks/period (study 2). Diets supplemented with either sodium chloride (NaCl) or NH4Cl were fed, by use of a 3 x 3 Latin-square design with 3 wk/period (study 3). In studies 2 and 3, urine samples were collected for the last 7 days of each period.

RESULTS

The HCl-insoluble sediment contained Tamm-Horsfall glycoprotein (THP; study 1). The high-protein diet (study 2) and dietary supplementation with NH4Cl (study 3) resulted in a decrease in urine pH, SAP, and the number of struvite crystals in urine. However, the high-protein diet decreased urine concentrations of HCl-insoluble sediment containing THP (study 2), in contrast to the NH4Cl supplementation that increased urine volume without a significant effect on the urine concentration of the HCl-insoluble sediment (study 3).

CONCLUSIONS AND CLINICAL RELEVANCE

Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats.

Management of nonobstructive idiopathic feline lower urinary tract disease

Consistently effective treatment and prevention of nonobstructive idiopathic lower urinary tract disease (LUTD) in male and female cats remains an enigma. Because clinical signs associated with this form are frequently self-limiting, considerable debate exists about the efficacy of various symptomatic therapies advocated for management of idiopathic feline LUTD. Any form of therapy might appear to be beneficial, as long as it was not harmful. The self-limiting nature of some forms of idiopathic feline LUTD underscores the need for controlled prospective double-blind clinical studies to prove the value of various forms of therapy.

Viral infections of the feline urinary tract

The exact cause of hematuria, dysuria, and urethral obstruction remains unknown in a large percentage of naturally occurring cases of feline lower urinary tract disease (FLUTD). One attractive hypothesis implicates viruses as the cause of some idiopathic forms of FLUTD; supporting this hypothesis is the fact that a gamma herpesvirus, a calicivirus, and a retrovirus have been isolated from urine and tissues obtained from cats with this type of disease. Although the clinical course and laboratory findings of cats with idiopathic FLUTD are suggestive of an infectious cause, the question of whether viruses have a pathologic role in some forms of naturally acquired FLUTDs has not been completely answered.

Feline lower urinary tract disorders. Definition of terms and concepts

Lower urinary tract disorders of male and female cats may be caused by a variety of fundamentally different causes. The term Feline urologic syndrome should be abandoned and substituted with descriptive etiopathogenic terms whenever possible. If the underlying cause cannot be identified, the term Idiopathic lower urinary tract disease is recommended.

Effect of chronic high protein intake on magnesium, calcium, and phosphorus balance in growing cats

The effects of high protein feeding on food and water intake, and the retention and urinary excretion of macrominerals (magnesium (Mg), phosphorus (P), and calcium (Ca)) were examined in growing cats. Seven female cats aged 4 months were fed diets containing 55% crude protein (n = 4) or 29% crude protein (n = 3) for 12 months on an ad libitum basis. Mineral balances were determined at 0.5, 2, 6, 10, and 12 months of feeding. The higher protein intake stimulated daily water intake and urine excretion throughout the study, although daily food intake was not affected by dietary protein levels. The urinary Mg concentration was decreased by the high protein intake, resulting from both increased urine volume and reduced excretion of urinary Mg. In contrast, the concentration and daily excretion of urinary P were increased by the high protein intake. The protein-induced increase in urinary P would not necessarily imply the increased excretion of PO4(3-), the anion responsible for struvite crystallization, because the dissociation of phosphate depends on urinary pH. Urinary Ca excretion was not affected by the dietary protein levels, but the high protein intake caused less retention of P and Ca as a result of enhanced urinary P excretion and lowered Ca absorption. The possibility of high protein feeding for the prevention of struvite crystallization in growing cats is discussed.

The role of uropathogens in feline lower urinary tract disease. Clinical implications

Bacterial, fungal, and parasitic uropathogens have small but significant roles as causative agents in naturally occurring feline lower urinary tract disease. However, the exact cause of hematuria, dysuria, and/or urethral obstruction remains unknown in a large percentage of cats. Feline calicivirus, feline syncytia-forming virus, bovine herpesvirus-4, mycoplasmas, and ureaplasmas are potential uropathogens whose etiopathogenic roles in idiopathic feline lower urinary tract disease remain, as of yet, unresolved.