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Urology

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PATHOLOGY –Struvites & Oxalates Crystals

RSS (Relative Super Saturation) index

RSS is calculated with a specific software, from the analysis of 13 minerals in the urine. It falls within 3 zones:

  • Zone of undersaturation:

Uroliths cannot form. Existing struvites crystals will dissolve. Str RSS<1

  • Zone of metastable saturation:

Pre-existing crystals can grow. But new uroliths won’t form. Str RSS<2.5 / Ox RSS<10-12

  • Zone of oversaturation:
  1. Urolith formation is highly likely. Str RSS>2.5 / Ox RSS>10-12

U-RSS.jpg

  1. Removal4:
  • Minimally invasive techniques (urohydropropulsion, transurethral cystoscopic stone removal and minilaparotomy-assisted cystoscopic stone removal)
  • Surgery (cystotomy, urethrotomy and urethrostomy)
  • Management of associated disorders and predisposing factors4: antibiotherapy if bacterial infection (Rilexine®, Suramox®, depending on the antibiogram), etc.
  1. Prevention4:
  • Stimulate drinking behaviour (water fountains…)
  • Surgery if multiple relapses: perineal urethrostomy (male)
  • Urinary tract diseases: around 7% cats presented at veterinary hospitals/practices1,2
  • Urolithiases: 7-22% of feline lower urinary tract diseases3
  • More than 80% of lower urinary tract uroliths are struvite or calcium oxalate4,5
  • Multifactorial origin (e.g. inappropriate diet, metabolic, hormonal, drinking behaviour, drugs)4.
  • Mostly sterile but can be associated with urinary tract infection (cause or consequence)4,6
  • More frequent in males and cats kept strictly indoor7.
  • Breed predispositions: Domestic Shorthair, Himalayan, Persian, Burmese and Siamese4,8
  • History and clinical signs (non-specific)7,9
    • Urination: dysuria, stranguria, pollakyuria, inappropriate urination and hematuria
    • Systemic signs (particularly if obstruction): reduced appetite, vomiting, lethargy, weight loss, polyuria and polydipsia, signs of abdominal pain
  • Radiography/ultrasonography of the urinary tract 4,9,10
  • Urinalysis: crystalluria, urine specific gravity (increased), urine pH (neutral or acidic pH for calcium oxalate calculi and alkaline pH for struvite calculi)4, presence of bacteria and/or blood cells in urine7
  • Urine culture and sensitivity if infection4
  • Blood biochemical profile to assess possible underlying cause and associated disorders (e.g. azotemia, hyperkalemia, metabolic acidosis often associated with obstruction)4,9
  • Analysis of removed or voided uroliths to determine the type4

Pathology – Feline idiopathic cystitis

  1. History and clinical signs of FIC (non-specific)3:
  • Dysuria, hematuria, periuria, pollakiuria and stranguria
  • Possibly small or distended urinary bladder with thickened walls
  • Environmental factors
  1. Exclusion of other causes of FLUTD after history and physical examination, urinalysis, urine culture and susceptibility, imaging and biopsy3,4
  2. Evolution: often self-limiting (resolution in 1-7 days if nonobstructive, in most cats) but sometimes persistent for weeks (15%). Recurrences of clinical signs within 1 to 2 years is frequent (65%). Can lead to urethral obstruction in males (15-20%) 3,4
  • Urinary tract diseases: around 7% cats presented at veterinary hospitals/practices.11.12 
  • Feline Idiopathic cystitis (FIC): around 55% of feline lower urinary tract disease (FLUTD)13 
  • Probably a syndrome (“Pandora Syndrome”) with multiple causes (unknown) and affecting different organs3.14
  • Could involve bladder and neuroendocrine system abnormalities and interaction with environment3
  • Risk factors : male, middle-aged (2–7 years), overweight cats, indoor housing and stress3
  1. Tion MT et al. A review on urolithiasis in dogs and cats. Bulgarian Journal of Veterinary Medicine. 2015; 18 (1) : 1-18
  2. Hill PB et al. Survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice. Vet Rec. 2006; 158(16):533-9.
  3. Forrester SD, Towell TL. Feline idiopathic cystitis. Vet Clin North Am Small Anim Pract. 2015; 45(4):783-806
  4. Bartges JW, Callens AJ. Urolithiasis. Vet Clin North Am Small Anim Pract. 2015; 45(4):747-68.
  5. Houston DM, Moore AE. Canine and feline urolithiasis: examination of over 50000 urolith submissions to the Canadian veterinary urolith centre from 1998 to 2008. Can Vet J. 2009; 50(12):1263-8.
  6. Smee N et al. UTIs in small animal patients: part 2: diagnosis, treatment, and complications. J Am Anim Hosp Assoc. 2013; 49(2):83-94
  7. Sævik BK et al. Causes of lower urinary tract disease in Norwegian cats. J Feline Med Surg. 2011; 13(6):410-7.
  8. Dorsch R et al. Feline lower urinary tract disease in a German cat population. A retrospective analysis of demographic data, causes and clinical signs. Tierarztl Prax Ausg K Kleintiere Heimtiere. 2014;42(4):231-9.
  9. Kyles AE et al. Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984-2002). J Am Vet Med Assoc. 2005; 226(6):932-6.
  10. Hecht S. Diagnostic imaging of lower urinary tract disease. Vet Clin North Am Small Anim Pract. 2015 Jul;45(4):639-63.
  11. Tion MT et al. A review on urolithiasis in dogs and cats. Bulg J Vet Med 2015; 18(1): 1-18.
  12. Hill PB et al. Survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice. Vet Rec 2006; 158(16): 533-9.
  13. Forrester SD, Towell TL. Feline idiopathic cystitis. Vet Clin North Am Small Anim Pract 2015; 45(4): 783-806.
  14. Tony Buffington CA, Westropp JL, Chew DJ. From FUS to Pandora syndrome: where are we, how did we get here, and where to now? J Fel Med Surg 2014; 16(5): 385-94.