Urinary tract medicine in rodents

Why are uroliths in herbivorous mammals so common?

Lower urinary tract infection

• Definition:
  result of microbial colonization of the urinary bladder and/or the proximal portion of the urethra
• Incidence/prevalence:
  urinary tract infection secondary to urolith rare in mouse and rat, described in hamster.
  More common in true herbivores and in older animals
• Clinical signs:
  - Historical findings: none, pollakiuria, hematuria, urine scald
  - Physical examination findings: the bladder may be enlarged and painful, automutilation of the penis (mouse), no abnormalities in some animals
• Causes: 
  - Bacteria - Esherichia coli and Pseudomonas sp. are common causes of bacterial cystitis. Urethral obstruction as a result of S. aureus preputial gland and P. pneumotropica bulbourethral infection are described in rats
  - Parasite - Bladder threadworm Trichomonas crassicauda in rat
  - Urolith and crystals - bladder stone of struvite, crystals of ammonium magnesium phosphate, mixed carbonate and oxalate, and mixed carbonate, phosphate, magnesium and calcium in rat
  - Mucoid calculi - part of copulatory plugs found in the urethra and bladder of rats
• Risk factors:
  - Inadequate water intake – dirty water bowl, unpalatable water, changing water source, inadequate water provision)
  - Inadequate cleaning of the cage – may cause some animals to avoid urinating for abnormally long period
  - Injury on the penis – seen from aggressive breeding activity and abrasion on the cage in male mouse
  - Obesity, lack of excercise
  - Diet - high calcium diet magnesium deficiency, elevated dietary phosphorus or calcium, and diet preparations with a low calcium-to-phosphorus ratio
• Diagnosis:
  - Differential diagnosis: Female with pyometra, uterine neoplasia, or other uterine disorder may expel blood or a thick, often blood-tinged vaginal discharge when urinating. This discharge may mix with urine and mimic lower urinary tract infection. Obtain urine sample via cystocentesis to differentiate
  - Lower urinary tract neoplasia
  - Differentiate from other causes by urinalysis, urine culture, radiography and ultrasonography

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