Presenting problem: Abnormal Urine in Rabbits

Understanding the problem

Abnormal urine in the rabbit (Oryctolagus cuniculus) typically appears white and chalky or pigmented. These changes can be related to the unique metabolism of calcium in the rabbit. Rabbits absorb nearly all calcium ingested; therefore blood levels vary substantially with the calcium content of the diet. The kidneys excrete the vast majority of blood calcium, and once the rabbit kidney has reached it relatively limited capacity for reabsorption, calcium precipitates within the rabbit’s alkaline urine. Calcium is then excreted as insoluble crystalline salts in cloudy, white urine. These crystalline salts are primarily composed of calcium phosphate or calcium carbonate crystals. Calcium oxalate is seen less commonly since rabbits do not readily absorb calcium-bound oxalate.

As the calcium content of the diet rises, the urine volume remains the same until the rabbit eventually develops thick bladder “sludge” or “sand”. Over a matter of weeks, this massive aggregation of crystals may form a concretion or urolith. Stones usually form within the urinary bladder; the ureters and kidneys are only rarely involved. See Calcium Homeostasis in the Rabbit for more information.

Causes of white chalky urine

• High calcium diet
• Calcium sand
• Urolithiasis

Red, orange, or brown urine in the rabbit is most commonly caused by porphyrin in the urine secondary to the diet or hematuria.

Causes of pigmented urine

• Diet
• Uterine disease
• Renal disease
• Stress

Hematuria is most frequently associated with uterine disease or disease of the urinary tract. Heavy bladder sludge or urolithiasis may promote hematuria. Blood may also be passed with uterine infection or uterine venous aneurysm.

Case management

History

Use a detailed history to help distinguish between the cause of abnormal urinations as well as appropriate case management:

• What is the calcium content of the diet? Does the rabbit eat high-calcium foods like alfalfa-based hay or pellets or dark, leafy greens.
• Has there been a change in litter box habits?
• Have pollakiuria, polyuria, dysuria, and/or stranguria been observed?

Physical examination

• Carefully palpate the abdomen to assess the kidneys and urinary bladder.
• Look for evidence of dribbling and urine scald around the perineum.

Diagnostics

• Complete blood count/biochemistry panel: Both ionized and total serum calcium concentrations are elevated in the normal rabbit compared with those in other species (ionized calcium, 3.4 ± 0.26 mEq/L; total calcium, 12.92 ± 1.0 mg/dL). Values may be even higher in rabbits on high calcium diets.

• Urinalysis +/- urine culture/sensitivity: Use the urine dipstick to distinguish porphyrins from blood in the urine. Calcium phosphate or calcium carbonate crystals are commonly found on the urine sediment. Also look for evidence of pyuria in addition to hematuria.

• Survey radiographs/abdominal ultrasound: Use imaging to evaluate the urogenital tract and distinguish between calcium “sludge” or urolithiasis in the urinary tract and disease of the uterus (Fig 1).

Figure 1. Survey lateral abdominal radiographi illustrating bladder sludge or sand in a rabbit. Photo credit: Dr. Ariana Finkelstein. Click image to enlarge.

Treatment

Management of hematuria will depend on the underlying but may include surgery for uterine disease or urolithiasis.

Management of white chalky urine

• Modify the diet by recommending a low-calcium, grass hay-based maintenance diet for adult rabbits
• Administer fluids to diurese the urinary tract.
• Provide pain relief such as meloxicam (0.1-o.2 mg/kg PO, SC IM q24h) and/or buprenorphine (0.01-0.05 mg/kg SC, IV q6-12h) as needed.
• Aseptically catheterize and lavage the bladder in selected cases.
• Prescribe antibiotics in selected cases. Keep in mind that the first generation beta-lactams can disrupt normal gastrointestinal flora causing potentially fatal dysbiosis.

See Antimicrobial Therapy and Dysbiosis in Rabbits and Rodents for additional advice on antibiotic selection. Monitor patient appetite and eliminations, including defecations and urinations, and follow the patient’s progress with the help of blood calcium levels, urinalyses, and imaging.

References