Bladder sludge (hypercalciuria) in rabbits is an accumulation of calcium crystals in the bladder that causes painful, gritty white urine, straining, and blood in the urine. Diet modification to reduce calcium load and increased hydration are the cornerstones of prevention and management.
Last reviewed: June 2026
What Is Bladder Sludge in Rabbits?
Bladder sludge — formally hypercalciuria — is an abnormal accumulation of calcium carbonate and calcium oxalate crystals in the urinary bladder. Unlike dogs and cats, rabbits excrete excess dietary calcium primarily through the urine rather than the gut; this makes them uniquely susceptible to calcium accumulation when dietary calcium intake is high, water intake is low, or exercise and urination frequency are reduced.
The result is a thick, chalky sediment in the bladder that may progress to true stones (uroliths) if crystals aggregate. As described in Quesenberry & Carpenter's Ferrets, Rabbits & Rodents, hypercalciuria is among the most common urinary presentations in pet rabbits and is closely linked to excess pellets and low hay intake.
The AEMV Pet Care Guides, 2024 identify diet modification and exercise as the primary intervention strategies for hypercalciuria in rabbits, with medical or surgical intervention reserved for cases that do not respond to husbandry changes.
Signs of Bladder Sludge in Rabbits
Urine changes — most distinctive:
- Thick, white, chalky or toothpaste-like urine
- Beige or white residue left on surfaces
- Blood in the urine (pink, red, or brown tinge)
- Strong-smelling urine
Behavioral and physical signs:
- Straining to urinate — posturing for a long time with little output
- Bruxism — tooth grinding during or after urination
- Hunching, reduced movement, perineal scalding from dribbling
- Reduced appetite, weight loss, lethargy
Signs indicating a complication (stones or obstruction):
- Complete inability to urinate — a life-threatening emergency
- Sudden distension and firmness of the lower abdomen
- Acute deterioration and collapse
Diagnosis and Treatment
Diagnosis: Radiographs reliably detect calcium sludge and stones (highly radio-opaque). Ultrasound assesses bladder wall thickness. Urinalysis quantifies crystals and detects concurrent infection.
Treatment:
- Bladder flush under sedation — the vet passes a urethral catheter and flushes saline to dilute and evacuate the sludge; effective for moderate-to-severe sludge accumulations
- Fluid therapy — SC or IV fluids dilute urinary calcium
- Diet modification — transition to unlimited grass hay; reduce pellets and calcium-rich vegetables (kale, broccoli); add water-rich greens (romaine, cucumber)
- Increased water access — fountains, multiple bowls; dilute urine is the primary prevention tool
- Exercise — regular free-roaming encourages urination frequency
- Surgical cystotomy — required for large stones that cannot be flushed; stones are physically removed from the opened bladder
Pain management with meloxicam, as described in Quesenberry & Carpenter's Ferrets, Rabbits & Rodents, is important since straining and inflammation suppress appetite and worsen GI motility.
When to See a Vet
Call your vet today if:
- You notice thick white, chalky, or bloody urine from your rabbit
- Your rabbit is straining to urinate or spending prolonged time in urination posture
- Your rabbit's perineal fur is wet or matted
- Your rabbit is eating less than normal alongside any urinary sign
Go to the ER immediately if:
- Your rabbit is not producing any urine and is straining repeatedly
- Your rabbit's lower abdomen is distended and firm to the touch
- Your rabbit has collapsed or is unresponsive
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Frequently Asked Questions
Is bladder sludge the same as bladder stones in rabbits? No, though they are related. Bladder sludge is calcium crystal sediment that remains dispersed and suspended in urine. Bladder stones are discrete, solid aggregates of calcium crystals that have fused. Sludge can progress to stones over time. Both require veterinary treatment, but stones typically require surgical removal while sludge can often be managed with flushing and diet changes.
What diet changes help prevent bladder sludge? Unlimited grass hay should make up 80% or more of the diet — it is low in calcium and high in fiber that supports gut motility. Pellets should be limited to one to two tablespoons per day for an average-sized rabbit. High-calcium greens (kale, parsley, spinach, broccoli) should be limited. Water-rich low-calcium greens (romaine lettuce, cucumber, bell pepper) are beneficial.
How much does treating bladder sludge cost? An initial exotic vet exam runs $80–180. Radiographs add $150–350. Bladder flushing under sedation typically costs $300–600. IV or subcutaneous fluid therapy adds $150–400. Surgical cystotomy for stones runs $800–2,000. Hospitalization for severe cases adds $300–600 per day. Dietary management — transitioning to hay-based diet — is inexpensive but dramatically reduces recurrence risk.
Can rabbits get bladder sludge more than once? Yes — recurrence is common without sustained diet change. Rabbits that return to high-pellet, low-hay diets frequently redevelop sludge within months. The goal of treatment is to permanently modify the diet and increase hydration, making single-episode resolution the exception rather than the rule without lifestyle change.
What is the long-term outlook for rabbits with hypercalciuria? Good with consistent management. Rabbits that transition to unlimited grass hay, reduced pellets, and adequate hydration rarely develop severe recurrent sludge. Rabbits whose husbandry does not change typically experience repeated episodes. Bladder stones that require surgery carry a good prognosis after surgical removal if no underlying infection or bladder wall damage is present.
Still Not Sure if Your Rabbit Needs a Vet?
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