Normal urine and “sludge” in rabbits
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Healthy rabbit urine

Rabbit urine always contains a certain amount of sediments. This is absolutely normal, the system of rabbits works this way to excrete the too much of calcium in their body.


Microscopic view of crystals contained in rabbit urine

The absence of sediments in the urine is indicative of renal failure.



Different color of urine produced by healthy rabbits. The red color is caused by the oxidation of plant pigments.



A thick paste that becomes a solid millimeter thick “cake” when drying.


Sludge can be treated via a non-invasive procedure. An effective way of washing the bladder without use of catheter, is the administration of subcutaneous fluids, followed by a diuretic drug like furosemide by your vet. One time is usually enough, it can be repeated in the next 24 hours. The administration of a small doses of valium will relax the sphincter of the bladder and lead to the voiding of this organ.

Another way is washing the bladder after introduction of a catheter. The procedure is done on an anesthesized rabbit. Since the procedure is accompanied by pain, the rabbit needs to be given pain relief medication. A stone need to be removed surgically.

The presence of sediment in the bladder may be accompanied by urine retention. If the amount of sediment is large, urination and complete voiding of the bladder is difficult. The bladder gradually gets distended et its size becomes larger and larger. In the picture of the male rabbit (below, right), the bladder contains a certain amount of sediment.


Michel Gruaz

Normal sized bladder (arrow) in a female rabbit (left)et huge sized bladder in a male rabbit filled with a large amount of sediment and urine (arrow)


Calcium and the formation of stones does not relate to the calcium in the diet only. There is much more involved, that we do not understand yet. One cause of uroliths (stone) may be increased pH of the urine, for some reason or another (e.g. diet, presence of bacteria). The increased urine pH favors the development of bacteria and UTI. Bacteria in the bladder will, on the other hand, start to excrete waste (ammonium) and an enzyme, urease that will break down the urea; both will increases the pH of the urine. An increased pH accelerates the precipitation of struvite crystal (struvite = magnesium, ammonium, and phosphate). Struvite stones develop only in the presence of an alkaline pH.

Commonly found bacteria are E. coli, Proteus sp and Staphylococcus sp, rarely true anaerobic bacteria are found. The presence of bacteria can be easily checked by sending a sample of urine for bacterial culture (urine is normally sterile). One can also keep the removed urolith, open it, and use the central part for bacterial culture or have the stone examined for the crystals composition. Indeed, some bacteria are associated with a particular type (e.g. Staphylococcus is associated to struvite stones).


C. Macey

A 1.9 cm bladder stone Photo:


Hematuria (urine with blood traces)

Thick urine, the presence of a bladder stone, a bladder or kidney infection, or infection of the urinary or reproductive organs are usually accompanied by the presence of blood spots in the urine.



Some dried blood in the urine circle




Heavy blood loss, caused by a cystitis in a female rabbit


After taking X-rays of the bladder, a vet may easily conclude that the rabbit has a huge bladder stone. Many rabbits have been operated on, as a vet was convinced to find the stone, and once the bladder open, nothing... Rabbit savvy-vet will know to differentiate between a stone and the presence of sludge/sediments.


For more details, see: "Nephroliths

 and Uroliths (calculi) in rabbits"


Huge thanks to Michel Gruaz (Switzerland) and Christine Macey for their pictures and permission to use in MediRabbit.