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Why is my rabbits pee milky yellow?

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WARNING : this file contains pictures that may be distressing for people.

When cleaning the environment in which rabbits live, it is strongly advised to check the excrements, their shape, quantity, size and color. The same is true of urine and other secretions.

This observation enables to detect the presence of unusual colors or mucus. In normal times, rabbits produce two types of excrement: hard and round droppings, and soft or caecotrophes. Hard droppings come from the intestines and contain much fibrous material. A rabbit smells them, but rarely eats them. Their color and size vary according to the diet. The more the diet contains dry and fibrous matter, such as hay and straw, the larger the fecal droppings will be, and have a brownish color. The more the rabbit eats fresh food, salads and other carrots, the more the droppings tend to become smaller and have a blackish color. The «fragrant» caecotrophes are formed in the cecum. Each grain is covered with a thin layer of mucus. These excrements are rich in vitamins, minerals, proteins, water and bacteria. In order to avoid the nutrient loss, rabbits will reingest these soft droppings directly from the anus and swallows them without chewing. This avoids breaking the membrane surrounding the grains and allows the continuation of the fermentation process as well as the survival of the bacteria when they are in the hostile environment of the stomach. Sometimes, the presence of mucus is observed among excrements. It can have a protective and nurturing role. However, it can also be the sign of a malfunction.

Protective and nurturing mucus

The reproductive tract of a female rabbit has different internal organs, including the vagina and two uterine horns. The lower part of each uterus forms the cervix that connects the vagina to each uterine horn. The cervix possesses numerous glands that secrete mucus. Their secretion is influenced by the reproductive hormones estrogen and progesterone as well as by other hormones. The role of this mucus is multiple. Its bactericidal properties protect the reproductive system of the female rabbit against pathogens and, more particularly, the uterus in which the pregnancy will take place. Its high pH ensures the survival of spermatozoa, while its richness in mineral salts provides necessary energy to the spermatozoa in order to continue their ascent in the reproductive system and fertilize the ovules. Finally, the tight mesh of the different components of the mucus will filter sperm, allowing the passage of well-formed gametes and eliminating malformed ones. Once the ovules are fertilized, the secretion becomes acidic again, coagulates and becomes opaque. Its expulsion is favored by the vascularization of the uterus for pregnancy and allows the removal of dead cells within the reproductive system of the doe. At this stage, the does often turn her living place upside down, stirring straw and manure. This is a sign that gestation has begun for the pregnant doe.

This white substance is a sign of fertilization and gestation in does.

Mucus and irritation of the urinary tract

Mucus is produced by specialized cells lining the urinary tract. This substance migrates with the production of urine and is used primarily to eliminate pathogens and prevent urinary tract infections of the bladder and, sometimes, kidneys. It also allows to eliminate sediments and crystals contained in rabbit urine, or small sized stones. In a healthy animal, the mucus is transparent and usually very fluid. It is rarely visible except when urine is epressed from the bladder. It may then be observed as filaments or as a «cloud». When the mucus present in the urine has a yellowish and opaque color, it is a sign of disease. This affects both males and females. In the latter, it may, furthermore, be caused by an infection of the urinary or reproductive tract. Female rabbits are, indeed, more likely to develop bladder infections than male rabbits because the bladder duct leading urine outwards is shorter. Migration is shorter for bacteria, which favors infections. The presence of mucus in the urine may also be the consequence of mineral deposits in the bladder or kidneys. These deposits may be in the form of «sand», resulting in a paste -like urine, or in the form of stones. In rabbits, the formation of stones is unrelated to the presence of calcium in the diet. An increase of the urinary pH in the bladder will, however, favor the development of bacteria, which will excrete waste (ammonium) and secrete a urease, enzyme capable of degrading urea. In addition, an alkaline pH promotes the precipitation of magnesium, ammonium and phosphate crystals, resulting in the formation of stones. The irritation caused by «sand» or stones leads to the hypersecretion of mucus in the urinary tract.

Paulette Foley

The presence of mucus among urine rich in sediments in a non-castrated male rabbit

Mucus and intestinal disorders

Mucus-producing cells are also found in the gastrointestinal wall surrounding the lumen. They produce small amounts of mucus to protect tissues and organs of the digestive system and reduce the damage caused by acids from the stomach, certain foods or pathogen organisms. Indeed, the destruction of the mucus layer represents a entry into the body via the bloodstream. Mucus is clear and little visible or invisible in a healthy animal. When a large amount of mucus is secreted, this is a sign of a digestive problem. Any irritation of the mucosal layer and the lining of the digestive tract will lead to an inflammatory process. The latter stimulates mucus secretory cells, which start to excrete excessive amount of this substance to protect the walls of the digestive system. The mucus has a yellowish, red or brownish color. Large amounts of this substance among the droppings are often a sign of slow peristaltic bowel movement, cramps, excessive gas or recent diarrhea. Dehydration can also lead to excessive intestinal mucus production.

Sandy Minshull

A big quantity of opaque mucus is typically observed after an intestinal blockage.

Mucus and the presence of parasites

Different parasites colonize the digestive system of rabbits. The most common are the protozoa responsible for coccidiosis or giardiasis (rare nowadays) and various parasitic worms, the most common of which is Passalurus sp. These parasites colonize the intestine, the cecum and sometimes the liver in order to reproduce. Their presence may be asymptomatic or may be accompanied by pain, cramps, bloating, liquid diarrhea, apathy and/or unexplained weight loss. If the worm population becomes excessive in the intestine, the mass of worms can cause a painful blockage with massive mucus production. It is sometimes possible to see white worms, live parasites, around the anus or in the freshly evacuated solid fecals . Parasitic worms should not be confused with the larvae (maggots) of flies, which are parasites of the skin! Indeed, adult intestinal worms migrate to the anus to lay eggs, causing itching. Their presence in the intestine or cecum causes irritation of the mucous membranes and hypersecretion of mucus. Filaments of clear or brownish (due to the presence of blood) mucus are often the only clinical manifestation of intestinal parasites in rabbits. In case of giardasis other symptoms are noted.

The presence of small amounts of mucus may be indicative for coccidiosis.


Big great thanks to Michel Gruaz (Switzerland), Luc Page (Switzerland), Paulette Foley (USA) and Sandy Minshull (Canada) for the permission to use their pictures .

Rabbit Urinalysis

The popularity of the pet rabbit is continuing to increase, as is the amount of diagnostic work that is being carried out for them. Here is a quick guide to rabbit urinalysis to help you out in practice.

Rabbit Urinalysis

Rabbits are herbivores and thus the urine is normally alkaline (pH 8-9) and turbid. Copius amounts are produced due to their inability to concentrate as well as other animals and daily volumes range from 20-350 ml/kg averaging about 130 ml/kg. The specific gravity varies significantly due to the presence of mineral deposits but should range between 1.003 and 1036, average 1.015. Traces of glucose and protein may be present.

Obtaining a urine sample can be done by free catch, manual expression of the urinary bladder (care has to be taken when there is a lot of sludge in the bladder in order not to rupture the wall), catheterisation or cystocentesis.

Normal rabbit urine varies in colour from yellow to orange, brown or red depending on nutrition and hydration status and may be influenced by medication. True hematuria may be caused by urolithiasis and cystitis as well as renal disease. The blood is usually uniformly distributed throughout the urine. The dipstick should be able to differentiate but it is always best backed up by sediment analysis. “Pseudohematuria” occurs where blood originates from the uterus in cases of uterine disorders. This can be differentiated from discolouration and hematuria as the blood is usually pushed out at the end of urination. Juvenile, pregnant or lactating animals often produce clear urine.

Rabbit Urine

White “Sludgy Urine” or calciuria is voided with excess dietary calcium and sometimes due to urinary tract infection and can lead to calculi formation. Extreme hypercalcinuria often creates problems when passing urine. Imaging techniques can be used to differentiate between sludge, which presents itself with a uniform radiodensity, and urolithiasis. The problem may be managed by diet adaptation and medical support when detected early but sometimes surgery remains the only option. Secondary development of cystitis and dermatitis, especially around the perineum and hind legs, is frequently observed in conjunction with this condition. Antibiotic treatment should follow sensitivity results wherever possible.

When repeated straining does not produce any urine, consider a complete blockage and treat as an emergency. Catheterisation can be used to remove sludge. This procedure benefits greatly from repeated saline flushes into the bladder and subsequent aspiration of diluted sediment but should only be performed on the anaesthetised rabbit.

Any invasive procedure should be backed up by analgesic treatment. A rabbit in pain will not perform and eat adequately and will most likely develop secondary problems such as gut stasis and hepatic lipidosis.

Cystic calculi or uroliths can be seen at any age and regardless of breed. Most are composed of mainly calcium carbonate and predisposed by a diet rich in calcium. They are frequently accompanied by nephrolithiasis. Clinical history often includes previous episodes of sludgy urine. On top of that the water intake of many rabbits is suboptimal due to a variety of reasons such as limited availability of clean fresh water. Rabbits are often kept in small cages with no or little opportunity to exercise and this has also been claimed to be a predisposing factor.

Uroliths have to be removed surgically as diet changes and medication will not dissolve them. Failure to do so usually results in the formation of even bigger stones, possible displacement in the urethra and complete blockage. The latter should be considered an emergency.

Nephroliths can also be taken out surgically after assessing kidney function by blood chemistry and imaging techniques. Renal failure will develop if they are not removed.

If you have any interesting or challenging cases that you would like help with when considering your diagnostic approach please do not hesitate to contact our veterinary surgeons on 01483 797707.

Greendale Veterinary Diagnostics
Lansbury Estate
Knaphill, Woking, UK
GU21 2EP
Tel:+44 (0)1483 797 707
Fax:+44 (0) 1483 797 552

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