The liver, a delicate organ in rabbits

Michel Gruaz - Esther van Praag, Ph.D.

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The liver is a large organ that occupies a significant portion of the rabbit's abdomen. Its surface is homogeneous and red-brown in color. The liver performs both endocrine and exocrine functions, including bile secretion.

The liver of rabbits is divided into two major lobes, right and left, separated by a median fissure. The accessory lobes, the caudate lobe and the square lobe, are located between these main lobes. The liver is maintained in place in the abdominal cavity by ligaments connected to the diaphragm and to the dorsal wall of the abdomen. The liver plays a central role in the synthesis of proteins, in the metabolism of sugars, and the storage of nutrients. It is also involved in the degradation of toxins and the treatment of organic waste produced by cells of the body. It furthermore has exocrine function, with bile secretion. This balance can be disrupted by various factors, including disease, the presence of bacteria, parasites, or toxins in the diet. Liver disorders are often underdiagnosed in rabbits because the clinical signs are non-specific and lack clear characteristics.

Single and double gall bladder

The gall bladder is a hollow, pear-shaped organ that lies against the liver in the caudal surface depression. It produces bile, a viscous yellow-greenish liquid that is released into the small intestine via the bile duct. This secretion facilitates the digestion of fatty foods. In rabbits, bile is produced continuously and is stored in the gallbladder before its release into the small intestine. Bile from rabbits is primarily composed of biliverdin, which possesses potent antioxidant properties, as opposed to bilirubin. The quantity of bile produced by this animal per day is substantial, at approximately 250 milliliters. Based on weight, this is seven times the amount produced by a dog.

Normal rabbit liver and gallbladder (arrow)

The presence of a double or bilobed gall bladder is an uncommon occurrence. The gallbladder undergoes its initial development during the embryonic phase. The gallbladder is subdivided, resulting in two complete vesicles of normal size and volume. Their respective ducts transport bile to the intestine. These ducts have the capacity to either merge halfway or to remain separate. The duplication of the gallbladder appears to affect herbivores more than carnivores or humans. The duplication of the gallbladder seems to affect herbivores more than carnivores or man: 1 case out of 28 in cattle and 1 case out of 85 in sheep. Some cases have been reported in rabbits as well. This congenital anomaly is associated with various clinical manifestations, including pain and loss of appetite. In other animals, a duplicate gallbladder is often associated with biliary colic, acute inflammation of the gallbladder, or the presence of gallstones.

Michel Gruaz

Liver and double gallbladder (pocket filled with green liquid - arrows) in a Harlequin rabbit aged 3 months. Since weaning, this rabbit had regular digestive problems and weighted only 2.3 kilos, while his littermates weighed 2.8 kg.

Liver lobe torsion

The torsion of a lobe of the liver is a sporadic (non-hereditary) event whose cause is not well clarified. It is likely associated with an abnormal dilation of the stomach and intestine following an intestinal obstruction. The ligaments that hold the liver in place in the abdomen are distended and weakened, allowing the twisting of a lobe. Other potential causes include external trauma, bacterial or parasitic infection, or congenital absence of ligaments. A genetic predisposition has been identified in the Madagascar lop rabbit population. However, this remains to be verified, as the line of affected rabbits could not be established. Gestation does not cause hepatic lobe torsion in rabbits or other animals.

Torsion of the caudate lobe is observed in 63% of cases in rabbits. This lobe is attached to the liver on a very small surface, facilitating its movement in the abdominal cavity or its torsion. This results in impaired blood circulation, leading to atrophy of the lobe. The lobe's consistency changes, becoming harder and acquiring a darker color. The condition is painful and leads to decreased appetite, shock, and death after a few days. In the event of a lobe rupture, the resulting hemorrhage can lead to rapid death. A small percentage of rabbits have a positive outcome when they receive supportive care consisting of oral food assistance with a syringe, sterile subcutaneous fluids, analgesic, antimicrobial/anticoccidial, and other intestinal motility drugs. (1 to 2 cc of olive oil has also been found to be effective.).

Michel Gruaz

Liver with torsion of the small caudal lobe and content of the caudal lobe.

Bacteria, coccidia and parasites

Bacteria have the potential to invade the liver, leading to the formation of abscesses. The most prevalent bacteria identified in such cases are Pasteurella sp. and Escherichia coli. In the event of contact with birds or cattle, there is also a risk of infection from salmonella, listeria, or Yersinia sp., which causes pseudotuberculosis. As for the parasitic protozoa infecting the rabbit's liver, they include those causing coccidiosis (Eimeria stiedae) and toxoplasmosis. Coccidiosis is a prevalent disease in young animals. Their digestive system is particularly sensitive to this parasite during the transition from milk to vegetable food, which is more difficult to digest. Indications of a potential infection may include a reduction in appetite, diarrhea, the presence of mucus between hard stools, weight loss, and, in severe cases, death. A swollen belly is often observed in young rabbits. Older and healthy rabbits develop immunity against this parasite. A thorough examination of the liver reveals the presence of yellow-colored nodules on the surface. These nodules are difficult to differentiate from a bacterial abscess.

Michel Gruaz

These white structures are difficult to differentiate between abscess and coccidia.

Parasitic worms of the liver are occasional in rabbits, typically resulting from the ingestion of food contaminated by snails, dogs, or foxes. The rabbit does not host the adult parasite, but rather an intermediate form. These include the liver fluke (Fasciola hepatica), commonly found in grasslands, as well as the dog tapeworm (Taenia sp.) and the fox worm (Echinococcus multilocularis). The two latter form hydatid cysts containing the larvae of the parasite. These cysts have the potential to occupy a certain volume in the abdomen, thereby exerting pressure on the rabbit's liver. It is challenging to detect these worms in live rabbits through clinical signs.

Toxemia and liver lipidosis

is a serious disorder that occurs when there is a disruption of the energy metabolism in the late gestational rabbit. Intrauterine growth of fetuses requires significant energy. If this demand is not met with a high-calorie diet, the blood glucose level of the doe drops rapidly. The adipose tissues are mobilized and begin releasing fats into the bloodstream, which can lead to systemic poisoning. The liver is no longer able to function properly and is unable to eliminate ketone bodies. Other vital organs are also affected, including the kidneys. The pH of the urine is reduced (5-6), its color is clear, and it contains little sediments. However, it contains ketones and proteins. The intestinal transit is decreased or even halted. It is not uncommon for affected rabbits to experience diarrhea and/or a decrease in the amount of feces produced. During autopsy, the organs, including the liver, thyroid, heart, kidneys, and adrenal glands, are observed to appear pale. These organs may exhibit signs of greasy infiltrations and necrotic foci. The stomach contains minimal food. Hemorrhages are visible in both the placenta and the uterus. Another possible consequence of a difficult gestation or lactation of a large litter is hepatic lipidosis. The alternation of feed intake and refusal to eat can lead to an accumulation of fats in the liver and kidneys of the doe. Their functionality is altered. The rabbit's appetite diminishes, it exhibits lethargy, and it experiences a reduction in body mass.

Liver lipidosis can also be caused by dental problems or a diet lacking in fiber. Rabbit obesity is characterized by an abnormal accumulation of fat in liver cells linked to a diet that is too rich in sugars (and not in lipids). Rather than metabolizing and eliminating excess, the liver stores lipids in its tissues.

Michel Gruaz

Pale liver in a doe that died from gestation toxemia.

Toxins, gas fumes and pesticides

Various toxins have been shown to affect the rabbit's liver and alter its functioning. Aflatoxin, a toxin produced by molds, can contaminate cereals, affecting their quality and safety. It is highly toxic to the liver and can result in a rapid onset of death. There is a suspected link between plant toxins and neurological problems, including head down syndrome. The rabbit exhibits signs of lethargy, including a lowered head and a hunched posture, often refusing to move or feed. The severity of these symptoms varies from case to case. The prognosis for rabbits varies, with some recovering after a few days, while others do not survive. Lead and heavy metals have also been identified as factors contributing to liver dysfunction. The use of wood products such as pine sawdust or cedar, vermiculite, and other materials should be avoided in a cage or a hutch, despite their pleasant smell. It has indeed been demonstrated that the emanations of these products have toxic effects on the liver.

The effects of Pesticides on the nervous system may include hyperactivity, hypersensitivity, and/or paralysis. These symptoms may be accompanied by breathing difficulties, diarrhea, hypothermia, and/or nasal bleeding. Younger rabbits are more sensitive and affected than adults. The general state of health and nutrition of the animal is also a contributing factor. Treatment is essentially supportive, involving the administration of assisted syringed food and fluids to prevent dehydration. The autopsy of intoxicated rabbits reveals that the liver exhibits a pale coloration, accompanied by cellular hypertrophy and fatty degeneration. These disorders frequently occur before the animal enters a coma and dies.

Typical hunched position of a female rabbit, with paralysis of the hind-limbs, after a pesticide intoxication.

Lungs of the above rabbit, showing multifocal hemorrhagic regions (arrows) in the lungs.

Deformation of the spinal cord

A less common cause of liver disease is bone deformity of the spine, such as lordosis have been observed in rabbits, though not consistently. The inward curvature of the spine exerts pressure on the abdominal mass and compresses the blood vessels that drain blood from the heart to the organs and vice versa. Liver and kidneys are primarily impacted. In the liver, blood flow from the inferior vena cava is restricted, resulting in reduced hepatic activity. The secretion of bile into the intestine is decreased, which leads to a poor digestion of the ingested food. Consequently, toxins accumulate in the liver, causing it to appear congested, dark red, slightly larger than normal, and rounded with rough edges. Passive congestion of the liver may be a secondary complication of heart failure.

Michel Gruaz

The following incidental findings were made during the necropsy: lordosis of the spine (see arrow) and congested liver in a young Champagne-silver rabbit. The spinal deformation is accompanied by liver congestion, which is a possible consequence of compressed blood vessels from the heart to this organ.

Finally, the rabbit's liver can develop cancerous or bile duct tumors. Liver diseases are thus prevalent among rabbits and often difficult to identify. Indeed, signs are not very indicative of the presence of a disease. Additionally, rabbits tend to hide any signs of illness. It is important to note the following observations: droppings, their smell and shape, the presence of mucus, and the amount of water drunk. In addition, veterinary tests must be performed to establish a more precise diagnosis of liver disease.

Further information

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Coudert P., Licois D., Drouet-Viard F., Provôt F. 2000. "Coccidiosis". In: Rosell J.M. (ed), (Enfermedades del conejo), vol.II, chapter XVI, pp 219-234, Mundi-Prensa Libros, Madrid, Spain.

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