Rabbit Radiology

Karen L. Rosenthal, DVM, MS, Diplomate ABVP-Avian
Director, Special Species Medicine
Clinical Studies-Philadelphia
University of Pennsylvania
School of Veterinary Medicine
Philadelphia, PA 19104

The normal rabbit radiographic presentation is also not unlike that of other mammals. Rabbits have a relatively small thoracic cavity. Heart disease is becoming a more recognized problem, especially in older rabbits. Radiographic signs include an enlarged heart shadow, an elevated trachea, and pleural effusion. Lower respiratory disease is common in rabbits and radiographic signs of inflitrative respiratory disease are frequently identified on rabbit radiographs. Thoracic masses (usually neoplastic) have also been identified on rabbit radiographs.

The normal rabbit radiograph reveals a relatively large abdominal region. Typically, in the rabbit abdominal radiograph the following organs can be identified: stomach, intestines, bladder, kidneys, and liver. The kidneys may appear displaced ventrally by fat in the retroperitoneal space. It is normal to be able to identify different areas of the gastrointestinal tract including the stomach, duodenum, cecum, and large intestine.

Gastrointestinal disease is common in rabbits. The most common disorder is gastrointestinal ileus. This is seen as a gas filled stomach and/or gas filled intestines, especially the cecum. A radio-opacity can also be seen in the stomach which may be a combination of ingesta, hair, and fluid. If only a greatly distended stomach is observed, this may represent a true obstruction. Usually, a pyloric obstruction is characterized by a large, fluid filled stomach and the intestines may look normal. A true obstructive pattern is rare in rabbits. If an obstruction is present and not treated, the stomach may rupture. The presence of a ruptured stomach in a rabbit is seen radiographically as free gas in the abdomen. Loss of detail may also occur if a significant amount of fluid has entered the abdominal cavity. Ileus is characterized by a diffuse gastrointestinal gas pattern. It is not uncommon to see a greatly enlarged cecum filled with gas. Contrast radiographs can be used to differentiate between ileus and obstruction but can be difficult to interpret in rabbits.

Urolithiasis is the most common urinary tract problem observed on rabbit radiographs. Urolithiasis describes the presence of either urinary tract calculi, bladder sand, or "bladder sludge." Renal and ureteral calculi are less commonly observed but can be present at the same time. It may be difficult radiographically to discriminate between renal calculi and renal mineralization and dystrophic calcification. Calculi are most common in the bladder. They can also be identified in the urethra. Bladder sand or bladder sludge are common forms of urolithiasis observed in rabbits. In intact females, check abdominal radiographs for evidence of an abnormal uterus. This is viewed radiographically as an increase in uterine size, increase in radio-opacity, and displacement of other organs. A diseased uterus is easily visible between the colon and bladder. The differential diagnoses for a prominent radiographic uterus includes neoplasia, endometrial hyperplasia, pyometra, hydrometra, and pregnancy. Pregnancy is characterized, usually, by multiple fetal skeletal outlines.

Radiographically, the rabbit skeleton shows a decreased bony radiopacity as would be expected in other mammals. The skeleton is only 8% of the rabbit's body weight. Orthopedic disease such as fractures and luxations are not uncommon. Vertebral fracture is a common sequel to improper handling procedures. Many of the vertebral fractures are present in the lumbar area and step fractures are not uncommon. Rabbit jaw abscesses are a common problem and quality skull radiographs are important in the characterization of this disease. Bony invasion of a jaw abscess is a poor prognostic indicator. Dental disease is another common problem in pet rabbits. The radiographic appearance of the dental arcades and tooth roots helps determine the extent of disease and allows for a prognosis and treatment planning.

Middle and inner ear disease are common problems found in pet rabbits. Chronic otitis media can lead to bulla disease. Good, quality skull radiographs taken while the rabbit is anesthetized are imperative in diagnosing chronic otitis media/interna. The bulla appear sclerotic in appearance with uneven edges to the bulla.