The relationship between pain levels and slow gastrointestinal motility in rabbits.

The Relationship Between Pain Levels and Gastrointestinal Hypomotility in Rabbits
(Pain scoring related to gastrointestinal hypomotility in domestic rabbits)
By Dr. Akkarapath Butsurin (Dr. Tong), Khwankham Animal Hospital

The group of gastrointestinal diseases in rabbits (rabbit gastrointestinal syndrome: RGIS) is the most common clinical issue encountered, consisting of gastrointestinal hypomotility (GIH), dysbiosis (imbalance of gut microbiota), and malocclusion (improper tooth wear). The severity of these diseases leads to the highest mortality rate in rabbits. Statistical data show that gastrointestinal diseases account for 78.24% of all rabbit deaths in captivity. Improper diet management is the primary cause of these diseases, such as insufficient hay consumption (<75%), low crude fiber intake (<20%), and high carbohydrate foods like fruits, vegetables, and treats (>5%). Additionally, stress and pain are also contributing factors.

Gastrointestinal hypomotility is the most prevalent condition in the group of gastrointestinal diseases in rabbits (44.62%). The role of dietary fiber is crucial in preventing this disease. Indigestible fibers stimulate gut motility and the function of the fusus coli, which helps form fecal pellets and produces automatic neural signals. Slow gastrointestinal motility leads to the accumulation of gas from fermentation, causing a condition known as "bloat" in rabbits.

Radiography is the standard method for diagnosing gas accumulation in the gastrointestinal tract of rabbits, and gas accumulation can be classified into four levels (grading) based on the Weerakhun method (2011). These levels are:

Level 1: Gas accumulation in the stomach, indicating the early stage after decreased gastrointestinal motility (Image 1).
Level 2: Gas accumulation in the stomach, spreading to the small intestine (Image 2).
Level 3: Gas spreading to the stomach, small intestine, and cecum (Image 3).
Level 4: Gas spreading throughout the entire gastrointestinal tract, including the large intestine.
Butsurin and Weerakhun (2012) divided the abdominal pain score in rabbits into four levels based on observations and tests:

Level 1: Slight pain and lethargy. The rabbit is still active, walking or running, but with reduced food intake and decreased or no fecal output.
Level 2: Increased abdominal pain, lethargy, curled-up posture, slightly bloated abdomen, reduced appetite, and decreased or no fecal output.
Level 3: Clear abdominal pain, severe lethargy, curled-up posture, severely bloated abdomen, and no fecal output.
Level 4: Severe abdominal pain, curled-up posture, teeth grinding due to pain, severely bloated abdomen, no fecal output, and possibly vocalizing from the pain.
Rabbits suffering from this disease typically show symptoms such as lethargy, loss of appetite, reduced or no fecal output, and abnormal fecal shapes (e.g., irregular-sized feces, jelly-like or clay-like feces). Abdominal distension occurs due to the accumulation of food, fluids, or gas in the gastrointestinal tract. Rabbits often die from abdominal pain, indicating that the level of abdominal pain significantly contributes to the mortality of this disease.

The relationship between gas accumulation levels and abdominal pain was studied in 100 rabbits with gastrointestinal hypomotility, including various sexes, breeds, ages, and weights (ranging from 6 months to over 4 years). The results showed that most rabbits exhibited pain at level 2, which was significantly different from other levels (P < 0.05). The number of rabbits in each level of gas accumulation was similar, but gas accumulation at level 4 was the least common compared to other levels (P < 0.05). Interestingly, level 4 gas accumulation was the only level where severe abdominal pain (level 4) was observed.

The classification of pain levels is highly beneficial, leading to better management decisions. Clinically, pain management often includes opioid pain relievers (e.g., buprenorphine, butorphanol, or morphine) to effectively alleviate pain. NSAIDs like meloxicam and carprofen are also used, while synthetic opioids such as tramadol have been used as alternatives to NSAIDs in Thailand for the past five years. Tramadol is typically used as the first choice for pain relief, with a dose of 2-4 mg/kg body weight, with higher doses (10-20 mg/kg body weight) used in Taiwan. Tramadol is effective for controlling pain at levels 1 and 2, but for higher levels, morphine and fentanyl are often used intravenously, with fentanyl being commonly preferred by veterinarians.

The results were satisfactory, but these medications can cause sedation, so careful dosage control is necessary. As the pain decreases or fecal output returns, it signifies a positive prognosis. In contrast, other levels of gas accumulation showed significant differences (P < 0.05), with higher levels of gas accumulation correlating with higher pain levels. Gas accumulation in levels 3 and 4 is primarily associated with pain levels 2 and 3, which were significantly different from levels 1 and 2 (P < 0.05).