Detecting Metabolic Bone Diseases
Authored by: Christina Miller CAHT/RVT, RLAT, BSc
In our continuing series Metabolic Diseases in Reptile and Amphibians we learn this week about the techniques and tools used to detect Metabolic Bone Disease in Reptiles
Creating an accurate diagnosis has a multi-modal approach from the veterinary team, which will likely include your veterinarian and a veterinary technician or nurse:
Husbandry Evaluation
Captive Reptile Husbandry (affiliate link)
Record keeping is probably the most underrated skill in the history of herpetoculture.
It never hurts and only helps to maintain records of feeding schedules, supplementation schedules, temperature checks, equipment changes, behavioural changes, and anything else that could be remotely useful (heads up, this is a future herp health article topic!).
That being said, the husbandry examination is also an assurance to the veterinary team; the pet won’t be going back to the same husbandry mistake(s) that lead them into the vet’s office in the first place. It’s the veterinarian’s onus to ensure there’s a valid client-doctor-patient relationship. If as a pet owner you refuse to disclose husbandry details or will not make husbandry changes based on the professional’s recommendation, this is a violation of that relationship that is in place for your companion’s benefit. Remember the veterinary team has to advocate for a patient who cannot speak for themselves. Veterinary professionals want to trust that you will provide them with accurate details, that you will comply with their recommendations, and if you have a problem with a recommendation that you discuss it with them instead of going home and doing something completely different.
It’s okay to ask more questions if you disagree with or do not understand a recommendation for your pet.
Physical Exam
A detailed physical exam is necessary to document all normal and abnormal findings, to later refer to when noting progress. Depending on the practice, the veterinary technician may begin the exam for the veterinarian. Details are very important, especially in diseases that have no single, typical presentation like with metabolic bone diseases. Some practices will take photographs to attach to your pet’s file to monitor progression or resolution of physical abnormalities. There is no typical, guaranteed set of deformities that occur in every suspected MBD patient (Mader 2006).
Diagnostic Tests
Your veterinarian will likely ask for permission to run some diagnostic tests to help develop a clearer picture of your pet’s diagnosis and to provide a more accurate prognosis.
Radiography (x-ray) should absolutely be performed on any animal who may be presenting with a metabolic bone disease. This type of diagnostic imaging will reveal the animal’s bone density, giving the veterinary team an idea of how far the disease process has progressed. It also helps screen for pathological fractures that need to be addressed and potentially stabilized, and may reveal other findings (Mader 2006). The veterinarian may perform one “full body” survey film for smaller animals, but larger animals may need more views, and areas to focus on (such as suspected fractures) may require additional views, as well.
Blood Work may be requested by the doctor to get a better idea of how the animal is doing overall. While calcium levels will be normal except in the most advanced stages of MBD, assessing organ function and blood cell counts can help diagnose or rule out other concurrent diseases. If the veterinarian has any suspicion that there may be other health problems occurring in your pet, it is justifiable to perform blood work. A good doctor treats the whole patient, not just the complaint being presented for.
Renal Secondary Hyperparathyroidism
The above diagnostic tools help to determine the cause of the metabolic bone disease, which is not always simple. Renal secondary hyperparathyroidism (RSHP) manifests clinically in a similar way to NSHP (Mader 2006). Kidney disease may be associated with hyperphosphatemia due to the kidneys’ reduced capacity to excrete excess phosphorus into the urine. As seen in part one, when blood phosphorus concentrations rise, calcium concentrations decrease, which initiates the parathyroid hormone loop (Thrall et al. 2004). This results in the same physiological response as NSHP. Renal disease requires management that differs from NSHP in reptiles and amphibians (Hernandez-Divers and Innis 2006), although RSHP-related pathologies also need to be treated accordingly.
Footnote: Cognitive bias is a very interesting and important area of psychology, and in the author’s opinion, being aware of your existing biases makes you a better scientist, and dare I say a better person. As veterinary professionals, we are working with people who are in a variety of mental states including fear and stress, and acknowledging that people (including ourselves) inherently have biases helps us make more rational decisions. While this is by no means a peer-reviewed journal, the following article on iO9 is a useful read: 12 Cognitive Biases that Keep you from being Rational
*Next Christina discusses the Prevention of Husbandry Errors
References:
Mader, DR. 2006. Metabolic Bone Diseases. In: Reptile Medicine and Surgery (2nd edition). DR Mader (editor). Saunders Elsevier, St. Louis, Missouri, USA.
Thrall, MA, TW Campbell, D DeNicola, MJ Fettman, ED Lassen, A Rebar, G Weiser. 2004. Veterinary Hematology and Clinical Chemistry. Lippencott Williams & Wilkins, Baltimore, Maryland, USA.
Hernandez-Divers, SJ and CJ Innis. 2006. Renal Disease in Reptiles: Diagnosis and Clinical Management. In: Reptile Medicine and Surgery (2nd edition). DR Mader (editor). Saunders Elsevier, St. Louis, Missouri, USA.