Computed tomography in small animals--basic principles and state of the art applications

Since its clinical introduction, computed tomography (CT) has revolutionized veterinary medicine and is considered to be one of the most valuable tools for the imaging work-up of neurological, oncological and orthopaedic canine and feline patients. In small animals with acute trauma, particularly those involving complex anatomic areas such as the head, spine or pelvis, CT has been established as a standard imaging method. With the increasing availability of radiation therapy in veterinary medicine, CT has also become the principal tool to stage a tumour, assess response, and guide radiation therapy. The increasing availability of helical CT in veterinary medicine has allowed novel techniques such as spiral CT angiography and high-resolution CT. This review provides a brief overview of the historical and technical development of CT and literature reviews of the major clinical CT applications in small animals such as intracranial and extracranial lesions, the spine, the appendicular skeleton, and abdominal and thoracic diseases.     

Application of Airway Pressure Therapy in Veterinary Critical Care: Part II: Airway Pressure Therapy

As the specialties of emergency medicine and critical care have grown and evolved in both human and veterinary medicine, so has the need for more advanced care of patients with primary lung disease. Treatment of acute respiratory failure has been the focus of several articles in the human medical literature of the past few years.^1,8 This paper deals with airway pressure therapy and its application in cases of acute respiratory failure in veterinary medicine. The reader is referred to part I of this paper for a reveiw of respiratory mechanics and hypoxemia as they apply to respiratory therapy.     

Ibuprofen toxicosis in a dog

Acute renal failure, vomiting, and melena developed in a 10-month-old dog after ingestion of ten 600-mg tablets of ibuprofen. After 5 days of IV fluid therapy, clinical signs resolved and azotemia decreased. With increased availability of nonsteroidal anti-inflammatory drugs, similar complications may become more common in veterinary practice. If acute renal failure should develop, the prognosis for recovery is good, with rapid institution of appropriate therapy. However, renal dysfunction may not be completely reversed.     

Photodynamic therapy for companion animals with cancer.

Photodynamic therapy is an emerging form of cancer therapy in veterinary medicine, which capitalizes on a photochemical reaction to kill malignant cells. Photodynamic therapy has been used to successfully treat a variety of veterinary cancers, with documented efficacy similar to radiation therapy. However, equipment expense and availability of photosensitizer have limited the widespread use of photodynamic therapy by veterinarians.     

Causes of respiratory failure.

There are many causes of respiratory failure in veterinary patients. Assessment of oxygenation is imperative for the diagnosis and monitoring of these patients. Oxygen therapy should be instituted when hypoxemia is diagnosed to prevent tissue hypoxia, end-organ damage, and death. Methods of administering oxygen include commercial oxygen cages, mask oxygen, nasal cannulation (for dogs), and intubation. Mechanical ventilation is an option in many referral hospitals for patients who are severely hypoxemic and are not responding to inspired oxygen concentrations achieved with other methods of oxygen administration. One rule of thumb used to assess need for mechanical ventilation is a PaO2 of less than 50 mm Hg despite aggressive oxygen therapy, or a PaCO2 of greater than 50 mm Hg despite treatment for causes of hypoventilation. A mechanical ventilator has the ability to vary the FiO2 by increments of one, from 21% to 100% (0.21-1) oxygen in inspired gas. Positive end-expiratory pressure (PEEP) is also available on most ventilators. PEEP allows the alveoli to remain open on expiration, allowing gas exchange to occur in both inspiration and expiration. PEEP also helps diseased alveoli to inflate, increasing the available surface area for gas exchange and improving arterial blood oxygen tension. Because patients requiring mechanical ventilation have severe respiratory failure that did not respond to conventional oxygen therapy, the prognosis is guarded for most of these patients unless ventilation is instituted due to primary hypoventilation and lung parenchyma is normal. Hypoxemia caused by respiratory failure is a common problem in small animal veterinary patients. Assessment of blood oxygenation and continual monitoring of respiratory rate and effort are essential in management of these patients. Oxygen therapy should be instituted if hypoxemia is diagnosed. The prognosis depends on the underlying disease process and response to treatment with an enriched oxygen environment.     

Feline ureteral obstructions Part 1: medical management

Feline ureteral obstructions are an increasingly recognised and challenging diagnostic and management problem. Many cats with ureteral obstructions are critically ill at the time of diagnosis, especially if there is dysfunction of the contralateral kidney. They may present with varying severities of acute kidney injury, electrolyte disturbances, and may have comorbidities such as heart disease that complicate perioperative and long‐term management. Medical management, which may consist of rehydration and restoration of intravascular volume with intravenous fluid therapy, osmotic diuresis, ureteral muscle relaxation, and antimicrobials for infection, is important in feline ureteral obstruction patients. Despite medical management, many cats with ureteral obstructions will require decompression of the obstructed kidney to relieve pressure‐nephropathy and restore urine flow. However, some cats may be too unstable for traditional medical management and require more emergent intervention to relieve the obstruction and address the life‐threatening sequelae to acute kidney injury, such as hyperkalaemia and fluid overload. Both surgical and interventional methods to address ureteral obstructions have been described in veterinary medicine, though debate continues as to the ideal approach.     

Application of Airway Pressure Therapy in Veterinary Critical Care: Part I: Respiratory Mechanics and Hypoxemia

Over the past several decades, recognition of acute respiratory failure as the cause of death in patients suffering from various clinical conditions has prompted aggressiv investigation into the area of respiratory physiology and supportive respiratory care. With the evolution of emergency medicine and critical care services in both human and veterinary medicine, many patients previously considered unsalvageable due to the severity of their underlying disease are now being resuscitated and successfully supported, creating a new population of critically ill patients. Where only a decade ago these patients would have succumbed to their underlying disease, they now survive long enough to manifest the complications of shock and tissue injury in the form of acute respiratory failure. Investigation into the pathophysiology and treatment of this acute respiratory distress syndrom (ARDS) has facilitated increased clinical application of respiratory theerapy and machanical ventilation.¹ The purpose of this paper is to provide a basic review of respiratory mechanics and the pathophysiology of hypoxemia as they relate to airway pressure therapy in veterinary patients and to review the use of airway pressure therapy in veterinary patients This paper is divided into two parts; part I reviews respiratory mechanics and hypoxemia as they apply to respiratory therapy, while part II deals specifically with airway pressure therapy andits use in clinical cases.     

Use of dopamine in acute renal failure

Objective: To review the current understanding of dopamine and its use in the prevention and treatment of acute renal failure (ARF). Data sources: Original research articles and scientific reviews. Human data synthesis: Low‐dose dopamine administration has been shown to increase natriuresis and urinary output in both healthy individuals and in a few small studies in human patients with renal insufficiency. However, in several large meta‐analyses, dopamine treatment did not change mortality or the need for dialysis. Due to the potential side effects, the use of dopamine for prevention and treatment of ARF is no longer recommended in human medicine. Veterinary data synthesis: Low‐dose dopamine increases urinary output in healthy animals and animal models of ARF if given before the insult. There are no available studies looking at the effect of low‐dose dopamine therapy in naturally occurring ARF in dogs or cats. Conclusion: Due to the potential side effects of low‐dose dopamine therapy, the results from large human trials, and the lack of information in veterinary medicine, the use of dopamine for treatment of ARF in veterinary patients should be further evaluated.     

Quality documentation challenges for veterinary clinical pathology laboratories

An increasing number of veterinary laboratories worldwide have obtained or are seeking certification based on international standards, such as the International Organization for Standardization/International Electrotechnical Commission 17025. Compliance with any certification standard or quality management system requires quality documentation, an activity that may present several unique challenges in the case of veterinary laboratories. Research specifically addressing quality documentation is conspicuously absent in the veterinary literature. This article provides an overview of the quality system documentation needed to comply with a quality management system with an emphasis on preparing written standard operating procedures specific for veterinary laboratories. In addition, the quality documentation challenges that are unique to veterinary clinical pathology laboratories are critically evaluated against the existing quality standards and discussed with respect to possible solutions and/or recommended courses of action. Documentation challenges include the establishment of quality requirements for veterinary tests, the use or modification of human analytic methods for animal samples, the limited availability of quality control materials satisfactory for veterinary clinical pathology laboratories, the limited availability of veterinary proficiency programs, and the complications in establishing species-specific reference intervals.     

Echocardiography for the diagnosis of congenital heart defects in the dog

Echocardiography utilizing M-mode and real-time techniques is a safe, noninvasive diagnostic technique for use in veterinary cardiology. It provides a means to assess structural sizes and relationships and can be used to provide quantitative data for diagnosis of congenital heart disease. Although its availability is largely limited to veterinary colleges and specialty hospitals, the practicing veterinarian should know of its advantages and disadvantages. He or she is also encouraged to consider the use of ultrasound in the diagnosis and management of heart disease in all species of veterinary patients.     

Phosphorus and phosphate metabolism in veterinary patients

Objective: To review phosphorus and phosphate metabolism and the importance of phosphate abnormalities in veterinary patients. Data sources: A review of recent human and veterinary medical literature. Human data synthesis: There is a significant amount of original research on human patients with phosphate abnormalities. Hypophosphatemia has been studied in patients with diabetic ketoacidosis (DKA), head trauma, refeeding syndrome, hypothermia and in ventilator patients that fail to wean. Hyperphosphatemia has been studied in patients with renal failure and malignancy. Phosphate levels have also been evaluated for prognostic value in sepsis and acute liver failure. Veterinary data synthesis: Although animal models were used in early experimental research, fewer studies have been published on the effects of phosphate abnormalities in veterinary patients. Hypophosphatemia has been studied in animals with DKA, with refeeding syndrome and with hyperparathyroidism. Hyperphosphatemia has been studied in animals with renal failure and with secondary hypoparathyroidism. Conclusion: Phosphorus and phosphate are important in many biological functions. This paper is a review of their role in normal metabolism and the clinical importance of phosphate imbalances for our emergency and critical care patients.     

The future of radiotherapy in small animals – should the fractions be coarse or fine?

Radiation therapy has been used to treat animal cancers for more than 100 years. Clinical experiences and experimental results have been widely published and provide a basis for the recognition of radiation therapy as an integral component of multimodal cancer management in veterinary oncology. As the expectations of pet owners and the demand for treatment of companion animals with cancer have increased, veterinary oncology itself has undergone dramatic advances in the past several decades both in terms of improved diagnostics and treatments, including increased accessibility of radiation therapy. Synchronous with development of the specialism of veterinary radiation oncology, confusion and controversy have arisen with regard to distinguishing between different types of radiotherapy and methods of treatment delivery. Importantly, the confusion extends beyond semantics, and includes opinionated debate about defining which forms of therapy (if any at all) are optimal for a given patient. This exemplifies how, despite marks of maturity including age and a robust publication history, the field of veterinary radiation oncology is in some ways still in its infancy. The purpose of this article is to review the evidence base for daily (fine) fractionation versus weekly (coarse) hypofractionation in veterinary oncology, using selected tumour types as examples.     

Colloids: current recommendations.

Colloids are increasingly becoming considered indispensable in the management of critically ill patients. Typical indications for colloid administration include patients with tissue edema, hypovolemia, and low oncotic pressure. Current guidelines for the use of colloids in veterinary patients balance the purported benefits of colloid fluid administration with the potential risks, such as volume overload and coagulation disturbances. This article focuses primarily on hydroxyethyl starches, because they are the most commonly used colloid in veterinary practice, and because recent advances in colloid therapy have been achieved with this colloid. Newer colloids have been modified to limit effects on the coagulation system, and they may be used to modulate the inflammatory response, which could prove to be particularly useful in the management of critically ill patients. A better understanding of how different fluids influence the host response may enable us to explore new applications of fluid replacement therapy beyond simply replenishing volume deficits.     

Paraneoplastic disorders in dogs with hematopoietic tumors

Often overlooked in the presence of neoplasia, PNDs constitute significant clinical entities in dogs with hematopoietic tumors. They may cause morbidity and mortality in such patients, with effects more severe than those caused by the associated tumor. Accurate clinical evaluation of these disorders is important in differential diagnosis and treatment, for failure to realize that cancer can produce many clinical signs similar to those of other diseases may lead to incorrect diagnosis and delayed therapy. Early recognition of the problem underlying the PND is essential to selecting the proper therapeutic approach and maximizing the patient's chances for remission and survival. The presence of these disorders may complicate or rule out the preferred therapy in some cases of hematopoietic neoplasia, because the addition of cytotoxic drugs may worsen the existing PND, predisposing the dog to a variety of complications. Appropriate management of the PND may be of more immediate importance than treatment of the tumor. The study and recognition of PNDs in dogs with hematopoietic tumors may be valuable for a number of reasons: to facilitate early diagnosis of the tumor, for the observed abnormalities may represent tumor cell markers; to allow assessment of premalignant states; to aid in the search for metastases; to help quantify and monitor response to therapy; to aid in the evaluation of tumor recurrence or progression; to aid in identifying specific pathophysiologic processes by which cancer produces systemic effects; and to provide insight into the study of malignant transformation. Recognition of PNDs is relevant to the diagnosis and treatment of many problems in veterinary cancer medicine. With increasing emphasis on diagnosis and treatment of canine hematopoietic tumors, PNDs will be recognized with greater frequency and will assume greater importance in the therapeutic management of those patients. Research in veterinary and human cancer medicine needs to be directed toward identifying more definitively those substances and pathways that are responsible for PNDs, because therapy directed toward arresting the specific pathophysiologic processes causing the PND may offer the best approach for successful management of cancer.     

The use of erythropoietin.

EPO is a hematopoietic growth factor produced in the kidney that stimulates erythropoiesis. It effectively treats hypoproliferative anemia associated with CRF, improving quality of life in these patients. Other uses that are poorly characterized in veterinary medicine include treatment of cancer patients on chemotherapy, hematologic disorders, and anemic FeLV-infected cats as well as preoperative conditioning for elective surgeries that may involve significant blood loss. Careful monitoring of therapy is necessary for optimal results. Several complications are associated with rHuEPO therapy. The production of anti-rHuEPO antibodies is the most significant and can be a life-threatening event. Alternatives to human EPO are being sought to provide beneficial effects while avoiding antibody formation.     

Applications and Outcome of Hemodialysis in Cats: A Review of 29 Cases

Hemodialysis (HO) has been used in the management of renal failure in dogs, but its feasibility has not been reported for uremic cats. Therefore, we investigated the technical possibility, efficacy, and complications of intermittent HD in cats with severe uremia. A total of 160 HD treatments were performed on 29 cats with acute renal failure (ARF) (n = 15), chronic renal failure (CRF) (n = 6), or acute on CRF (n =8) between November 1993 and June 1996. Hemodialysis treatments were performed with transcutaneous dialysis catheters using a bicarbonate-based delivery system, sodium modeling, and volumetric-controlled ultrafiltration. Presenting serum chemistries (mean ± SD) for all cats were creatinine, 16.4 ± 7.5 mg/dL; blood urea nitrogen (BUN), 229 ± 87 mg/dL; phosphate, 15.4 ± 5.4 mg/dL; potassium, 6.0 ±1.6 mEq/L; and HCO^-₃, 16.0 ± 4.4 mEq/L. For intensive HD treatments, pre-HD versus post-HD creatinine changed from 10.3 ± 4.4 to 1.6 ± 0.9 mg/dL and BUN from 105 ± 33 to 8 ±10 mg/dL. One or more adverse events occurred during 111 (69%) treatments. Dialysis-related events included hypotension, dialysis dysequilibrium, clotting, and bleeding. Nine of 15 (60%) cats with ARF and 1 cat with CRF recovered sufficiently to survive without ongoing need for HD. For the remaining cats, the proximate causes of death were dialysis related in 9 cats, uremia related in 6 cats, and iatrogenic or unknown in 4 cats. Hemodialysis is technically feasible and effectively controls the biochemical disturbances of uremic cats. It is especially valuable for the management of severe ARF, permitting recovery in a large number of cats refractory to conventional therapy. Technical complications and chronic debility, however, may limit its usefulness for cats with advanced CRF.     

Animal health in organic agriculture: new guidelines and perspectives for food animal practitioners

In the last decade, the organic agriculture in Switzerland has been substantially increased due to the interest of consumer and financial incentives of the federation. Ruminants take directly or indirectly the largest part from grassland used within the organic managed surfaces. As the contacts between veterinary practice and organic agriculture has increased, the potential for veterinary activity in this area has developed considerably. The organic agriculture guidelines stipulate that all the preventive measures should be taken in feeding, keeping and breeding to insure animal health safety. This requires veterinary services for herd management. The organic status of a farm affects veterinary practice also in the form of alternative therapy/drugs administration and measures like dehorning and tail-docking. An important point in organic managed herds requests that treatment of animals should depend on alternative medical preparations or procedures based on veterinarian's experience and also on the therapeutic effect on the animal species concerned as well as on the disease. However, there are no restrictions on the veterinarian to use registered drugs as long as no alternative therapy, according to experience and possible success, is available to treat the animals. The prophylactic administration of allopathic veterinary drugs is not permissible. Further features in organic farms regarding the use of drugs are the keeping of withholding/withdrawal time, the documentation and the treatment frequency tolerated by organic marketing. Despite the above measures, the animal health has a priority regardless of its organic status. Although management of organic farms represent a unique responsibility, there are still obvious deficits in the education of veterinary practitioners for this new situation. However, in the future the extension of veterinary activity to include the alternative medical therapy should be regarded for the practitioner as a challenge and an opportunity at the same time.     

Dietary principles in disease management

Nutritional management of medical and surgical animal patients to provide better total health care is not a new concept, but one that has gained credibility in veterinary medicine in the 1980s. Therapeutic dietary management is an alteration of diets intended to provide optimal health in pets by restricting, moderating, or enhancing nutrients and/or manipulating dietary ingredients. In many cases, dietary therapy is an integral component of animal patient management that may complement or even replace drug administration or surgery.     

Transfusion issues in the cancer patient

Blood transfusions are a lifesaving but transient therapy used to correct deficiencies of blood cells and coagulation factors that occur in cancer patients. Anemia can occur in cancer patients as a result of hemolysis, blood loss, or bone marrow failure. The blood component most commonly recommended for the treatment of anemia is packed red blood cells. Coagulation disorders are common with hemangiosarcoma and diffuse hepatic tumors. Fresh frozen plasma is used as a source for replacement coagulation factors for the treatment of disseminated intravascular coagulation or other cancer-associated coagulopathies. Although thrombocytopenia and neutropenia can be the result of bone-marrow failure from tumor infiltration, chemotherapy, or radiation therapy, these platelets and neutrophils are rarely transfused to veterinary cancer patients. Pretransufsion testing consists of blood typing in cats, and cross matching in dogs and cats if the dog has previously been transfused. Cancer patients receiving transfusions should be monitored on a continual basis during and immediately following the transfusion to enable early identification of an adverse event, allowing the transfusion to be discontinued.