Journal of Feline Medicine and Surgery

Patient group It is estimated that 15–30% of geriatric cats will develop chronic kidney disease (CKD), and that 30–65% of these cats will develop anemia as their renal disease worsens. Anemia of renal disease is multifactorial in its pathogenesis, but the main cause is reduced production of erythropoietin, a renal hormone that controls the bone marrow's production of red blood cells, as kidney disease progresses.

Practical relevance It is important to recognize the presence of anemia of renal disease so that adequate treatment may be instituted to improve quality of life and metabolic function. Erythrocyte-stimulating agents (ESAs), such as epoetin alfa, epoetin beta and darbepoetin alfa, have been developed to counteract the effects of decreased erythropoietin production by the kidneys. These treatments, which are the focus of this review, have 83% similarity in amino acid sequence to the feline hormone. On average, the target packed cell volume (>25%) is reached within 3–4 weeks of ESA therapy.

Clinical challenges The use of ESAs has been associated with a number of complications, such as iron deficiency, hypertension, arthralgia, fever, seizures, polycythemia and pure red cell aplasia (PRCA). Darbepoetin has a prolonged half-life compared with epoetin and thus can be given only once a week, instead of three times a week. The incidence of PRCA appears to be decreased with darbepoetin use when compared with epoetin use in cats.

Evidence base There is limited published evidence to date to underpin the use of ESAs in cats. This review draws on the relevant publications that currently exist, and the authors’ personal experience of using these therapies for over 5 years.

Practical relevance Primary hyperaldosteronism is probably the most common adrenocortical disorder in cats. As in humans, it is often unrecognised, which excludes a potentially large number of cats from appropriate treatment.

Patient group Affected cats present at a median age of 13 years (range 5–20 years). A breed or sex predilection has not been documented. The excessive secretion of mineralocorticoids usually leads to hypokalaemia and/or systemic arterial hypertension. Most affected cats present with muscular weakness and/or ocular signs of arterial hypertension.

Diagnostics In any cat presenting with hypokalaemia and/or arterial hypertension, other potential causes should be excluded. The ratio of plasma aldosterone concentration to plasma renin activity (aldosterone:renin ratio) is currently the best screening test for feline primary hyperaldosteronism. Diagnostic imaging is required to differentiate between adrenocortical neoplasia and bilateral hyperplasia, and to detect any distant metastases.

Clinical challenges The differentiation between adrenocortical neoplasia and bilateral hyperplasia is imperative for planning optimal therapy, but the limited sensitivity of diagnostic imaging may occasionally pose a problem. For confirmed unilateral primary hyperaldosteronism, unilateral adrenalectomy is the treatment of choice, and offers an excellent prognosis, but potentially fatal intra- and postoperative haemorrhage is a reported complication and risk factors have yet to be identified.

Evidence base Only a few case reports are available on which to base the optimal diagnostic and therapeutic approach to feline primary hyperaldosteronism. This article reviews the physiology of aldosterone production and the pathophysiology of primary hyperaldosteronism, and summarises the currently available literature on the feline disease. Practical suggestions are given for the diagnostic investigation of cats with suspected primary hyperaldosteronism.

Practical relevance Calcium oxalate (CaOx) containing stones are among the most common of the urinary tract stones identified in cats.

Risk factors Risk factors for CaOx stone formation include such things as breed, gender and diet; stress and obesity have also been hypothesized to be risk factors for this disease.

Management approach A tailored, individual management strategy for preventing CaOx stone recurrence is important and should include addressing the diet, environment and any other comorbid conditions present. Increasing the cat's moisture intake is one of the key mechanisms for preventing recurrence.

Clinical challenges CaOx ureterolithiasis has emerged as a difficult and sometimes life-threatening problem for cats. In those cats where stones are found incidentally, periodic monitoring may be required to assess for disease progression. Interventional procedures such as ureteral stent placements are now increasingly being performed for recurrent cases or those with larger stone burdens. Periodic radiographs for more severe cases and frequent client communication can help ensure successful outcomes for cats with lower and upper CaOx stone disease.

Evidence base Limited evidence-based studies are published regarding management of feline upper and lower urinary tract CaOx stone disease, making this a difficult condition to manage in some cats. Studies designed to evaluate the relationship to dietary modifications, medical management, stress, obesity and surgical techniques are warranted in cats with upper and lower urinary tract CaOx stones.

Ethical issues Caring for cancer patients presents many ethical issues for veterinarians and other veterinary health workers. The issues that most veterinarians think of relate to management of the patient when the owners’ preferences for treatment do not appear to be in the animal's best interest, as well as concerns about toxicities and about costs of veterinary services (advanced imaging, surgery, radiation therapy and chemotherapy). While not limited to the veterinary profession, we are more often faced with dilemmas about the appropriateness of palliative care and decisions about euthanasia than our medical colleagues. Equally important are the ethics of not treating patients, and the integration of unproven and alternative strategies into conventional care. A separate ethical issue arises from investigational therapies and research. Less often considered, but nonetheless relevant, are the ethics of suboptimal evaluation (staging) of patients prior to treatment, or of not informing owners about all the options available.

Client communication Ethical veterinary care is intertwined with good client communication. Without good communication, it is impossible, for example, to gain informed consent; and without informed consent, the ethics of cancer treatment are uncertain.

Goal This article, which draws in part on published research, where stated, and otherwise on the author's personal experiences/opinions and those of veterinary colleagues, is intended to provoke further thought and discussion on the ethics of caring for our cancer patients.

Presentation and lesion localisation Seven adult domestic shorthair cats were presented with a 1- to 6-day history of progressive neurological signs. A focal skin puncture and subcutaneous swelling over the dorsal part of the head were detected on physical examination. Neurological examination indicated lesion(s) in the right forebrain in four cats, multifocal forebrain in one cat, left forebrain in one cat, and multifocal forebrain and brainstem in the remaining cat. In all cats, magnetic resonance imaging revealed a space-occupying forebrain lesion causing a severe mass effect on adjacent brain parenchyma.

Clinical approach and outcome All cats were managed with a combination of medical and surgical treatment. At surgery a small penetrating calvarial fracture was detected in all cats, and a tooth fragment was found within the content of the abscess in two cats. The combination of surgical intervention, intensive care and intravenous antimicrobials led to a return to normal neurological function in five cats.

Practical relevance As this series of cases indicates, successful resolution of a brain abscess due to a bite injury depends on early recognition and combined used of antimicrobials and surgical intervention. A particular aim of surgery is to remove any skull and foreign body (tooth) fragments that may represent a continuing focus of infection.