Adrenalectomy and Caval Thrombectomy in a Cat With Primary Hyperaldosteronism

Surgical findings and outcomes after unilateral adrenalectomy for primary hyperaldosteronism in cats: a multi-institutional retrospective study

CASE SERIES SUMMARY

Twenty-nine cats from different institutions with confirmed or highly suspected primary hyperaldosteronism treated by unilateral adrenalectomy were retrospectively included in this study. The most frequent clinical signs were lethargy (n = 20; 69%) and neck ventroflexion (n = 17; 59%). Hypokalaemia was present in all cats, creatinine kinase was elevated in 15 and hyperaldosteronism was documented in 24. Hypertension was frequently encountered (n = 24; 89%). Preoperative treatment included potassium supplementation (n = 19; 66%), spironolactone (n = 16; 55%) and amlodipine (n = 11; 38%). There were 13 adrenal masses on the right side, 15 on the left and, in one cat, no side was reported. The median adrenal mass size was 2 × 1.5 cm (range 1-4.6 × 0.4-3.8); vascular invasion was present in five cats, involving the caudal vena cava in four cats and the renal vein in one. Median duration of surgery was 57 mins. One major intraoperative complication (3%) was reported and consisted of haemorrhage during the removal of a neoplastic thrombus from the caudal vena cava. In 4/29 cats (14%), minor postoperative complications occurred and were treated medically. One fatal complication (3%) was observed, likely due to disseminated intravascular coagulation. The median duration of hospitalisation was 4 days; 97% of cats survived to discharge. The potassium level normalised in 24 cats within 3 months of surgery; hypertension resolved in 21/23 cats. Follow-up was available for 25 cats with a median survival of 1082 days. Death in the long-term follow-up was mainly related to worsening of comorbidities.

RELEVANCE AND NOVEL INFORMATION

Adrenalectomy appears to be a safe and effective treatment with a high rate of survival and a low rate of major complications. Long-term medical treatment was not required.

Feline abdominal ultrasonography: what's normal? what's abnormal? The adrenal glands

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Ultrasound examination of the adrenal glands can provide important information pertaining to several conditions including hyperaldosteronism and hyperadrenocorticism.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even for the experienced ultrasonographer, differentiating between incidental findings, such as adrenal mineralisation, and clinically significant pathological changes can be challenging.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses the ultrasonographic examination of the normal and diseased adrenal glands. Aimed at general practitioners who wish to improve their knowledge of and confidence in feline abdominal ultrasound, this review is accompanied by high-resolution images and videos available online as supplementary material.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although the use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Primary Hyperaldosteronism in Cats: An Underdiagnosed Disorder

Primary hyperaldosteronism, also known as Conn's syndrome, is the most common adrenocortical disease in cats. As in humans, this disease is underdiagnosed in cats. Cats presenting with systemic arterial hypertension, hypokalemia, or both quite often are only treated symptomatically without further investigations. This practice may potentially exclude a significant number of cats from receiving appropriate treatment. It is therefore important for general practitioners to be aware of the disease. This article describes the (patho)physiology, clinical presentation, diagnostic approach, and treatment options of for feline primary hyperaldosteronism.

Serum aldosterone and cortisol concentrations before and after suppression with fludrocortisone in cats

Primary hyperaldosteronism is an increasingly recognized syndrome in cats, and diagnosis can be difficult. A potential diagnostic method has been reported, utilizing oral fludrocortisone administered twice daily for 4 days followed by collection of urine. In the current study, we sought to determine if blood sampling and a shorter dosing period would provide a possible means to test for primary hyperaldosteronism. Also, cortisol concentrations were measured to assess the potential of fludrocortisone to act as a glucocorticoid in cats. In phase I, 8 healthy laboratory cats were studied in a placebo-controlled, crossover design. Serum aldosterone and cortisol concentrations were measured before and on the second, third, and fourth day of treatment and compared within groups. In phase II, based on the results obtained in phase I, 8 healthy client-owned cats were administered 3 doses of fludrocortisone or placebo. Serum aldosterone and cortisol concentrations were compared before and after treatment within groups. In both phases, serum aldosterone and cortisol concentrations were significantly suppressed in fludrocortisone-treated cats. Thus, it was determined that oral administration of fludrocortisone causes suppression of serum aldosterone in healthy adult cats after only 3 doses. Further research is needed to determine the effects of oral fludrocortisone in cats with primary hyperaldosteronism and cats with other disorders causing hypertension and/or hypokalemia to determine if this protocol can be used as a tool for the definitive diagnosis of primary hyperaldosteronism.

Treatment of aldosterone-secreting adrenocortical tumors in cats by unilateral adrenalectomy: 10 cases (2002-2012)

Background

Primary hyperaldosteronism (PHA) in cats occurs as a consequence of excessive hormone production by an adrenocortical tumor. Median survival time, association between tumor type and prognosis, and the likelihood that cats require continued medical therapy after surgery have not been systematically evaluated.

Objectives

To determine the median survival time of cats with PHA treated by unilateral adrenalectomy. To examine if tumor type, anesthesia time, or tumor location (left or right side) affect survival and if affected cats require continued postoperative treatment for persistent hypertension or hypokalemia.

Animals

Ten client‐owned cats.

Methods

Retrospective study. Cats were diagnosed with PHA based on clinical signs, increased plasma aldosterone concentration, and advanced imaging. Cats underwent unilateral adrenalectomy. Survival time (days alive after surgery) was determined for each cat. Factors affecting median survival time were investigated, including histopathology, anesthesia time, and location (side) of the tumor.

Results

Eight of 10 cats survived to discharge from the hospital post adrenalectomy. Overall median survival was 1,297 days (range 2–1,582 days). The only significant factor affecting median survival time was anesthesia time >4 hours. Tumor type and location (side) did not significantly affect median survival time. No cats required continued medical treatment for PHA.

Conclusions and Clinical Importance

Although PHA in cats is still considered an uncommon condition, it should be considered in middle to older aged cats with hypokalemic polymyopathy and systemic hypertension. Surgical correction by unilateral adrenalectomy is a viable approach to definitive treatment of PHA with no need for continued medical management.

Ultrasonographic appearance of adrenal glands in healthy and sick cats

The first part of the study aimed to describe prospectively the ultrasonographic features of the adrenal glands in 94 healthy cats and 51 chronically sick cats. It confirmed the feasibility of ultrasonography of adrenal glands in healthy and chronically sick cats, which were not statistically different. The typical hypoechoic appearance of the gland surrounded by hyperechoic fat made it recognisable. A sagittal plane of the gland, not in line with the aorta, may be necessary to obtain the largest adrenal measurements. The reference intervals of adrenal measurements were inferred from the values obtained in the healthy and chronically sick cats (mean ± 0.96 SD): adrenal length was 8.9–12.5 mm; cranial height was 3.0–4.8 mm; caudal height was 3.0–4.5 mm. The second part of the study consisted of a retrospective analysis of the ultrasonographic examination of the adrenal glands in cats with adrenal diseases (six had hyperaldosteronism and four had pituitary-dependent hyperadrenocorticism) and a descriptive comparison with the reference features obtained in the control groups from the prospective study. Cats with hyperaldosteronism presented with unilateral severely enlarged adrenal glands. However, a normal contralateral gland did not preclude a contralateral infiltration in benign or malignant adrenal neoplasms. The ultrasonographic appearance of the adrenal glands could not differentiate benign and malignant lesions. The ultrasonographic appearance of pituitary-dependent hyperadrenocorticism was mainly a symmetrical adrenal enlargement; however, a substantial number of cases were within the reference intervals of adrenal size.

Primary Hyperaldosteronism

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.

Endocrine hypertension in small animals

Hypertension is classified as idiopathic or secondary. In animals with idiopathic hypertension, persistently elevated blood pressure is not caused by an identifiable underlying or predisposing disease. Until recently, more than 95% of cases of hypertension in humans were diagnosed as idiopathic. New studies have shown, however, a much higher prevalence of secondary causes, such as primary hyperaldosteronism. In dogs and cats, secondary hypertension is the most prevalent form and is subclassified into renal and endocrine hypertension. This review focuses on the most common causes of endocrine hypertension in dogs and cats.

Diagnostic and prognostic value of serum creatine-kinase activity in ill cats: a retrospective study of 601 cases

In veterinary medicine, serum creatine-kinase (CK) activity is mostly used to assess skeletal muscle damage. This retrospective study aimed to evaluate the prevalence of increased CK activity in a large, ill-cat population and to characterise associated diseases, clinical and laboratory findings and its prognostic value. Cats with a complete serum biochemistry analysis were consecutively enrolled, divided into two CK activity-based groups (within and above reference interval) and compared. The study included 601 cats. Median serum CK was 402 U/l (range 16-506870). Increased CK (>250 U/l) was observed in 364 (60%) cats, and>30-fold its upper reference limit in 43 (7%). Cats with increased CK had greater (P < or = 0.05) body weight, and were more likely to have a history of collapse, dyspnoea, abnormal lung sounds, cyanosis, shock and paraplegia, higher median serum alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase activities and total bilirubin and triglyceride concentrations, but lower, median total protein, albumin, globulin and cholesterol concentrations and proportion of anorexia than cats with normal CK. Cardiac diseases, trauma, bite wounds, systemic bacterial infections, prior anaesthesia and intramuscular injections were more common (P < or = 0.05) in cats with increased compared to normal CK activity. The hospitalisation period was longer (P=0.007) and treatment cost and mortality were higher (P<0.005) in cats with increased CK activity. However, CK activity was an inaccurate outcome predictor (area under the receiver operator characteristics curve 0.58). Increased CK activity is very common in ill cats.

Hyperaldosteronism and Hyperprogesteronism in a Cat

Clinical findings and investigations A 14-year-old female neutered domestic shorthair cat was referred for investigation of progressive hair loss, muscle wasting and hind limb weakness. Diabetes mellitus had been diagnosed 8 months earlier and was well controlled. Abnormalities on serum biochemistry included persistent mild azotaemia, hypochloridaemia, hypokalaemia, metabolic alkalosis and elevated creatine kinase. Physical examination revealed a pot-bellied appearance, with muscle wasting, marked thinning and fragility of the skin, bilaterally symmetrical alopecia, a gallop rhythm and systolic hypertension (173 mmHg). A large, lobulated left adrenal mass was identified using abdominal ultrasound.

Confirmation of diagnosis Primary hyperaldosteronism was diagnosed based on an elevated plasma aldosterone concentration and normal plasma renin activity. Hyperprogesteronism was confirmed by adrenocorticotrophic hormone stimulation test.

Practical relevance This is only the second reported case of hyperaldosteronism and hyperprogesteronism in the cat. Clinicians should be alert to the possibility of concurrent hyperaldosteronism and hyperprogesteronism in cats with adrenal tumours showing clinical signs referable to both conditions. The putative mechanism is either increased secretion of aldosterone and progesterone from neoplastic cells of the zona glomerulosa and fasciculata/reticularis, respectively, or increased production of progesterone, as an intermediate in the synthesis of aldosterone, from neoplastic cells of the zona glomerulosa alone.

Urinary cortisol/cortisone ratios in hypertensive and normotensive cats

Hypertension is a common problem in older cats, particularly associated with chronic kidney disease (CKD). Reduced activity of 11β-hydroxysteroid dehydrogenase type 2 predisposes to hypertension in human patients by allowing excessive stimulation of the mineralocorticoid receptor by cortisol. This study was designed to test the hypothesis that reduced conversion of cortisol to cortisone contributes to the development of systemic hypertension in some cats with CKD and idiopathic hypertension (iHT). The study included 60 client-owned cats: 21 clinically normal, 16 normotensive cats with CKD (NTCKD), 14 hypertensive cats with CKD (HTCKD) and nine iHTs. Urine cortisol and cortisone were extracted into dichloromethane and chloroform, respectively, prior to analysis by radioimmunoassay. Data are reported as median and range. The Kruskall–Wallis test was used to compare cortisol:cortisone ratios between groups with post-hoc testing using the Mann–Whitney U test. Wilcoxon signed-ranks test was used to compare results before and after treatment of hypertensive cats with amlodipine. The urinary cortisol:cortisone ratio was significantly higher in clinically normal cats (0.87; 0.46–1.39) when compared to NTCKD (0.60; 0.35–1.20; P<0.001), HTCKD (0.62; 0.34–1.00; P=0.002) and cats with iHT (0.65; 0.46–0.85; P=0.015). No statistical difference was detected between NTCKD, HTCKD and iHT groups. No effect of anti-hypertensive treatment on the urinary cortisol–cortisone ratio was detected ( P=0.327). Reduced urinary cortisol to cortisone conversion does not appear to be associated with systemic hypertension in cats. In fact, the cortisol to cortisone shuttle appears to be more effective in cats with CKD (hypertensive and normotensive) and iHT than clinically normal cats. The mechanism for this potentially adaptive response to kidney disease is not clear.