Abdominal ultrasonographic findings in acromegalic cats

Acromegaly in humans and cats: Pathophysiological, clinical and management resemblances and differences

OBJECTIVE

Acromegaly is a disorder associated with excessive levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). In general, GH/IGF-1 excess leads to morphologic craniofacial and acral changes as well as cardiometabolic complications, but the phenotypic changes and clinical presentation of acromegaly differ across species. Here, we review the pathophysiology, clinical presentation and management of acromegaly in humans and cats, and we provide a systematic comparison between this disease across these different species.

DESIGN

A comprehensive literature review of pathophysiology, clinical features, diagnosis and management of acromegaly in humans and in cats was performed.

RESULTS

Acromegaly is associated with prominent craniofacial changes in both species: frontal bossing, enlarged nose, ears and lips, and protuberant cheekbones are typically encountered in humans, whereas increased width of the head and skull enlargement are commonly found in cats. Malocclusion, prognathism, dental diastema and upper airway obstruction by soft tissue enlargement are reported in both species, as well as continuous growth and widening of extremities resulting in osteoarticular compromise. Increase of articular joint cartilage thickness, vertebral fractures and spine malalignment is more evident in humans, while arthropathy and spondylosis deformans may also occur in cats. Generalized organomegaly is equally observed in both species. Other similarities between humans and cats with acromegaly include heart failure, ventricular hypertrophy, diabetes mellitus, and an overall increased cardiometabolic risk. In GH-secreting pituitary tumours, local compressive effects and behavioral changes are mostly observed in humans, but also present in cats. Cutis verticis gyrata and skin tags are exclusively found in humans, while palmigrade/plantigrade stance may occur in some acromegalic cats. Serum IGF-1 is used for acromegaly diagnosis in both species, but an oral glucose tolerance test with GH measurement is only useful in humans, as glucose load does not inhibit GH secretion in cats. Imaging studies are regularly performed in both species after biochemical diagnosis of acromegaly. Hypophysectomy is the first line treatment for humans and cats, although not always available in veterinary medicine.

CONCLUSION

Acromegaly in humans and cats has substantial similarities, as a result of common pathophysiological mechanisms, however species-specific features may be found.

Feline Comorbidities: Hypersomatotropism-induced diabetes in cats

PRACTICAL RELEVANCE

Diabetes mellitus is the second-most common feline endocrinopathy, affecting an estimated 1/200 cats. While the underlying causes vary, around 15-25% of cats with diabetes mellitus develop the condition secondarily to progressive growth hormone (GH)-induced insulin resistance. This typically results in a form of diabetes that is challenging to manage, whereby the response to insulin is very variable or high doses are required to achieve even minimal diabetic control.

CLINICAL CHALLENGES

Although uncontrolled chronic excessive GH may result in phenotypic changes that raise suspicion for acromegaly, many cats with hypersomatotropism (HST) do not have these changes. In these situations, a clinician's index of suspicion may be increased by the presence of less dramatic changes such as marked polyphagia, stertor or uncontrolled diabetes mellitus. The current diagnostic test of choice is demonstration of a markedly increased serum insulin-like growth factor 1 (IGF1) concentration, but some affected cats will have only a marginal increase; additionally, chronic insulin administration in cats results in an increase in serum IGF1, making the diagnosis less clear cut and requiring additional confirmatory tests.

EVIDENCE BASE

Over the past two decades, HST has increasingly been recognised as an underlying cause of diabetes mellitus in cats. This review, which focuses on diagnosis and treatment, utilises data from observational studies, clinical trials and case series, as well as drawing on the experience of the authors in managing this condition.

Ultrasonographic Detected Adrenomegaly in Clinically Ill Cats: A Retrospective Study

This retrospective study aimed to assess the prevalence of ultrasonographic detected adrenomegaly in clinically ill cats, evaluating the final established diagnosis, describe adrenal ultrasound findings and if the adrenomegaly was suspected or incidental. Abdominal ultrasonography reports of cats presenting to a veterinary teaching hospital between October 2018 and February 2021 were retrospectively reviewed. Cats showing adrenomegaly (one or both glands having a dorsoventral axis >4.8 mm) were selected and medical records respectively evaluated. Nine-hundred and eighty-three ultrasonographical reports were selected, of which, 68 (7%) disclosed adrenomegaly. European/Domestic Short-Hair (62/68; 91%) male (44/68; 65%) castrated (35/44; 80%) cats were overrepresented. Adrenomegaly was an incidental finding in 62/68 (91%) cats while in 6/68 (9%) it was identified in the context of investigating a potential adrenal disease. Concerning established diagnosis, chronic kidney disease was overrepresented (25/68; 37%), followed by endocrinopathies (20/68; 29%). Adrenomegaly was bilateral in 53% (36/68) of cases. In unilateral cases (32/68; 47%), it was more prevalent on the left side (23/32; 72%), with a normal-sized contralateral adrenal gland. Left adrenal demonstrated a larger size and a tendency to oval shape. This study assesses the prevalence of adrenomegaly in clinically ill cats, reinforcing it can be an incidental ultrasound finding.

Ultrasonographic evaluation of adrenal gland size in two body weight categories of healthy adult cats

OBJECTIVES

Adrenal gland size and its association with body weight have been rarely evaluated in cats. This study was undertaken to assess the association between feline body weight and adrenal gland thickness, and to propose reference intervals (RIs) for adrenal gland thickness in healthy cats.

METHODS

This was a cross-sectional study in which 39 healthy cats were included. The cats were divided into two weight categories, classified as ⩽4.0 kg and >4-8 kg of ideal body weight (with 13 and 26 cats in each group, respectively), which took into consideration the body condition score of the cats. All cats underwent an ultrasound examination that was taken from a subcostal position. Maximum dorsoventral thicknesses of the left (MTL) and right (MTR) adrenal glands were measured in a sagittal plane. RIs were obtained for the maximum thickness (MT), which included the MTLs and MTRs of each cat. RIs with the 90% confidence intervals were calculated according to American Society for Veterinary Clinical Pathology guidelines on RIs.

RESULTS

No statistical differences for adrenal gland thickness were observed between the left and right (P = 0.543) adrenal glands or between male and female cats (P = 0.943). Mean MT was significantly greater in the group of cats weighing >4-8 kg compared with the group of cats weighing ⩽4 kg (3.7 ± 0.6 vs 3.2 ± 0.4 mm; P <0.005). The lower limit of the RI for MT was 2.4 mm (range 2.2-2.6 mm) in the group weighing ⩽4 kg and 2.6 mm (range 2.4-2.8 mm) in the group weighing >4-8 kg. The upper limit of the RI for MT was 3.9 mm (range 3.7-4.1 mm) in the group of cats weighing ⩽4 kg and 4.8 mm (range 4.6-5.1 mm) in the group of cats weighing >4-8 kg.

CONCLUSIONS AND RELEVANCE

The use of RIs based on two group sizes allows for a more accurate ultrasonographic evaluation of adrenal gland thickness in cats. The maximum normal adrenal gland thickness is lower in smaller cats (3.9 mm for those weighing ⩽4 kg and 4.8 mm for those weighing >4-8 kg).

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.

CT characterisation of feline adrenal glands

OBJECTIVES

The objectives of this study were to describe the CT characteristics of the adrenal glands in healthy cats, to provide normal reference biometry for adrenal gland size and attenuation values, and to investigate the association with age, sex, laterality and body weight.

METHODS

Retrospective evaluation of 30 CT studies of healthy adult cats recruited from September 2013 to July 2015 was performed. Healthy cats >1 year of age were included based on the absence of clinical signs, unremarkable physical examination, normal results of the complete blood count, biochemical profile, feline immunodeficiency virus, feline leukaemia virus and Bartonella species infection tests. The relationship between gland biometry (size and attenuation values) and the age, sex, laterality and body weight of cats were tested by two-way ANOVA. The intraclass correlation coefficient was assessed and mean, SD, range and reference interval provided.

RESULTS

Twenty-seven cats were included. Bilobed, arrowhead and oval adrenal gland shape patterns were recognised, the first being most common. No statistically significant differences were observed between the biometric parameters (length, height and attenuation values) and age, sex, laterality or body weight of the cats. Regarding the width of the adrenal glands, there was a statistically significant effect of sex and laterality. The length (11.6 ± 2.1 mm) and height (6.1 ± 1.3 mm) were the most consistent biometrical parameters to describe adrenal glands.

CONCLUSIONS AND RELEVANCE

Adrenal gland shape, size and attenuation CT data of healthy feline patients are provided in this study, as well as normal reference intervals for morphometric characterisation based on adrenal length and height.

Sciatic neuropathy in an acromegalic cat without concurrent diabetes mellitus

Case summary

A 17-year-old neutered male European Shorthair cat was presented owing to an inability to jump and respiratory stridor. The owner did not report any other clinical signs. On physical examination, the main findings were plantigrade stance, broad facial features and inspiratory stridor. Neurological examination revealed posterior paraparesis, hypotonia and right hindlimb muscle atrophy. Laboratory findings were unremarkable and glycaemia was normal. Serum insulin-like growth factor 1 concentration was elevated (>1000 ng/ml). A total body CT scan showed an enlarged pituitary gland, thickening of the nasal turbinates and an L7-S1 right foraminal stenosis. Electrodiagnostic testing confirmed the presence of a neuropathy affecting both sciatic nerves. The cat was treated with gabapentin only and was still alive and euglycaemic 16 months after the diagnosis.

Relevance and novel information

This case describes for the first time sciatic neuropathy, an occasional complication of acromegaly in people, as a possible clinical presentation in acromegalic cats without concurrent diabetes mellitus.

Acromegaly and ultrasound: how, when and why?

BACKGROUND

Acromegaly is a rare disease caused by an excess of growth hormone and insulin-like growth factor 1. It is usually diagnosed because of typical signs such as macroglossia, acral enlargement, jaw prognathism and malocclusion. Systemic complications are a major cause of morbidity and mortality in acromegaly, and many patients remain undiagnosed for several years. Increased ultrasound (US) application in the general population, and including among acromegaly patients, has revealed many suggestive features which, taken together with clinical suspicion, could induce suspicion of this disease.

PURPOSE

This review describes main US features in acromegaly. Echocardiography shows a typical cardiomyopathy, characterized by left ventricular hypertrophy, diastolic and systolic dysfunction, aortic and mitral regurgitation, and increased aortic root diameters. US preclinical markers of atherosclerosis, such as intima media thickness (IMT), seem also to be impaired. Visceromegaly and increased organ stiffness are other features of acromegaly, including enlarged prostate, kidneys, liver, and thyroid. In addition, other US findings are: renal cysts, micronephrolithiasis, impairment of renal haemodynamic parameters, gallstones and gallbladder polyps, hepatic steatosis, thyroid nodules, multinodular goiter, and polycystic ovaries. Musculoskeletal US findings are increased cartilage thickness, impaired density and elasticity of bones, nerve enlargement, carpal and cubital tunnel syndrome, and trigger finger.

CONCLUSIONS

Acromegaly patients frequently present systemic complications and a diagnostic delay. US features of acromegaly are not specific, but could potentially have a key role in early detection of the disease in the presence of typical clinical features.

Comparison of ultrasonographic findings in cats with and without azotaemia

Objectives The objective of this study was to identify the renal ultrasonographic (US) findings most strongly associated with azotaemia in cats. Methods US findings in 238 cats with (serum creatinine >180 μmol/l) and 270 cats without azotaemia were compared in a retrospective case-control study. Cats with pre-renal azotaemia or urethral obstruction were excluded. Data extracted from the medical records included age, body weight and body condition score (BCS). Quantitative and subjective US findings were extracted from archived ultrasound images and contemporaneous reports. Results In non-azotaemic cats, mean ± SD renal length was 40.1 ± 5.5 mm. Male cats had larger kidneys than female cats (mean difference 5.2 mm; P = 0.001) and, on average, the right kidney was slightly larger than the left (mean difference 1.6 mm; P = 0.01). Azotaemic cats had significantly lower mean body weight and BCS, and greater mean age and renal pelvic diameter. Renal pelvic diameter was negatively correlated with urine specific gravity (ρ -0.44, P <0.001). Compared with non-azotaemic cats, there was no difference in mean renal length of azotaemic cats because the numbers with enlarged kidneys and small kidneys were similar. Radiologists' subjective assessments of renal size differed markedly between azotaemic and non-azotaemic cats, with azotaemic cats more likely to be recorded falsely as having abnormally small or enlarged kidneys. US findings significantly associated with azotaemia were perinephric fluid (odds ratio [OR] 26.4, 95% confidence interval [CI] 3.4-207.7), small kidneys (OR 8.4, 95% CI 4.0-17.4), hyperechoic renal cortex (OR 4.1, 95% CI 2.2-7.6), loss of corticomedullary differentiation (OR 4.1, 95% CI 1.8-9.6), renal calculi (OR 2.7, 95% CI 1.4-4.9), enlarged kidneys (OR 2.5, 95% CI 1.2-5.5) and dilated renal pelvis (OR 1.6, 95% CI 1.3-1.9). Conclusions and relevance Perinephric fluid was the US finding most strongly associated with azotaemia in this study and may merit more emphasis than it has received to date. Bias in radiologists' subjective assessments of renal size suggests that other subjective findings will also be biased.

Peculiarities of feline hyperadrenocorticism: Update on diagnosis and treatment

Practical relevance: Hyperadrenocorticism (HAC) is a relatively uncommon endocrinopathy of older cats, with a mean age at diagnosis of 10 years. In addition to pituitary-dependent and adrenal-dependent hypercortisolism, clinical signs of HAC can result from adrenal sex steroid-producing tumours. Clinical challenges: While HAC in cats has many similarities to canine HAC, there are key differences in presentation, diagnosis and response to therapy. Most, but not all, cats with HAC have concurrent diabetes mellitus, which is often insulin resistant. Up to a third of cats with HAC have extreme skin fragility and are at high risk of debilitating iatrogenic skin tears during diagnostic or therapeutic interventions. Infections of the skin and nail beds, and urinary, respiratory and gastrointestinal tract, secondary to cortisol-induced immune suppression, are also common. Cats respond differently to dogs to adrenal function tests including adrenocorticotropic hormone (ACTH) stimulation and dexamethasone suppression tests; a 10-fold higher dose of dexamethasone is recommended in cats to screen for HAC. Curative treatment options include adrenalectomy or transsphenoidal hypophysectomy. Radiation or medical treatment may improve clinical signs. The response to mitotane therapy is poor. While trilostane is the medical treatment of choice based on retrospective studies, investigations into the pharmacokinetics of this drug in cats are lacking. Global importance: Feline HAC occurs worldwide and is not associated with any purebreed predisposition. Although uncommon, adrenal sex steroid-producing tumours have a higher prevalence in cats than in dogs. Evidence base: The information in this review is drawn from over 180 reported cases of feline HAC. Reports investigating clinical presentation, clinicopathological findings and treatment outcomes are observational, retrospective multiple case series (EBM grade III) or single case reports (EBM grade IV). While most endocrine testing studies for diagnosis are cohort controlled analytical studies (EBM grade III), prospective, randomised, placebo-controlled studies have been performed (EBM grade I).