Primary hyperaldosteronism, a mediator of progressive renal disease in cats

In recent years, there has been renewed interest in primary hyperaldosteronism, particularly because of its possible role in the progression of kidney disease. While most studies have concerned humans and experimental animal models, we here report on the occurrence of a spontaneous form of (non-tumorous) primary hyperaldosteronism in cats. At presentation, the main physical features of 11 elderly cats were hypokalemic paroxysmal flaccid paresis and loss of vision due to retinal detachment with hemorrhages. Primary hyperaldosteronism was diagnosed on the basis of plasma concentrations of aldosterone (PAC) and plasma renin activity (PRA), and the calculation of the PAC:PRA ratio. In all animals, PACs were at the upper end or higher than the reference range. The PRAs were at the lower end of the reference range, and the PAC:PRA ratios exceeded the reference range. Diagnostic imaging by ultrasonography and computed tomography revealed no or only very minor changes in the adrenals compatible with nodular hyperplasia. Adrenal gland histopathology revealed extensive micronodular hyperplasia extending from zona glomerulosa into the zona fasciculata and reticularis. In three cats, plasma urea and creatinine concentrations were normal when hyperaldosteronism was diagnosed but thereafter increased to above the upper limit of the respective reference range. In the other eight cats, urea and creatinine concentrations were raised at first examination and gradually further increased. Even in end-stage renal insufficiency, there was a tendency to hypophosphatemia rather than to hyperphosphatemia. The histopathological changes in the kidneys mimicked those of humans with hyperaldosteronism: hyaline arteriolar sclerosis, glomerular sclerosis, tubular atrophy and interstitial fibrosis. The non-tumorous form of primary hyperaldosteronism in cats has many similarities with "idiopathic" primary hyperaldosteronism in humans. The condition is associated with progressive renal disease, which may in part be due to the often incompletely suppressed plasma renin activity.     

Gastrointestinal pythiosis in two cats.

Two young adult male Domestic Shorthair cats living in the southeastern United States were evaluated for signs attributable to partial intestinal obstruction. Physical examination indicated a palpable abdominal mass in each animal. Exploratory laparotomy revealed a large extraluminal mass involving the ileum and mesentery with adjacent mesenteric lymphadenopathy in cat No. 1 and an abscessed mass in the distal duodenum in cat No. 2. Mass resection and intestinal anastomosis were performed in both cats. Histologic evaluation indicated that the intestinal lesions involved primarily the outer smooth muscle layer and serosa and consisted of eosinophilic granulomatous inflammation with multifocal areas of necrosis. In Gomori methenamine silver-stained sections, broad (2.5-7.5 microm), occasionally branching, infrequently septate hyphae were observed within areas of necrosis. A diagnosis of Pythium insidiosum infection was confirmed in both cats by immunoblot serology and by immunoperoxidase staining of tissue sections using a P. insidiosum-specific polyclonal antibody. Cat No. 1 was clinically normal for 4 months after surgery but then died unexpectedly from an unknown cause. Cat No. 2 has been clinically normal for at least 9 months after surgery and appears to be cured on the basis of follow-up enzyme-linked immunosorbent assay serology.     

Primary hyperaldosteronism in a dog with concurrent lymphoma

An 11-year-old, male castrated English springer spaniel was presented for muscle weakness, lethargy and anorexia while undergoing treatment of Stage IV lymphoma. Persistent hypokalemia prompted multiple diagnostic tests. Serum aldosterone levels, surgical exploration and histopathology confirmed primary hyperaldosteronism. Hyperaldosteronism is a rarely reported endocrinopathy in the dog. This report describes a case in which immunohistochemistry was utilized to confirm the diagnosis of an aldosterone-secreting tumour.     

Primary hyperaldosteronism: expanding the diagnostic net

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.     

Acquired portosystemic shunting in two cats.

Acquired portosystemic shunts (PSS) are a clinical entity distinct from congenital PSS. Their apparent incidence in cats is low, which may reflect the rarity of predisposing hepatic parenchymal disease, such as cirrhosis, in this species. Two cats with acquired PSS associated with primary hepatobiliary disease are described. Relevant findings in acquired PSS are discussed, as are potential reasons for the apparently low incidence in the cat.     

Phycomycosis in fifteen dogs and two cats.

Phycomycosis was confirmed by histologic examination of biopsy specimens from 15 dogs and at necropsy in 2 cats. The fungal infections occurred most frequently in young adult dogs (1-3 yr) of the larger breeds. The gastrointestinal tract was the organ most commonly involved. Treatment by surgical excision, amphotericin B, and sodium iodide alone or in combination was attempted in five cases. Mortality was 100%.     

Evaluation of two applanation tonometers in cats.

Comparisons of the MacKay-Marg and Tono-Pen applanation tonometers in open and closed in vitro systems were made for the eyes of cats. Both instruments significantly underestimated intraocular pressure (IOP) vs direct manometry (P less than 0.001), but in readily predictable manner, with high coefficients of determination (r2 = 0.99). For tonometer 1 (MacKay-Marg), calculated actual IOP = 1.36 x (MacKay-Marg measurement) - 1.67 mm of Hg; and for tonometer 2 (Tono-Pen), calculated actual IOP = 1.37 x (Tono-Pen measurement) + 0.8 mm of HG, using measurements from 11 enucleated eyes. In vivo comparisons were initially made in 81 clinically normal eyes (n = 41 cats) by applying the Tono-Pen first followed by the MacKay-Marg. Compared with the MacKay-Marg, the Tono-Pen significantly (P less than 0.001) underestimated IOP in these cats. When the order of tonometer applanation was subsequently reversed in 73 clinically normal eyes (n = 37 cats) the Tono-Pen again significantly (P less than 0.001) underestimated IOP, compared with the MacKay-Marg. Alterations in tonometer order did not result in significant differences in measured IOP for the MacKay-Marg when compared with itself, but Tono-Pen measurements were significantly (P less than 0.05) less when its use followed, rather than preceded, that of the MacKay-Marg. Mean (+/- SD) IOP in clinically normal cats when each tonometer was used first was 22.6 +/- 4.0 mm of Hg (range, 14 to 32 mm of Hg) for the MacKay-Marg and 19.7 +/- 5.6 mm of Hg (9 to 31 mm of Hg) for the Tono-Pen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrometra in two cats

Chronic abdominal distension in two female cats 2½ and 13 years old respectively was due to bilateral hydrometra. In both cases the condition resulted from absence of an internal cervical os with consequent accumulation of normal uterine secretions. The most likely cause was a segmental failure in the development of the Müllerian duct system.     

Megaesophagus in two cats

Megaesophagus was diagnosed in 2 cats. Both had a history of regurgitation, and one was dyspneic. Radiography of the thorax and abdomen revealed generalized megaesophagus and gastric distention with gas. There was no esophageal motility during fluoroscopic observation. The prognosis for cats with megaesophagus is guarded. Although they may be satisfactory pets, cats with this condition should not be used for breeding because the condition is believed to be inherited through recessive genes.     

Lymphangiosarcoma in two cats

Lymphangiosarcoma is a malignant neoplasm of the lymphatic endothelium that is rare in cats. This report describes two cases of feline lymphangiosarcoma that originated in the distal limb, causing intractable lymphoedema and serosanguineous discharge with ecchymoses in local and distant sites. In association with the neoplasia, one cat had cortical bone lysis of multiple metacarpal bones of the affected limb and the other had severe immune-mediated haemolytic anaemia (IMHA). The disease in both cases affected young cats and progressed rapidly. Persistent distal limb lymphoedema with serosanguineous discharge is suggestive of lymphangiosarcoma especially when local or distal ecchymoses are evident.     

Primary glaucoma in Burmese cats

OBJECTIVE: To document the clinical signs and management of primary glaucoma in Burmese cats. DESIGN: A retrospective study of six affected Burmese cats, from 1996 to 2001. Procedure Six Burmese cats diagnosed with primary glaucoma were managed over periods varying from 3 months to 4.5 years. Clinical details were obtained from practice records. Gonioscopic examination of the drainage or iridocorneal angle in eyes of these affected cats was made. RESULTS: Six desexed female Burmese cats (ages 7.0 to 10.5 years) presented with complaints of either unilateral (n = 4) or bilateral (n = 2) red eye, dilated pupil or enlarged eye. In one of the affected cats, one eye had been enucleated prior to the commencement of the study, thus a total of 11 eyes were examined. Clinically, all affected eyes (n = 8) had injected episcleral blood vessels and elevated intraocular pressure. Gonioscopy revealed the presence of nine narrow and two closed iridocorneal angles. Medical therapy included topical 2% dorzolamide (n = 8), 0.5% timolol maleate (n = 1), 0.005% latanoprost (n = 1) and 0.5-1.0% prednisolone acetate (n = 8). Surgery was performed in six eyes using either diode laser (n = 5) and/or cryothermy (n = 2) and one eye was eviscerated, with implantation of a prosthesis. With therapy, five affected eyes maintained vision and normal intraocular pressure, one eye remained blind with normal intraocular pressure, one eye remained blind with elevated intraocular pressure and one eye was eviscerated. CONCLUSIONS: The Burmese cat may be predisposed to primary narrow-angle glaucoma. Early diagnosis and continuous antiglaucoma therapy can help control intraocular pressure and maintain vision.     

Protothecosis in two cats

Protothecosis was diagnosed in 2 cats from Florida with nodular skin lesions. Microscopically, lesions were composed of macrophages and multinucleated giant cells arranged in solid sheets in the dermis and subcutis. In both cats, characteristic algal endospores identified as Prototheca wickerhamii were observed within the cytoplasm of infiltrating cells.     

Trichosporonosis in two cats

Infection with Trichosporon spp was diagnosed in 2 cats. In one cat, infection consisted of a granulomatous dermatitis and was concurrent with disseminated lymphoblastic lymphosarcoma. In another cat, urinary cystitis caused by T beigelii was diagnosed.     

Primary hyperaldosteronism in the cat: a series of 13 cases

Thirteen cases of feline primary hyperaldosteronism were diagnosed based on clinical signs, serum biochemistry, plasma aldosterone concentration, adrenal imaging and histopathology of adrenal tissue. Two cases presented with blindness caused by systemic hypertension, whilst the remaining 11 cases showed weakness resulting from hypokalaemic polymyopathy. Elevated concentrations of plasma aldosterone and adrenocortical neoplasia were documented in all cases. Seven cases had adrenal adenomas (unilateral in five and bilateral in two) and six had unilateral adrenal carcinomas. Three cases underwent medical treatment only with amlodipine, spironolactone and potassium gluconate; two cases survived for 304 and 984 days until they were euthanased because of chronic renal failure, whilst the third case was euthanased at 50 days following failure of the owner to medicate the cat. Ten cases underwent surgical adrenalectomy following a successful stabilisation period on medical management. Five cases remain alive at the time of writing with follow-up periods of between 240 and 1803 days. Three cases were euthanased during or immediately following surgery because of surgical-induced haemorrhage. One cat was euthanased 14 days after surgery because of generalised sepsis, whilst the remaining cat was euthanased 1045 days after surgery because of anorexia and the development of a cranial abdominal mass. It is recommended that primary hyperaldosteronism should be considered as a differential diagnosis in middle-aged and older cats with hypokalaemic polymyopathy and/or systemic hypertension and should no longer be considered a rare condition.     

Primary hyperparathyroidism in dogs and cats

The most common cause of primary hyperparathyroidism in dogs and cats is a solitary adenoma involving an extracapsular parathyroid gland. The prognosis is excellent if the affected parathyroid gland is removed. Nonsurgical methods are discussed, although there are no current data to support any benefit over conventional surgery. The common postoperative complication to consider is hypocalcemia. Hypocalcemia can be successfully managed in these animals if it is anticipated and treated promptly.     

Primary intratracheal lymphosarcoma in four cats

Four cats presented with clinical signs suggestive of respiratory disease, including dyspnea, wheezing, cyanosis, inspiratory stridor, coughing, and gagging. Radiographs revealed intratracheal masses. Bronchoscopy allowed for lesion localization and collection of samples for cytopathological and histopathological evaluation, which confirmed a diagnosis of lymphosarcoma. Cats treated with systemic chemotherapy or radiation were able to achieve complete remission and long-term resolution of clinical signs.     

Tracheal collapse in two cats

Two cats examined bronchoscopically to discover the cause of tracheal collapse were found to have tracheal obstruction cranial to the collapse. Cats with this unusual sign should be examined bronchoscopically to ascertain whether there is an obstruction, as the cause in these 2 cats was distinct from the diffuse airway abnormality that causes tracheal collapse in dogs.     

Oral masses in two cats

Incisional biopsies from the oral cavity of 2 adult cats were submitted for histological investigation. Cat No. 1 showed a solitary well-circumscribed neoplasm in the left mandible. Cat No. 2 demonstrated a diffusely infiltrating neoplasm in the left maxilla. Both tumors consisted of medium-size epithelial cells embedded in a fibrovascular stroma. The mitotic index was 0 to 1 mitosis per high-power field. The epithelial cells showed an irregular arrangement forming nests or streams in cat No. 1, whereas a palisading growth was noted in cat No. 2. Both tumors, especially that of cat No. 1, showed multifocal accumulations of amyloid as confirmed by Congo red staining and a distinct green birefringence under polarized light, which lacked cytokeratin immunoreactivity as well as and AL and AA amyloid immunoreactivity. In addition, the amyloid in cat No. 2 was positive for the odontogenic ameloblast-associated protein, formerly termed APin. In sum, both cats suffered from an amyloid-producing odontogenic tumor, but their tumors varied with respect to morphology and type of amyloid produced.     

Disseminated melioidosis in two cats

Melioidosis was diagnosed in two cats at necropsy. The first cat presented with jaundice and anaemia but died of overwhelming sepsis soon after admission, despite blood transfusion and other supportive measures. The second cat died several days after developing neurological signs; an infected digital wound may have been the primary focus of infection in this patient. The cats had presumably acquired the infection in Malaysia and northern Australia, respectively, and in both cases disease may have represented reactivation of a latent infection brought on by the stress of relocation. The epidemiology, clinical presentation, diagnosis and treatment of melioidosis are discussed from a feline perspective.