Brain magnetic resonance imaging and computed tomography findings in cats and dogs with central nervous system cryptococcosis in Australia: 23 cases (2009-2020)

OBJECTIVE

To describe the imaging findings in Australian cats and dogs with CNS cryptococcosis.

ANIMALS

23 cases (10 cats; 13 dogs) with CNS cryptococcosis and brain MRI or CT studies available to review.

METHODS

Retrospective, multi-institutional case series. Brain MRI or CT studies were reviewed by a board-certified radiologist. Imaging findings were described and the differences between cats and dogs explored.

RESULTS

Morphologic features were consistent with extra-axial lesions in all (n = 13) dogs and either intra-axial (5/10) or extra-axial (4/10) lesions in cats, with 1 cat having no detectable lesions in low-field brain MRI scans. Meningeal abnormalities were most common, followed by forebrain and cerebellar lesions. Intracranial MRI lesions were typically T2 hyperintense and T1 hypo- to isointense. Four cases had T2 hypointense lesions affecting the brain, sinonasal cavity, or regional lymph nodes. Intracranial CT lesions were mostly soft tissue attenuating. Contrast enhancement was present in all cases with contrast series available, with ring enhancement shown only in cats. Osteolysis was more common in dogs than cats, particularly affecting the cribriform plate. All 13 dogs and many (6/10) cats had at least 1 lesion affecting sinonasal or contiguous tissues, and locoregional lymphadenomegaly was common (7/10 cats; 11/13 dogs).

CLINICAL RELEVANCE

Imaging lesions in cryptococcal meningoencephalitis were extra-axial in dogs but could be intra-axial or extra-axial in cats. Careful examination for extracranial lesions (sinonasal, retrobulbar, facial soft tissue, tympanic bullae, or locoregional lymph nodes) is important to provide alternative safe biopsy sites. T2 hypointense lesions, while rare, should prompt consideration of cryptococcosis.

Investigation of scan delays for CT evaluation of inner wall layering and peak enhancement of the canine stomach and small intestine using a 20 second fixed-injection-duration and bolus tracking technique

Many gastrointestinal diseases affect the mucosal layer, suggesting that on computed tomography (CT) examination, detection of consistent inner wall layering of the gastrointestinal tract may aid in detection of disease. Changes in wall enhancement can also characterise specific diseases and provide prognostic information. The objectives of this mixed retrospective and prospective analytical study were therefore to identify the scan delays for peak detection of canine stomach and small intestinal inner wall layering and enhancement when using a 20 s fixed-injection-duration and bolus tracking technique. For each patient, 700 mg I/kg iohexol was administered intravenously. Bolus tracking was used to determine aortic arrival. Diagnostic scans were performed after a post-aortic arrival scan delay. Postcontrast CT series were grouped according to post-aortic arrival scan delay: 5 s (n = 17), 10 s (n = 18), 15 s (n = 23), 20 s (n = 10), 25 s (n = 6), 30 s (n = 14), 35 s (n = 17), 40 s (n = 24), and 180 s (n = 60). The stomach and small intestine were assessed for the presence of a contrast-enhancing inner wall layer and wall enhancement. Statistical modeling showed that the scan delays for peak inner wall layering and enhancement were 10 and 15 s for the small intestine, respectively, and 40 s for the stomach. For the injection protocol used in this study, assessment of the canine gastrointestinal tract may use scan delays of 10-15 s and 40 s.

Caval foramen hernia in a cat

Case summary

A 3-year-old neutered female domestic shorthair cat presented for a 2-week history of hyporexia, lethargy and weight loss. Aspartate aminotransferase, alanine aminotransferase and cholesterol were mildly elevated. Thoracic radiographs identified a lobulated soft tissue opacity in the caudal thorax to the right of midline, with the border effacing the caudal vena cava and broad-based towards the diaphragm. The broad base was suggestive of diaphragmatic hernia, with the other radiographic features and location suggestive of caval foramen hernia. Ultrasound confirmed diaphragmatic hernia with liver herniation. CT showed the herniation of multiple liver lobes and the gallbladder through a defect at the caval foramen. Herniorrhaphy was performed via ventral midline coeliotomy. Following this procedure, the cat's clinical signs resolved and its weight has been regained.

Relevance and novel information

To our knowledge, this is the first report of successful caval foramen herniorrhaphy in a cat. Caval foramen hernia is a type of congenital diaphragmatic hernia. The authors suggest that its embryopathology involves defective septum transversum development. The case was detected during the standard diagnostic investigation of non-specific clinical signs. Its radiographic findings may easily be mistaken for a pulmonary mass. Although not seen in our case, caval foramen hernia is commonly associated with caudal vena cava obstruction, which can potentially result in Budd-Chiari-like syndrome.

Peripartum clinical manifestations of a mesentericorenocaval shunt in a Burmese cat

Case summary

A 3-year-old entire female Burmese cat was presented for investigation of intermittent lethargy during gestation followed by persistent hypersalivation and ataxia postpartum. The cat had queened three litters in total, with clinical signs worsening during the most recent lactation period. Mild anaemia (26%), hypoglycaemia (2.4 mmol/l; reference interval [RI] 3.9–8.3 mmol/l) and increased postprandial serum bile acids (74 µmol/l; RI <25 µmol/l) were identified on initial bloodwork. Multiphase contrast-enhanced CT identified a mesentericorenocaval portosystemic shunt; this was attenuated surgically with an ameroid constrictor. Clinical signs resolved after surgery. Follow-up 3 months postoperatively revealed normal pre- and postprandial serum bile acids (2 µmol/l and 3 µmol/l, respectively) with repeat CT identifying evidence of shunt attenuation. The cat continued to be healthy and free of clinical signs 12 months postoperatively.

Relevance and novel information

Mesentericorenocaval portosystemic shunt morphology has not been previously reported in the cat and should be considered as a differential diagnosis for cats presenting with peripartum onset of malaise, ptyalism or ataxia.

Zinc toxicosis in a dog secondary to prolonged zinc oxide ingestion

Zinc toxicosis is commonly associated with ingestion of metallic zinc objects. This report documents an uncommon presentation of zinc toxicosis, secondary to prolonged ingestion of a zinc oxide cream. A 5.6 kg 6-year-old ovariohysterectomised female Poodle cross presented as a transfer to an emergency practice for severe anaemia, pigmenturia, weakness, and inappetence. She had a history of vomiting and nine days of diarrhoea. Amongst other supportive treatments, a zinc oxide cream had been applied to her hind end due to severe diarrhoea scalding, and in hindsight, the owners realised she had ingested large quantities of this cream. She developed a severe Heinz body haemolytic anaemia, along with spherocytosis, left-shift neutrophilia, prolonged activated partial thromboplastin time, and mildly elevated blood urea nitrogen. The serum zinc concentration was markedly elevated. She was treated supportively and made a full recovery. This case illustrates the importance of a thorough medical history. Zinc toxicosis can have a good prognosis when diagnosed and treated promptly.