Comparison between ultrasound and genetic testing for the early diagnosis of polycystic kidney disease in Persian and Exotic Shorthair cats

Molecular detection of polycystic kidney disease in Persian and Persian-related breeds in Iran

Objectives

This study was aimed at detecting feline autosomal dominant polycystic kidney disease in a population of Persian and Persian-related breeds by a molecular method in Iran.

Methods

Buccal swab samples were collected from 47 cats and examined with a touchdown PCR method. Additionally, partial sequencing was performed in two cats with bilateral renal cysts.

Results

Twenty-two cats (46.8%) were diagnosed as heterozygous for this mutation. Sequence analysis of two cats showed C to A point mutation in the PKD1 gene, as in previous studies.

Conclusions and relevance

Prevalence of this disease is high in Iran, highlighting the need for molecular screening tests before including cats in breeding programmes.

Feline Polycystic Kidney Disease: An Update

Polycystic kidney disease (PKD) is a disease that affects felines and other mammals, such as humans. The common name is autosomal dominant polycystic kidney disease (ADPKD) and causes a progressive development of fluid-filled cysts in the kidney and sometimes in other organs as the liver and pancreas. The formation and growth of cysts progress slowly, causing deterioration of kidney tissue and a gradual decrease in kidney function, leading to irreversible kidney failure. Feline PKD or ADPKD in humans are hereditary pathologies of autosomal dominant transmission. ADPKD is one of the genetic diseases with the highest prevalence in humans. In cats, this disease also has a high prevalence, mainly in the Persian breed, being one of the most common feline genetic diseases. Imaging tests seem to be the most reliable method for diagnosis of the disease, although more genetic tests are being developed to detect the presence of the responsible mutation. In this review, we summarize the current knowledge about feline PKD to guide future research related to an adequate diagnosis and early detection of causal mutations. It can allow the establishment of selection programs to reduce or eliminate this pathology in feline breeds.

Imaging techniques in Veterinary Medicine. Part I: Radiography and Ultrasonography

In Veterinary Medicine all the Imaging techniques are used and described but, due to organizational, managerial and, mostly, economical reasons, Radiography and Ultrasonography are the most used.

Veterinary Radiology teaching has a relatively small number of educational credits in the degree courses but, nowday, educational opportunities are remarkably increased thanks to a number of post-degree courses and masters, organized both by the universities and private veterinary associations. The relevance of Diagnostic Imaging is particularly true in Veterinary Medicine, in which Radiology could be considered “indispensable” for diagnosis, prognosis and follow up. Furthermore, it should not be forgotten that the diagnostic image represents a “document” and, has a relevant role in legal medical debats.

In this first part, Radiography and Ultrasonography are described.

Prevalence of autosomal dominant polycystic kidney disease in Persian and Persian-related cats in Brazil

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disease in cats. However, scarce data on its prevalence are available in Brazil. Persian cats and Persian-related breeds were assessed by molecular genotyping for a C to A transversion in exon 29 of PKD1 gene to determine ADPKD prevalence in a Brazilian population. Genomic DNA extracted from peripheral whole blood or oral swabs samples was used to amplify exon 29 of PKD1 gene employing a PCR-RFLP methodology. From a total of 616 animals, 27/537 Persian and 1/17 Himalayan cats showed the single-nucleotide variant (C to A) at position 3284 in exon 29 of feline PKD1. This pathogenic variation has been identified only in heterozygous state. The prevalence of ADPKD in Persian cats and Persian-related breeds was 5.03% and 1.6%, respectively. There was no significant association between feline breed, gender or age with ADPKD prevalence. Of note, the observed ADPKD prevalence in Persian cats and Persian-related breeds in Brazil was lower than the ones reported in other parts of the world. This finding may be related to genetic counseling and consequent selection of ADPKD-free cats for reproduction.

Prevalence of PKD1 gene mutation in cats in Turkey and pathogenesis of feline polycystic kidney disease

Polycystic kidney disease (PKD) is one of the most common hereditary diseases in cats, with high prevalence in Persian and Persian-related cats. PKD is caused mainly by an inherited autosomal dominant (AD) mutation, and animals may be asymptomatic for years. We screened 16 cats from various breeds exhibiting a renal abnormality by ultrasound examination and genotyped them for the c.10063C>A transversion on exon 29 of the polycystin-1 (PKD1) gene, by PCR-restriction fragment length polymorphism (PCR-RFLP). Among these cats, a Siamese nuclear family of 4 cats with ancestral hereditary renal failure were screened by whole-genome sequencing (WGS) to determine novel variations in genes associated with both AD and autosomal recessive PKD in humans. During the study period, one cat died as a result of renal failure and was forwarded for autopsy. Additionally, we screened 294 cats asymptomatic for renal disease (Angora, Van, Persian, Siamese, Scottish Fold, Exotic Shorthair, British Shorthair, and mixed breeds) to determine the prevalence of the mutation in cats in Turkey. Ten of the symptomatic and 2 of the asymptomatic cats carried the heterozygous C → A transversion, indicating a prevalence of 62.5% and 0.68%, respectively. In the WGS analysis of 4 cats in the Siamese nuclear family, novel variations were determined in the fibrocystin gene (PKHD1), which was not compatible with dominant inheritance of PKD.

Epidemiological evaluation of cats associated with feline polycystic kidney disease caused by the feline PKD1 genetic mutation in Japan

Feline polycystic kidney disease (PKD), an inherited autosomal dominant disease, has been reported to occur mostly in Persian or Persian related cats, and to be associated with a mutation from C to A at position 10063 in exon 29 of the feline PKD1 gene (PKD1 mutation). Many clinical cases have been recognized in Japan, but the mutation rate in cats has not been reported. The objective of this study was to determine epidemiological characteristics and clinical features in cats with the PKD1 mutation. Referring veterinarians sent blood samples of 377 cats for the PKD1 gene evaluation. The blood samples were from 159 cats with renal cysts confirmed by ultrasonography, 60 cats without renal cysts, and 158 cats that did not undergo ultrasonography. In total, 150 cats carried the PKD1 mutation and the signalment, site and number of renal cysts, and results of blood test were evaluated in cats with the PKD1 mutation. The breeds with the highest rate of the PKD1 mutation were Persian (46%), Scottish Fold (54%) and American Shorthair cats (47%). However, mixed breed cats also showed high rates of the PKD1 mutation. Of cats with the mutation, the incidence of high plasma creatinine (≥1.6 mg/dl) was greater in cats ≥3 years old, although a few cats ≥9 years of age had low plasma creatinine (<1.6 mg/dl). The coincidence of renal and hepatic cysts was 12.6%, with the high prevalence in Persian cats (31%).

Age-based ultrasonographic criteria for diagnosis of autosomal dominant polycystic kidney disease in Persian cats

OBJECTIVES

The aim of this study was to establish ultrasound criteria for the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) in Persian cats.

METHODS

Eighty-two Persian cats were assessed using renal ultrasound and genotyped for the C→A transversion in exon 29 of PKD1. The animals were also submitted to hematological characterization, serum biochemistry analyses and urinalysis.

RESULTS

Age, sex and neutering status did not differ between ADPKD (n = 12) and non-ADPKD (n = 70) cats. After integrated molecular genetics/ultrasonographic analysis, the presence of at least one renal cyst was sufficient to establish a diagnosis of ADPKD in animals up to 15 months of age. Two or more cysts were required for diagnosis in cats aged 16-32 months, and at least three cysts warranted diagnosis of ADPKD in animals aged 33-49 months. Finally, four or more cysts led to diagnosis in cats aged 50-66 months. Although cats with ADPKD exhibited higher serum calcium levels than non-affected cats, hematological, urinalysis and other biochemical parameters did not differ between the two groups.

CONCLUSIONS AND RELEVANCE

Integrated analyses of imaging and molecular genetics data enabled, for the first time, the establishment of age-based ultrasonographic criteria for the diagnosis of ADPKD in Persian cats. The development of imaging criteria is particularly relevant and useful in the clinical setting given the current limitations to access and the cost of molecular genetics-based diagnostic tests.

Survey of polycystic kidney disease and other urinary tract abnormalities using ultrasonography in Persian and Persian related cats in Iran

Ultrasonography is an accurate and accessible method for detecting polycystic kidney disease (PKD), an inherited autosomal dominant disease, and other urinary tract diseases. The present work is a preliminary study of PKD and urinary tract abnormalities using ultrasonography in Persian and other long hair cats in Iran. This study was conducted on 83 cats including 68 Persian cats and 15 Persian related cats from December 2013 to March 2015. The age of cats ranged 3 to 72 months. Cats were classified as PKD-positive when at least one renal cyst was observed. Other urinary system abnormalities were recorded ultrasono-graphically. Association of personal and nutritional characteristics with PKD and other urinary tract disease detected by ultrasonography was statistically analyzed. The prevalence of PKD among Persian cats and in the total population was 33.80% and 31.30%, respectively. PKD was more prevalent among male cats compared to those in female cats. PKD occurrence was significantly more among cats fed by commercial dry foods compared to those fed by homemade foods. There was no significant association between PKD and age, hair color, eye color, related clinical signs and other kidney abnormalities in ultrasonographic findings. The prevalence of renal calculi, urine sediments and bladder calculus were 2.40%, 32.80% and 3.60%, respectively. Urine sediments were significantly raised with increasing age. Screening program is essential for on-time diagnosis of PKD and to plan therapeutic management and control of the disease.

Congenital hepatic fibrosis and polycystic kidney disease not linked to C >A mutation in exon 29 of PKD1 in a Persian cat

CASE SUMMARY

We describe the case of a 1-year-old male Persian cat diagnosed with congenital hepatic fibrosis (CHF) associated with renal polycystic disease and, for the first time, we have shown that there was no C >A mutation in exon 29 of PKD1 (polycystic kidney disease 1). The cat presented with a history of chronic weight loss, anorexia, vomiting, depression and lethargy, with profuse salivation and ascites on clinical examination. A mild elevation in liver-associated plasma enzymes suggested a hepatic disease. Owing to the cat's deteriorating condition, it was euthanized. During necropsy, the liver was found to be enlarged, firm and reddish, and the kidney had multiple small cortical cysts. Immunohistochemistry revealed that bile duct cells and epithelial cells of renal cysts showed positive immunoreactivity to keratin 19. Collagen fibers surrounding bile ducts within portal areas demonstrated reactivity to type IV collagen antibody, confirming the congenital nature of the process. A diagnosis of ductal plate malformation consistent with CHF associated with polycystic kidney in a young Persian cat was made. Interestingly, genetic testing revealed a wild-type sequence at position 3284 in exon 29 of PKD1.

RELEVANCE AND NOVEL INFORMATION

The absence of the classic genetic mutation associated with the particular clinical presentation supports the hypothesis of a distinct etiopathogenesis among fibropolycystic diseases in domestic cats. Moreover, congenital hepatic fibrosis is a rare but important differential diagnosis for young Persian cats and their crosses with clinical signs of chronic end-stage liver disease.

Multiple recurrent pancreatic cysts with associated pancreatic inflammation and atrophy in a cat

Previous reports of true pancreatic cysts in cats have suggested that pancreatic cysts in cats are benign incidental findings. This case report describes the progressive clinical course and diagnostic findings in a cat with multiple recurrent pancreatic cysts. The presenting clinical signs included diarrhea, intermittent vomiting, polyphagia, and marked weight loss. Pancreatic cysts were identified via abdominal ultrasound and computed tomography (CT). An exploratory celiotomy and lesion histopathology confirmed multiple true pancreatic cysts of unknown etiology. One month after surgery the cat presented for lethargy and decreased appetite. Clinical re-evaluation was diagnostic for diabetes mellitus and an abdominal ultrasound confirmed recurrence of the pancreatic cysts. The recurrent nature of the pancreatic cysts and the concurrent development of diabetes mellitus were suggestive of progressive loss of pancreatic function or insulin resistance. This is the first described case of multiple recurring pancreatic cysts in a cat associated with pancreatic inflammation, atrophy and endocrine dysfunction.

Polycystic kidney disease in a Chartreux cat

Polycystic kidney disease (PKD) is one of the most common genetic diseases in cats. It has been widely described in Persians and Persian-related cats and sporadically in other breeds. The purpose of the present paper is to describe the first reported case of PKD in a 12-year-old female Chartreux cat. The cat was referred with polyuria and polydipsia and enlarged and irregular kidneys at palpation. Multiple renal cysts and a single liver cyst were identified by ultrasound and the inherited pattern was confirmed by genetic test (polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) assay). Chartreux cats should be included in the screening programme of PKD, and PKD should be always considered as a possible cause of chronic renal failure in this breed.