EQUINE VETERINARY EDUCATION / AE / MAY 2019


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evacuated using gentle suction. There was no evidence of sabulous material accumulation within the bladder. The majority of the bladder mucosa appeared grossly normal; however, there were multiple small, polypoid structures projecting from the mucosa throughout the bladder (Fig 1). Haemorrhage from the mucosal attachment of several of these lesions was evident. Several pinch biopsies were collected from lesions and the adjacent (grossly normal) bladder mucosa and submitted for histopathology. Urine expelled from both ureters appeared grossly normal. Following cystoscopy, palpation of the bladder per


rectum was performed with no abnormalities appreciated. Transrectal ultrasonography revealed focal thickening of the bladder wall and focal irregularities of the bladder mucosa. Transcutaneous ultrasonography of the kidneys was considered normal.


Histopathology results Histological examination of the pinch biopsy samples identified intracellular swelling and cystic vacuolation of epithelial cells and there was accumulation of mildly degenerate neutrophils forming microabscesses (Fig 2a). The urothelium was hyperplastic with neutrophilic infiltration accompanied by diffuse oedema of the submucosa and dilation of submucosal vessels (Fig 2b). Superficially, the epithelium was intact with


fibrinosuppurative exudation. There were moderate numbers of Gram-positive cocci located within fibrinosuppurative exudate in one (the largest) sample but this was not observed in others. Histopathology of the apparently normal mucosa revealed mildly oedematous epithelium with minimal evidence of inflammation. No evidence of atypical cells or mitotic figures to suggest a neoplastic process was present in


any of the sections examined. Based on the histological findings, a diagnosis of chronic polypoid cystitis was made.


Differential diagnoses Neoplasia of the urinary tract was considered most likely at the time of initial evaluation at the VTH, although the


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Fig 2: a) Biopsy of urinary bladder displaying markedly hyerplastic urothelium with neutrophilic infiltrate and intraepithelial microabscess formation, supported by loose oedematous submucosa. Haematoxylin and eosin stain. b) Biopsy of urinary bladder (at higher magnification) showing projections of hyperplastic urothelium with multifocal neutrophil infiltration, supported by oedematous stroma containing marked dilated vessels. Haematoxylin and eosin stain.


Fig 1: Cystoscopic view of one of the polyps emerging from the bladder mucosa at the initial visit.


appearance of the bladder mucosa was not consistent with previously described bladder neoplasms. Squamous cell carcinoma (Fischer et al. 1985; Serena et al. 2009), transitional cell carcinoma (Lisowski et al. 2015), lymphosarcoma (Sweeney et al. 1991; Meyer et al. 2006) and leiomyosarcoma (Hurcombe et al. 2008) have been reported as causes of haematuria in horses, although they are typically associated with difficulty urinating and/or systemic illness which was not evident in this patient. Other differentials included benign fibromatous/fibroepithelial polyps (Fischer et al. 1985), urothelial papilloma or polypoid formation secondary to cystitis, although the latter two have not been previously described in horses (Tsuzuki and Epstein 2005). Pyelonephritis as a cause of the haematuria was considered unlikely given the pony’sgood health and the absence of signs of a systemic illness on physical examination, haematological analysis and urinalysis.


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