Cystitis

Introduction

Cystitis is inflammation of the bladder. Under normal conditions, the bladder is resistant to bacterial infection. Anything that disrupts normal passage of urine can damage and lead to irritation of the bladder wall lining, predisposing to inflammation and infection. Predisposing factors include urine stasis, incomplete voiding of urine, bladder trauma, glycosuria and dilute or alkaline urine. Anatomy also plays a role in that females are more prone to bacterial cystitis due to ease of entry through the urethra. In males, the relatively long urethra protects against ascending infection. Causes include ascending infections, such as metritis, vaginitis and balanopsthitis, urolithiasis, infected catheters or trauma due to catheters and prolonged administration of some anticancer drugs such as cyclophosphamide. Bacterial pathogens which can cause the condition include Escherichia coli, Staphylococcus, Streptococcus in small animals, Corynebacterium renale in cattle and Eubacterium suis in pigs, Haemophilus haemoglobinophilus

Acute cystitis

This is a catarrhal inflammation initially and may be haemorrhagic depending upon the cause of trauma or virulence of the infection organism. Mild cases usually resolve completely whereas others will lead to chronic cystitis.
Gross pathology includes cloudy urine, hyperaemic and oedematous mucosa, haemorrhages and blood clots and catarrhal exudate on the mucosal surface in severe inflammation Histopathology will show epithelial degeneration and necrosis, leukocyte infilatration and dilation of submucosal vessels.

Chronic cystitis

Urolithiasis is the most common cause of chronic cystitis. A condition called follicular cystitis can occur which is a chronic cystitis of unknown aetiology common in the dog. The gross pathology includes grey/white nodular lesions cover the surface of the bladder. Histopathology will show clumps of lymphocytes just beneath the epithelial layer which may be normal or ulcerated. Polypoid cystitis is the type of chronic cystitis seen in most species. Gross pathology may show polyp like projections from the mucosa that resemble neoplasms. Histopathology may show the mucous membrane to have villous projections covered by epithelium.

Emphysematous cystitis

This occurs in some dogs and cats with diabetes mellitus. The cause is likely related to the fermentation of sugar by glucose-fermenting bacteria.