Cystitis

Introduction

The definition of cystitis is inflammation of the bladder. Under normal conditions, the bladder is resistant to bacterial infection, but anything that disrupts the 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 of acute cystitis include ascending infections, such as metritis, vaginitis and balanoposthitis, infected catheters or trauma due to catheters and prolonged administration of some anticancer drugs such as cyclophosphamide. Chronic cystitis is more likely to have an underlying cause such as urolithiasis, polyps, prostatitis, pyelonephritis and endocrinopathies such as hyperadrenocorticism.

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 in dogs.

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 infiltration and dilation of submucosal vessels.

Chronic cystitis

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.

Follicular cystitis 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.

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.

Clinical Signs

Signs demonstrated by individual animals varies enormously, with some showing no clinical signs at all. However the following signs may all be associated with cystitis:

• Dysuria
• Pollakiuria
• Stranguria
• Haematuria

If the condition has a bacterial component the following signs can also be seen:

• Abnormal urine odor
• Pyrexia
• Cloudy urine
• Systemic signs including lethargy and anorexia

Diagnosis

Urinanalysis and bacterial culture should be performed on all animals presenting with signs of cystitis. Urine should be collected by cystocentesis, urinary catheterisation or free-flow - the ideal method being cystocentesis due to the lack of contamination. One sample should be spun and the sediment examined for inflammatory cells, bacteria and crystals. Another sample should be sent for culture. The results of these findings can guide diagnosis.

Ultrasound and plain and contrast radiographs should be performed on the bladder in any chronic cases. Ultrasound can help identify pathology such as uroliths and masses within the bladder. Radiopaque crystals and some bladder masses will be apparent on pneumocystogram studies, but double contrast radiographic studies are required to see radiolucent crystals and the bladder lining in more detail.

Haematology and biochemistry may also be useful in detecting underlying disease.

Treatment

Treatment may be medical or surgical, dependant on the type of cystitis and the underlying cause. Acute cystitis is often bacterial in origin and therefore managed medically. Antibiotics should be selected in accordance with culture results. Chronic cystitis is more likely to have an underlying cause (such as uroliths or polyps) that requires further diagnostics or surgical treatment.

If an underlying urolithiasis is diagnosed then treatment varies in depending on which calculus is present. Some case may be managed medically with antibiotics and diet change. This can also cause the resolution of polyps in some cases, however surgery is normally indicated for the removal the majority of uroliths and chronic polyps.

The procedure is a ventral cystotomy which allows good visualisation of the bladder (achieved by everting it), removal of any calculi and complete surgical excision of any polyps present. The surgery does not involve the placement of any intraluminal sutures and instead uses haemostats to provide haemostasis. Therefore haemorrhage and clot formation are a risk. As any clots could potentially cause a urinary tract obstruction, the risk should be reduced by using fluid therapy to encourage urination. It is important to send any excisional biopsies for histopathological analysis to confirm a diagnosis of polypoid cystitis. Any uroliths should sent for bacterial culture.

Prognosis

The prognosis for acute cystitis is very good. With chronic or recurrent cases, the diagnosis and treatment options available for the underlying cause determines the prognosis.

Cystitis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Abdominal and Metabolic Disorders Q&A 05

References

Dunning, M & Stonehewer, J (2002) Urinary tract infections in small animals: Pathophysiology and Diagnosis In Practice 2002 24: 418-432

Stonehewer, J (1997) Differential diagnosis of urinary tenesmus in the dog In Practice 1997 19: 134-143

Tennant, B (1999) Self-Assessment Colour Review Small Animal Abdominal & Metabolic Disorders Manson

RVC staff (2009) Urogenital System RVC Integrated BVetMed Course, Royal Veterinary College

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