Blocked Bunnies: When Bladders Build Walls

Development of septa in the urinary bladder of client-owned rabbits leading to urinary outflow obstruction, urinary retention, and urinary bladder distension

Giulia Bersanetti, Paolo Selleri, Alice Reginato, Elvio Lepri, Marco Masi, Nicola Di Girolamo

Background
Urine outflow obstruction is a frequent clinical issue in rabbits, traditionally linked to urolithiasis, urinary sludge, or neoplasia. This study describes a novel bladder pathology involving intravesical septum formation that contributes to urinary retention and obstruction. Unlike previously documented proliferative disorders such as polypoid or pseudomembranous cystitis, this septal formation appears to be a distinct, benign but clinically significant entity.

Methods
A retrospective multicenter case series was performed, including seven rabbits treated between 2017 and 2023. Inclusion criteria were histopathological analysis of the urinary bladder and documented presence of septa or membranes via imaging or necropsy. Clinical data, imaging, endoscopic and surgical findings, histopathology, and outcomes were reviewed.

Results
All seven rabbits exhibited signs of urinary tract disease and anorexia. Septa were confirmed via rigid cystoscopy in every case, causing varying degrees of bladder neck narrowing. Histologically, septa displayed urothelial hyperplasia in all cases and inflammation in most. Endoscopic septum removal resolved obstructive signs in six rabbits; one rabbit died post-procedure. Long-term follow-up showed no recurrence of symptoms in surviving animals, despite persistent urinary sludge in some.

Limitations
Study limitations include its retrospective design, small sample size, limited urine culture data (only two cases), lack of advanced imaging (e.g., contrast CT), and superficial nature of most biopsy samples, which may have missed deeper pathology or infectious etiologies.

Conclusions
Intravesical septa represent a previously undescribed cause of urinary obstruction in rabbits. These benign proliferations can lead to clinical signs of outflow obstruction but are responsive to endoscopic treatment. Recognition of this condition may improve diagnostic and therapeutic strategies for rabbits presenting with lower urinary tract signs. Further research is warranted to clarify etiology and optimize management.

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