Brunn's cyst: A rare cause of lower urinary tract symptoms

Abstract

Brunn's cyst in the region of the bladder neck is a rare cause of lower urinary tract obstruction. This case describes the ultrasonographic and intra-venous urographic findings of Brunn's cyst in a 53-year-old male presenting with lower urinary tract symptoms.

INTRODUCTION

Bladder outlet obstruction in an adult male usually results from either benign hyperplasia of the prostate or from a urethral stricture. Brunn's cyst is one of the rarest causes of bladder neck obstruction.[1] These cysts result from inflammation in the Brunn's nests located within the urothelium. They are seldom seen in the region of the bladder neck and rarely cause outlet obstruction.[2,3]

CASE REPORT

A 53-year-old male patient presented with the chief complaints of urinary hesitancy, increased urinary frequency, and urgency with a sense of incomplete voiding. His urine examination and serum chemistries were within normal limits.

Ultrasonography of the kidney urinary bladder (KUB) region revealed a 7 mm × 8 mm, small, well-defined cystic lesion at the bladder neck, separate from the ureterovesical junctions and above the prostate [Figure 1]. Bilateral upper tracts and the prostate were within normal limits. However, the post void residual urine was significant (>30% of the pre-void volume).

Figure 1.

Sonographic images showing a small cystic lesion (arrow) in the bladder neck region above the prostate and separate from the ureterovesical junctions

An intravenous urography revealed a small filling defect in the region of the bladder neck[Figure 2]. A radiological diagnosis of Brunn's cyst was formulated based on ultra-sonography and intravenous urography. The patient underwent transurethral de-roofing and resection of the cyst and after which his symptoms resolved.

Figure 2.

Full bladder film of Intravenous urography showing the filling defect (arrow) in the bladder neck region. The sonographic and urographic findings were consistent with the diagnosis of Brunn's cyst

DISCUSSION

Brunn's cysts originate from the Brunn's nests which result from pinching off of the epithelial nests from urothelial buds.[3] In a study by Weiner et al., 89% of the specimens of Brunn's cysts and cystitis cystica contained Brunn's nests. In their report, none of the cysts involved the bladder neck, rather the involvement of ureters was common.[4]

Prostatic cysts are one of the differential diagnosis of a cystic lesion near the bladder neck. In comparison to a Brunn's cyst which is located at the bladder neck above the prostatic parenchyma, the prostatic cysts are intraparenchymal and originate from the posterior structures such as the utricle or the ejaculatory duct. Also, whereas the prostatic cysts are usually asymptomatic, the Brunn's cyst at the bladder neck presents with lower urinary tract symptoms (LUTS).[5] Another important differential diagnosis is a ureterocele in an ectopic ureter. The ultrasonographic findings may be non-diagnostic and thus intravenous urography plays an important role in differentiating a ureterocele from the bladder neck cyst. Cystoscopy plays diagnostic as well as therapeutic role in the management of Brunn's cysts. Cystoscopy reveals a cystic lesion at the neck which can be managed by transuretheral deroofing and resection of the cyst in the same sitting.[5]