Brunn’s cyst presenting as a rare cause of lower urinary tract symptoms – A case report

INTRODUCTION

The most common causes of bladder outlet obstruction in adults are benign prostatic hyperplasia and urethral strictures. Brunn’s cyst is one of the rare causes of lower urinary tract symptoms. It results from inflammation and benign proliferation of cells in the Brunn’s nest, leading to cyst formation. This creates a ball valve^[1] mechanism when located in the bladder neck and causes difficulty in voiding and an increase in post-void residual urine.

CASE REPORT

A 27-year-old male patient with complaints of urinary hesitancy and sensation of incomplete voiding followed by retention of urine presented in the urology outpatient clinic. The patient also had complaints of decreased urine flow, straining while voiding for 6 months, and was not on any medications.

On clinical examination, there was suprapubic fullness. The patient was catheterized and the retention volume was 800cc. He was advised to undergo a urine routine examination, ultrasound (USG) kidney, ureter, bladder (KUB), computed tomography (CT) urography, and cystoscopy.

Urine examination was normal, no significant findings were noted. USG of KUB showed a small, well-defined anechoic cystic lesion arising from the bladder neck, just above the prostate, anteriorly with no vascularity on color Doppler suggestive of Brunn’s cyst [Figure 1]. It measured about 1 cm in size. Mild diffuse wall thickening of the bladder was also noted. On CT urography, a well-defined cystic lesion measuring 1.2 cm × 0.8 cm was seen in the midline just anterior to the urethral opening, consistent with Brunn’s cyst. There was mild diffuse bladder wall thickening, suggestive of chronic cystitis changes [Figure 2]. Biopsy revealed von Brunn nests in lamina propria, consistent with diagnosis of Brunn’s cyst. Cystoscopy showed a 1.5 cm size smooth surfaced cyst in the bladder neck at 11–1 O’clock position, obstructing the bladder outlet. Mild trabeculations were seen in the bladder wall [Figure 3]. Complete resection of bladder cyst was done. Post-operative period was uneventful. The patient is currently asymptomatic.

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Figure 1:

(a-b) The above figure shows two ultrasound (USG) images. Both images show a small anechoic cystic lesion in the bladder base in midline, anterior to the bladder neck (white arrows) (a) transverse USG image, and (b) coronal USG image.

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Figure 2:

(a) Coronal and (b) Sagittal CT urography images reveal a small Brunn’s cyst located in the midline anterior to the bladder neck, as indicated by the arrows (black arrows- Folley’s Bulb and yellow arrows- Brunn’s cyst). CT: Computed tomography.

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Figure 3:

(a and b) Cystoscopic images illustrate Brunn’s cyst, marked with arrows from various angles. (c) After cystoscopic resection, as indicated by the white arrow, the (d) resected specimen of Brunn’s cyst is shown. The postoperative image reveals the cyst that has been resected through cystoscopy and transurethral resection.

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Histopathology of resected specimen showed a few von Brunn nests within lamina propria showing central cystic dilation with spaces lined by transitional. Lamina propria shows very mild inflammation, congestion, and hemorrhage – features consistent with Brunn’s cyst.

DISCUSSION

Brunn’s cyst or mucus cyst of the urinary bladder originates from von Brunn’s nest, which results from pinching off the epithelial nest^[2] from urothelial buds. Common locations of Brunn’s cysts are ureters^[3] and bladder floor. If present in the vicinity of the bladder neck, they may produce lower urinary tract symptoms and cause bladder neck, they may produce lower urinary tract symptoms and cause bladder neck obstruction by way of ball-valve mechanism.

Cystoscopy plays a diagnostic and therapeutic role. It reveals a cystic lesion at the neck and can be managed by transurethral deroofing or resection of the cyst.^[4]

DIFFERENTIAL DIAGNOSIS

Differential diagnosis of Brunn’s cyst includes prostate cyst, cystitis cystica, ureterocele in ectopic ureter, intravesical ureterocele and other lesions [Table 1].

CONCLUSION

Presence of Brunn’s cyst at bladder neck though rare but should be kept in mind, especially in young and otherwise healthy patient, who presents with persistent LUTS. Transurethral deroofing or excision of cyst results in resolution of the obstructive symptoms and resumption of normal voiding.

TEACHING POINTS

1. Brunn’s cyst is one of the rarest causes of bladder outlet obstruction.

2. Cystoscopy plays both diagnostic and therapeutic roles.

MCQs

1. What is a Brunn’s cyst?

   1. A type of renal cyst commonly found in adults

   2. A benign cyst found in the prostate gland

   3. A fluid-filled cyst within the thyroid gland

   4. A benign cystic lesion originating from the urothelium in the urinary bladder

   Answer Key: d

2. Which of the following is a common characteristic of Brunn’s cysts?

   1. They are always symptomatic and require immediate treatment.

   2. They often contain malignant cells.

   3. They are typically asymptomatic and discovered incidentally but may cause symptoms when present in vicinity of the bladder neck.

   4. They frequently cause hematuria and dysuria.

   Answer Key: c

3. How are Brunn’s cysts usually diagnosed?

   1. Through blood tests

   2. Through ultrasound and other imaging modalities

   3. By cystoscopy

   4. By identifying symptoms like severe abdominal pain and fever

   Answer Key: b and c