I have a 4.6 cm cystic lesion adjacent to the right bladder on imaging; what is the likely diagnosis and how should it be evaluated and managed?

Bladder Diverticulum: Diagnosis and Management of a 4.6 cm Cystic Pelvic Lesion

A 4.6 cm cystic lesion adjacent to the bladder is most likely a bladder diverticulum, and you should confirm this diagnosis with pelvic ultrasound followed by office cystoscopy to visualize the communication with the bladder lumen and rule out malignancy within the diverticulum. 1

Initial Diagnostic Approach

First-Line Imaging: Pelvic Ultrasound

• Perform transabdominal pelvic ultrasound with a full bladder as your initial imaging study to characterize the cyst's wall features, internal architecture, and relationship to the bladder. 1

• Document whether the lesion communicates directly with the bladder lumen, which is the defining feature of a bladder diverticulum. 1

• Scan from multiple perspectives with varying degrees of bladder distention to clarify the connection between the mass and bladder wall. 2

• Obtain postvoid images to assess whether the lesion empties with bladder emptying, confirming communication. 2

• Use color Doppler interrogation to evaluate for internal vascularity that would suggest a solid component or malignancy. 2

Key Sonographic Features of Bladder Diverticulum

• Look for a cystic structure with a narrow neck connecting to the bladder wall, which distinguishes a diverticulum from other pelvic cysts. 2

• The lesion should contain anechoic fluid similar to bladder urine and should change in size with bladder filling and emptying. 2

• Absence of internal solid components or thick irregular walls suggests a benign uncomplicated diverticulum. 1, 2

Mandatory Urologic Evaluation

Office Cystoscopy

• Perform office cystoscopy to directly visualize the bladder mucosa and identify the diverticular opening, which is essential for confirming the diagnosis. 1

• Carefully inspect the interior of the diverticulum for any mucosal irregularities, masses, or suspicious lesions, as diverticula can harbor malignancy in 2-10% of cases. 3, 4

• Obtain urine cytology to screen for malignant cells, particularly important given the stagnant urine in diverticula increases cancer risk. 1

Advanced Imaging When Indicated

• Order contrast-enhanced CT abdomen/pelvis (CT urography protocol) if cystoscopy reveals any solid component, irregular wall thickening, or suspicious mucosal changes to stage potential malignancy and evaluate the upper urinary tracts. 1

• Consider CT imaging before cystoscopy if the ultrasound shows concerning features such as wall thickening, nodularity, or internal solid components. 1

Differential Diagnosis Considerations

In Female Patients

• Obtain transvaginal ultrasound in addition to transabdominal views to definitively exclude an adnexal origin (ovarian cyst, paraovarian cyst, peritoneal inclusion cyst). 1

• Determine whether the lesion is separate from or arising from the ovary/adnexa using the superior resolution of transvaginal imaging. 1

• If the lesion is confirmed to be separate from gynecologic structures and communicates with the bladder, proceed with urologic evaluation. 1

Other Urologic Lesions to Exclude

• Urachal cyst: typically located at the bladder dome in the midline, may not communicate with the bladder lumen. 1

• Bladder wall cyst/mass: requires cystoscopy for definitive assessment and may represent a neoplasm. 1

Management Algorithm Based on Findings

Asymptomatic Diverticulum Without Complications

• Conservative management with observation is appropriate if the diverticulum is asymptomatic, shows no evidence of malignancy on cystoscopy, and urine cytology is negative. 3

• Address any underlying bladder outlet obstruction (such as benign prostatic hyperplasia in men) with medical or surgical treatment, as this is the primary cause of acquired diverticula. 5, 3, 4

• Small diverticula may resolve spontaneously once bladder outlet obstruction is relieved. 4

Indications for Surgical Intervention

Proceed with diverticulectomy if any of the following are present:

• Symptomatic diverticulum causing pain, recurrent urinary tract infections, or urinary retention. 4

• Large size (>4 cm) with persistent symptoms despite treatment of bladder outlet obstruction. 5, 4

• Suspicion of malignancy based on cystoscopy findings, positive cytology, or imaging features. 3, 4

• Stones within the diverticulum that cannot be managed endoscopically. 3

Surgical Approach Selection

• For diverticula >4 cm, both laparoscopic diverticulectomy and endoscopic fulguration are effective options. 5

• Laparoscopic diverticulectomy achieves 100% therapeutic success (complete resolution or >80% size reduction) but requires longer operative time (median 185 minutes) and carries a 15% risk of grade III complications. 5

• Endoscopic transurethral resection of the diverticular neck with fulguration achieves 75% therapeutic success with shorter operative time (median 62.5 minutes) and no early postoperative complications. 5

• Combine diverticulectomy with transurethral resection of the prostate in the same operative session if bladder outlet obstruction is present. 5

• Open diverticulectomy is reserved for giant diverticula or when laparoscopic approach is not feasible. 4

Critical Pitfalls to Avoid

• Do not assume a cystic pelvic mass is gynecologic in origin without confirming its relationship to the bladder, as bladder diverticula can mimic adnexal masses. 6, 2

• Do not perform cystoscopy before cross-sectional imaging if ultrasound reveals solid components or irregular walls, as staging imaging is required first. 1

• Do not ignore the malignancy risk in bladder diverticula—always perform cystoscopy and cytology even if the lesion appears benign on imaging. 3, 4

• Do not treat the diverticulum alone without addressing underlying bladder outlet obstruction, as failure to relieve obstruction will lead to recurrence. 5, 3, 4

Specific Diagnostic Workup Summary

1. Pelvic ultrasound with full bladder and postvoid images 1, 2
2. Office cystoscopy to visualize diverticular opening and inspect for malignancy 1
3. Urine cytology 1
4. Contrast-enhanced CT abdomen/pelvis if cystoscopy shows concerning features 1
5. Urodynamic studies if detrusor dysfunction is suspected 3
6. Voiding cystourethrography to delineate anatomy and assess for vesicoureteral reflux 3