Bladder Diverticulum

A bladder diverticulum is a herniation of bladder mucosa through the detrusor muscle fibres. It forms a sac, usually lacking a muscular wall, that communicates with the bladder lumen through a neck. It is found in 1.7 percent of adults with urinary complaints, mostly men over 60.

Types:

• Congenital (primary) diverticula are usually solitary and lie posterolateral to the ureteral orifice at the ureteric hiatus. They are found in children (more often boys) and are associated with Ehlers-Danlos, Menkes and Williams syndromes, and prune belly syndrome.
• A Hutch diverticulum commonly causes vesicoureteral reflux due to the weakness of the ureteral hiatus.
• Acquired (secondary) diverticula are multiple and much more common. They result from chronic bladder outlet obstruction (benign prostatic hyperplasia, urethral stricture, posterior urethral valves) or neurogenic bladder with high intravesical pressures. These cause trabeculation and cellules and then diverticula.
• Iatrogenic diverticula follow bladder surgery.

Complications:

• Urinary stasis with recurrent infection.
• Stone formation.
• Ureteral obstruction (mass effect on the ureter) and vesicoureteral reflux.
• Urinary retention.
• Tumour development (carcinoma in 0.8 to 10 percent of diverticula). Tumours are high grade and stage, as the wall lacks muscle, so early muscle invasion and perforation occur.

• Often asymptomatic, found at imaging.
• Symptoms of the underlying obstruction: poor stream, hesitancy, frequency, nocturia and incomplete emptying.
• Characteristic double voiding or "two stage" micturition (the patient voids, then the diverticulum empties back into the bladder, and the patient voids again), and a post-void residual.
• Recurrent urinary tract infection, haematuria, pelvic pain and urolithiasis.
• Acute urinary retention (large diverticulum compressing the bladder neck), ureteral obstruction and hydronephrosis.
• In children: urinary tract infection and reflux; large diverticula can produce a palpable abdominal mass.

• Ultrasound: a cystic structure that communicates with the bladder, with residual urine, bladder wall thickness, and stones or tumour inside.
• Voiding cystourethrogram (shows the sac filling and emptying, reflux, and outlet obstruction).
• Cystoscopy: a diverticulum ostium, with trabeculation and cellules; inspect the interior of the diverticulum (use a flexible scope) and biopsy any suspicious lesions, with urine cytology.
• CT urography or MRI for tumour or ureteral involvement; urodynamics to evaluate the outlet (pressure flow) before surgery.
• Urinalysis, culture, and renal function.

• Asymptomatic small diverticulum: observation; treat the underlying cause.
• Treatment of bladder outlet obstruction is first: alpha blocker (tamsulosin 0.4 mg daily) and 5-alpha-reductase inhibitor (finasteride 5 mg daily) for benign prostatic hyperplasia, transurethral resection or laser enucleation of the prostate, urethral stricture repair, or clean intermittent catheterisation in neurogenic bladder with anticholinergic therapy.
• The diverticulum often does not shrink but symptoms improve.
• Surgical diverticulectomy is indicated for large diverticula (above 3 to 4 cm) with persistent infection, stones, retention, obstruction of the ureter, haematuria, or tumour. Options are open surgery (extravesical dissection, or transvesical approach), laparoscopic or robotic (preferred, with 90 to 95 percent success).
• The sac is dissected free from surrounding tissues, with care to protect the ureter (place a ureteral catheter). Its neck is divided, and the bladder defect is closed in two layers with absorbable suture. A drain and urethral catheter stay for 7 to 10 days; a cystogram before removing the catheter.
• Ureteral reimplantation is done if the ureter is involved (Hutch diverticulum with reflux).
• Combined treatment of outlet obstruction (transurethral resection of the prostate) at the same time or before.
• Transurethral resection or incision of the diverticular neck is used for small diverticula and for the neck; endoscopic fulguration of the mucosa is reserved for poor candidates.
• Stones: endoscopic removal with laser lithotripsy.
• Tumour in a diverticulum: partial cystectomy with wide margins or radical cystectomy for muscle invasive disease, with pelvic lymph node dissection, and neoadjuvant chemotherapy where appropriate. Transurethral resection is risky (perforation) because of the thin wall.
• Children: antibiotic prophylaxis (trimethoprim 2 mg/kg at night) for small diverticula with reflux, and surgery for large, symptomatic or complicated diverticula with endoscopic or open excision and reimplantation.
• Follow up: post-void residual, urinary flow rate, ultrasound, and cystoscopic surveillance in older patients with persistent diverticula and risk factors (smokers) for tumour.