A bladder diverticulum is an outpouching of the bladder wall that is either congenital or acquired. Bladder diverticula can be clinically silent or cause symptoms related to obstruction, urinary stasis, and other mechanisms as well. In many cases, it is diagnosed accidentally.
A bladder diverticulum is defined as the herniation of mucosal tissue through the bladder wall, hence creating an outpouching of the wall. Bladder diverticula are either congenital (primary) or acquired (secondary)  and the size and number are variable. The former type includes primary congenital bladder diverticulum (PCBD) and congenital syndromes such as Ehlers-Danlos syndrome, Prune-belly syndrome, Diamond-Blackfan syndrome, and others as well. The bladder outpouching in PCBD is not related to obstruction but is a consequence of an inadequate bladder wall due to a deficiency in the detrusor layer . Investigators in one study managing predominantly male children with PCBD revealed that common manifestations included urinary tract infection with fever and hydronephrosis .
The acquired form is more common and develops in response to high pressure on the trabeculated bladder wall, which is typically secondary to bladder outlet obstruction in the setting of benign prostatic hypertrophy (BPH) . Although BPH accounts for most cases of bladder diverticula , other causes include urethral stricture, bladder neck stenosis, neurogenic bladder, posterior urethral valves, and ureterocele. Diverticula may also result as a postoperative complication.
Regarding the clinical presentation, a majority of diverticula do not produce symptoms and are found incidentally through evaluation for hematuria, urinary tract infection, or bladder outlet obstruction . Men with obstruction secondary to BPH will report trouble with urination and incomplete voiding .
Due longstanding urinary stasis, patients with bladder diverticula are at risk for developing bladder stones and infection . Other serious complications include bladder rupture  and intra-diverticular transitional cell carcinoma .
While many bladder diverticula are typically discovered incidentally during a workup for urinary features , symptomatic cases associated with congenital syndromes, BPH, or other causes should raise the clinician's suspicion for this bladder defect. The diagnosis is confirmed through imaging studies as well as the patient's history and physical exam.
Very importantly, investigations such as the voiding cystourethrography (VCUG), ultrasonography (abdominal and bladder), and a nuclear renal scan will collectively guide the urologic team with preoperative and postoperative assessment . Specifically, VCUG is the superior imaging technique for the diagnosis of bladder diverticula . This test produces optimal results when lateral and obliques views are obtained and fluoroscopy is used throughout the procedure .
Bladder ultrasonography with color doppler enhancement is another beneficial modality since it helps detect the defect, differentiates it from other lesions, and identifies dilated distal ureters . Furthermore, an intravenous pyelography (IVP) is particularly useful in diagnosing lateral bladder diverticula. Finally, the upper urinary tract should be imaged since bladder diverticula can lead to hydroureteronephrosis .