Diverticula of the bladder Definition

The normal intravesical pressure during voiding is about 35—50 cmH2O. Pressures as great as 150 cmH2O may be reached by a hypertrophied bladder endeavouring to force urine past an obstruction. This pressure causes the mucous lining between the inner layer of hypertrophied muscle bundles to protrude, so forming multiple saccules. If one or more, but usually one, saccule is forced through the whole thickness of the bladder wall, it becomes a diverticulum (Fig. 65.32). Congenital diverticula are due to developmental defect.

Aetiology of diverticulum

       Congenital diverticulum — This is rare. It may be situated in the mid line anterosuperiorly and represent the unobliterated vesical end of the urachus. It empties with the bladder and is symptomless. Others in the usual situation on the base of the bladder can occur without obstruction, and may require excision because of the risk of chronic infection or stone formation in a young adult

Pulsion diverticulum — the usual causative obstructive lesion is bladder outflow obstruction

Pathology

Usually the mouth of the diverticulum is situated above and to the outer side of one ureteric orifice. Exceptionally, it is near the midline behind the interureteric ridge. The size varies from 2 to 5 cm, but may be larger. It is lined by bladder mucosa and the wall is composed of fibrous tissue only (com­pare traction diverticulum). A large diverticulum enlarges in a downward direction and sometimes may obstruct a ureter  probably because of peridiverticular inflammation.

Complications

Most patients who develop a small bladder diverticulum secondary to bladder outflow obstruction develop no symptoms after the prostate is resected. The presence of a diverticulum per se is not an indication for open resection and surgical treatment.

Recurrent urinary infection

As the pouch cannot empty itself there remains a stagnant pool of urine within it. Once infected, the infection persists. In long standing cases, peridiverticulitis causes dense adhesions between the diverticulum and surrounding structures. Squamous cell metaplasia and leucoplakia are infrequent complications.

Bladder stone

This develops as a result of stagnation and infection. The stone often protrudes into the bladder.

Hydronephrosis and hydroureter

This is extremely rare and is a consequence of peridiverticular inflammation and fibrosis.

Neoplasm

Neoplasm arising in a diverticulum is an uncommon complication (< 5 per cent). The prognosis is dependent on the stage of the tumour (see a later section).

Clinical features

An uninfected diverticulum of the bladder usually causes no symptoms. The patient is nearly always male (95 per cent) and over 50 years of age.

There are no pathognomonic symptoms; they are those of lower urinary tract obstruction, recurrent urinary infection and pyelonephritis. Haematuria (due to infection, stone or tumour) is a symptom in about 30 per cent. In a few patients, micturition occurs twice in rapid succession (the second act may follow a change of posture).

Cystoscopy

This is the usual means of discovering the diverticulum. Most often its orifice is seen as a clear-cut hole about 5 mm in diameter, the depths of which are black and un-illuminated (Fig. 65.33). With inadequate distension of the bladder, the mouth of the diverticulum is closed with epithelium thrown into radiating pleats (Fig. 65.34). Full distension of the bladder is needed if searching for a diverticulum.

Intravenous urography

IVU may give information regarding the size of the diverticulum.

Retrograde cystography

In practice, this is only used during a video urodynamic investigation which may have been carried out in the investigation of voiding dysfunction. This test will also give information about the emptying characteristics of the bladder and diverticulum.

Ultrasonography

A diverticulum may be detected during an ultrasound scan carried out to measure the residual urine after voiding (Fig. 65.35).

Indications for operation

Operation is only necessary for the treatment of complications. Provided the diverticulum is small and the associated outflow obstruction has been dealt with, there is no reason to resect the diverticulum. Even a large diverticulum may not require treatment in the absence of infection or other complications.

Preoperative treatment

When the urine is infected, suitable preoperative antibiotic treatment is given. In the presence of gross sepsis and retention of urine, it is necessary to resort to an indwelling urethral catheter for a period.

Combined intravesical and extravesical diverticulectomy

This is the standard operation. Cystoscopy is performed, a ureteric stent is passed up the ureter on the affected side, as damage or devascularisation of the ureter is the most common serious complication. The anterior bladder wall is exposed through a suprapubic incision, the peritoneum is displaced upwards and the side of the bladder bearing the diverticulum is cleared from surrounding structures until the pouch is identified. The bladder is then incised in the mid-line and the diverticulum is packed with a strip of gauze. Usually the neck of the diverticulum can be separated from the ureter and when the pouch is free it is severed from its attachment to the bladder with a diathermy knife. The resulting defect is closed in two layers. A suprapubic catheter is left in place and an extravesical drain is inserted.

An alternative method, if the sac is densely adherent, is to carry the incision in the bladder down to the rim of the diverticular orifice, then to detach the diverticulum, together with its fibrous rim. The incision in the bladder is closed and the diverticulum left in position with a corrugated drain into it for 2—3 days. The track fibroses rapidly after removal of the drain.

If bladder outlet obstruction is part of the picture, prostatectomy should be carried out at the same time as the diverticulectomy.

Traction diverticulum (syn. hernia of the bladder)

A portion of the bladder protruding through the inguinal or femoral hernial orifice occurs in 1.5 per cent of such herniae treated by operation (Fig. 65.36).