Instrumental and endoscopic examination of the urinary tract - catheterization, urethrocystoscopy, lithotripsy, biopsy

A urinary catheter is a tube that collects urine from the urinary bladder and drains it into a bag. Catheters are used where there is a risk of urinary retention, which means the bladder cannot empty normally. Catheterisation is one of the most common instrumental procedures in urology and general practice, and it is used for diagnosis, monitoring and treatment.

Urinary catheterisation is indicated in the following situations:

• obstruction of the urethra
• urogenital surgery
• neurological damage, whether of the central or the peripheral nervous system
• a condition that impairs mental function, such as dementia
• medicaments that limit the ability of the bladder muscle to empty the bladder

Other indications in routine practice include acute urinary retention from any cause, drainage of the bladder during and after pelvic or urethral surgery, and accurate measurement of urine output in critically ill patients.

There are three main types of urinary catheter. Each is chosen for a different purpose.

Indwelling catheters

Indwelling catheters are the catheter type most people think of first. They can be urethral, passed through the urethra, or suprapubic, placed through the abdominal wall into the bladder. A suprapubic catheter is used when a urethral catheter cannot be passed or is unwanted for long-term use. The balloon is normally inflated with sterile water, and it holds the catheter in place inside the bladder.

Intermittent catheters

Intermittent catheters are the usual choice for a patient with an emptying problem who can learn to catheterise themselves, for example someone with a neurogenic bladder. Because the catheter is removed after each emptying, the bladder is not left with a catheter in place, which lowers the risk of long-term infection.

The most important complication of urinary catheters is urinary tract infection (UTI), which can in turn lead to urosepsis. Other risks include:

• allergic reaction
• bladder stones
• bladder or urethral trauma
• kidney damage, with long-term indwelling catheters

Other recognised complications include blockage of the catheter by encrustation or blood clot, catheter-associated bacteraemia, and urethral stricture after prolonged indwelling use. Infection is the reason catheters should be used only when they are needed and removed as soon as the indication has passed.

A urethral catheter is placed using a sterile technique with a lubricant. The size of the catheter is matched to the urethra, and the standard unit of size is the French gauge (Ch).

Before a urethral catheter is passed, the clinician looks for signs of urethral injury. These include blood at the urethral meatus, a perineal or scrotal haematoma, a high-riding prostate on examination, and resistance to passing the catheter. If urethral injury is suspected, catheterisation through the urethra must not be attempted, and a suprapubic route or specialist review is used instead.

The balloon of an indwelling catheter is inflated only once the tip is seen to lie in the bladder, which is confirmed by the return of urine. The catheter is secured to the thigh to prevent traction on the urethra. The drainage bag is kept below the level of the bladder so that urine does not flow back into the bladder.

Endoscopic examination of the lower urinary tract is done through a procedure known as cystoscopy. It uses irrigation, illumination and optics to allow direct observation of the urethra and the urinary bladder. A flexible endoscope is typically used, although fixed (rigid) cystoscopes also exist.

The examination follows a systematic approach. The examiner looks at the urethra, the prostate, the bladder walls, the bladder dome and neck, and the urethral orifice, to detect any abnormality. Sterile irrigation fluid is passed through the instrument to distend the bladder so that its walls can be seen clearly. The position and the efflux of each ureteric orifice are also noted.

1% lidocaine is typically applied as the local anaesthetic, usually as a gel placed in the urethra before the scope is passed.

The most common indication is for haematuria and tumour surveillance, and for the removal of ureteric or urethral stents. The indications are:

• evaluation of patients with voiding symptoms
• gross or microscopic haematuria
• evaluation of urologic fistulas
• evaluation of urethral or bladder diverticula
• congenital anomalies in paediatric populations
• biopsy
• retrograde pyelography
• treatment of urethral strictures
• treatment of bladder stones, ulcers or tumour removal
• reflux treatment in paediatric populations

Cystoscopy is also the usual route for follow-up of bladder cancer, for investigation of recurrent urinary tract infection without a clear cause, and for assessment of persistent bladder pain.

The instrument has a working channel, so the examiner can pass tools through the scope while looking at the lesion. This design allows biopsies to be taken from the bladder where required, and it allows stones, tumours and strictures to be treated at the same session.

Complications include:

• urinary tract infection
• haematuria
• dysuria
• bladder or urethral injury

Other complications that are recognised in practice are urethral stricture after repeated instrumentation, bleeding after biopsy or resection, and, rarely, sepsis. Active urinary tract infection is a reason to postpone elective cystoscopy, because instrumentation can introduce bacteria into the blood.

Lithotripsy is a technique for focusing externally generated shock waves at a stone so that it breaks into fragments small enough to pass. The shock waves are generated outside the body and passed through the tissues to the stone.

There are three methods of generating shock waves.

Lithotripsy is best used for small stones, less than 1 cm across, in a favourable anatomical location. It is less effective for larger stones, for stones in the lower pole of the kidney, for stones within a calyceal diverticulum, and for stones of a harder composition. The harder compositions are cystine and calcium oxalate monohydrate stones.

Lithotripsy causes a certain amount of structural and functional renal damage. The common effects are:

• haematuria
• oedema
• urinary tract infection, caused by bacteria released from the stone

A perirenal haematoma is a rare complication. Effective renal plasma flow appears to fall in about 30% of cases.

The absolute contraindications are:

• pregnancy
• blood clotting disorders

Other factors that prevent the procedure in practice include untreated urinary tract infection, an obstruction below the stone that would prevent fragments from clearing, and an aortic or renal artery aneurysm.

Stones can also be fragmented directly by endoscopy, which is an alternative when shock-wave treatment is unsuitable. Ureteroscopic lithotripsy is performed through a ureteroscope and uses a laser (commonly holmium), pneumatic or ultrasonic energy applied to the stone. The stone is seen directly, which makes this approach suitable for stones in the ureter and for stones that do not respond to shock waves.

Biopsy is indicated where there is a query regarding malignancy. A tissue sample taken from a suspicious lesion allows the diagnosis to be confirmed under the microscope.

Bladder biopsy is taken during cystoscopy through the working channel of the instrument. The examiner sees the lesion, takes a sample, and sends the tissue for histological examination. Biopsy of a lesion at the bladder neck, or a deep sample taken during resection of a tumour, is done in the same way. Urethral biopsy is taken in a similar fashion from a suspicious lesion of the urethra.

Common complications of biopsy are bleeding and infection. Perforation of the bladder is rare, and the risk is higher in a small or contracted bladder.

Biopsy of the upper urinary tract, such as a lesion in the renal pelvis or ureter, is done through a ureteroscope or by percutaneous approach under imaging guidance. Biopsy of the kidney itself is performed percutaneously with ultrasound or CT guidance. Prostate biopsy is taken through the rectum or the perineum, and it is discussed with prostate cancer. The main point is that any suspicious lesion found on endoscopy or imaging should have a histological diagnosis before treatment.