Ureteroscopy

and Raj Kucheria³

(1)

East of England Deanery, Papworth Hospitals NHS Trust, Papworth Everard, UK

(2)

Department of Urology, East of England Deanery, Peterborough City Hospital, Bretton Gate, Peterborough, PE3 9GZ, UK

(3)

Department of Urology, East of England Deanery, The Royal Free and UCL, Pond St, Hampstead, London, NW3 2NG, UK

Introduction

Ureteroscopy (URS) allows for proper visualisation of the upper urinary tract . It is valuable as a diagnostic tool and with recent advances can be utilised for effective therapeutic intervention. The endoscope is commonly either ‘semi-rigid’ which has replaced many of the rigid ureteroscopes, or ‘flexible’ with manoeuvrability of the head. When introduced beyond the ureters into kidney, it is termed ureteropyeloscopy or ureterorenoscopy .

This chapter aims to provide the reader an overview of the instrumentation, indication, procedure and complications.

Relevant Anatomy

The ureter is divided into three approximate segments:

1.

Distal/pelvic—extravesical and intramural region
2.

Middle—between the extremities of the sacroiliac joint
3.

Proximal/renal—from the urinary pelvis to the proximal portion of the sacroiliac joint

Typically the normal ureter has a diameter of 3 mm and is easily distendable. It can have a variable calibre dependent upon anatomical or functional factors. There are two areas of increased calibre (ureteral spindles) in the lumbar and pelvic areas with a diameter of 510 mm. Conversely, there are also three physiological narrowings that the endoscopist must account for that divide the three segments:

The vesico-ureteric junction (VUJ)
The crossing of the ureter over the iliac vessels as it enters the pelvis
The pelvi-ureteric junction (PUJ)

In addition to being sites of ureteral stone obstruction, these serve as natural barriers to the ureteroscope.

The distal intramural ureter (portion within the bladder wall) is the narrowest segment (lumen diameter 1.5–3 mm). Beyond this, in the middle segment the ureter has a diameter of approximately 4 mm and iliac artery pulsations can be observed posteriorly through the ureteral wall. As the endoscope advances this portion of the ureter has a relatively straight trajectory, located on the psoas muscle. The final portion is represented by the PUJ (lumen diameter 2–4 mm). As the examiner approaches there may be synchronous movement with respiration transmitted from the diaphragm, confirming the presence of the endoscope in the proximal ureter. Some or even all of these anatomical findings may not be evident in some patients.

The Ureteroscope

These instruments form an extension of cystoscopes and have developed rapidly in recent decades. From the inception of the endoscope by Bozzini in 1807 to the first known evaluation of the ureters from Hugh H. Young in 1912 with a 9.5 Fr paediatric cystoscope; there have been significant advances in the development of the modern ureteroscope. These have included developments in the reduction of diameter, addition of a working channel, the ability to run irrigation fluid, ports for instrumentation, fibre-optics and optimisation of light deflection. Recent advances in digital imaging have also allowed for improved resolution and sensitivity in comparison to fibre-optics.

Ureteroscopes are much longer and thinner than their cystoscope counterparts to enable access towards the upper portion of the ureters. The semi-rigid endoscope emerged due to concerns of the rigid endoscope being unable to access the upper portion of the ureter without causing significant trauma to the urothelial lining. They have mostly replaced the rigid ureteroscope.

Semi-rigid Ureteroscopes

Previously semi-rigid ureteroscopes tended to have distal portions with smaller diameters with gradual enlargement towards the proximal end (to facilitate distension and passage). Currently with the progression of instruments and miniaturisation, most semi-rigid diameters tend to be the same diameter throughout, in the range of 4.5–7.5 Fr.

Most ends of the distal ureteroscope are circular or ovoid however recent designs have been triangular to facilitate approach of the ureteral orifice and reduce risk of trauma. The tip of the ureteroscope is also tapered to facilitate access through the ureters. The total length of the models is in the range of 31–40 cm (note the ureter length to typically be 2230 cm). In men a length of approximately 40 cm is required to approach the renal pelvis; in women a smaller length suffices.

Typically there are two working channels in the ureteroscope. They can range from 2.1 Fr to 6.6 Fr though generally there is one channel that is at least 3.4 Fr to allow passage of accessory instruments and adequate irrigation. The viewfinder of the instrument can be positioned within the axis (looking straight down the ureteroscope) or adjacent to it as in Fig. 3.1.

Fig. 3.1

A semi-rigid ureteroscope . It consists of (a) an outer tube (b) working channel (c) instrument port (d) light post (e) eyepiece

In most models light transmission occurs through optic fibre fascicles . The resolution is proportional to the number of optical fibres in each fascicle. Due to the diameters of semirigid ureteroscopes being larger than their flexible counterparts, there is room for more fascicles and subsequently higher quality images. With the advent of the digital imaging there are newer models of ureteroscopes with improved imaging resolution.

Flexible Ureteroscopes

These were introduced with increased flexibility and reduced size with the advent of fibreoptics . The addition of active deflection provided these instruments with superior mobility inside the upper urinary tract. Pushing the mobile piece on the body of the ureteroscope allows for the tip to deflect (typically bi-directionally in a range of 170^–180^o). Some models allow for exaggerated deflections up-to 270^o or a secondary deflection e.g. an additional 130^o by attaching a second mobile piece on the opposite end. Flexible URS allows for proper intra-renal inspection through the use of its deflection (Fig. 3.2).

Fig. 3.2

A flexible ureteroscope . Similarly it has a more flexible outer tube, working channel, instrument port, light post and eyepiece. Note the mobile piece below the light post, this allows for active deflection

Recent advances allow for more fibres to be packed into bundles allowing for the reduction in ureteroscope diameter without as much loss in quality. However, these images still tend to be inferior in quality to those transmitted from their semi-rigid counterparts. In recent years digital imaging has been implemented into newer models with improved resolution and quality.

A Comparison

Semi-rigid ureteroscopes are more firm than their flexible counterparts. They allow for potential access to the upper calyx of the renal pelvis; however for a complete examination of the kidney, a flexible ureteroscope is required to visualise the middle and lower calyces. At the level of the upper ureters a flexible ureteroscope may be preferred due to its ability to manoeuvre the anatomical path. More distal examination up to the level of the renal pelvis is easier in female ureters, due to more direct access and reduced length compared to male ureters. It may be possible in male ureters if they are dilated e.g. previous ureteric stenting.

Semi-rigid ureteroscopes tend to have longer functional lifespans in comparison to flexible ureteroscopes. Single use versions of flexible ureteroscopes are also available however these tend to provide poorer imaging quality, with most operators preferring the re-usable models. The exact choice will depend on the case and indications for the examination.

Accessory Equipment

Guidewires
Ureteral catheters—single-lumen or dual-lumen
Balloon dilators
Ureteral access sheaths
Biopsy forceps
Baskets (for stone extraction)
Laser therapy—most commonly the Holmium:YAG (Ho:YAG).

Guidewires allow for easy access into the ureter. Guidewires have a length commonly of 145 cm and are coated with polytetrafluoroethylene (PTFE) for visualisation during fluoroscopy. One commonly used is the ‘sensor’ guidewire with a flexible tip but rigid end. The rigidity allows the passage of a catheter or stent. A ‘roadrunner’ guidewire may be used in cases of difficult access e.g. a stricture. Although some groups have demonstrated success without safety guidewires, usage of a safety wire is strongly recommended in case there is loss of vision or significant trauma as this allows for easier and quicker placement of a ureteric stent.

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