the use of ureteric access sheaths prior to flexible ureterorenoscopy can be both a surgical preference and case - specific .
they facilitate multiple passages of the ureterorenoscope , reduce intra - renal pressure and help improve irrigation flow
. however , the surgeon must be aware that access sheaths carry a risk of ureteric ischaemia and can lead to ureteric injury . when using an access sheath , it is important to be aware of the size of the flexible ureteroscope , so that the access sheath of the correct size is used , since some of the new digital flexible ureteroscopes will only pass down certain - sized access sheaths ( > 10 fr ) .
we advocate performing an initial semi - rigid ureteroscopy before placement of the access sheath .
this enables the uo to be optically dilated , ensures that any simultaneous ureteric stones are identified and gives an assessment as to whether the ureter is a  friendly  , capacious ureter or not .
we do not advocate the use of ureteric balloons to dilate the ureter to aid sheath placement nor the use of other ureteric dilators .
although these might be an option in very particular circumstances , in most cases involving an unfavourable ureter , it is usually preferable to place a stent and return for the definitive operation at a later date the decision to leave a safety wire outside an access sheath is one of personal preference .
some newer access sheaths enable a single wire to be used for placement and results in the wire being situated outside the sheath after placement .
such sheaths offer the cost benefit of a single guidewire for the procedure ( although this must be offset against the cost of the access sheath itself ! ) .
once the access sheath of the desired size and length has been chosen , pass the sheath over the guidewire using the seldinger technique .
the sheath passage should be monitored with pulsed fluoroscopy during ureteric passage , preventing possible buckling in the bladder or to identify early resistance and failure to progress .
ensure that the wire does not kink , or coil in the bladder , which will make advancement of the sheath impossible .
if this should occur , gradual step - wise withdrawal of the wire , under close fluoroscopic control , is needed to straighten the wire , and then retry the insertion with particular attention to the sheath crossing the ureteric orifice and lowermost ureter ( see figure 1 ) .
if the access sheath progresses up the ureter well , consider placing it just below the puj , allowing the flexible scope to be fully deflectable .
if you choose not to use an additional safety wire outside the access sheath , be careful when passing the flexible scope through the upper ureter / puj area to avoid unnecessary ureteric injury .
when the procedure is completed , withdraw the ureteroscope and access sheath together with the tip of the ureteroscope placed just at the end of the sheath , watching the ureteric mucosa move past .
any ureteric injury can then be noted and stented accordingly . if a safety wire is not already in place , a wire can be pre - emptively inserted through the flexible ureterorenoscope to allow stent insertion if required .
a straight safety wire is present , but the working wire , over which the access sheath is being passed , is substantially coiled in the bladder .
further advancement of the sheath will not only fail to access the ureter , but is likely to result in displacement of the working wire to the bladder .
the working guide wire has been withdrawn slightly , such that the coiled loop is of smaller diameter .
the working wire is now straight , and the tip of the access sheath has been moved along it towards the left ureteric orifice .
, the access sheath can be advanced under fluoroscopic control to ensure there is no  buckling  in this part of the ureter .
once the lower third has been successfully traversed , the image intensifier can be moved to the proximal ureter to allow precise positioning of the tip of the sheath in the upper ureter .
if unable to pass the access sheath into the uo or much beyond the lower third of the ureter , despite prior normal rigid ureteroscopy , consider using only the inner obturator of the access sheath over your wire , enabling an initial ureteric dilatation by advancing the obturator to the upper ureter .
if this is unsuccessful , one can consider using a stiff wire , rather than the standard guide wire , to aid sheath placement .
be aware that these wires can cause intra - renal bleeding if forced too hard or pushed through the urothelium .
if you are still unable to place the sheath , discretion is much better than valour .
change tack , pass the flexible scope over the stone wire and perform your flexible ureteroscopy without a sheath ( see below ) or simply stent the patient and come back another day .
some surgeons prefer to place the flexible ureteroscope over a wire , without using an access sheath . in order to aid scope passage
, one should use lubrication for the scope and urethra ( such as instillagel ) to reduce resistance , particularly in the male urethra .
one can consider using a double - tipped hydrophilic wire , thereby reducing damage to the fragile working channel of the flexible ureteroscope .
when initially placing the ureteroscope , we would advocate having it free of all attachments ( irrigation channel , light and camera leads ) , enabling smoother passage .
it can then be passed over the wire , again using limited pulsed fluoroscopy to check progress .
if passage is obstructed at the level of the uo , as with semi - rigid ureteroscopy , rotate the flexi scope 180 , enabling the beak of the scope to pass through the uo more easily . if you are still unable to pass the flexible scope , stent the ureter with a view to performing a repeat procedure in approximately 26 weeks .
when manipulating the flexible ureteroscope using the dominant hand , with the thumb controlling deflection , consider holding the shaft of the ureterorenoscope just distal to the urethral opening / access sheath with the opposite hand ( pincer grip technique ) , to aid scope advancement and rotation .
it is pertinent and useful to remember that the ureterorenoscope has 3 user inputs to manipulate the tip : in / out movement , thumb up / down and torque left / right . trying to  waggle  the handle of the ureterorenoscope towards
the patient 's left or right leg in a movement similar to a car 's windscreen wiper will not influence the tip of the scope .
deliberate , slow movements will get one around the whole collecting system faster than wild , fast movements .
once the ureterorenoscope is in the kidney , it is useful to orientate the endosopic view with a fluoroscopic  route map  of the collecting system , with a retrograde study performed via the scope .
complete tour or walking the calyces  of the kidney can then be performed , visiting each calyx in turn , in much the same way that a diagnostic flexible cystoscopy is performed , i.e. in a methodical fashion that ensures complete coverage of the collecting system . as each calyx
is entered , a  snap - shot  on the image intensifier , saved to the memory , will allow a confirmatory review during the case that all calyces were successfully seen .
furthermore , it can aid the rapid reintroduction of the scope towards the calyx of interest ( stone or tcc bearing ) later in the procedure ( see figure 2 ) .
the ureterorenoscope is directed to the upper medial calyx as the starting point for an anti - clockwise tour of the collecting system .
the upper middle calyx will be visualised ( where the safety wire is located ) as the scope is moved to the upper lateral calyx .
the interpole , not well seen on the images 3a - c is filled with contrast via the scope to confirm it has been visualised .
the scope is placed in the next calyces down , in the lateral part of the lower pole .
this required use of the secondary ( passive ) deflection from the renal pelvis / infundibulum to the interpole ( arrow ) .
before performing laser fragmentation in the kidney , consider repositioning the stone into a more favourable position ( upper calyx or even upper ureter if feasible ) . the aim is to keep the ureteroscope as straight as possible while fragmenting , reducing the risk of damage to the flexible ureterorenoscope ( see figure 3 )
it is important to be aware of the individual properties of the different intra - renal baskets available , and especially to understand the pros and cons of the preferred basket .
it is to be noted that increasing the size of the basket ( corresponding to shaft diameter ) will significantly reduce irrigant flow .
the stone has been identified in the lower pole , and is grasped in a basket to prepare for relocation . 3b and c. the ureterorenoscope is manoeuvred out of the lower calyx towards the renal pelvis .
the presence of the safety wire in the upper calyx can aid this both under endoscopic and fluoroscopic control .
the stone is then released from the basket , which is withdrawn from the scope , and replaced with an appropriate laser fibre for stone fragmentation .
. it will be easier to re - pass the ureterorenoscope back and forth to this upper calyx for basket stone retrieval than to direct it repeatedly to the lower calyx where the stone was originally , particularly as the safety wire
there is debate amongst surgeons whether to laser the stone to dust or fragment and retrieve intra - renal fragments , and sometimes the best results are achieved by a combination of the two techniques .
sometimes , it will not be feasible to remove multiple fragments ( such as with a tight ureter and no access sheath or safety wire in a  wireless  ureterorenoscopy ) , so it is important for all endourologists to be aware of the different stone fragmentation effects , when varying the energy and frequency settings .
the different laser settings and their effect on stone fragmentation have been highlighted in a recent publication .
it is helpful to liaise with the anaesthetist to control the patient 's respiratory movement during stone fragmentation in the kidney .
this will not only increase efficacy of lasertripsy but also reduce the risk of compromising the view from bleeding ( through increased accuracy of laser onto the stone as opposed to the urothelium ) , and both factors will help reduce the overall operating time as well .
when the laser fibre is inserted , ensure that the ureterorenoscope is straight in a non - deflected , neutral position 
one of the advantages of having an additional wire in the kidney is maintaining a straight ureterorenoscope .
if the wire is straight , and can be seen running parallel with the direction of vision of the scope , then it stands to reason that the scope is also straight  a quick  flash  of the image intensifier ( regardless of the presence of the additional wire ) will confirm this .
maintaining the scope straight as the laser fibre is passed reduces the risk of working channel damage , avoiding costly repairs .
reusable laser fibres can result in small microfractures , which then contribute to flexible ureterorenoscope damage .
the use of disposable laser fibres is increasing , and they have been shown to be cost - effective and reduce ureteroscope damage .
vision is key to achieving good fragmentation and stone - free rates , particularly in the kidney .
whilst the use of contrast improves vision ( clears dust / blood ) it can cause refractory errors if saline is introduced .
ureteric access sheaths enable improved irrigation rates , with larger access sheaths ( 12/14fr ) offering better flow compared to smaller sheaths ( 10/12fr ) .
however , as noted above , it is important to note that larger access sheaths can potentially cause ureteric ischaemia and even direct ureteric trauma including perforation . simple hand held pump devices can be used and will help increase irrigant flow .
blood will affect vision and may result in a premature end to the procedure . with minor bleeding , increasing the irrigation for a few minutes may help improve the view .
aspiration of the collecting system may result in further bleeding ; therefore , be patient and wait for the vision to improve .
other factors that can affect the quality of vision include the focusing of optical scope , adjusting the brightness of light , correct white balancing and appropriate use of vision enhancement features on the stacking system .
digital ureterorenoscopes use  chip - on - tip  technology and are increasingly commonplace in endourology operating theatres . in vitro assessment
has shown improved image resolution and colour reproducibility without compromising depth of field , image distortion , grayscale imaging and ureteroscope deflection . whilst field of view may be reduced in some comparisons , this is counteracted by an increase in image size .
improved optical characteristics translate to improved clinical outcomes with significant improvements in mean operative time , flexible ureterorenoscopy time and efficiency of stone fragmentation [ 8 , 9 ] .
the placement of a ureteric stent , particularly in an emergency setting , such as relieving obstruction in an infected system , can be a daunting task .
problems might arise with guide wire placement , but hopefully the tips discussed earlier will aid this . when placing a stent
it is useful to try and deploy the proximal coil ( especially multi - length stent ) in the upper calyx , thus enabling a smaller component of the stent in the bladder .
consider the use of a ureteric catheter or tethered stent if feasible , for short - term drainage .
one must always consider whether a stent is really needed , as they have associated morbidity . if considering leaving a stent , good preoperative counselling of the patient is vital .
patients will need to be aware that they might have some pain or discomfort postoperatively .
when placing the stent , if one is having difficulty with buckling at the uo , bring the cystoscope closer to the uo and push slowly under vision .
if the stent is not moving , use fluoroscopy to check the wire placement in the collecting system .
excess wire in the renal end can equally hamper progress . by pulling back the wire slightly under fluoroscopy ( monitoring the renal end )
do not forget to check that your assistant is maintaining adequate stiffness of the wire whilst the stent is being inserted .
some surgeons prefer to place the stents under radiological guidance , using fluoroscopy alone with a  freehand  technique , as opposed to inserting the stent via a cystoscope under direct vision .
in such cases , care must be taken to ensure the distal end of the stent is not pushed too high in the ureter .
it is best to visualise and ensure its position in the bladder before sending the patient to recovery 
if there is any doubt from the final fluoroscopic image , it is best to be sure by passing the cystoscope and having a look ! it is important to remember that bilateral ureteroscopy may result in bilateral stent insertion . finally , regardless of the circumstances leading to stent placement , it is important to ensure that an appropriate postoperative plan is in place to track and remove the stent .
depending on the local set - up , the use of stent registers , or tracking emails or web - based applications might be useful to avoid these  missed stents.
diagnostic ureterorenoscopy and biopsy has been recommended for cases of upper tract tumors [ 3 , 10 ] .
this can be achieved by administrating 20 mg of furosemide in the anaesthetic room . after a diagnostic cystoscopy
, a previously saline - filled ureteric catheter can be placed in the ureter to collect selective cytology from one or both ureters relatively quickly .
this reduces the chance of mucosal trauma , therefore reducing the risk of unnecessary biopsy .
this technique can be technically challenging and is not universally practised . for safety reasons ,
one may prefer to use a guidewire in diagnostic cases . when performing a ureteric / renal tumor biopsy there are two common methods used .
one biopsy technique is by performing a cold cup technique biopsy , utilising a tip - less stone basket .
the base of the tumor can be snared , and then avulsed with some traction .
the second technique utilises single use biopsy devices . once tumor specimens are taken and still in the grasper , consider pushing the biopsy device forward to gently avulse the biopsy .
if one pulls back on the device , the graspers may slip and offer a degraded specimen .
it pays to be careful when avulsing tissue as perforation of the collecting system may occur .
ureteroscopic biopsies have been shown to yield a 90% diagnostic rate for tumor grade , with low false negative rates .
recent evidence suggests that placing the biopsies in bouin 's solution may offer better preservation of nuclear detail .
the use of routine access sheaths for biopsies and laser fragmentation of tumours is discouraged , as any minor trauma of the ureter may theoretically result in tumor seeding , but this might be necessary in selected cases where multiple passes need to be made for biopsy from the pelvicalyceal system .
in addition , the presence of an access sheath will result in lower intra - renal pressure , and allow better irrigation , both of which are valuable in cases of tcc , which , unlike stones , bleed with compromised views under low irrigation flow rates .
newer techniques such as pdd , nbi or spies might be increasingly used for greater diagnostic accuracy in these cases .
the indications for endoluminal surgery continue to widen , mainly through technological advances , such that this branch of urological practice continues to increase year on year . as with most forms of surgery
if one tries to envisage the potential problems preoperatively , appropriate solutions can be considered beforehand . despite the majority of cases being relatively straightforward
we hope the above  tips and tricks  will enable the practitioner to offer safe , effective and successful upper tract surgery .
 our  tips and tricks  focuses on all aspects of upper tract endourology and we hope these will be of use to all trainees and consultants who perform ureteroscopy . 
 we report an  expert consensus view  from experienced endourological surgeons , on all aspects of advanced ureteroscopic techniques , with a particular focus on avoiding and getting out of trouble while performing ureteroscopy . in this paper 
 we provide a summary of placing ureteric access sheath , flexible ureteroscopy , intra renal stone fragmentation and retrieval , maintaining visual clarity and biopsy of ureteric and pelvicalyceal tumours . 
Placing a ureteric access sheath
Flexible ureteroscope insertion 
Laser fragmentation and basket technique
Improving vision in the kidney
Ureteric stenting
Ureteric and renal tumors
CONCLUSIONS
CONFLICTS OF INTEREST