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Keywords:

  • supine;
  • percutaneous nephrolithotomy;
  • position

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES

Study Type – Therapy (case series)

Level of Evidence 4

What's known on the subject? and What does the study add?

Supine percutaneous nephrolithotomy (PCNL) has been described for over a decade and has equivalent success rates when compared with the more widely used prone position. The supine position offers a shorter operative duration with better access to the airway for the anaesthetist and also allows for simultaneous retrograde intra-renal surgery (RIRS). Various supine positions have been described but there is little data regarding their differing benefits and disadvantages.

The present study looks at the different supine PCNL positions and compares the strengths and weaknesses of each. Each of the previously described supine PCNL positions have some limitations, e.g. ease of puncture under image guidance, the ability and ease of making and dilating multiple tracts, and allowing simultaneous RIRS. The new ‘Barts flank-free modified supine position’ is described, which seems to offer a good compromise and addresses some of these issues. It is important to highlight that one supine position does not fit all and the endourologist should familiarise themselves with these positions so the appropriate position can be used for the right patient and stone burden.

OBJECTIVE

  • • 
    To discuss the relative merits of the different described supine positions for percutaneous nephrolithotomy (PCNL) and highlight the new ‘Barts flank-free modified supine position’, as the last decade has seen the emergence of various supine positions for PCNL.

MATERIALS AND METHODS

  • • 
    We reviewed English publications on supine PCNL to look at the different positions being used to carry out PCNL and their relative merits.
  • • 
    We describe the new ‘Barts flank-free modified supine position’, which we think will add significantly to the armamentarium of the endourologist.

RESULTS

  • • 
    Five different supine positions are discussed.
  • • 
    These include the complete supine, the Valdivia, the Galdakao modified Valdivia, the Barts modified Valdivia and the herein described Barts flank-free modified supine position
  • • 
    These positions all differ in regard to ease of puncture under image guidance, operative field availability, ability to make multiple tracts and the ease of combining retrograde intra-renal surgery.

CONCLUSIONS

  • • 
    All of the supine positions decrease operative duration, as there is no need for repositioning and allow quick access to the airway for the anaesthetist.
  • • 
    However, one supine position does not fit all and the right one must be chosen for the right patient with the right stone burden. It is important for endourologists of today to familiarise themselves with these positions to be able to make these judgements.

Abbreviation
PCNL

percutaneous nephrolithotomy

RIRS

retrograde intra-renal surgery

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES

The last three decades has seen the evolution of percutaneous nephrolithotomy (PCNL) as the ‘gold standard’ treatment of large renal stones. Initial experience with PCNL was in the prone position [1] and it was done this way almost exclusively until the last decade. Although prone is still the most widely practised position, the last decade has seen the practise of various different positions for PCNL. These include, prone flexed [2], lateral [3], split-leg [4], supine [5,6] and modified supine positions [7,8].

Prone PCNL has potential disadvantages, as it may cause circulatory and ventilatory compromise, especially in the obese patient. Additional difficulties of prone anaesthesia include direct and indirect pressure effects, e.g. vascular, peripheral nerve and cervical spine injuries, tracheal compression and ocular injury. Simultaneous anterograde and retrograde access is also not feasible in the prone position.

Two recent meta-analyses have shown supine PCNL to be as effective as prone PCNL when comparing stone-free rates, transfusion, complications and it was noted to be significantly quicker than the prone position [9,10]. Today, the debate is not merely whether prone or supine is the best position. There are various supine positions available and we would like to discuss the relative merits of each.

The first described supine position was that of Valdivia [5] with a 3-L saline bag below the flank. This original position does not allow for easy concurrent retrograde instrumentation and also provides limited space for choosing an access and hence has never been universally popularised. A modification of this was the Galdakao-modified Valdivia position [7] with again a saline bag below the flank with the legs in lithotomy, the affected side extended with the contralateral leg abducted. This allows access to the entire urinary tract without the need for repositioning and allows simultaneous retrograde access if required.

The Barts modified Valdivia position [8] offers a large surface area for access with easy manipulation of the nephroscope, as the trunk is placed at 90 ° to the operating table. However, renal access is not always a straightforward and easy endeavour. The position results in rotation of the kidney such that the calyces are viewed end on and also the spine lies in the field of the collecting system. Therefore puncture is difficult to achieve under fluoroscopy alone and often requires ultrasound localisation. Simultaneous retrograde intra-renal surgery (RIRS) is possible although ureteroscopy is performed from a position of relative unfamiliarity due to the rotated position.

With the modified Valdivia position there is not quite the radical rotation of the torso, as with the Barts technique, and therefore puncture under fluoroscopic control is much easier. In this position the kidney is hypermobile. There is therefore the risk that puncture and guidewire manipulation is more difficult. In obese patients especially this leads to longer tracts, which themselves lead to reduced nephroscope mobility. There is therefore a greater torque required to manipulate the scope, which can lead to damage to the renal parenchyma and risk increased bleeding form the tract. The tract is more lateral in the supine position thus there is less radiation exposure for the surgeon and also the surgeon is able to sit during the procedure. The more horizontal access also leads to lower intra-renal pressures and easier washout of fragments. However, there is an inability to distend the pelvi-calyceal system and it is more difficult to employ multiple punctures. Although there is not as much space as the Barts position for multiple punctures this is offset by the relative ease of puncture under fluoroscopy. Ureteroscopy again is performed in a much more familiar and conventional position.

Recently, we have started using a supine position that we have termed ‘the Barts flank-free modified supine position’, involving a 15 ° tilt by using a 3-L saline bag under the ipsilateral rib cage and a small gel pad under the ipsilateral pelvis, with the ipsilateral arm brought across the chest to the contralateral side (Fig. 1). The legs are placed in lithotomy, with the ipsilateral side relatively extended and the contralateral side abducted (Fig. 2). There is no support under the loin thus allowing more space for ideal renal access and the ability to use image-guided access with relative ease. Fluoroscopy is easier and conventional in this supine position, with the surgeon's hands being further from the operative and radiological field. Additionally, the kidney lies in a neutral position as compared with the semi-supine positions, e.g. the modified Valdivia and Barts positions, and therefore it is less likely to displace anteriorly. The kidney is therefore also less mobile and puncture and dilatation are consequently easier. This supine position also offers great flexibility in planning surgery, in that primary ureteroscopy may be embarked upon in this position quite readily and then if percutaneous access is required then no further adjustment is required. However, there is a smaller operative field with the tract being fairly horizontal, even more so than the modified Valdivia, and again this facilitates lower intra-renal pressures and washout of fragments. The more horizontal angle may on occasion make the scope more difficult to manoeuvre due to the low position of the tract with the operating table getting in the way.

image

Figure 1. ‘The Barts flank-free modified supine position’. Please note gel pad one under the ipsilateral pelvis and gel pad two under the rib cage leaving the flank free, allowing around 15 ° rotation of the patient. The ipsilateral arm is brought across the chest to the contralateral side. The ribs are marked. P.A.L, posterior axillary line; I.C, iliac crest.

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image

Figure 2. The ipsilateral leg is relatively extended and the contralateral leg is relatively abducted.

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The complete supine position [6] allows limited space for planning renal access, as the flank is relatively poorly exposed and may result in reduced ability to manoeuvre the nephroscope, especially for anterior calyceal calculi. There is also no readily available retrograde access to the urinary tract and hence combined procedures are not possible.

The traditionally used prone position offers a wide operative field with ease of puncture under image and indeed ultrasound guidance, easy ability to make and dilate multiple tracts but has a significant disadvantage in that simultaneous RIRS in not practical if not impossible. The increased operative time and anaesthetic concerns are well recognised and described in this position. Table 1 shows a comparison of the ease of puncture under image guidance, ability to make and dilate multiple tracts and to carry our simultaneous RIRS between all the mentioned supine together with the prone positions.

Table 1. Comparison of the ease of puncture under image guidance, ability to make and dilate multiple tracts and to carry our simultaneous RIRS between the supine and the prone positions
MethodPosition
ProneComplete supineValdiviaGaldakao modified ValdiviaBarts modified ValdiviaBarts flank-free modified supine
Ease of puncture under image guidanceA-P image, puncture routineA-P image, puncture routine30° torso rotation makes puncture more difficult30° torso rotation makes puncture more difficultDifficult and usually requires ultrasound-guided puncture15° torso rotation but a 5–10° rotation of c-arm gives an A-P view and hence easy puncture
Ease of tract dilatationRoutine with shorter tracts compared with supine positionsRoutine, but tract usually longer than with prone positionKidney more mobile in this position and hence tract dilatation can be more difficultKidney more mobile in this position and hence tract dilatation can be more difficultKidney more mobile in this position and hence tract dilatation can be more difficultKidney less mobile than with the Valdivia and modified Valdivia positions but more mobile than with prone and complete supine
Multiple puncturesLarge operative field, multiple punctures routineDifficult due to lack of exposure of flankMore difficult than prone due to support under flank and hence limited exposureMore difficult than prone due to support under flank and hence limited exposureRoutine as flank well exposedGood exposure as flank is free from support but still less exposure than with prone and Barts modified Valdivia position
Combined RIRSDifficult even in split leg prone positionDifficult as legs not in lithotomyDifficult as legs not in lithotomyRoutinely performed but trunk rotation makes position of ureteroscopy unfamiliarRoutinely performed but rotation makes position of ureteroscopy unfamiliarRoutinely done and relatively little trunk rotation makes ureteroscopy easier than with Galdakao and Barts modified Valdivia positions

In summary, all of the supine positions decrease operative duration, as there is no need for re-positioning and allow quick access to the airway for the anaesthetist. However, they vary in the ease of puncture, tract dilatation, ability to make multiple tracts and ability to combine RIRS. There is a lack of high level evidence comparing the various positions used for supine PCNL or indeed any high quality randomised studies comparing the supine with the prone position and this will need to be addressed. Also, there does not appear to be any consensus as to which is the ideal supine position but the modified Valdivia and complete supine positions appear to have been the most widely published. What is important is to say that one supine position does not fit all and the right one must be chosen for the right patient with the right stone burden. It is important for endourologists of today to familiarise themselves with these positions to be able to make these judgements.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES