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Simon K. S. Choong

Simon K. S. Choong

Simon K. S. Choong MBBS(Lon), FRCS(Eng), FRCSEd, MS(Lon), FRCS(Urol) Consultant Urologist & Honorary Senior Lecturer

Simon K. S. Choong

MBBS(Lon), FRCS(Eng), FRCSEd, MS(Lon), FRCS(Urol)

Consultant Urologist & Honorary Senior Lecturer





Oundle School, Oundle, Peterborough, UK

M.B.B.S. University College Hospital, London






M.S. (University of London)


Hunterian Professorship





Aug.1989-Jan.1990                 House Physician to Dr. P. McIntyre and Dr. A.Young

Queen Elizabeth II Hospital , Welwyn Garden City.

Feb.1990-July1990                  House Surgeon to Mr.R.C.G.Russell and Mr. J.Scurr.

University College Hospital, London.

Aug.1990-Jan.1991                  SHO in Accident & EmergencyDepartment

Hammersmith Hospital, London.

Feb.1991-July1991                   SHO to Professor R.C.N.Williamson and Mr. N.Habib

Hammersmith Hospital, London.

Feb.1992-July1992                   SHO in Orthopaedics to ProfessorS.Hughes,

Ealing Hospital, London.

Feb.1993-July1993                   SHO in Urology to Mr.C.R.J.Woodhouse

St. George's Hospital, London.

Aug.1993-Jan.1994                  SHO in Vascular and General Surgeryto

Mr. R.S.Taylor and Mr. J.A.Dormandy

St. George's Hospital, London.

Feb.1994-Jan.1995                  SHO in Urology and GeneralSurgery

to Mr. P.Abel and Mr. D.Sellu.

Ealing Hospital, London.

Feb.1995-April1997                 Research Fellow to Mr. H.N.Whitfield

Institute of Urology and Nephrology, London.

May1997-Sept.1998                Specialist Registrar (SpR) in Urologyto

Mr. H.N. Whitfield & Mr. M. Gleeson

Central Middlesex Hospital NHS Trust, London.

Oct.1998-March1999               SpR in Urology to Mr. R. Miller and Mr. M.Emberton

Whittington Hospital, London.

April1999-Sept.1999                SpR to Mr. C.R.J. Woodhouse and Mr. P.M.Cuckow

Institute of Urology and Nephrology, London.

Oct.1999-Sept.2000                 SpR to Mr. Roger Kirby, Mr. Mike Bailey, Mr.Ken

Anson, Mr. John Boyd and Mr. Chris Anderson

St. George's Hospital, London.

Oct.2000-Oct. 2001                 SpR to Mr. R.C. Tiptaft, Mr. J. Glass & Mr. S.Khan

Guy’s Hospital, London.

Oct2001-June2002                   SpR to Mr. S. Carter, Mr. JWARamsay,

Charing Cross Hospital, London.

July2002-Present                       Consultant Urological Surgeon & HonorarySenior

Lecturer, Institute of Urology, University College London Hospitals

Sept2009-Present                      Honorary Consultant UrologicalSurgeon

Great Ormond Street Hospital for Children, London




Introduction: There is no objective encrustation result on urological devices in current use and mechanisms of encrustation are incompletely understood. Consequently, the use of urological devices in the urinary tract carries significant complications [1,2,3,4].


Methods: An in vitro encrustation model was developed and validated [5] to quantify encrustation on polymers, urinary catheters and ureteric stents using fresh human urine under standard conditions (pH 6.0 and 37 0C). The same materials tested in vitro were implanted into the bladders of rats to extend the study to an in vivo situation.


Ten different types of ureteric stents in current use were studied. The amount of encrustation was correlated with the surface roughness, the number and shape of side-holes, the different materials used in their construction and their hydrophobicity.

To identify novel biomaterial, 20 different polymers were screened by the in vitro encrustation model and those which encrusted least were implanted into the bladders of 48 male Wistar rats. Of the latter group those that encrusted least were made into ureteric stents.


In addition, variation in the chemical composition of urine influences encrustation, in particular, the relationship between urinary pH and [Ca2+]. This relationship was studied in fresh urine samples collected from urinary catheter ‘blockers’ and ‘non-blockers’. The pH at which crystals precipitated and its correlation with [Ca2+] was determined. Chemical analysis and bacteriological studies of the urine samples were performed using standard chemical pathological techniques.


Results: The amounts of encrustation on the ureteric stents in current use were measured using the in vitro model. Silicone stents encrusted least. Stents coated with hydrogel encrusted more than the same uncoated stents. Examination of the currently used devices by scanning electron microscopy revealed several features that enhanced encrustation. These included manufacturers’ surface markings, increased roughness and irregular side-holes.

Hydrophobicity did not confer resistance to encrustation.

Novel biomaterials that encrusted less than silicone in vitro and in vivo were identified and manufactured into urological devices. These included hyaluronidase-coated materials [6] and Chronoflex, a polyurethane.

The relationship between urinary pH and [Ca2+] and the pH at and above which crystallisation occurred (crystallisation pH) were also measured. The voided urine was alkaline in catheter ‘blockers’ with (7.86±0.55) and without (7.36±0.67) urine infection and crystallised at a more acidic pH (7.79±0.80 and 6.45±0.65 respectively). The voided urine of catheter ‘non-blockers’ was acidic (5.97±0.80) and crystallised at an alkaline value (7.46±0.73), p=0.005.


Conclusions: The in vitro encrustation model has provided objective data on existing urological devices and it has been adopted by several device manufacturers to test new polymers. The model will enable alternative designs and new biomaterials to be examined quantitatively to produce improved urological devices for clinicians and fewer complications for patients.

Catheter ‘non-blockers’ have a large safety margin between the acidic voided pH and alkaline crystallisation pH. In contrast, catheter ‘blockers’ who have acidic crystallisation pH and alkaline voided pH have a significantly reduced safety margin. The identification of crystallisation pH has opened a ‘therapeutic window’ for chemical manipulation to reduce encrustation.


1.      Kohler-Ockmore J and Feneley RCL 1996 Long-term catheterisation of thebladder: prevalence and morbidity. Br J Urol 77:347-351

2.      Kunin CM, Chin QF, Chambers S 1987 Indwelling urinary catheters in the elderly. Am J Med 82:405-411

3.      Sassoon E, Abercrombie F, Goodrum P 1991 The permanent indwelling catheter:a domiciliary survey. Health Trends 23(3):109-111

4.      Keane PF, Bonner MC, Johnston SR et al 1994 Characterization of biofilm and encrustation on ureteric stents in vivo. Br J Urol 73:687-691

5.      Choong SKS, Whitfield HN 1997 The validation of a novel in vitro encrustation modeland corroboration with in vivo animal studies. J Endourol 11: S1:p2

6.      ChoongSKS,WhitfieldHN,AmbrosioL,ParvesioA1998Encrustation-resistantcoating for urological devices. J Urol 159: (5):324


Results achieved in brief:

1.        Developed and validated an in vitro encrustation model as there was no objective encrustation data on the encrustation potential of urological devices in currentuse.

2.        Quantified encrustation on urological devices in currentuse.

3.        Identified a novel surface coating and a polyurethane, which encrusted significantlyless than silicone, the current ‘gold standard’biomaterial.

4.        The in vitro encrustation model is being used by several device manufacturers intesting new biomaterials to identify encrustation-resistantbiomaterials.

5.        Identified the urinary pH values at which crystals precipitated out of urine in catheter ‘blockers’ and ‘non-blockers’, which explained the association of alkaline voidedurine with encrustation. The identification of crystallisation pH has opened a ‘therapeutic window’ for chemical manipulation to reduceencrustation.

6.        These studies have advanced our understanding of the multifactorial mechanisms of encrustation and they have identified new encrustation-resistant biomaterials toproduce improved urological devices for clinicians and fewer complications forpatients.



·         Hunterian Professorship2000

The Royal College of Surgeons of England


      ·         BAUS / BJU International Travelling Fellowship2001

·         Organized and run annual national live surgery and hands-onendourology masterclasses for the last 10 yearson:

1.      Percutaneousnephrolithotomy

2.      Flexibleureterorenoscopy

3.      Rigid ureterolithotomy and holmium lasering ofstones

4.      Nephro-Uro-Radiologicalsymposium

5.      Live surgery and hands-on courses for theatre nurses, 16th to date, Feb2017

6.      Innovations in Percutaneous Surgery, UCL, London, June,2016

7.      Second International Innovations in Percutaneous Surgery, UCL, London, March 2017

·         Hosted British Annual Endourology Meeting at UCLH, May2008

Annual Dinner at House of Lords

·         Pump-priming award, Royal College of Surgeons of England2003

·         Grants - St. Peter’s Research Trust -£26,029

The effect of urinary infection on encrustation of urological devices

·         Funding - Biocompatibles Ltd. -£100,000

Encrustation studies on urological devices based on patented encrustation model

·         Funding - Cook Urological Ltd. -£15,000

Studies on the effect of infection on encrustation

·         Best Presenting Team (St. George’s Hospital) - Coliseum London Teaching Hospital Challenge. Institute of Urology and Nephrology, November1999

·         Best podium presentation - 4th Asian Congress in Urology, Singapore. Sept 1998. Objective encrustation analysis of currently used uretericstents. Choong SKS, Wood S, WhitfieldHN.

·         Best poster awards -14th World Congress of Endourology, Melbourne, Nov96.

1.  Current design faults in uretericstents.

Choong SKS, Whitfield HN, Petrik A, Nicholas C.

2.  The scientific basis of catheterencrustation.

Choong SKS, Fry C, Whitfield HN.

   ·        Highlighted presentationsat

BAUS Annual Meeting, Birmingham 2000

9th International Symposium on Urolithiasis, Cape Town, Feb 2000.

17th World Congress on Endourology and SWL, Rhodes Island, Greece, Sept 99. BAUS Annual Meeting, Glasgow, June 1999

AUA, San Diego, 1998

13th Congress of European Association of Urology, Barcelona 1998. 15th World Congress of Endourology, Edinburgh 1997

·        Established an encrustation database on existing ureteric stents and urethral catheters and identified novel biomaterials and surface coating whichresisted encrustation better than silicone, the current                  goldstandard.

·        Patented the design of a model to quantifyencrustation.


·        Determined the optimum period lignocaine gel should be left in the urethra for maximal effect prior to intraurethral manipulation - a prospective,randomised, double-blindstudy



·         BAUS representative and committee member of the British Standards Institution on CH/1 ‘Catheters’

·         Specialty Training Committee Member in Urology for North & South Thames,London

·         College Tutor, Institute of Urology, University College London

·         Director of Teaching Programme in Urology for North & South Thames,London

·         Referee for British Journal of Urology International 1999 tocurrent

·         Referee for Journal ofUrology

·         Committee Member and referee for UrologicalResearch

·         Examiner for MB,BS examinations in Surgery, University College London.

·         MD Supervisor to Ms Sian Allen on mechanism of crystallisation and stoneformation, 2008

·         MD Supervisor to Mr Senthy Sellatury on measurement of urinary salts using ion selective electrodes,2008

·         Junior Doctor Representative in Urology, St. George’s Hospital, London,2000.

·         Trainee representative, Brainstorming Meeting, Section of Urology, Royal Society of Medicine, October2000

·         Chairman, podium session on BPH, The 4th Asian Congress in Urology, Sept 1998, Singapore.

·         Chairman of Stones Poster Session, SIU, Honolulu,2004

·         Teacher in Anatomy for Urologists course 2004 &2005

·         Course organiser for MSc inUrology

·         Course organiser for North & South Thames SpRs teachingprogramme

·         Chairman & Course Organiser, Flexible ureterorenoscopy BAUS2005

·         Participating in live surgery teaching at St Peter’s Course, UCLH, 2007 &2008

·         Examiner for Master of Surgery / MDThesis

·         Chaired Urolithiasis session during 1st World Congress of Urology, Beijing, China,2015

·         Urology Module Lead for Royal College of Surgeons of England,2016



AUA 2017

Ureteric Rendezvous to treat complex discontinuities

Arumuham V, Mazzon G, Bolgeri G, Allen C, Allen S, Smith D, Choong S


AUA 2016

Rendezvous procedure to treat complex ureteric discontinuities

Mazzon G, Bolgeri M, Arumuhan V, Allen S, Smith D, Philp T, Allen C, Walkden M, Ramachandran N, Choong S


Peri-operative outcomes of percutaneous stone surgery in patients with urinary diversions.

Bolgeri M, Mazzon G, Dale R, Arumuhan V, Allen S, Smith D, Allen C, Choong S


EAU 2016

Can post-operative white cell count, C-reactive protein or stone culture help predict length of stay after percutaneous nephrolithotomy?

Dale R., Mazzon G., Bolgeri M., Pal P., Longhorn S., Choong S., Philp T., Smith R., Allen S


Functional outcomes of rendezvous procedure to treat complex ureteric discontinuities Mazzon G, Choong S, Smith D, Allen S, Pallavi P, Bolgeri M, Dale R, Allen C, Ramachandran N, Philp T

Papers submitted to 13th International Symposium on Urolithiasis, July 2016

Do multiple access tracts increase peri-operative complications in percutaneous management of complex renal stones?

Giorgio Mazzon, Marco Bolgeri, Vimoshan Arumuham, Rebecca Dale, Clare Allen, Sian Allen, Daron Smith, Simon Choong


Comparison of stone culture using two different sampling methods (wet and dry) Marco Bolgeri, Paula Pal, Rebecca Dale, Vimoshan Arumuham, Giorgio Mazzon, Bruce Macrae, Daron Smith, Simon Choong, Sian Allen

Can we identify predictors for the risk of embolization following percutaneous nephrolithotomy?

Marco Bolgeri, Rebecca Dale, Vimoshan Arunuham, Giorgio Mazzon, Miles Walkden, Sian Allen, Daron Smith, Simon Choong


Management of Spina Bifida patients with urinary tract stones

Vimoshan Arunuham, Marco Bolgeri, Rebecca Dale, Giorgio Mazzon, Sian Allen, Daron Smith, Simon Choong


Papers for Submission in 2016

Early multi centre experience of Ultra-Mini Percutaneous Nephrolithtomy in the UK

B Pullar, E Havranek, AJR Blacker, SN Datta, B Somani, S Sriprasad, H Ratan, S Scriven, S Choong, RD Smith, S Mackie, G Watson, OJ Wiseman

Bisphosphonates: novel inhibitors of calcium oxalate crystallisation

Allen S, Choong SKS, Fry C, Robertson W

Master of Surgery MS / MD Thesis Supervisor

Physicochemical basis for struvite stone formation

Thesis by Senthy Sellaturay

Postgraduate degree awarded by University of London, 2011


Physicochemical factors influencing the crystallisation of calcium oxalate in the urinary tract

Postgraduate degree awarded by University of London, 2011

Examiner for Master of Surgery MS / MD Thesis

Invited Speaker at Guangzhou Annual Meeting, China, Jan 2016


Faculty Member & Speaker, PERCON & IAU Meeting, Nov 2016, New Delhi, India


Published Papers


Using bisphosphonates to effectively inhibit calcium oxalate crystal aggregation

S.E. Allen, S. Choong, C.H. Fry, W.G. RobertsonMar 2013 European Urology Supplements

Computerised Tomography (CT) is not required for safe and effective Percutaneous Nephrolithotomy (PCNL) in children

A. Barnacle, S. Choong, W. Van't Hoff, N. SmeuldersOct 2011 European Urology Supplements

Portable extracorporeal shock wave lithotripsy in paediatric urolithiasis under general anaesthesia

M. Lalla, M. J. Cabrai, P. Duffy, S. Choong, A. Barnacle, W. Van't Hoff, N. SmeuldersOct 2011 European Urology Supplements

Is Routine Post-Operative Renal Tract Stone Culture Necessary?

D. Allen, J. Bycroft, T. Philp, S. Choong, D. SmithSep 2011 Urology

Renal stone disease

Nikhil Johri, Philippe Jaeger, William Robertson, Simon Choong, Robert Unwin Jul 2011 Medicine

Primary hyperoxaluria type 3 in children with renal calculi

E Williams, D Bockenhauer, N Smeulders, A Barnacle, S Choong, G Rumsby, W vant Hoff Apr 2011 Archives of Disease in Childhood


Percutaneous Urinary Drainage and Ureteric Stenting in Malignant Disease

D.J. Allen, S.E. Longhorn, T Philp, R.D. Smith, S ChoongNov 2010 Clinical Oncology

An Update and Practical Guide to Renal Stone Management

Nikhil Johri, Bruce Cooper, William Robertson, Simon Choong, David Rickards, Robert Unwin


Oct 2010 Nephron Clinical Practice

Flexible ureteroscopy for lower pole stones—Is it effective? One year's experience in a major stone unit

S. J. Graham, C. Nathaniel, S. Longhorn, T. Philp, R. D. Smith, S. C. S. ChoongMay 2010 British Journal of Medical and Surgical Urology

Is endourological management of upper tract TCC the way forward? Experience from a major endourological centre

S. J. Graham, P. Gurung, S. Longhorn, T. Philp, R. D. Smith, S. C. S. ChoongMay 2010 British Journal of Medical and Surgical Urology

Day case rigid and flexible ureterorenoscopy

O. Wiseman, S. Longhorn, T. Philp, S. ChoongMar 2007 European Urology Supplements

Recent technological developments in the management of urinary tract stones

Simon Choong


Mar 2007 Trends in Urology Gynaecology & Sexual Health

Heat-shock protein 25 ameliorates calcium oxalate crystal-mediated oxidative stress in renal epithelial cells

Amit B Patel, William G Robertson, Simon Choong, John S Hothersall Dec 2006 BJU International

Endoscopic management of impassable ureteric strictures: 8 year experience

G. Lee, S. Longhorn, M. Kellett, C. Allen, D. Rickards, S. Choong, T. PhilpApr 2006 European Urology Supplements

Calcium Oxalate Monohydrate crystals inhibit the expression of heat shock protein 25 in canine

renal distal tubule cells

A. Patel, S. Choong, W. Robertson, J. HothersallApr 2006 European Urology Supplements

Thermo-expandable ureteric stent in the management of complex refractory benign ureteric strictures: Longterm efficacy and risk factors associated with complications

G. Lee, S. Longhorn, M. Kellett, C. Allen, D. Rickards, S. Choong, T. PhilpApr 2006 European Urology Supplements

Pelvi-calyceal height, a predictor of success when treating lower pole stones with extracorporeal shockwave lithotripsy

A Symes, G Shaw, D Corry, S Choong Sep 2005 Urological Research

Management of Renal-Vein Perforation during a Challenging Percutaneous Nephrolithotomy

G Shaw, T.M. Wah, M.J. Kellett, S.K.S. Choong Jul 2005 Journal of Endourology

Encrustation of biomaterials in the urinary tract

Greg L Shaw, Simon K Choong, Christopher Fry Mar 2005 Urological Research

A guide to renal stone disease.

Robert J Unwin, Giovambattista Capasso, William G Robertson, Simon Choong Feb 2005 The Practitioner

Dystrophic ureteral calcification associated with Churg-Strauss vasculitis

A Symes, V Kalsi, D Rickards, C Allen, S Choong, T Philp Jan 2005Urology

Rupture and perforation of urinary reservoirs made from bowel

Sadmeet Singh, Simon Choong


Oct 2004 World Journal of Urology


Renal Stone Disease: The Urological Perspective

Jean Amiel, Simon Choong


Feb 2004 Nephron Clinical Practice

Epidemiology of paediatric renal stone disease in the UK

RJMCoward,C.J.Peters,P.G.Duffy,DCorry,MJKellett,SChoong,WGvan'tHoff Dec2003·ArchivesofDiseaseinChildhood

The management of intractablehematuria

S.K.S. Choong, M. Walkden, R. KirbyDec 2001 BJU International

Squamous cell carcinoma of the bladder, intermittent self-catheterization and urinary tract infection - Is there an association?

S Pattison, S Choong, C.M. Corbishley, M.J. Bailey Oct 2001 BJU International

Catheter associated urinary tract infection and encrustation

S Choong, S Wood, C Fry, H Whitfield


May 2001 International Journal of Antimicrobial Agents

Couch or crouch? Examining the prostate: A randomized study comparing the knee- elbow and the left-lateral position

J Frank, K Thomas, S Oliver, S Andrews, S Choong, R Taylor, M Emberton Mar 2001 BJU International

The management of intractable haematuria

S K Choong, M Walkden, R Kirby Jan 2001 BJU International

Biofilms and their role in infections in urology

S Choong, H Whitfield

Dec 2000 BJU International 86: 935-941

The management of pediatric urolithiasis

S Choong, H Whitfield, P Duffy, M Kellett, P Cuckow, W Van't Hoff , DCorry Dec 2000 BJUInternational

Amodel to quantify encrustation on ureteric stents, urethral catheters and polymers intended for urologicaluse

S.K.S. Choong, S Wood, H.N.WhitfieldOct 2000 BJUInternational

Urinary Encrustation of Alloplastic Materials

Simon KS Choong, Hugh N. Whitfield Mar 2000 Journal of Endourology

Acute Urinary retention

S Choong, M Emberton


Feb 2000 BJU International

The influence of urinary biochemistry on catheter blockage

Choong SKS, Wood S, Fry C, Whitfield HN. Urolithiasis 2000 1: 90-91

Encrustation on urological devices

Choong SKS, Wood S, Whitfield HN. Urolithiasis 2000 1: 88-89

The physicochemical basis of urinary catheter encrustation

S.K.S. Choong, P Hallson, H N Whitfield, C H FryJun 1999 BJU International

An encrustation-resistant polyurethrane for urological use

Simon Choong, Hugh Whitfield, Luigi Ambrosio Apr 1999 The Journal of Urology

Conservative management of a spontaneous rupture of a continent cutaneous urinary diversion

S.K.S. Choong, M Gleeson

Nov 1998 British Journal of Urology

Polyethylene glycol containing polyurethanes for biomedical applications

Siska Corneillie, Pham Ngoc Lan, Etienne Schacht, Martyn Davies, Alex Shard, Rebecca Green, Stephen Denyer, Mike Wassall, Hugh Whitfield, Simon Choong


Jul 1998 Polymer International

Effects of Tamm-Horsfall protein with normal and reduced sialic acid content upon the crystallization of calcium phosphate and calcium oxalate in human urine. Br J Urol

P C Hallson, S.K.S. Choong, G P Kasidas, C T Samuell Nov 1997 British Journal of Urology

A prospective, randomized, double-blind study comparing lignocaine gel and plain lubricating gel during flexible cystoscopy

S Choong, HN Whitfield, V Meganathan, MS Nathan, A Razack, M Gleeson Aug 1997 British Journal of Urology

The scientific basis of urinary catheter encrustation

S. Choong, C. Fry, H. Whitfield, M. Craggs, J. Shah, P. Hallson, C. SamuellJan 1997 British Journal of Urology

The Role of 'Metabolic Syndrome' in the formation of uric acid containing stones

W.G. Robertson, D. Nair, C. Laing, S. Choong, P. Jaeger, R.J. UnwinUrol Res 2008;36:177-178

The inhibitory effect of bisphosphonates on calcium oxalate crystal formation in vitro

Sian Elizabeth Allen, Simon Choong, Christopher Fry, William G RobertsonUniversity College London 2006 Proc Physiol Soc 3

The prevention of urinary infection in Urological surgery

Choong SKS, Whitfield HN.

European Urology Update Series. 1996 Volume 4; Number 6.


Can surgical gloves be made thinner without increasing their liability to puncture?

Carter S, Choong SKS, Marino A, Sellu D. Ann. R. Coll. Surg. Engl. 1996; 78: 186-187.



1.Choong SKS, Whitfield HN, Petrik A. Design faults in currently availableureteric stents. In Yachia D eds, Stenting the urinary system. Chapter 19. Oxford: ISIS Medical Media, 1998:151-159


2.Stones. In Shah J eds, Urology Highlights 2004-2005. Health Press Ltd, Oxfordshire, UK. In Press for Feb2005


3.Design faults in currently available ureteric stents. In Yachia D eds, Stenting the urinary system. Chapter 26. Oxford: ISIS Medical Media, 2004:151-159


4.Stones. In Shah J eds, Urology Highlights 2002-2003. Health Press Ltd, Oxfordshire,UK.



Member, Chelsea Clinical Society.

Committee Member, British Standards Institution. Member, Royal Automobile Club, Pall Mall, London. Member, British Association of Urological Surgeons. Member, International Alliance of Urolithiasis, IAU.

Fellow, Urological Section, Royal Society of Medicine.

Member of the European Association of Urology. Member, British Medical Association.

Member, British Biofilm Club. Member, Home House, London.

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