title: Natural history of asymptomatic gallstones: differential behaviour in male and female subjects.
abstract: OBJECTIVE
  The natural history of asymptomatic (silent) gallstones has been inadequately studied. Existing information derives from studies based on oral cholecystography or relatively small sample sizes. We planned a retrospective cohort study in subjects with gallstones to determine conversion rates from asymptomatic to symptomatic.
  
  
  METHODS
  We extracted data from computerised databases of one government hospital and two private clinics in Malaysia. Files were scrutinised to ensure that criteria for asymptomatic gallstones were fulfilled. Patients were called on telephone, further questioned to confirm that the gallstones at detection were truly asymptomatic, and asked about symptoms that were consistent with previously defined criteria for biliary colic. Appropriate ethical clearances were taken.
  
  
  RESULTS
  213 (112 males) patients fulfilled the criteria for asymptomatic gallstones and could be contacted. 23 (10.8%) developed pain after an average follow up interval of 4.02 years (range 0.1-11 years). Conversion rates from asymptomatic to symptomatic gallstones were high in the first two years of follow up, averaging 4.03±0.965 per year. Over time the conversion rates slowed, and by year 10 the annual conversion rate averaged only 1.38±0.29. Conversion rates were much higher for females compared to males (F:M hazard ratio 3.23, SE 1.54, p>z 0.014). The lifetime risks for conversion approached 6.15% for males, and 22.1% for females.
  
  
  CONCLUSIONS
  In conclusion, asymptomatic gallstones are much more likely to convert to symptomatic in females than in males. Males in whom asymptomatic stones are discovered should be advised conservative treatment. Surgery may be preferable to conservative management if the subject is a young female.
authors.affiliation: Monash University Malaysia, Jeffrey Cheah School of Medicine, 8 Jalan Masjid Abu Bakar, 80100 Johor Bahru, Johor, Malaysia. suneet.sood@monash.edu.
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authors.initials: S
authors.lastname: Sood
authors.affiliation: MAHSA University, Jalan University Campus, Kuala Lumpur, Malaysia.
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authors.affiliation: Hospital Putrajaya, Putrajaya, Selangor, Malaysia.
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authors.affiliation: Mahameru International Medical Centre, Kuala Lumpur, Malaysia.
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authors.affiliation: Twin Tower Medical Center, Kuala Lumpur, Malaysia.
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authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.lastname: Yasmin
authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.affiliation: National Defence University of Malaysia, Faculty of Medicine and Defence Health, Kuala Lumpur, Malaysia.
authors.forename: A
authors.initials: A
authors.lastname: Devi
authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.initials: AA
authors.lastname: Karim
authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
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authors.initials: KJ
authors.lastname: Obaid
authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
authors.forename: N H
authors.initials: NH
authors.lastname: Haron
authors.affiliation: Hospital Selayang, Selangor, Malaysia.
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authors.initials: H
authors.lastname: Fitjerald
authors.affiliation: Universiti Teknologi MARA, Faculty of Medicine, Malaysia.
authors.forename: M
authors.initials: M
authors.lastname: Koshy