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Weighing up the risks

01 January 2009

Miss F was a 30-year-old bank clerk. She worked very hard and found little time to take exercise. She was obese, weighing 105kg and with a BMI of 45. She went to see Dr Y, asking for contraception as she had a new partner. She had not used any contraception in the past few years but had previously had an IUD that had suited her well. Dr Y checked her blood pressure, which was normal, and asked her if she smoked, which she denied. Dr Y explained that the doctor who fitted coils for the surgery was off sick. They discussed other options and Miss F decided she would prefer the regularity that a combined oral contraceptive pill gave.

Several weeks later Miss F woke one morning with terrible abdominal pain. The pain did not ease but got steadily worse. Her partner called an ambulance and she was taken to A&E, where she was found to have an acute abdomen. The surgeons did an emergency laparotomy and found infarcted bowel. Miss F needed extensive surgery with considerable risks due to her BMI. The overall diagnosis was acute ischaemia of the small intestine due to mesenteric venous thrombosis, most likely precipitated by the use of the COCP.

Miss F spent several weeks in hospital with a difficult recovery period. She developed a chest infection postoperatively and had to be given antibiotics for a wound infection. So much bowel had been infarcted and consequently removed that Miss F needed life-long parenteral nutrition. She found this devastating and felt it ruined her quality of life. She also needed life-long warfarin treatment. Miss F began a claim against Dr Y.

Expert opinion

GP experts were critical of Dr Y for prescribing the pill without consulting a national formulary (BNF) for contraindications. Dr Y should have calculated her BMI. The British National Formulary advises prescribing with caution if the BMI is above 30kg/m2 but states that prescribing should be avoided if the BMI is above 39kg/m2. The claim was settled for a substantial sum.

Learning points

  • Most national formularies set out clear risk factors for venous thromboembolism when prescribing the COCP. Mesenteric venous thrombosis is rare, but it is still worth checking that a patient does not have a family history of thombophilia before prescribing the COCP.
  • If you do not follow current advice when prescribing, perhaps because this is a shared (informed) decision with the patient, it is important to document your reasons.
  • Always calculate a BMI – weight alone is not sufficient.
  • With obesity on the increase, treatments and procedures that have hitherto been routine may become more complex.