Background The time-honoured mnemonic of ‘5Fs’ is a reminder to students that patients with upper abdominal pain and who conform to a profile of ‘fair, fat, female, fertile and forty’ are likely to have cholelithiasis. We feel, however, that a most important ‘F’—that for ‘family history’—is overlooked and should be introduced to enhance the value of a useful aide memoire.

Methods To assess the usefulness of each of the existing factors of a popular mnemonic, 398 patients admitted with upper abdominal pain between March 2009 and April 2010 were studied. The clinical features expressed in the cholelithiasis mnemonic in patients with sonographic evidence of cholelithiasis were compared with those of patients without.

Findings In the cholelithiasis group, significantly more patients were women (150/198 (75.8%) vs 111/200 (55.5%), p<0.001), fair (144/198 (62.9%) vs 54/200 (32.1%), (p<0.001)), fertile (135/198 (68.2%) vs 50/200 (25%) (p<0.001)) and had a body mass index >30 (56/198 (28.3%) vs 19/200 (9.5%) (p<0.001)) compared with controls; but age over 40 years did not predict cholelithiasis (82/198 (41.4%) vs 79/200 (39.5%) (p=0.697)). In the cholelithiasis group, 78/198 (39.4%) had a family history in at least one first-degree relative, compared with 27/200 (13.5%) of controls, (p<0.001). Where the phenotypic elements of the history existed in combination, that patient was found to be at an increased risk of cholelithiasis.

Interpretation Our study found that the validated ‘students’ 5Fs’ mnemonic retains a role in clinical diagnosis of patients suspected of cholelithiasis but the factor ‘familial’ should be substituted for ‘forty’ in recognition of the role of inheritance and the changing demographics of gallstone incidence.