Map of the Month Feb 10 - The Surgical Sieve

This month’s map - The Surgical Sieve, is a concept in cartography, combining mapping and medicine. It is highly visual, simple, works on many levels, illustrates complex relationships and is potentially very practical.

Just before Christmas, my wife passed me her BMJ (British Medical Journal) and showed me a map about something called The Surgical Sieve (which meant nothing to me). After I looked a bit closer it seemed to be a brightly coloured, schematic transport map with a number of related ‘ailment’ stops, but what was it all about? Unfortunately there was no explanatory text, so hopefully after a bit of background research the following summary will help the lay-person:


BMJ 19-26 Dec 2009, Volume 339, page 1450, reproduced with permission from the BMJ Publishing Group. Click on the map to enlarge.

The map was created by Tom Turmezei, a specialist registrar in radiology who confesses to a fascination with maps, especially those with coloured schematic themes such as the underground networks. These inspired him to create this particular experimental map to visually represent the rather complex process of considering all the different possible causes of abdominal pain to see what it would look like, to see if it could be done!

In the map the circling line unites the concept in the form of a surgical sieve. In medical terms the surgical sieve is the systematic process of a structured examination with the aim of diagnosing and managing the illness correctly. It is especially useful in difficult cases. [This technique is often used by the maverick doctor House M.D. (Hugh Laurie) in the US TV series House]. For this map the sieve is used to identify the cause of the acute abdomen - ‘sore stomach’ or ’belly ache’ to the non-medical.

The idea is to enter the network at the left at ‘abdominal pain’ and travel around the yellow (aka Circle line – The Surgical Sieve) and then change lines at each of the intersections as appropriate for each of the different human biological systems. Travelling each of these system lines could then remind the user of each individual diagnosis and how they cross over. The red line is for absolute emergencies ‘Do Not Miss These’ – deal with immediately.

Some of the halts have a list of ‘differentials’ which are simply the alternatives or the other possible diagnoses. Differential diagnosis is another common technique used to narrow down the possibilities by first considering the most likely diagnosis and moving through the list removing unlikely options until (hopefully) one remains.

Another element on the map I noted was the ‘Medical/Surgical Dividing Waters’. This help to delineates when treatment by surgery (north of the river) is preferred to medical action (south of the river). But it is not so clear cut, there is no settled border here. The small subheading ‘NB: changes with the tide’ was included on the map to remind the user that there can be surgical causes of abdominal pain that are managed medically and some medical causes of abdominal pain that can be wrongly diagnosed (and even treated) as surgical.

So this map is more than a light-hearted item in the Christmas edition of the BMJ. More than a process diagram or flow chart. It is a complex process translated into a handy solution in the form of a map. But is it useful, does it work? It could become an aide memoir for clinical identification, a map on the GP’s surgery wall or even a page in a possible Collins Handy Pocket Atlas for the Treatment of Ailments?

Tom Turmezei created this map while he was writing some chapters for The Oxford Handbook of Clinical Medicine. He thought that the differential diagnosis for acute abdominal pain was a structure that could work in the style of an underground map and this seemed like a novel way of mapping it out. For further information contact tom@turmezei.com.

Surgical Sieve map on the BMJ website

Related item - Human Body as a Tube Map on Going Underground's Blog