User:Bron766/Haematuria/Systematic causes

There are lots and lots of causes of haematuria! How will you manage to remember them all?

As with many things in medicine, the key is to have a system. There are several ways to classify causes of medical illnesses, including three different systems that we can try out in this tutorial using Haematuria. These systems are based on:
 * 1) Anatomy
 * 2) Pathology
 * 3) Epidemiology.

Let's start with anatomy. Using anatomy to divide up the causes of Haematuria is easy, because each section is just a different part of the renal tract. If you are quizzed by the boss on ward rounds, having this system can get you out of trouble because it is easy to remember from top to bottom: you might start with some causes of Haematuria affecting the kidney (or outside the renal tract), then some causes affecting the ureter, bladder then urethra. Later when you are seeing your own patient, an anatomical system can be useful too, for example: if a patient presents with painful haematuria, you can often distinguish pain of the upper renal tract (e.g. flank pain) from the lower renal tract (pelvic / groin). Other things like the microscopic appearance of the red blood cells can also point you to an anatomical region (e.g. deformed red blood cells from disease of the kidney glomerulus).

So, try sorting the causes of Haematuria by an anatomical classification system, using a table like the one below. See what you can fill out from memory first, then revise your list of Haematuria causes from the previous lesson or look up a reliable source.

Some people further divide the kidney origins of Haematuria into glomerular and non- or extra-glomerular sections. Do you think this is useful? (It may depend on how many detailed / rarer causes are on your list.) A different system for classifying the causes of Haematuria is by pathological cause. This is good because it gets you thinking in mechanisms, which are more resilient than a single fixed diagnosis, especially when things change and the 'clear-cut' case of renal colic may not be clear-cut when the scan comes back with no stone! Another example of the usefulness of thinking in pathological systems is if you are confident a patient has an infection but you're not sure where... Treatments can often be grouped better by pathology (e.g. antibiotics for bacterial infections) than by anatomy (would you treat a kidney mass the same way as a kidney infection?).

Unfortunately, remembering the different pathological processes is not as easy as remembering the anatomical divisions, so many people come up with a mnemonic to help, also called a Surgical Sieve. Here is an example of the VITAMIN C mnemonic. Do you know of a better one?

Can you complete this table with the causes of Haematuria classified by types of pathology? If you did the table above, you should be able to remember a few more causes from memory this time. (Yes, the repetition here is on purpose, it is part of the Deliberate Practice approach, aiming to get you actively processing the information in different ways for better learning and retention. So have a go...) A third classification system is by epidemiology, which is good to keep in mind since common things occur commonly. Unfortunately, students have a peculiar tendency to come up with the most fascinating (but least likely) explanations for a presenting problem. Another way of putting this is the famous aphorism:

 When you hear hoofbeats, think of horses not zebras. - Theodore Woodward, ~1940s.

Another very useful extension of this idea is John Murtagh's 5 step diagnostic model, which is well worth reading about.

So, for our third table, you might try sorting the causes of Haematuria into common vs. rare. But it is also worth considering some of Murtagh's model here, especially the most dangerous (cancer has surely got to be in there somewhere, and what about the rare but scary leaking AAA?) and most often missed.

So which system is the best? Each has their uses. While knowing the most common causes is no doubt useful, some patients will inevitably have other causes for their haematuria and thinking of mechanisms can be more helpful. As we will explore in the next section, it is also about using the diagnostic clues available to you. For example, if a patient presents with very well localised right flank pain, you may consider a kidney cause most likely. If a patient presents with unexplained weight loss and sweats, pathological causes like infection or cancer may be suspected. If you are lucky enough to join the dots between your anatomical (kidney) and pathological (cancer) dimensions, you may be getting near a diagnosis! That is, as long as your assumptions hold about where (the anatomy) and what (the pathology) the problem is. If you find that your diagnosis doesn't fit (e.g. renal colic with no stone found on CT), it helps to have a context to move laterally in. For example, you may still think it is an upper renal tract problem, but a different pathological process (e.g. infection or infarction). Also, when grilled by the boss on ward rounds you might say: "well, the causes of Haematuria can be divided by anatomical origin AND by pathological process, such that causes in the kidney include vascular infarction, infections (pyelonephritis), trauma... and the causes of haematuria in the ureter include... (by now said boss will probably lose interest and move on, but if you get all the way down to the urethra, finish with:)... and in this part of the world, the most likely causes are stones or infection with... but I would need to exclude tumours and make sure I didn't miss a leaking AAA! (Hopefully the boss has now left the building, so you survived.)

One final challenge:
 * It is tempting to want to combine these systems together, to create some kind of 3-D monster that could classify each cause of Haematuria on axes for anatomical location, pathological process and epidemiology... But it sounds unwieldy at best! However, if you can come up with a way of combining two of these systems into a single table/illustration, it might be interesting (like anatomy and epidemiology, or anatomy by physiology). The key idea is that if you are aware of the anatomical/physiological/epidemiological context or environment of your chosen diagnosis, you have room to move in a new direction when your first diagnosis isn't working out.

{Which of these causes of Haematuria involve the kidney? + Pyelonephritis - Cystitis + Renal cell carcinoma - Ureteric calculi
 * type="[]"}

{Which of these causes of Haematuria are autoimmune pathological processes? - Pyelonephritis - Cyclophosphamide cystitis - Radiation cystitis + Wegener's granulomatosis + IgA nephropathy
 * type="[]"}

{Which of these causes of Haematuria is NOT common in Australia? - UTI - Ureteric stones - BPH - Menstruation - Exercise + Benign renal tumours
 * type=""}