Bigger isn’t always better and small is beautiful…a couple of English idioms with which we are all familiar.  And like many sayings, not universally true.  For instance, last month I mentioned Mousa, a pussy-cat with a urinary problem. Happily, not a serious one in his case but it could have been due to the unfortunate anatomy of the male cat urethra; it’s too narrow! That’s the main reason it blocks with crystals and sludge from the bladder, causing urinary retention. This is a critical emergency.  So any male cat trying to pass urine without success needs a veterinary check-up as soon as possible.  The right size? Bigger is better for a urethra!

Another example might be the width of the small intestine.  Perhaps not something many people dwell on. At least, not until your dog starts vomiting and x-rays show an object lodged in the intestine causing an obstruction.  There’s another design fault here, that of being able to swallow something that successfully navigates the oesophagus, only to get stuck in the narrower small intestine.

Dogs in particular are prone to this. The last case we saw in Sherborne this week with a screw-cap from a wine bottle wedged in poor Vinny the Spaniel’s gut.  We couldn’t work out what it was from the x-ray – only the rim of the cap was visible and appeared oval-shaped. In hindsight, we realised that was due to the oblique angle of view.  Kate and the nurses worked their magic and Vinny has made a complete recovery after a long, complicated operation.  So when it comes to urethras and intestines, size clearly matters.

On the other hand, for wounds and tumours small is beautiful.  We see a lot of both and although a well-repaired and appropriately-treated big wound can heal as quickly as a small one, surgical time increases costs and extensive tissue damage increases complication rates. The size and location of a lump can have as major an effect on prognosis as the tumour type.  For example, a melanoma’s size (in dogs and cats these are not sunlight-induced) is critical for successful treatment. Larger (greater than 4cm) tumours frequently metastasise.  A large fatty-tissue tumour (a lipoma), on the other hand, will have a similar prognosis (good) as a small one. Although obviously, time and effort spent on removal means it’s a bigger deal, surgically and financially. 

When it comes to lumps and bumps, or any other disease, the problem is they don’t come with labels attached.  Although some tumours have a characteristic appearance, the only way to identify the nature of the beast is either by cytology (taking a few cells using a needle), or by histology, a more accurate technique of microscopic examination of a biopsy.  The former is quick and easy but sometimes unreliable. The latter is much more reliable but often requires a general anaesthetic and a surgical procedure similar to removing the lesion in its entirety.  So that’s what we do in many cases to save the patient returning for another procedure.  The downside of this is without a specific diagnosis, surgical planning of margins is not possible. 

By this, I mean how much tissue to take around the tumour in an attempt to remove all abnormal cells. This may depend on the location.  Tricky to take a big lump off a small toe as there’s no spare skin to close the resulting wound. So for lesions on distal extremities or near critical structures like eyes and lips, small is most definitely beautiful.

Our bodies and those of our pets, along with all other animals, are governed by the laws of physics, although which set of laws are most useful at the time seems to depend on size.  Although Quantum theory may hold sway in the sub-atomic world, Newton’s traditional laws of motion and Taylor’s work (and others) on fluid mechanics explains the phenomena we experience in the macroscopic world.  This might seem irrelevant to medicine but in fact the behaviour of our blood as it flows through the heart and blood vessels is critical to prevent a very common affliction of humans and cats, that of thrombosis.  The story behind blood clotting is fascinating but I’ll confine myself here to what happens when blood stops flowing smoothly and becomes turbulent, which can happen in an enlarged or fibrillating heart.

Both can be caused by underlying heart disease but atrial fibrillation commonly occurs spontaneously in humans.  The result? A tendency to form blood clots (thrombi), which can block arteries in the limbs, lungs and brain.  Little thrombi trap in the lungs or other capillary beds and the fibrinolytic system breaks then down, our counter-balance to blood clotting.  Big clots in the brain cause stroke and in the lungs pulmonary thrombosis, tragically both quite common in humans.  Cats tend to suffer thrombosis of the arteries in the pelvis (the iliac arteries) which sadly can be as catastrophic.  That’s why we feel for femoral pulses and warm paws in lame cats.

So…size matters.  May you and your pets’ tubes stay wide, your blood clots small and your hearts just the right size!