Recently it has become clear that the vast majority of bladder problems in cats are very similar to what is known in humans as ‘bladder pain syndrome.’ Bladder wall irritation, which should not be underestimated, leads to pain during urination, blood peeing, frequent urination, and sometimes (severe) pain in the lower abdomen. In humans, no identifiable cause has yet been found. It is more of a factor disease, so something that occurs when different circumstances all happen at the same time unfavorably. It, therefore, occurs to varying degrees in different patients.
Understanding Idiopathic Cystitis
To understand what’s going on, we first need to know that the lining of a bladder is a mucous membrane. The layer of mucus must protect the bladder wall from urine, which would irritate the bladder wall on direct contact. Glycosaminoglycans (GAGs) are essential as building blocks of the mucous layer. These proteins are also found in the cartilage of joints. And are therefore often prescribed for people and animals with joint problems.
Secondly, we need to know that there are all kinds of nerves in a body, including nerves that specialize in pain stimulants. These nerves have receptors, which are sensitive to substances produced in the body when a painful stimulus occurs. When such a receptor is stimulated, the body feels pain. Cats with ‘bladder pain syndrome’ have more of these pain nerves in the bladder. This means that when a pain stimulus in the bladder occurs, more pain is felt than in an average cat. By the way, the pain nerves in the spinal cord and brain of these cats also have more pain receptors, just like in some people with bladder pain syndrome. These people have besides bladder problems, even often a headache and lower back pain. We don’t know if cats suffer from that too.
Mucus Layer
For some reason, something in the mucus layer of cats with Idiopathic Cystitis goes wrong. The mucus layer no longer covers the entire bladder wall adequately. In some areas of the bladder, urine can come into direct contact with the bladder wall. This causes the release of a substance that stimulates the receptors of painful nerves. The stimulation of these nerves then causes the release of two other substances: histamine and heparin. Histamine is known from hay fever, the substance that causes swelling and irritation of mucous membranes in the nose and eyes that hay fever patients suffer from. Heparin is known as a blood thinner.
When histamine and heparin are released into the bladder wall, two things happen: the bladder wall thickens and leaks blood. Not very much, but enough to discolor the urine recognizably. Three things happen together: pain, swelling, and blood leaking.
In some cats, this doesn’t seem to be the only problem. Some cats don’t drink enough, resulting in crystals or grit in their urine. Other cats always make grit, whether they drink enough or not. In yet other cats, clumps of the defective mucus layer can become loose. If there is already a swollen, painful bladder, the presence of grit or mucus layer clots in males is sometimes just enough to obstruct the drainage of the bladder. Not being able to urinate is a life-threatening problem!
One does not know for every cat why something goes wrong with the mucus layer of the bladder in the first place. Stress seems to be an important factor. Stress in cats can be caused by very unimportant things, such as changes in nutrition, litter pellets, and the boss’s daily routine. Even weather changes can have an influence. Arguing with another cat (even if it is a roommate they get along with) is also often seen as a cause of bladder problems in sensitive cats.