Many connective tissue disorders cause a loosening of structures containing larger amounts of connective fibers. Such organs are the lung, the intestines as well as blood vessels, joints and ligaments.
Veins contain a lot of connective fibres, so they are affected by connective tissue disorders as are arteries. Because of the blood pressure differences in veins and arteries both types of vessels react differently, as soon as the pressure rises.
Arteries tend to develop aneurysms whereas veins tend to dilate more generally.
The greater distensibility of veins is the reason for their easier compression if they are set under pressure from the outside. The venous segment which lies before the compression site reacts with a widening (dilatation), later on the vessel starts to elongate and begins to meander like a river which has not enough force to overcome a long stretching obstacle. If the driving force and the obstructing force are nearly equal, as in a river in a flat plane, it starts meandering. If the venous pressure is nearly equal to the compressive force, the vein starts first to widen, as a river flooding it’s banks and later becomes varicose, as a meandering river.
If there is no connective tissue disorder the vein would be less distensible and the pressure inside the vein would increase faster than in a soft and lax vein of a patient with the connective tissue disorder. Thus the transport of blood would remain intact.
If the pressure increases further, the blood is bypassed through connecting veins which serve as collaterals. These collaterals guide the blood to areas with lower pressure. Over time these collaterals also lose their normal shape, they dilate and form varicoses. Such varicose veins are well-known from the lower limbs but also exist within the abdomen. Their wall is excessively stretched and thus becomes damaged. Microfractures of the connective tissue attract white blood cells which are specialised on repairing damaged tissues. These white blood cells secrete interleukins as mediators of an inflammatory reaction. The hallmarks of inflammation are well-known: Pain, swelling, redness and loss of function can be experienced by the patient.
But not only the vessels are affected in connective tissue disorders. With respect to vascular compressions the loosening of the ligaments of the spine is especially devastating. Over time the spine develops large curves under the gravitational forces. In the beginning a lumbar lordosis and a thoracic kyphosis are the most eye-catching changes of the spine. In the course of the disease severe scoliosis may develop. Scoliosis is a consequence of lordosis and kyphosis. Its development can be illustrated by a crank drill. The crank is a lever to turn the drill. The bending of the spine produces a crank-like deformation which also functions as a lever to drag the spinal curvature from a sagittal towards a frontal orientation. That means in the beginning the bending of the spine is directed forward and backward. The forward curvature develops in the abdominal area and the backward curvature within the thorax. At the apex of this curvature which works as a crank muscles drag the spine towards the side. Such a sideward deformation of the spine is called scoliosis. This is a general mechanims, not only but more gravely in patients with connective tissue disorders.
The strong lordotic bending of the spine produces a pressure against structures which lie in front of the spine. Very frequently, only some millimetres remain between the front of the spine and the inner lining of the abdominal wall. This is quite often invisible for the naked eye, since the spine is hidden by the surrounding muscles and subcutaneous fatty tissue. The very extent of the scoliosis and its effect on the shaping of the abdominal cavity can best be seen with ultrasound. It is often surprising, how narrow the space is which is left by the spine. The abdominal cavity then resembles a dumbbell and all the structures which have to pass from the one side of the abdomen towards the other side has to pass the narrow grip of the dumbbell.