In the past, kidney involvement in APS patients was poorly recognised. However, it is now known that kidney disease is not uncommon and can, in fact, be the first and only sign of the condition. Early detection of kidney problems often improves the outlook for many patients. Symptoms usually include high blood pressure and pain in the abdomen or back.
The kidneys can be affected in several ways:
Renal artery thrombosis
The renal arteries supply a large proportion of blood to the kidneys and, occasionally, a clot can form in an artery which then blocks the blood flow to the kidney. This can cause raised blood pressure, abdominal or back pain - in a few cases, it can be life-threatening. Treatment options include anticoagulation and angioplasty - an invasive procedure where the artery is mechanically widened.
Renal artery stenosis
APS can cause the arteries leading to the kidney to narrow - known medically as renal artery stenosis. This narrowing of the renal artery can impede the blood flow to the kidney resulting in high blood pressure and can lead to kidney failure if it is not treated. If diagnosed quickly, anticoagulation can have a very positive effect; however, if the blood pressure cannot be controlled or if the kidney function deteriorates, then invasive angioplasty treatment may be necessary.
Renal vein thrombosis
This is where a blood clot develops in a vein that drains the blood from the kidney. The main symptom is usually sudden abdominal pain and the clot can often damage the kidneys, causing them to leak large amounts of protein into the urine (known medically as nephrotic syndrome). Sometimes these vein clots can permanently affect the kidney function and lead to high blood pressure. Treatment with oral anticoagulants such as warfarin can be effective; however heparin injections can be ineffective as heparin binds to an enzyme which is lost through the leaking protein.
As well as blood clots occurring in the major ‘motorway’ renal artery and veins, the blood can clot in the specialised small blood vessels of the kidney. This condition can lead to low platelets, spots of bleeding under the skin (known as purpura) and changes in renal function which, if left untreated, can cause permanent damage.