Renal Infarction - Specialists and Information

The kidneys are crisscrossed by many arteries and veins and thus have a rich blood supply. If a blood clot (or even trapped fat or an air bubble) is carried along with the blood, it can block an artery or vein in the kidney (embolism). If this blockage affects an artery, part of the kidney is no longer supplied with blood. If the artery is completely blocked, the affected tissue dies.

Illustration of a calcified narrowing in an artery (top) that is blocked by a blood clot (bottom)

If a vein is blocked, blood pools in the kidney tissue. The deoxygenated blood cannot drain away, and as a result, oxygen-rich blood cannot flow in to replace it. In this case as well, the tissue is not adequately supplied and will eventually die.

The severity of the symptoms depends primarily on the extent of the renal infarction. In many cases, only small areas of the kidney are affected, and often no symptoms are present at all. In such cases, the renal infarction is usually detected later through impaired kidney function.

If a larger blood vessel is blocked, the loss of blood supply affects more extensive parts of the kidney—or, in the worst-case scenario, even the entire kidney. This often results in severe and persistent pain in the flank. Fever, vomiting, nausea, abdominal pain, and high blood pressure may also occur.

In 90 percent of cases, an embolism is responsible for a renal infarction. In this process, a clot travels with the blood to the kidney and becomes lodged in a blood vessel there.

In rarer cases, a thrombosis in a renal artery is responsible for the infarction. This involves a tear or narrowing in a renal artery, where a localized blood clot then forms.

However, other foreign bodies in the blood are also possible, such as tumor tissue in cancer patients, cholesterol crystals, fat deposits, or air bubbles in the blood. The effect is the same regardless of the cause: Blood can no longer flow properly (or at all) to or from the kidney.

Risk factors for a renal infarction include:

• Diabetes mellitus (diabetes)
• Vascular diseases such as atherosclerosis
• Heart diseases such as atrial fibrillation, right-sided heart failure, or a history of heart attacks
• Connective tissue diseases such as systemic lupus erythematosus
• X-ray examinations of the renal vessels
• Vascular injuries caused by surgery

The first indications of a renal infarction often emerge simply from the patient’s description of symptoms and a physical examination of the abdomen and flanks. In addition, the doctor will inquire about other medical conditions that may be risk factors for a renal infarction.

Blood and urine tests can be helpful, but unfortunately they are usually nonspecific. Possible signs may include an increase in white blood cells or serum creatinine (a metabolic byproduct that provides information about kidney function). An ultrasound examination (possibly with Doppler sonography) can usually clearly demonstrate reduced blood flow to the kidney.

A CT scan or angiography (imaging of the blood vessels) may also be necessary to definitively diagnose a renal infarction. It must be distinguished from a kidney tumor, a kidney cyst, renal colic, kidney stones, and pyelonephritis.

In most cases, renal infarcts are treated with medication. Pain relievers alleviate acute symptoms, blood pressure-lowering medications regulate blood pressure, and heparin inhibits blood clotting and, ideally, dissolves any small existing blood clots.

If an underlying condition is present, it must also be treated.

In cases of severe renal infarction, surgical removal of the blood clot or lysis therapy may also be considered. However, surgical removal carries high risks and is therefore rarely performed. In lysis therapy, the doctor inserts a catheter into the affected blood vessel and administers a medication directly to the blood clot. This dissolves the clot, allowing blood to flow freely again.

If kidney function is severely impaired, dialysis may be necessary after the infarction to temporarily take over the kidneys’ functions.

The course of a renal infarction depends heavily on the extent of the infarction and the duration of the impaired blood flow. The longer the tissue has been deprived of adequate blood flow, the greater the risk that it will die. In the case of an extensive infarction, there is a risk that the affected kidney (or even both kidneys) cannot be saved. In most cases, however, the renal infarction is not severe enough to prevent extensive or even complete recovery. Even if temporary dialysis is necessary, the kidneys can resume their function afterward.

A prompt diagnosis and treatment are crucial for a good prognosis. If you experience sudden, severe flank pain, you should therefore see a doctor as soon as possible.