Renal Infarction

What is Renal Infarction?

Renal infarction is a rare condition where the blood supply to the kidneys is blocked completely or partly. This usually happens because of a blood clot that comes from the heart or forms in place in the kidney. Other possible causes include blood clots in the aorta (the main blood vessel in the body), kidney injury, splitting of the kidney artery, blood clotting disorders, or other diseases which result in an increased number of blood clots.

If a patient experiences sudden stomach or back pain, decreased kidney function, high lactate dehydrogenase (an enzyme found in the body), blood in urine, or excess protein in urine, and these symptoms are not due to kidney stones or another identifiable cause, renal infarction could be a possibility. The likeliness of this increases for people above 60 or those with heart diseases, particularly atrial fibrillation (an irregular and fast heart rate).

The diagnosis usually starts with a CT scan of the abdomen, which creates a detailed picture of the kidneys. If this doesn’t show anything, a follow-up scan is done with a contrast dye to highlight the kidneys more clearly. An early diagnosis is crucial because it allows doctors to start the treatment – aimed at restoring blood flow to the kidney – promptly which is crucial for kidney function recovery. The treatment can be a variety of strategies including drugs dissolving clots, systemic thrombolysis, anticoagulation, and antiplatelet therapy. Factors such as how the patient presents, underlying factors, how long the symptoms have been occurring, and the severity of kidney artery blockage all affect the overall success of treatment and the chance of kidney recovery.

Renal infarction can often resemble other common kidney problems – like kidney stones or kidney infection. As a result, the diagnosis can be missed completely. This is evident from the fact that renal infarction is more often found during post-mortem studies than when looking back at patient cases. Missing a diagnosis can lead to an irreversible loss of kidney function, as treatment to restore blood flow to the kidney doesn’t work if the presentation is delayed.

What Causes Renal Infarction?

Renal infarction, which is when blood flow to the kidneys becomes blocked, can be caused by a number of factors. These can generally be grouped into several categories:

1. Heart-related issues
2. Blood clot in the kidney’s artery
3. Injuries or physical harm
4. Problems with the aorta or kidney arteries
5. Blood clotting conditions
6. Diseases that affect the arteries

Heart-related issues are the most common cause of renal infarction and account for over half of the cases. A heartbeat that is irregular or out of sync, known as atrial fibrillation, is responsible for about two-thirds to three-quarters of these cases. Hence, in many instances, renal infarction could be the first sign of this irregular heartbeat. It’s observed that this condition usually occurs in older people. Certain heart-related problems such as valve disease, heart attack and certain types of heart tumor can also cause renal infarction.

Renal infarction can also be caused by a blood clot in the aorta or kidney’s arteries. If the walls of the aorta or kidneys weaken and expand (known as an aneurysm), they increase the chance of blood clots forming, resulting in renal infarction. It’s important to manage high cholesterol and high blood pressure to limit this risk.

Physical injuries that cause harm to the kidney or kidney arteries can lead to renal infarction. This may be caused by a severe blunt injury to the abdomen, but other procedures involving the aorta or its branches, or indeed the kidneys, could also contribute.

Issues with the aorta or kidney arteries are also a common cause of renal infarctions. Sometimes, the simple use of medical devices can lead to issues with these arteries. Dissection of the aorta, where the inner layer of the artery tears, can affect the renal artery as well. Conditions involving abnormal arteries like fibromuscular dysplasia also result in renal infarction. This condition, which primarily affects women under 50, can cause the renal arteries to narrow, form an aneurysm, or dissect, leading to renal infarctions. However, this condition is rare but can have serious complications for otherwise healthy patients.

Conditions that lead to the formation of excessive blood clots, known as hypercoagulability, can also lead to renal infarction. Disorders such as protein C and protein S deficiency, systemic lupus erythematous, polycythemia vera, and prothrombin gene mutation are some examples. Other circumstances like use of oral contraceptives, COVID-19 infection, and abuse of anabolic steroids and cocaine can also cause this condition.

A disease that affects the arteries, known as atheroembolic disease, can cause renal infarction. Individuals who undergo a test that uses dye to observe blood vessels, known as angiography, are at higher risk due to their significant disease of the arteries. This disease can cause irregularly shaped artery plaques to form that result in renal artery blockage and infarction. Ultimately, this reduces the flow of blood and causes kidney injury over time.

Despite thorough testing, sometimes the cause of renal infarction cannot be found, accounting for about 20% to 30% of cases. In these situations, it may indicate overall poor blood vessel health. Hence, risk factors such as high blood pressure, high cholesterol, and diabetes should be closely managed. Studies suggest that individuals with unidentifiable causes of renal infarction are likely to be younger and smokers.

Risk Factors and Frequency for Renal Infarction

Research from autopsies suggests that out of 1,000 people, approximately 14 will have a condition called renal infarction, which equates to about 1.4% of the population. However, studies of patients admitted to the emergency room suggest a much lower rate of 0.004% to 0.007%. As renal infarctions are often diagnosed late or misdiagnosed, autopsy studies may provide a more accurate picture. In terms of patterns of occurrence, 81% of diagnosed cases tend to affect one kidney (unilateral), while the remaining 19% affect both kidneys (bilateral). Patients with an increased likelihood of forming blood clots may have multiple and bilateral infarcts. The average age of patients diagnosed with renal infarction is approximately 63 years, and it affects both men and women equally. Risk factors for renal infarction include irregular heart rhythms (atrial fibrillation), high blood pressure (hypertension), diabetes, and a history of an embolic infarction (a type of stroke).

• Autopsy studies suggest that renal infarctions affect around 14 per 1,000 people, or 1.4%.
• Emergency room admission studies find a much lower incidence rate, between 0.004% and 0.007%.
• Due to late or misdiagnoses, autopsy studies might be more reliable.
• Among the cases, 81% affect only one kidney, while 19% involve both kidneys.
• Patients prone to blood clots are more likely to have multiple and bilateral infarctions.
• The average age for people presenting with renal infarction is around 63 years.
• Men and women are equally affected by renal infarction.
• Irregular heart rhythms, high blood pressure, diabetes, and a history of a certain type of stroke are all risk factors for renal infarction.

Signs and Symptoms of Renal Infarction

Acute renal infarctions (when blood flow to your kidneys is blocked) usually start with a sudden stomach or side ache, coupled with symptoms like nausea, vomiting, blood in urine, and sometimes fever. About one-third of patients may notice their skin changing color, like “blue toe” syndrome or a mottled skin condition known as livedo reticularis.

Unfortunately, these symptoms are not unique and can be mistaken for more common conditions, like kidney stones, kidney infection, or stomach flu. This often leads to delays in diagnosis, with less than half of patients getting the correct diagnosis within the first two days after their symptoms start. Signs of injury to the kidney might only show up several weeks after the damage has occurred. Sudden pain in the stomach or side, high levels of an enzyme called lactate dehydrogenase (LDH), and blood or protein in the urine can all point towards renal infarction.

Because the symptoms can be unclear, it’s crucial for doctors to consider the possibility of renal infarction in patients who are at higher risk for artery-clogging diseases. These high-risk factors include being male, being a smoker, having high blood pressure, high cholesterol, diabetes, being older, and having a heart condition called atrial fibrillation that could lead to blood clots. It’s also recommended that patients suspected of having blood clots due to arterial disease have an eye examination for possible abnormalities in the retina.

If the blood supply to a kidney is suddenly cut off, it can cause a type of high blood pressure that’s caused by too much of the hormone renin. This high blood pressure usually improves once the renal infarction is treated, though it often goes unnoticed as it’s attributed to pain. Some patients might not show any symptoms, contributing to renal infarction often not being diagnosed. In some instances, renal infarction is found by accident in patients having imaging tests for unrelated reasons.

If renal infarction is caused by artery-narrowing due to cholesterol-rich plaques (atherosclerotic renal emboli), some telltale signs include:

• A history of an event in the last 6 months that might have caused a plaque to break off and block an artery (like angiography)
• Acute or gradually worsening kidney injury
• Skin color changes
• Presence of cholesterol crystals in the retina (known as Hollenhorst plaques).

Testing for Renal Infarction

If your doctor suspects a kidney (renal) infarction, they’ll order several laboratory tests. You might have increased levels of certain blood cells, proteins, and enzymes such as leukocytes, C-reactive protein, lactic dehydrogenase (LDH), creatinine, and creatine kinase. A kidney infarction might also cause blood or excess protein in your urine.

LDH is a substance that cells release when they’re damaged. In kidney infarction, the rise in LDH can be four to five times higher than usual. You don’t see this in conditions involving the kidneys such as kidney stones, renal colic, or kidney infection (pyelonephritis). It’s worth noting that high LDH levels can be seen in other conditions such as heart attack (myocardial infarction), the breakdown of red blood cells (hemolysis), or kidney transplant rejection.

Cholesterol emboli, which can cause kidney infarction, are often associated with a high number of white blood cells, known as eosinophils, and a decrease in a specific protein (complement) in the bloodstream. These changes typically disappear within about a week.

When it comes to imaging, a noncontrast CT scan of the abdomen and pelvis is usually the starting point. If symptoms and laboratory results don’t confirm the condition, a contrast-enhanced abdominal CT might be necessary. A contrast CT makes the kidneys (and potential areas of infarction or damage) show up more clearly on the scan.

A typical CT scan with contrast often shows a clear, wedge-shaped area of decreased blood flow in the kidney. If the renal infarction is segmental (only affecting a segment of the kidney), a thin rim of normal appearing kidney tissue may be visible. This is known as the cortical rim sign. In severe cases, there may be a loss of contrast enhancement in the entire kidney.

In case of a traumatic injury to the renal artery, the CT scan might show a hematoma, or a collection of blood that’s leaked from the artery.

Renal CT arteriography is considered the best way to confirm that you have a renal infarction. MRI can also be helpful, but it takes longer. There are other tests available like a radioactive scan called dimercaptosuccinic acid (DMSA), Doppler ultrasound, intravenous pyelogram (IVP), which forms an image of the urinary system, and invasive vascular ultrasound (IVUS) – but these are less frequently used.

If the cause of the renal infarction isn’t clear, your doctor might also order heart tests to check for irregular heart rhythms like atrial fibrillation. An echocardiogram, which is an ultrasound of the heart, might be used to see if there are any blood clots in your heart.

Treatment Options for Renal Infarction

CT renal angiography is a type of imaging test used to get a detailed view of the blood vessels in the kidneys. It helps doctors identify particular blood vessels involved in a condition and determine the level of blood flow blockage. Revascularization, a treatment process aimed to restore blood flow, may not be helpful if this test shows a severely shrunk kidney or a dense scar indicating an old injury.

The treatment of kidney injury can include various methods such as targeted clot-dissolving procedures, system-wide clot-dissolving procedures, anticoagulation therapy, surgery, and experimental treatments. Factors that determine whether revascularization would benefit a patient include the time since the onset of the blood supply cut-off to the kidney, current kidney function, the size and extent of the kidney damage, involvement of other blood vessels, and whether kidney blood flow obstruction is partial or complete.

If a kidney’s blood flow is blocked, it can typically be reversed if detected within six hours. The severity of the blockage can also be determined by a CT renal angiography. Partial blockage with some blood flow still to the kidney tissue suggests that the kidney might recover.

Catheter-directed thrombolysis is a procedure where a catheter is used to deliver blood clot-dissolving medication directly to a blood clot in a kidney. It is used when the blockage is at the start of the kidney artery or on both sides and to restore blood flow in a solitary kidney. This procedure can also be considered for selected patients with significant blockage in smaller arteries. This treatment works best when performed as soon as possible after the onset of symptoms. After treatment, the improvement in kidney function may take some time to reflect in lab tests.

Other treatment methods include systemic thrombolysis, where clot-dissolving medication is administered throughout the body. This approach can be considered if clot-targeted treatment is unavailable. However, the risk of bleeding is higher with this method, compared to the targeted approach.

Anticoagulation or antiplatelet agents, which are medicines that prevent blood clots, are used for patients presenting several days or more after a kidney injury, as a revascularization therapy is not expected to be beneficial. In most cases, long-term anticoagulation therapy is prescribed for those with pre-existing conditions that increase blood clotting or heart-related diseases.

Surgical therapy is mainly considered in the event of trauma-related kidney artery injury and a tear in the aorta (the main blood vessel) extending to the kidney artery. Various surgical options are available, but they come with significant risks.

Treatment for high blood pressure often develops in the first week after a kidney injury due to increased renin levels, a hormone the kidney produces. Medications that inhibit the renin-angiotensin system are preferred in such cases. The associated high blood pressure usually improves in the following weeks unless the patient has an underlying, long-term high blood pressure condition. Long-term management of high blood pressure should be the same as that of any patient suffering from high blood pressure.

In cases where kidney injury is due to atherosclerotic emboli (cholesterol plaque caused blood clots), treatment is primarily supportive. Patients should follow general measures such as using aspirin, stopping smoking, controlling high blood pressure, managing weight, and controlling blood sugar.

Long-term follow-up for patients with kidney injuries due to blood clots has not been standardized. Monitoring patients for complications related to ongoing therapy and regularly checking renal function is reasonable. Lifelong aspirin therapy is typically recommended as well.

Follow-up imaging is recommended, and some experts have suggested regular abdomen imaging, preferably with MRI, at 6 and 12 months. Patients with pre-existing kidney or heart conditions will require closer and long-term monitoring.

What else can Renal Infarction be?

When diagnosing a kidney infarction (the blockage of blood supply to the kidneys), doctors will also consider other possible causes that may have similar symptoms. These include:

• Aortic aneurysm
• Aortic dissection
• Appendicitis
• Diverticulitis
• Gastroenteritis (stomach flu)
• Mesenteric ischemia (lack of blood flow to the intestines)
• Nephrolithiasis (kidney stones)
• Pyelonephritis (kidney infection)
• Renal cell carcinoma (a type of kidney cancer)
• Various gynecological disorders

Misdiagnosing kidney infarction for kidney stones or kidney infection is not uncommon, and can delay crucial treatment. A key element in distinguishing these conditions is using blood tests to check for high levels of lactate dehydrogenase (LDH), which is typically not present in kidney stones or infections but can indicate a kidney infarction.

A CT scan with contrast of the abdomen is also particularly important in order to differentiate kidney infarction from other abdominal pain causes. Doctors need to be vigilant about ruling out issues with blood supply to the intestine, as those with conditions increasing blood clot risks can potentially block off the vessels leading to the intestine, causing acute bowel infarction. In these cases, testing with angiography may be necessary.

What to expect with Renal Infarction

A large study found that about 20% of patients diagnosed with kidney infarction, a condition where the blood flow to the kidneys is blocked, had passed away within 40 months. However, only 2% of these patients had developed End-Stage Renal Disease (ESRD), which is the last stage of chronic kidney disease where the kidneys stop doing their job. This suggests that kidney infarction often points to fatal heart conditions and other deadly diseases.

Spotting kidney infarction early improves patients’ chances of recovery. Factors such as the length of time the kidney was without blood flow (warm ischemia time), the flow of blood through nearby vessels (collateral flow), and any pre-existing kidney disease can shape a patient’s outcome after undergoing a procedure known as catheter-directed thrombolysis. This is a treatment where a thin tube (catheter) is used to directly deliver medicine that dissolves the blood clot in the kidney.

The prognosis can also be affected if there’s embolic infarction (blockage caused by a blood clot) in other organs such as the spleen, intestine, liver, and lungs. The presence of these extra kidney blockages can lead to longer hospital stays and increase the overall sickness and fatality rates.

Possible Complications When Diagnosed with Renal Infarction

Common complications that can occur include sudden kidney damage, long-term kidney disease, and high blood pressure. The degree of damage from the initial kidney issue can often determine if it progresses to long-term kidney disease. The main risks for long-term kidney disease include being older in age and having a more severe initial kidney issue. In up to 58% of kidney damage cases, patients later developed long-term kidney disease, as detected through follow-up kidney imaging tests.

Common Complications:

• Sudden kidney damage
• Long-term kidney disease
• High blood pressure
• Progression from sudden to long-term kidney disease
• Possible risk factors for long-term kidney disease include advanced age and severe initial kidney damage
• Almost 58% of kidney damage cases may progress to long-term kidney disease, detected through follow-up tests

Preventing Renal Infarction

If you are being treated with warfarin, it’s important that you understand how it works, and what an INR range is. In simple terms, anticoagulation means that the medicine helps to thin your blood to prevent clots, and the INR is a test used to monitor how long it takes your blood to clot. If you are experiencing repeated clots even when on medication, it’s crucial to understand how to properly take your medication and how it interacts with certain foods.

Doctors should also guide patients on how to address other factors that could be contributing to their heart problem, such as smoking. Making lifestyle changes, like quitting smoking, can have a big impact on your overall health.