Continuing Education Activity

Renal artery thrombosis is a rare pathology that may be overlooked when evaluating impaired renal function. It is the formation of a blood clot in one or both of the arteries supplying blood to the kidneys, and it can result in kidney failure. This activity reviews the evaluation and treatment of renal artery thrombosis and highlights the role of the interprofessional team in the care of patients with this condition.

Objectives:

• Identify the etiology of renal artery thrombosis.
• Review the appropriate evaluation of renal artery thrombosis.
• Outline the management options available for renal artery thrombosis.
• Summarize the importance of collaboration amongst the interprofessional team to enhance the care of patients with renal artery thrombosis.

Introduction

Renal artery thrombosis is a rare pathology that may be overlooked when evaluating impaired renal function. It is the formation of a blood clot in one or both of the arteries supplying blood to the kidneys. This results in decreased renal perfusion and may result in kidney injury or failure. There appears to be a correlation with traumatic injury, particularly with blunt abdominal trauma, but an embolic event emanating from the heart remains the most common cause. In the appropriate clinical context, renal artery thrombosis should be evaluated early on with both laboratory testing and imaging studies to prevent permanent renal impairment.[1][2][3]

Renal artery thrombosis has gained renewed attention in the recent global pandemic as it has been associated with the 2019 novel coronavirus (COVID-19). It is reported in some studies that renal artery thrombosis can present itself secondary to coronavirus infection, along with the usual association of thromboembolism in major blood vessels and stroke.[4][5]

Etiology

Underlying endothelial injury predisposes a patient to the development of renal artery thrombosis. Those with a history of known atherosclerosis, blunt traumatic injury,[6] or renal artery stents should be considered to be at an increased risk. But the most common cause of renal artery thrombosis is thromboembolism originating in the heart or large arteries like the aorta.[7] Almost 95% of the thromboemboli originate in the heart.[8] Hypercoagulability is another major risk factor. A diagnosis of cancer, regular use of oral contraceptives, and systemic inflammatory processes can lead to this intravascular state being present. Genetic conditions that surge the risk of blood clot formation are important to elicit in the patient history. Decreased blood flow and increased blood viscosity are factors that may create a situation in which a renal artery thrombosis can be formed.[9][10][11][12] 

The other possible causes are polycythemia vera, nephrotic syndrome, pregnancy, systemic lupus erythematosus, Ehlers-Danlos syndrome, infective endocarditis, and renovascular hypertension. Arterial injury due to surgical interventions can complicate the development of renal thrombosis. This includes renal angiography, intra-aortic balloon placement, renal surgery, renal transplantation, etc.[7] In a sporadic case, it has also been seen secondary to acute pyelonephritis.[13]

As mentioned above, it is usually associated with other diseases or causes, and isolated spontaneous cases are extremely rare.[14]

Epidemiology

Even though this kind of thrombosis is seen most commonly in the age group of 30 to 50 years, it can occur at any age. There seems to be no gender predominance or domination of the right over the left artery.[7] Prior data, collected from more than 14,000 autopsy reports, has shown a prevalence of renal infarction at 14/1000. Another study, however, puts the prevalence much lower. The estimate from a case series done in the USA puts the prevalence at 0.02/1000. This disparity highlights the limited data available and the differences in current data available on the subject.[2]

History and Physical

Patient presentation of a renal thrombosis leading to ischemia of the kidney most often includes flank pain and sometimes isolated abdominal pain. Hematuria is frequently present as well. Fever has been noted in addition to nausea and vomiting.[15] The pain is typically persistent and can mimic the symptoms seen with nephrolithiasis and pyelonephritis. Many of these symptoms imitate other more common pathologies, and arriving at a diagnosis can be considerably difficult. Renal artery thrombosis leading to partial obstruction and ischemia without infarction may not cause any symptoms, but eventually, progress as decreased perfusion persists.[2][3][16]

Evaluation

After obtaining a history, imaging in the form of computed tomography (CT) angiography of the abdomen and pelvis should be pursued. In the setting of traumatic injury, this may already be included in the diagnostic workup should blunt trauma have occurred. In the absence of trauma, a dedicated study in the presence of clinical signs and symptoms of renal artery thrombosis should nonetheless prompt healthcare providers to order an imaging study rapidly. It is also better to evaluate with an IV contrast study to rule out thrombosis of the renal artery.[15]

In atraumatic occurrences, an echocardiogram should be ordered to evaluate for the possibility of an embolus emanating from the heart. This is especially important in those with a cardiac valvular prosthesis and a history of atrial fibrillation.

Laboratory studies should include a comprehensive metabolic panel, complete blood count, urinalysis with urine culture, and lactate dehydrogenase (LDH). A strong correlation with hematuria, proteinuria, elevated aspartate aminotransferase (AST), and elevated LDH has been noted once the thrombosis has progressed to renal infarction. These laboratory tests may not be as definitive in the setting of a partial thrombosis without infarction.

Additional laboratory testing for intraabdominal pathology should be considered as well, especially if the patient presents with the main complaint of abdominal pain in the absence of flank pain and urinary symptoms.[17][18]

Treatment / Management

Even though rare, renal artery thrombosis is life-threatening, and it is frequently misdiagnosed.[2] Hence, it is crucial for a proper diagnosis and immediate treatment.[14] The first step in management is to initiate anticoagulation with heparin. With the possibility of interventional radiology intervention with local thrombolysis, enoxaparin therapy may be inappropriate. This is especially true in the context of underlying renal dysfunction. Close communication with both the nephrologist and the interventionalist is essential for anticoagulation therapy and ongoing management.

Secondarily, as stated, thrombolysis may be indicated should the thrombotic burden be determined through imaging to be significant. Kidney function testing, underlying comorbidities, and imaging results should guide therapeutic management. The main concern is to prevent renal infarction and potential sequela. Surgical intervention should be pursued in the setting of significant blunt abdominal trauma, and hemodynamic instability should the context be appropriate.

Chronic anticoagulation post-diagnosis in patients with atrial fibrillation, a history of coagulopathy, and the presence of mechanical heart valves is important to consider for the prevention of future events.[2][18]

Differential Diagnosis

The differential diagnosis initially is quite broad as patients often present with flank pain but may only have a chief complaint of abdominal pain. Isolated abdominal pain should include an appropriate workup with attention also given to the renal function. In the absence of identified gastrointestinal pathology, a renal cause of the pain may provide an explanation. Certainly, nephrolithiasis, as well as pyelonephritis, should be considered.[2]

Prognosis

The prognosis is assessed by the size of the thrombosis, duration of time in place, and the amount of resulting infarction. In the case of an infarction, 8% of patients will have progressively worsening kidney function that will result in the initiation of dialysis therapy. Most patients, however, will experience resolved renal function once improved perfusion of the kidney is achieved. Without infarction, laboratory testing findings are likely to be transient and not have major long-term implications for the patient. Prevention of further events with anticoagulation, sometimes chronically, will lead to better prognoses in the future.[2]

Complications

Renal infarction is the major complication that may result from an untreated renal artery thrombosis. Hypertension, sometimes refractory to medical management, is another serious sequela that clinicians need to be aware of and manage. Renal infarction could lead to significant renal impairment that, in some cases, may be irreversible. Dialysis therapy may need to be pursued should the patient already have chronic kidney disease or have major impairment in kidney function post-diagnosis.[15] Delayed treatment due to misdiagnosis usually results in irreversible damage to the kidney resulting in a nephrectomy.[14] 

It has been recently reported that the COVID-19, which usually is associated with thromboembolism in major blood vessels and stroke, can even present secondarily with renal artery thrombosis.[4][5]

Deterrence and Patient Education

Ensuring that patients with significant risk factors are compliant with prescribed therapy and therapeutic on medications like warfarin in the setting of atrial fibrillation or mechanical heart valves is a major preventative step. Educating patients on the known complications of poor compliance with anticoagulation therapy should be pursued during inpatient and outpatient encounters when appropriate. Those with an underlying inheritable coagulopathy predisposing them to thrombosis formation may benefit from the involvement of a hematologist.

Pearls and Other Issues

In the setting of blunt abdominal trauma with sudden changes in a patient’s renal function, a diagnosis of renal artery thrombosis should be investigated. This does include bilateral distribution and can impact those with no underlying renal pathology and patients who are not at significant pre-trauma risk for hypercoagulability.

Enhancing Healthcare Team Outcomes

Open communication between the interprofessional team is critical to managing this condition. The patient may first be seen by a trauma service, emergency medicine clinician, or even a primary clinician. Involving the appropriate specialists to ensure thrombus resolution and prevent kidney injury will improve patient outcomes. This is a disorder that is unlikely to be successfully managed by any one single provider, and using a team approach is critical from early on. Many of those diagnosed with renal artery thrombosis will continue to experience clinical deterioration should appropriate therapy not be started promptly.