Kawasaki disease is a febrile condition resulting in inflammation of blood vessels all through the body. This disease predominantly affects children below five years of age. It affects all the vessels, including the coronary arteries of the heart, thus contributing to one of the major causes of acquired heart disease in kids. The children usually present with fever, rashes, swollen lips, hands, and feet. If diagnosed earlier, most children can be treated successfully with a possibility of complete recovery.

What Causes Kawasaki Disease?

The exact cause of this disease is unknown. However, considering the presence of fever and swollen lymph nodes, the etiology of this disease may be traced to an infectious origin (either viral or bacterial).
A genetic predisposition may also be considered.
Studies have also suggested that certain environmental factors contribute to the development of Kawasaki disease.
Kawasaki disease does not spread from one person to another.

What Are the Risk Factors Associated With Kawasaki Disease?

Certain factors increase the risk of the child developing Kawasaki disease. They are as mentioned below:

Age: Kawasaki disease has a greater propensity for children under five.
Sex: Boys are more prone to developing this disease.
Climate: More often seen during winter and spring seasons.
Ethnicity: Children of Asian or Pacific lineage display a greater incidence of this disease.

What Are the Symptoms of Kawasaki Disease?

The symptoms do not appear simultaneously; instead, they appear in phases.

First Phase:

This phase can last up to two weeks.
A high fever can last for five days or more.
Blood-red eyes.
Rashes throughout the body and more prominently in the genital areas.
The tongue will have a thick white coating with small tiny red bumps (strawberry-tongue).
Sore throat.
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Swollen hands, feet, and lymph nodes.

Second Phase:

Peeling of the skin on the hands and feet.
Abdominal pain due to gall bladder distention.
Joint tenderness.
Nausea.
Diarrhea.

What Are the Complications of Kawasaki Disease?

Kawasaki disease is one of the chief causes of the development of acquired heart disease in children. This disease is mainly characterized by inflammation of blood vessels throughout the body. However, the progression of the disease could further involve the blood vessels of the heart, especially the coronary arteries (major blood vessels of the heart), thus leading to cardiac complications. Furthermore, inflammation of coronary arteries can consequently lead to other cardiac problems as mentioned below:

Muscles of the heart can get inflamed.
Abnormal heart rhythms.
Aneurysms (the coronary artery wall gets weakened and damaged, which results in bulging of the arteries). Giant aneurysms can obstruct the blood flow and cause a heart attack that may prove fatal.
Damages heart valves (mitral valve is most commonly affected).
Pericardial effusion (fluid accumulates around the heart).

How Is Kawasaki Disease Diagnosed?

Kawasaki disease is usually diagnosed based on a physical examination and a detailed medical history. There are no definite laboratory tests to identifyKawasaki disease per se. The diagnostic workup is as given below:

Blood Tests:

To rule out scarlet fever, a Streptococcal infection causing similar symptoms as Kawasaki disease.
To check for the complete blood cell count.
Increased white blood cells, decreased hemoglobin, increased ECR (erythrocyte sedimentation rate), and CRP (C-reactive protein) are indicative of Kawasaki disease.

Imaging Tests:

Chest X-ray, electrocardiogram, echocardiogram, and angiogram may be advised to rule out any cardiac complications.

What Is the Role of Imaging in Kawasaki Disease?

Imaging plays a crucial role in identifying cardiac complications. Appropriate and timely intervention is crucial to prevent such complications in children. Early diagnosis would require palliative therapy, and kids achieve complete recovery within a few days. The risk of developing cardiac complications is considered low if no changes are seen in the coronary artery within six to eight weeks from the onset of the disease. In children with known cardiac complications, regular imaging procedures will be required to keep their cardiac health in check.

What Are the Various Imaging Techniques Used in Kawasaki Disease?

The goal of the imaging procedures is to rule out any heart complications. In children with coronary artery complications, imaging techniques can help prevent the risk of developing myocardial ischemia. In addition, periodic screening in these children can avert any fatal consequences. The imaging procedures used in Kawasaki disease are as mentioned below:

Chest X-Ray:

Chest X-rays are not routinely done in Kawasaki disease as they usually do not show significant changes.
Occasionally, certain non-specific features may be seen as mentioned below:

Pleural effusion (fluid accumulation in the lungs).
Atelectasis (lung collapse).
Peribronchial cuffing (thickening of the bronchial wall).
Reticulogranular appearance of the lung field (hazy net-like opacities).
Advanced cases which have resolved over time may present as calcifications in the site of the coronary artery (aneurysmal calcification).

Echocardiography:

Echocardiography is considered the first-line imaging tool to assess children with cardiac complications.
Echocardiography is a diagnostic procedure used to assess the structure and functions of the heart. It is an ultrasound of the heart, which can check the valves and chambers, the blood flow, and the cardiac rhythms.
Two-dimensional echocardiography has the highest sensitivity and specificity in detecting coronary artery aneurysms.
A coronary Z-score is obtained with 2D echocardiography. A score greater than ten is highly suggestive of risk for thrombosis and blockage of blood vessels.
Echocardiography should be done at the time of diagnosis, repeated at one to two-week intervals, and then repeated in five to six weeks.
High-risk patients and severe cases should be screened regularly.
Echocardiography is performed to check for coronary artery dilation, blood clot or obstruction of the blood vessels, left ventricular abnormality, and mitral valve damage.
Pericardial effusion can also be seen distinctly in echocardiography.

Electrocardiography (ECG):

ECG is a simple, non-invasive procedure used to assess the rhythm of the heart.
Electrodes will be attached to the skin to detect the electrical impulse produced with each heartbeat.
Abnormal signals indicate irregular rhythms and, thereby, an underlying heart disease.
ECG is used in Kawasaki disease to detect irregular heart rhythms.

Computed Tomography (CT):

CT is used in advanced cases to detect coronary artery calcification.
A contrast-CT may prove more beneficial in the acute phase.
The location and size of the coronary artery aneurysm can be selected using CT.
A gall bladder distension can also be distinctly seen in the CT.
Enlarged lymph nodes, which are common in Kawasaki disease, can be detected.
Multidetector CT is more sensitive and specific in diagnosing coronary artery aneurysms and blockage.
Single-photon emission computed tomography (SPECT) is a novel technique that can be used for more precision. They can be used to evaluate myocardial perfusion (blood flow through the heart), ischemia, and scarring of the tissues. However, it is generally avoided in children due to increasing doses of ionizing radiation in SPECT.

Magnetic Resonance Imaging (MRI):

MRI, though not routinely indicated, can detect coronary aneurysms.
MRI can be used to evaluate myocardial perfusion and myocardial wall thinning.
However, the gadolinium contrast agent used in MRI is considered nephrotoxic and should be avoided in children with renal diseases.

Coronary Angiography:

Coronary angiography is an invasive procedure to check if there is any block in the coronary arteries.
This procedure involves injecting a dye through the vein in the arms, followed by an X-ray to view the blood vessels of the heart.
This procedure can also be done using CT or MRI.
Angiography is extremely sensitive in detecting even tiny aneurysms and thrombus (blood clots).
However, considering the invasiveness of this procedure and the radiation exposure, their usage is restricted in the pediatric population unless other techniques have proved less successful.

Abdominal Ultrasonography:

Abdominal ultrasonography may be indicated if liver dysfunction or gallbladder distention is suspected.

Conclusion:

Kawasaki disease is a common febrile illness in childhood. Though the cause of this disease remains unknown, early diagnosis promises a thorough recovery and zero complications. There are numerous imaging modalities complementing each other; however, the role of any imaging technique would be to diagnose and assess the severity of the associated complications and thereby aid in the management and follow-up of the patients.