WBR0043

Author	PageAuthor::Gonzalo Romero (Reviewed by Will Gibson and Yazan Daaboul)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 6-year-old boy is brought to his pediatrician by his father for severe headache and nosebleeds over the past six months. The patient complains that his feet become very cold at night for which he has been wearing two pairs of thick socks. At school, he gets occasional cramps in his legs and is easily winded when running in gym class. He denies using any drugs or drinking alcohol. His grades are stable and he has a girlfriend, but is not sexually active. His blood pressure is 170/95mmHg in the both upper extremities and 100/70 mmHg in both lower extremities, heart rate is 80/min, and respiratory rate is 15/min, temperature is 37 °C (98.6 °F). On physical examination, he has clear breath sounds bilaterally, but a continuous murmur is heard over the inter-scapular area. A chest x-ray is ordered and is shown below. Which of the following findings is the most specific radiographic finding associated with this patient's condition?]]
Answer A	AnswerA::Kerley B lines
Answer A Explanation	[[AnswerAExp::Kerley B lines are abnormal, short, horizontal shadows that are present in the costophrenic angles that are present in thickened interlobular septa in cases of pulmonary edema and neoplasms.]]
Answer B	AnswerB::Rib notching
Answer B Explanation	[[AnswerBExp::The following are radiologic findings in aortic coarctation: Irregularities or notching of the inferior margins of the posterior ribs results from collateral flow through dilated and pulsatile intercostal arteries. These collaterals appear after 6 years of age if the coarctation is significant. An inverted "3" sign or a "3" sign on a highly penetrated chest radiograph may be visualized. Post-stenotic dilation of the aorta results in a classic reverse 3 sign on x-ray. The characteristic bulging of the sign is caused by dilatation of the aorta due to an indrawing of the aortic wall at the site of cervical rib obstruction, with consequent post-stenotic dilation. This physiology results in the reversed 3 image for which the sign is named. Signs of congestive heart failure, including: cardiomegaly, pulmonary edema, and prominent pulmonary vasculature. These signs of congestive heart failure are not specific to this coarctation of the aorta.]]
Answer C	AnswerC::Cardiomegaly
Answer C Explanation	[[AnswerCExp::There are many causes of cardiomegaly, including medications, genetic conditions, endocrine conditions, infectious processes, toxins and iatrogenic causes. Therefore cardiomegaly is not a specific radiologic finding. In particular, cardiomegaly is not associated with this patient's underlying condition, coarctation of the aorta.]]
Answer D	AnswerD::Pleural effusion
Answer D Explanation	[[AnswerDExp::The most common causes of transudative pleural effusions in the United States are left ventricular failure, pulmonary embolism, and cirrhosis (causing hepatic hydrothorax). Conversely, the most common causes of exudative pleural effusions are bacterial pneumonia, cancer (with lung cancer, breast cancer, and lymphoma causing approximately 75% of all malignant pleural effusions), viral infection, and pulmonary embolism. Pleural effusion therefore, is not a specific finding in general, and furthermore, pleural effusion is not associated with aortic coarctation.]]
Answer E	AnswerE::Patchy alveolar infiltrates
Answer E Explanation	[[AnswerEExp::Patchy alveolar infiltrates are not associated with coarctation of the aorta. Cardiogenic pulmonary edema can be distinguished from noncardiogenic pulmonary edema by the presence of redistribution of blood flow to the upper lobes (increased blood flow to the higher parts of the lung) and interstitial edema. In contrast, patchy alveolar infiltrates with air bronchograms are more indicative of noncardiogenic edema. Therefore patchy alveolar infiltrates are not specific for aortic coarctation. [1]]]
Right Answer	RightAnswer::B
Explanation	[[Explanation::This patient is most likely presenting with symptoms and signs of post-ductal coarctation of the aorta (COA), which is a localized narrowing or abrupt constriction of the aortic arch after the ligamentum arteriosum. COA is commonly associated with aortic aneurysms and bicuspid aortic valve. In severe cases, COA may be present in infancy. Diagnosis may be delayed in less severe narrowing, where patients may be diagnosed during childhood, adolescence, or even early adulthood. It is more common in males than females with a male:female ratio of 2:1. Clinically, patients often present with headaches, epistaxis, dizziness, syncope, dyspnea, chest pain, cold feet or legs, leg cramps with exercise, differential hypertension, poor growth and decreased exercise performance. There are 3 potential sources of a murmur: multiple arterial collaterals (continuous murmur), an associated bicuspid aortic valve (systolic ejection click) and the coarctation itself, which can be heard over the left infraclavicular area and under the scapula. The following are radiologic findings in aortic coarctation: Irregularities or notching of the inferior margins of the posterior ribs results from collateral flow through dilated and pulsatile intercostal arteries. These collaterals appear after 6 years of age if the coarctation is significant. An inverted "3" sign or a "3" sign on a highly penetrated chest radiograph may be visualized. Post-stenotic dilation of the aorta results in a classic reverse 3 sign on x-ray. The characteristic bulging of the sign is caused by dilatation of the aorta due to an indrawing of the aortic wall at the site of cervical rib obstruction, with consequent post-stenotic dilation. This physiology results in the reversed 3 image for which the sign is named. Signs of congestive heart failure, including: cardiomegaly, pulmonary edema, and prominent pulmonary vasculature. These signs of congestive heart failure are not specific to this coarctation of the aorta. Shown below is an image depicting rib notching in blue and the classic reverse 3 sign in green. Educational Objective: Aortic coarctation can produce specific signs on chest x-ray such as: irregularities or notching of the inferior margins of the posterior ribs and an inverted "3" sign of the barium-filled esophagus. References: Brown ML, Burkhart HM, Connolly HM, et al. Coarctation of the aorta: lifelong surveillance is mandatory following surgical repair. J Am Coll Cardiol. 2013;62(11):1020-1025. First Aid 2014 page 283]]
Approved	Approved::Yes
Keyword	WBRKeyword::Heart, WBRKeyword::Aorta, WBRKeyword::Vessels, WBRKeyword::Vasculature, WBRKeyword::Coarctation, WBRKeyword::Cardiology, WBRKeyword::Pulmonology, WBRKeyword::Radiology, WBRKeyword::Chest, WBRKeyword::Chest X ray
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