WBR0043

Author	PageAuthor::Gonzalo Romero (Reviewed by Will Gibson)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 17-year-old male is brought to his pediatrician by his father for severe headache and nosebleeds over the last six months. He 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. On physical exam his vitals are heart rate of 80 beats/min, respiratory rate of 15/min, blood pressure of 170/95 mm Hg in the upper extremities and 100/70 mm Hg in the lower extremities. 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 is the most specific radiographic finding for the patient's condition?]]
Answer A	AnswerA::Kerley B lines
Answer A Explanation	[[AnswerAExp::Kerley lines are short parallel lines at the lung periphery. These lines represent distended interlobular septa, which are usually less than 1 cm in length and parallel to one another at right angles to the pleura. They are located peripherally in contact with the pleura, but are generally absent along fissural surfaces. They may be seen in any zone but are most frequently observed at the lung bases at the costophrenic angles on the posterior-anterior radiograph, and in the substernal region on lateral radiographs. These lines are present when interstitial edema is present, and are therefore not specific for aortic coarctation.]]
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 teenager is presenting with symptoms of post-ductal aortic stenosis, which is a localized narrowing or abrupt constriction of the aortic arch after the ligamentum arteriosum. This condition is also referred to as coarctation of the aorta. Aortic coarctation may be associated with a bicuspid aortic valve and it is is more common in males than females with a 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: 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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