Horizontal fissure
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The horizontal fissure (also called the minor fissure) is a unilateral structure in the right lung that separates the right middle lobe from the right upper lobe.
Gross anatomy
The horizontal fissure arise from the right oblique fissure and follow the fourth intercostal space from the sternum until it meets the oblique fissure as it crosses right 5th rib 1.
Variant anatomy
The horizontal fissure is highly variable and can be found to be incomplete or absent in some patient. According to different postmortem dissection study incomplete of horizontal fissure can vary between 8-35% and absent in 3-50% of the patients' right-sided lungs 2,3,4.
Radiographic features
The horizontal fissure can be visualised on both conventional radiography and computed tomography (CT) scans.
Conventional radiograph
- seen on
~ 65~65% (range 5-80%) of normal frontal chest x-rays as a thin line running horizontally from the edge of right lung towards the right hilum, at approximately the level of the anterior fourth rib 5
-<p>The <strong>horizontal fissure </strong>(also called the<strong> minor fissure</strong>) is a unilateral structure in the right lung that separates the <a href="/articles/right-middle-lobe">right middle lobe</a> from the <a href="/articles/right-upper-lobe">right upper lobe</a>.</p><h4>Gross anatomy</h4><p>The horizontal fissure arise from the right <a href="/articles/oblique-fissure">oblique fissure</a> and follow the fourth <a href="/articles/intercostal-space">intercostal space</a> from the <a href="/articles/sternum">sternum</a> until it meets the <a href="/articles/oblique-fissure">oblique fissure</a> as it crosses right 5th <a href="/articles/rib">rib</a> <sup>1</sup>.</p><h4>Variant anatomy</h4><p>The horizontal fissure is highly variable and can be found to be incomplete or absent in some patient. According to different postmortem dissection study incomplete of horizontal fissure can vary between 8-35% and absent in 3-50% of the patients' right-sided <a href="/articles/lung">lungs</a> <sup>2,3,4</sup>.</p><h4>Radiographic features</h4><p>The horizontal fissure can be visualised on both conventional radiography and computed tomography (CT) scans.</p><h5>Conventional radiograph</h5><ul><li>seen on ~ 65% (range 5-80%) of normal frontal chest x-rays as a thin line running horizontally from the edge of right <a href="/articles/lung">lung</a> towards the <a href="/articles/right-hilum">right hilum</a>, at approximately the level of the anterior fourth rib <sup>5</sup>- +<p>The <strong>horizontal fissure </strong>(also called the<strong> minor fissure</strong>) is a unilateral structure in the right lung that separates the <a href="/articles/right-middle-lobe">right middle lobe</a> from the <a href="/articles/right-upper-lobe">right upper lobe</a>.</p><h4>Gross anatomy</h4><p>The horizontal fissure arise from the right <a href="/articles/oblique-fissure">oblique fissure</a> and follow the fourth <a href="/articles/intercostal-space">intercostal space</a> from the <a href="/articles/sternum">sternum</a> until it meets the <a href="/articles/oblique-fissure">oblique fissure</a> as it crosses right 5th <a href="/articles/rib">rib</a> <sup>1</sup>.</p><h4>Variant anatomy</h4><p>The horizontal fissure is highly variable and can be found to be incomplete or absent in some patient. According to different postmortem dissection study incomplete of horizontal fissure can vary between 8-35% and absent in 3-50% of the patients' right-sided <a href="/articles/lung">lungs</a> <sup>2,3,4</sup>.</p><h4>Radiographic features</h4><p>The horizontal fissure can be visualised on both conventional radiography and computed tomography (CT) scans.</p><h5>Conventional radiograph</h5><ul><li>seen on ~65% (range 5-80%) of normal frontal chest x-rays as a thin line running horizontally from the edge of right <a href="/articles/lung">lung</a> towards the <a href="/articles/right-hilum">right hilum</a>, at approximately the level of the anterior fourth rib <sup>5</sup>