Internal Medicine Coding Alert

Question: What distinguishes a thoracic aortic aneurysm from an abdominal aortic aneurysm?

Maryland Subscriber

Answer: The diaphragm is the dividing line between the thorax and abdomen, so the thoracic aorta leaves the heart and arches,and descends through the chest until it reaches the diaphragm. The aorta becomes the abdominal aorta after it passes the diaphragm and continues down the abdomen. When a blood vessel wall weakens, an abnormal vessel ballooning or widening, called an aneurysm, can result. If an aneurysm ruptures, it can lead to massive bleeding and death. Abdominal aortic aneurysm (AAA) occurs in the abdominal region. Use 441.3 (Aortic aneurysm and dissection; abdominal aneurysm, ruptured) or 441.4 (...abdominal aneurysm without mention of rupture) to report the condition with or without rupture.

Thoracic aortic aneurysm (TAA) occurs in the thoracic region. Report TAA as 441.1 (... thoracic aneurysm, ruptured) or 441.2 (... thoracic aneurysm without mention of rupture), depending on whether a rupture is present. For an aneurysm between the two regions, report 441.6 (... thoracoabdominal aneurysm, ruptured) or 441.7 (... thoracoabdominal aneurysm, without mention of rupture), depending on rupture status. For an unspecified site, use 441.5 (... aortic aneurysm of unspecified site, ruptured) or 441.9 (... aortic aneurysm of unspecified site without mention of rupture).

Watch for: The physician also may diagnose the patient with a related condition, aortic dissection, which occurs when blood enters through a tear in the aorta's lining into the space between the vessel's middle and outer layers, causing a separation. This can occur in the abdominal or thoracic aorta, and you'll assign the proper code (441.0x, Dissection of aorta ...) based on the site.

Aortic ectasia, which involves dilation of the aorta but to a lesser degree than an aneurysm, is getting its own set of codes effective Oct. 1, 2010. ICD-9 also distinguishes these codes by anatomic location:

• 447.70 -- Aortic ectasia, unspecified site
• 447.71 -- Thoracic aortic ectasia
• 447.72 -- Abdominal aortic ectasia
• 447.73 -- Thoracoabdominal aortic ectasia.