Every other Tuesday, NYACP members are sent a Board Review Question from ACP's MKSAP 18 to test professional knowledge and help prepare for the exam. Participant totals and answer percentages are distributed on Thursday in IM Connected, the Chapter's eNewsletter, and are also published on this page.
A 68-year-old man is evaluated during a routine examination. He is asymptomatic. Medical history is significant for hypertension and hyperlipidemia. He has a 50-pack-year smoking history but quit smoking at age 45 years. Medications are low-dose aspirin, atorvastatin, and amlodipine.
On physical examination, vital signs are normal.
An abdominal aortic duplex ultrasound shows an abdominal aortic aneurysm with a maximum diameter of 3.5 cm.
Manage an abdominal aortic aneurysm with surveillance.
The most appropriate next step in the management of this patient with an abdominal aortic aneurysm (AAA) is repeat abdominal aortic ultrasonography. The optimal surveillance frequency for abdominal aortic aneurysm is controversial. As aneurysm size increases, risk for rupture also increases. For AAAs with a diameter smaller than 4.0 cm, the 5-year risk for rupture is 2%, and some guidelines recommend a surveillance interval of 24 to 36 months. AAAs with a diameter between 4.0 cm and 5.0 cm have a 5-year risk for rupture of 3% to 12%, and surveillance imaging is recommended more frequently (for example, every 6 to 12 months). AAAs with a diameter between 5.0 and 6.0 cm have a 5-year risk for rupture of 25%. Once an AAA reaches 5.5 cm in maximum diameter, surgical or endovascular repair is warranted, owing to the elevated risk for death due to aortic rupture. Repair is also indicated in patients with symptoms from AAA (abdominal tenderness or pain) and those with rapid expansion in AAA size (>0.5 cm/year). This patient with an AAA with a maximum diameter of 3.5 cm can be managed with surveillance abdominal ultrasonography. Because he is asymptomatic, he does not require surgical repair at this time.
Anatomic imaging tests, such as CT angiography or magnetic resonance angiography, are indicated to determine the exact location of the AAA (suprarenal, juxtarenal, or infrarenal) in planning for aortic repair. When an AAA does not meet the maximum diameter threshold for repair, such as in this patient, anatomic imaging with CT angiography is not indicated. Abdominal ultrasonography is preferred for serial monitoring of an AAA.
Pursuing no further testing or intervention would be inappropriate in this patient. An AAA predisposes the patient to an elevated risk for aortic rupture and death, and surveillance of the aneurysm is recommended.
Patients with an abdominal aortic aneurysm smaller than 5.5 cm should undergo surveillance ultrasonography, with frequency determined by aneurysm size.
Chaikof EL, Brewster DC, Dalman RL, Makaroun MS, Illig KA, Sicard GA, et al. SVS practice guidelines for the care of patients with an abdominal aortic aneurysm: executive summary. J Vasc Surg. 2009;50:880-96. [PMID: 19786241] doi:10.1016/j.jvs.2009.07.001
Copyright 2018, American College of Physicians.
A 60-year-old woman is admitted to the hospital with sudden-onset, cramping abdominal pain of moderate severity in the right lower quadrant, followed several hours later by a bloody bowel movement. She has coronary artery disease; medications are atorvastatin, metoprolol, sublingual nitroglycerin, and low-dose aspirin.
On physical examination, the patient appears comfortable. Pulse rate is 110/min; BMI is 35. Other vital signs are normal. The abdomen is nondistended with normal bowel sounds. Deep palpation elicits tenderness in the right lower quadrant with no rebound or guarding.
A CT scan without contrast shows thickening of the ascending colon. Colonoscopy results show a segment of subepithelial hemorrhage, edema, and erythema from the cecum to the hepatic flexure.
Evaluate isolated right-colon ischemia.
CT angiography is the best next test for this patient, whose clinical presentation with the sudden onset of right-sided, cramping abdominal pain followed by a bloody bowel movement is typical of isolated right-colon ischemia. A CT scan showing thickening of the ascending colon and the colonoscopy features are helpful in confirming this diagnosis. The most common cause of colon ischemia is a nonocclusive low-flow state in the colonic microvasculature. Most cases of colonic ischemia involve the left colon, which is supplied by the inferior mesenteric artery; as with ischemia involving the right colon, the diagnosis is clinical and supported by CT and colonoscopy. Patients with left-sided colonic ischemia tend to heal well with conservative therapy alone, whereas isolated right-colon ischemia can be the harbinger of acute mesenteric ischemia caused by a focal thrombus or embolus of the superior mesenteric artery. This artery supplies both the small intestine and right colon, and the consequences of acute mesenteric ischemia involving the small bowel are severe, with mortality rates that can approach 60%. For this reason, patients with isolated right-colon ischemia require urgent, noninvasive imaging of the mesenteric vasculature to assess the extent of ischemia and nature of the intervention. CT angiography is the recommended method of imaging for diagnosing acute mesenteric ischemia because it can be obtained rapidly. CT angiography visualizes the origins and length of the vessels, characterizes the extent of occlusion, and aids in planning revascularization.
Doppler ultrasonography of the mesenteric vessels is an effective, low-cost tool that can assess the proximal visceral vessels but has limited ability to visualize distal vessels. It is best reserved for the evaluation of patients with chronic mesenteric ischemia, which typically presents with postprandial abdominal pain, sitophobia, and weight loss.
MR angiography provides information about mesenteric arterial flow and avoids the potential harms of radiation and use of contrast that are associated with CT angiography; however, MR angiography takes longer to perform, lacks the required resolution to identify arterial occlusion, and can overestimate the severity of stenosis.
Selective catheter angiography was the standard method for diagnosing mesenteric ischemia; however, it is now used after a revascularization plan has been chosen because CT angiography can be obtained rapidly and is noninvasive.
Isolated right-colon ischemia may be a warning sign of acute mesenteric ischemia caused by embolism or thrombosis of the superior mesenteric artery and should be evaluated using CT angiography.
Clair DG, Beach JM. Mesenteric ischemia. N Engl J Med. 2016;374:959-68. [PMID: 26962730] doi:10.1056/NEJMra1503884
Copyright 2018, American College of Physicians.