Acute Aortic Dissection Presenting as Rectal Tenesmus

Introduction

Acute aortic dissection (AAD) results from a tear within the wall of the aorta and disruption of flow. This can be caused by abnormal blood flow, hemodynamic stressors, or genetic disorders [1,2]. Management is based on the Stanford classification into either Type A (TAAD) or Type B (TBAD). TAAD involves the ascending aorta, whereas TBAD occurs distal to the left subclavian artery.

Acute aortic dissection (AAD) is a rare but potentially fatal disease. The incidence rate ranges from 3.5 to 30 cases per 1 000 000 population per year [1,2], and mortality ranges from 13% to 27% [1,3], with rates increasing by 1–2% for every hour during which the disease is left untreated [4]. Unfortunately, AAD can be difficult to diagnose as it can have various presenting symptoms that often mimic other disease pathologies, including acute coronary syndrome, syncope, and intra-abdominal diseases. The median time between arrival in the Emergency Department and identification of AAD is 4.3 h. Untreated AAD has a reported cumulative mortality rate of 68% at 48 h after symptom onset [5], and misdiagnosis of the disease can lead to serious complications, including pericardial effusion, hemorrhagic shock, and death [6].

Case Report

A 69-year-old woman with a past medical history of anxiety, depression, fibromyalgia, irritable bowel syndrome, hypertension, hyperlipidemia, and COPD presented to the ED with a chief concern of abdominal pain and back pain. Prior to arrival, she had rectal tenesmus, an abrupt onset of “gas pains” along with abdominal distention, which were symptoms she would typically experience while constipated. Given her history of irritable bowel syndrome (IBS), she initially thought that she was experiencing symptoms related to her IBS and self-administered an enema, but she had no output and experienced poor relief of her symptoms. Her gastrointestinal symptoms persisted for 12 h. When the symptoms evolved and she began experiencing abdominal pain radiating to her back, she came the Emergency Department.

In the Emergency Department, her blood pressure was 170/68, but other vital signs were within normal limits. Pertinent risk factors included hypertension, chronic obstructive pulmonary disease (COPD), and first-degree relatives with aortic and brain aneurysms. She also noted that her pain began wrapping around her abdomen to her back and radiating up into her chest. Physical exam revealed only diffuse abdominal tenderness with no pulse discrepancies. Using the ADD-RS (Aortic Dissection Detection Risk Score), the patient was considered high risk and underwent computed tomography (CT) of the chest, abdomen, and pelvis with intravenous contrast. The imaging study revealed a Stanford Type A aortic dissection extending from the aortic root to the aortic bifurcation (Figures 1, 2). She was started on a nicardipine infusion with a systolic pressure goal of less than 120 and an esmolol infusion with a heart rate goal of less than 60. Cardiothoracic Surgery was consulted and she was taken to the operating room for emergent intervention. She spent 8 days in the hospital, during which she made a complete recovery and then was discharged.

Discussion

AAD is a severe, life-threatening diagnosis that remains challenging to identify and manage. Although the disease is rare, research has improved the process of diagnosis, management, and treatment. With the increased use of CT and recent advances in endovascular procedures, in-house mortality of TAAD decreased from 31% to 22% from 1995 to 2013 [7]. Registries such as the International Registry of Acute Aortic Dissections (IRAD) are the main sources for research on AAD. IRAD is a database comprising 58 international centers in 13 countries, which collect prospective data on the presentation, management, and outcomes of patients with aortic dissection. As of 2018, IRAD had collected data from more than 7300 individuals with aortic dissection [4]. We discuss IRAD’s conclusions together with the imaging modalities and the risk stratification tools that can be utilized.

The presentation of AAD can be highly variable and depends on the location, sex, and age of the patient [4], often misleading clinicians to an alternative, incorrect diagnosis. A small retrospective study of 66 patients who presented to a tertiary care center and were later diagnosed with AAD found that 39% of these patients were initially misdiagnosed, most commonly with acute coronary syndrome. This had severe implications, as they were given antithrombotic medications, leading to an increased number and severity of complications, including hemorrhagic pericardial effusion, hemorrhagic pleural effusions, hemodynamic instability, and ultimately, a significant increase of in-hospital mortality (27% in-house mortality rate for the misdiagnosed group vs 13% for the correctly diagnosed group) [6].

AAD, as classically taught, presents as a sudden, severe, ripping, or tearing chest pain/abdominal pain that radiates to the back. However, atypical presentations are common, which likely explains the frequency of misdiagnosis. IRAD showed that the most common presenting symptoms of AAD are chest pain (72.7%), followed by back pain (53.2%), abdominal pain (29.6%), and syncope (9.4%). The pain was most often described as “severe” (90.6%), “abrupt in onset” (84.8%), “sharp” (64.4%), “ripping or tearing” (50.6%), or “radiating” (28.3%) [8], with 6.3% of patients reporting no pain whatsoever. Syncopal episodes were associated with approximately 13% of cases and carried a higher mortality rate, as they typically indicated progression to cardiac tamponade or stroke [4]. We found no references to tenesmus in AAD in our literature search. We believe tenesmus is likely secondary to mesenteric malperfusion – an obvious part of the AAD pathology, although clearly a less common symptom.

Physical exam findings also varied in AAD. Most patients had hypertension (49.0%), many were normotensive (34.6%), and hypotension was noted in 16.4%. Other physical exam findings correlated poorly with AAD, although aortic insufficiency murmur was the most common (31.6%). Interestingly, a pulse deficit was only present in 15.1% of patients, and congestive heart failure was present in 6.6% of cases [8]. Overall, this highlights the poor diagnostic utility of physical exam findings.

A nationwide Danish 20-year cohort study evaluated the clinical characteristics of 2719 AAD patients to identify risk factors. Hypertension was the most common comorbidity in both TAAD and TBAD, with a prevalence of 55.2% and 64.1%, respectively. The other 2 common comorbidities for TAAD were thoracic aortic aneurysm (14.6%) and COPD (13.1%). For TBAD, they were aortic aneurysm (7.5–12%) and COPD (15.7%). Less common comorbidities for TAAD and TBAD included history of stroke (5.6%, 4.6%), atrial fibrillation (5.3%, 3.9%), acute myocardial infarct (4.6%, 3.4%), heart failure (2.5%, 2.5%), diabetes mellitus (2.3%, 3.4%), chronic kidney disease (1.4%, 2.8%), peripheral vascular disease (1.0%, 2.1%), and Marfan syndrome (0.9%, 0.5%). TAAD patients had a mean age of 63.5±12.9, whereas TBAD patients had a mean age of 67.5±12.2. Men accounted for 67.5% of TAAD cases and 67.0% of TBAD cases, whereas women accounted for 32.5% of TAAD cases and 33% of TBAD cases. Incidence was higher for men for both TAAD (2.9/100 000 vs 1.6/100 000) and TBAD (1.9/100 000 vs 1.1/100 000) [3].

The risk factors identified in the Danish cohort were similar to those in IRAD. Additional risk factors identified in the IRAD database included a history of atherosclerotic disease (27%), previous cardiac surgery (16%), and cocaine use (1.8%). Furthermore, patients <40 years of age that presented with AAD were more likely to have Marfan syndrome or bicuspid aortic valve (59%) as their prevailing risk factors.

Additionally, our literature review demonstrated that there is a lack of standardized protocol for the diagnosis of AAD. EKG, laboratory test results, and chest X-ray results are typical for chest pain patients presenting in the ED. Abnormal EKG findings are often nonspecific and may delay a proper diagnosis. Biomarkers are of limited use in diagnosing or excluding AAD. Utilizing a D-dimer with a cutoff level of 500 ng/mL has been used to rule out AAD, with a sensitivity ranging from 91% to 100%. However, there are conditions causing false-negative D-dimer results, such as age, onset of symptoms, thrombosed false lumens, and chronicity of disease [1]. Chest X-rays can be helpful in diagnosing TAD but can provide false reassurance when normal. Widening of the mediastinum or aortic knob is seen in only 40–60% of patients with AAD [3] because dissections can occur with a non-dilated aorta [7]. According to IRAD, only 60% of patients had a maximum aortic diameter greater than 5.5 cm, with 40% having a diameter less than 5.0 cm [4].

Although clinical suspicion is important, imaging studies play a crucial role in diagnosis of AAD. IRAD data showed that the initial diagnostic modality was CT (69%) followed by echocardiography (25%), magnetic resonance imaging (MRI) (4%), and aortography (2–3%) [4]. A meta-analysis of 16 studies involving a total of 1139 patients with AAD sought to identify the best imaging modality specifically for the diagnosis of TAD. The review compared the sensitivities, specificities, and positive and negative likelihood ratios of transesophageal echocardiography, CT, and MRI. All 3 modalities provided “clinically equally reliable diagnostic for confirming or ruling out thoracic aortic dissection.” However, it highlighted a key finding regarding the use of CT. Although conventional CT appears to be the most common modality for the identification of TAD, it has relatively poor sensitivity (83–94%) and specificity (87–100%). The newer, helical CT, was identified as the best imaging modality for low-risk patients (pre-test probability <5%) as it had a sensitivity of 100% and a specificity of 98%. With increased availability, improved sensitivity, and shorter scanning times for completion of the study, helical CT appears to be the imaging modality of choice for TAD and thus AAD when available [5].

Analysis of the IRAD database led to the creation of the Aortic Dissection Detection Risk Score (ADD-RS). In 2010, the American Heart Association, in conjunction with the American College of Cardiology, released a set of guidelines for risk-stratifying patients with potential AAD into low-risk (0 points), intermediate-risk (1 point), and high-risk categories (2–3 points). The system incorporates 12 factors divided into 3 categories: high-risk conditions, high-risk pain features, and high-risk exam features, with 1 point designated to each category [2]. This guideline was retrospectively validated the following year. In the case presented above, the patient was in the high-risk category based on her past medical history and clinical presentation.

In 2018, the ADvISED study, which was a multicenter prospective observational trial, incorporated the use of a D-dimer in conjunction with the ADD-RS in the hopes of improving diagnostic accuracy in the detection of AAD. The study discovered that an ADD-RS=0 with a negative D-dimer had a sensitivity of 99.6% and a negative predictive value of 99.7%. Additionally, an ADD-RS≤1 with a negative D-dimer had a sensitivity of 98.8% with a negative predictive value of 99.7% [9]. Through the analysis of the IRAD database, the ADvISED trial has illustrated that obtaining a thorough history, physical examination, and use of a D-dimer can be a very useful for ruling out AAD in clinical practice.

Conclusions

AAD is an extraordinarily fatal disease that can mimic many other pathologies in its presentation as demonstrated by this case of AAD with tenesmus. We examined common and uncommon risk factors, presenting symptoms, and physical exam findings associated with AAD. We suggest that clinicians implement the ADD-RS tool with a D-dimer test to improve diagnostic accuracy in patients presenting with atypical symptoms of AAD.