Pulmonary embolism: An abdominal pain masquerader.

Abdominal pain is an uncommon presenting symptom for pulmonary embolism (PE). A delay in the diagnosis when a patient presents with atypical symptoms can postpone proper treatment and can be catastrophic. We report the case of a 48-year-old male who presented to the emergency department with worsening right upper quadrant abdominal pain. Abnormal findings on biliary ultrasound and chest radiograph could have resulted in misdiagnosis. Instead, the physician maintained a high index of suspicion, and further diagnostic testing revealed a large central PE in the right main pulmonary artery. The present article discusses the dangers of using a pattern recognition approach to medical decision making in patients with abdominal pain. Included are the various pathophysiologic mechanisms that may contribute to the development of abdominal pain in patients with PE. Additionally, we review the role of chest radiography in the setting of PE and present the findings that ultimately lead to the diagnosis.

INTRODUCTION

The consequences of missing a pulmonary embolism (PE) can be catastrophic. It is believed to be responsible for 50,000-200,000 deaths yearly. Overall mortality for PEs without treatment is estimated to be 30%. The diagnosis can be elusive, since there is no pathognomonic sign or symptom for PE. Clinicians often take solace in clinical decision rules in patients without any clear risk factors. We present a case report on a patient with abdominal pain who was ultimately diagnosed with a large PE. The diagnostic considerations that lead to the consideration of this abdominal pain masquerader are discussed in the present article.

CASE REPORT

A 48-year-old male presented to the emergency department with a 1-year history of intermittent right upper quadrant abdominal pain. He had been seen by his primary care physician 1 week earlier for the same pain and had an ultrasound performed. The patient stated he was unaware of the results and that today the pain became acutely worse. The patient denied any other associated symptoms. He denied any personal history or family history of medical problems. The patient was a smoker, drank up to a six-pack of beer daily, and used marijuana. He did not take any medications.

The vital signs were as follows: Blood pressure 112/52, pulse 82, respiratory rate 16, oxygen saturation 99% on room air. He was afebrile. Physical exam revealed a well appearing male in moderate distress secondary to pain. His abdominal examination was remarkable for severe right upper quadrant pain to palpation without guarding or rebound. There was no costovertebral angle tenderness. His lung sounds were clear bilaterally. The patient remarked that the abdominal pain was made worse with deep inspiration. His cardiac exam was normal.

Laboratory analysis revealed a normal complete blood count, complete metabolic profile, urinalysis, and lipase. A right upper quadrant ultrasound examination was performed, which demonstrated a positive sonographic Murphy's sign and slight dilation of the common bile duct at 0.66 cm [Figure 1a and b]. A chest radiograph was significant for a right lower lobe infiltrate in the lung periphery [Figure 2]. At this time, it was felt that this could represent a Hampton's hump; however, the patient had a low pre-test probability for having a PE. A d-dimer test was added and was positive (1.0 mg/mL fibrinogen equivalent units, normal <0.05) at which point a computed tomography angiogram (CTA) of the chest was performed. On CT a large central PE was identified in the right main pulmonary artery [Figure 3a and b]. The right lower lung lobe contained a peripheral based wedge-shaped opacity consistent with pulmonary infarct [Figure 3c]. Anticoagulation was started in the emergency department and the patient was admitted. A formal echo done during the patient's admission showed a small atrial septal defect with left to right shunting that did not require closure. No other etiology for thromboembolism was identified.

Figure 1

(a) Normal sagittal gallbladder (b) Mildly dilated common bile duct in left lateral decubitus position (arrow)

Figure 2

Right lower lobe pulmonary infarct (arrow)

Figure 3

(a) Axial CTA chest demonstrating large central pulmonary embolism(arrow) in the right main pulmonary artery (b) Coronal CTA chest demonstrating large central pulmonary embolism (arrow) in the right main pulmonary artery (c) Coronal CTA chest demonstrating right lower lobe pulmonary infarct (arrow)

DISCUSSION

PE is the new syphilis; the great masquerader. As this case clearly illustrates, physicians should always consider the possibility of PE in their patients with abdominal pain. In this particular case, not only did the patient present with abdominal pain, but he had two positive test findings in the emergency department that could have lead the physician to an incorrect diagnosis. A mildly dilated common bile duct raised the possibility of a biliary etiology for the patient's pain. The chest radiograph (incidentally read later by the radiologist as “suspicious for pneumonia”) could have been misinterpreted as infection. Instead, the physician carefully considered the radiographic findings and determined that the patient needed further diagnostic testing.

The consequences of missing a PE can be catastrophic. Rapid diagnosis and treatment are essential in order to decrease mortality. Up to 70% of PEs are misdiagnosed by practitioners to whom the patient presents and are discovered postmortem.[1] This was true of our patient. He had previously seen his primary care physician who suspected, as we did initially, that the patient had an abdominal etiology for his symptoms. The diagnosis remains elusive because there is no pathognomonic sign or symptom for PE. In patients presenting with a PE in the main or lobar pulmonary arteries the “classic” symptoms of dyspnea or tachypnea occur in 92%.[2] However, when smaller subsegmental PEs are taken into account, only 73% of patients presented with dyspnea, 70% with tachypnea and 66% had pleuritic chest pain.[3] Our patient had no classic symptoms.

Abdominal pain may be seen in 6.7% of cases of PE.[4] The mechanism of abdominal pain is unknown, but may be due to hepatic congestion (secondary to right heart strain), distension of Glisson's capsule, or diaphragmatic pleurisy resulting from pulmonary infarction.[5] Additionally, there may be abdominal pain related to tension on sensory nerve endings or vascular emboli resulting in infarctions within the microvasculature of the mesentery.[5]

Clinical decision rules can provide a false sense of security in patients that present without any clear risk factors. As this case shows, neither atypical presentation in a young individual nor a very low pre-test probability ruled out the diagnosis. Without a high index of suspicion and careful review of this patient's chest radiograph, it is likely that the patient would have been discharged home with antibiotics for pneumonia.

Due to its low sensitivity and specificity, the role of chest radiography in the setting of PE is limited to excluding other potential etiologies for the patient's symptoms such as pneumothorax and pneumonia.[6] There was, however, a finding on the patient's radiograph that eventually led to the consideration of PE. The Hampton's hump is a shallow, pleural based triangular opacity with the apex pointing towards the lung hilum.[7] The characteristic shape is seen because obstructed pulmonary arteries cause a wedge-shaped infarction, whereas the bronchial arterial circulation is preserved.[8] Our patient had Hampton's hump identified by the emergency physician [Figure 2]. A Westermark's sign is a darkened area distal to the area of embolism that is produced by dilation of the proximal arteries in conjunction with collapse of distal vasculature.[7] Additional radiographic signs that may be indicative of a PE include a raised hemidiaphragm, pleural effusion, and Fleicher's sign (enlargement of the ipsilateral pulmonary artery).[6]

Without a high index of suspicion, PE is an easily missed diagnosis with dire consequences. As a result, it should be considered in the differential for a variety of symptoms, including abdominal pain. A PE can masquerade as a variety of other entities and physicians should be aware of the various signs, symptoms, and radiographic findings that can lead to this life-saving diagnosis.