Atypical Presentation of Pulmonary Embolism: Flank Pain as the Sole Symptom in a PERC-Negative Patient–The Role of POCUS in Early Detection

Atypical Presentation of Pulmonary Embolism: Flank Pain as the Sole Symptom in a PERC-Negative Patient–The Role of POCUS in Early Detection | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Atypical Presentation of Pulmonary Embolism: Flank Pain as the Sole Symptom in a PERC-Negative Patient–The Role of POCUS in Early Detection Abdolghader Pakniyat, Sabrina Berdouk This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6315035/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Pulmonary embolism (PE) is a potentially life-threatening condition with diverse clinical presentations. While dyspnea and pleuritic chest pain are the hallmark symptoms, atypical presentations such as isolated flank pain can obscure timely diagnosis. We report a case of a 39-year-old male smoker who presented with left-sided flank pain exacerbated by deep inspiration. Despite meeting Pulmonary Embolism Rule-Out Criteria (PERC), the crucial role of lung point-of-care ultrasound (POCUS) in identifying localized B-lines and an elevated D-dimer prompted CT pulmonary angiography, confirming segmental PE. This case underscores the diagnostic utility of POCUS and highlights the limitations of PERC in atypical presentations. Critical Care & Emergency Medicine Pulmonary embolism flank pain point-of-care ultrasound PERC D-dimer CT pulmonary angiography Figures Figure 1 Figure 2 Introduction Pulmonary embolism (PE) is a leading cause of cardiovascular morbidity and mortality, with an estimated incidence of 60–70 cases per 100,000 individuals annually [ 1 ] . It results from the obstruction of pulmonary arteries by thrombi, most commonly originating from deep vein thrombosis (DVT) in the lower extremities. PE presents with a broad spectrum of clinical manifestations, ranging from asymptomatic cases to sudden cardiac arrest. The classical triad of dyspnea, pleuritic chest pain, and hemoptysis is well recognized; however, a significant proportion of patients exhibit non-specific or atypical symptoms, leading to frequent misdiagnoses and delayed treatment [ 1 , 2 , 3 ] . Atypical presentations of PE include syncope, isolated cough, upper abdominal pain, and, as in this case, flank pain. Flank pain as the sole presenting symptom of PE is uncommon and often leads to misattribution to renal, musculoskeletal, or gastrointestinal etiologies. Studies show that up to 30% of PE cases present with atypical symptoms, increasing the likelihood of diagnostic challenges. Given the potential for fatal complications, including right heart failure and hemodynamic collapse, timely diagnosis and intervention are vital [ 4 , 5 ] . Although risk stratification tools such as the Pulmonary Embolism Rule-Out Criteria (PERC) are extensively used in the emergency department (ED) due to their simplicity and reliability, clinicians must be cautious about their limitations [ 4 ] . We present a case that illustrates these points: an atypical presentation of PE (flank pain as the sole symptom in a PERC-negative patient) in which POCUS played a critical role in early detection and management. Case Presentation A 39-year-old male with a history of smoking (10 pack-years) presented to the emergency department with a 12-hour history of sharp, left-sided flank pain without radiation rated 6/10 in intensity. The pain was slightly exacerbated by deep inspiration and changing position but was not associated with dyspnea, cough, fever, hemoptysis, or leg swelling. He had recently undertaken 11-hour flight four weeks prior but had no personal or family history of venous thromboembolism, recent surgery, malignancy, or chronic illness. On initial evaluation, his vital signs were stable: blood pressure 142/89 mmHg, heart rate 60 bpm, respiratory rate 16 breaths/min, oxygen saturation 98% on room air, and temperature 36°C. Physical examination revealed normal heart sounds with no murmurs. The respiratory assessment was unremarkable, with no wheezing or rales. His abdominal exam was normal, with no tenderness, guarding, or distention. His extremities showed no signs of edema or deep vein thrombosis. Point-of-care ultrasound (POCUS) ruled out hydronephrosis or nephrolithiasis and revealed localized B-lines in the 10th-11th intercostal space of the left posterior chest, suggestive of lung pathology. Figure 1 . Given his stable hemodynamic status, an initial workup included an electrocardiogram (ECG), which demonstrated normal sinus rhythm without signs of right heart strain, normal finding on bedside echocardiography, normal bilateral Ultrasound scan of leg veins and Haziness in the left lower zone at the CP angle noted in a chest x-ray. Figure 2 . A routine laboratory panel was within normal limits, but his D-dimer level was elevated at 1.8 mg/L (normal < 0.5 mg/L), prompting further investigation. To further evaluate the possibility of PE, CT pulmonary angiography (CTPA) was performed. This revealed multiple filling defects in the segmental and subsegmental branches of the right lower pulmonary artery, reaching the posterior basal subsegmental branch. Additionally, occlusive filling defects were seen in the left lateral-basal subsegmental pulmonary arteries. The scan also showed heterogeneous ground-glass opacification in the left lower lobe, indicative of pulmonary infarction, with minimal left pleural fluid. Figure 2 . Based on these findings, a diagnosis of segmental PE with pulmonary infarction was established despite the patient being PERC-negative. He was promptly initiated on therapeutic anticoagulation with subcutaneous enoxaparin (Clexane) 80 mg. Pain management included intravenous paracetamol. The patient remained hemodynamically stable throughout his hospital course and was monitored closely for 24 hours. He was subsequently admitted under pulmonology care for further observation and discharged with oral anticoagulation therapy. At his 3-month follow-up, he was asymptomatic, with no recurrence of PE. Discussion Diagnosing PE can be particularly challenging when symptoms deviate from the typical presentation of dyspnea and pleuritic chest pain. In this case, flank pain was the primary complaint, a presentation reported in less than 5% of PE cases. The absence of common PE symptoms can lead to misdiagnosis, often resulting in an initial workup focused on renal or musculoskeletal causes rather than a thromboembolic process. Studies suggest that such atypical cases frequently result in delayed diagnosis and increased risk of complications [ 3 , 5 , 6 ] . Physicians should consider pulmonary embolism when diagnosing patients with isolated flank pain. Unexpected pulmonary findings on abdominal CT scans can suggest PE in the right clinical context [ 5 ] . Using integrated point-of-care lung ultrasound (POCUS) and assessing the lungs at the bedside, especially in cases with flank pain without obvious pathologies like hydronephrosis, may detect related lung pathology. This can lead to prompt investigation and diagnosis of PE in suspected cases. One possible explanation for the patient's presentation is pleural irritation due to pulmonary infarction, which can manifest as pain referred to the flank due to shared innervation of the diaphragm and lower thoracic structures [ 5 , 6 ] . Additionally, embolic obstruction of subsegmental pulmonary arteries has been associated with localized inflammation and infarction, as seen in the heterogeneous ground-glass opacification noted on CTPA. This correlation highlights the importance of imaging in atypical cases, particularly when clinical signs alone do not strongly indicate PE. POCUS played a crucial role in this case, demonstrating localized B-lines suggestive of pulmonary infarction. Lung ultrasound has been shown to have high diagnostic accuracy in PE, with a sensitivity of 81% and specificity of 83% when combined with clinical assessment. The use of POCUS in this patient guided further evaluation despite his PERC-negative status. Literature supports that multi-organ ultrasound assessment, incorporating lung, cardiac, and venous ultrasound, significantly improves diagnostic accuracy in suspected PE, studies linked B-lines to peripheral PE infarcts, demonstrating a specificity of 78% when evaluated in the appropriate clinical context [ 7 , 8 , 9 ] . Additionally, cardiac POCUS findings, such as McConnell's sign (RV free wall hypokinesis), have been reported to have a specificity of 77% for PE, reinforcing its role in risk stratification [10]. Given the diagnostic limitations of PERC, as highlighted in a meta-analysis by Singh B et al. showing a 1.5% PE prevalence in PERC-negative patients, clinical suspicion should not be dismissed solely based on scoring criteria, particularly in high-risk individuals with risk factors such as malignancy, smoking, and recent travel [ 11 ] . This case highlights the role of prolonged travel and smoking as contributing risk factors for PE. Long-distance travel increases VTE risk, peaking within the first two weeks post-travel and normalizing by eight weeks .Despite being PERC-negative, this patient's history warranted further evaluation, demonstrating the limitations of PERC and Wells' criteria in atypical cases. A comprehensive clinical assessment incorporating history, risk factors, and imaging remains crucial for timely diagnosis and management [ 12 – 14 ] . Conclusion This case emphasizes the importance of clinical vigilance for pulmonary embolism, even in patients presenting atypically with isolated flank pain. It demonstrates the diagnostic value of POCUS, especially in scenarios where standard clinical decision tools like PERC fail to capture underlying risks. Emergency clinicians should consider integrating multi-organ ultrasound into their routine evaluation of unexplained or atypical presentations of PE. Further research is warranted to refine clinical decision rules, incorporating the role of bedside ultrasound, to enhance timely diagnosis, reduce unnecessary radiation exposure, and ultimately improve patient outcomes. Declarations Patient Consent Statement: Written informed consent was obtained from the patient for the publication of this case report, including all clinical details and relevant medical information. Conflict of Interest None Declared. Financial Disclosure None. Acknowledgments I would like to express my sincere appreciation to the Emergency Medicine team at …. , as well as the Radiology department, the Pulmonologist, and all staff members for their invaluable assistance in managing this case. Data availability The data that support the findings of this study are not openly available due to reasons of privacy and sensitivity and are available from the corresponding author upon reasonable request. References Agnelli G, Becattini C. Acute pulmonary embolism. N Engl J Med. 2010 Jul 15;363(3):266-74. doi: 10.1056/NEJMra0907731. Epub 2010 Jun 30. PMID: 20592294. Aujesky D, Obrosky DS, Stone RA, et al. Derivation and validation of a prognostic model for pulmonary embolism. Am J Respir Crit Care Med . 2005;172(8):1041-1046. doi:10.1164/rccm.200506-862OC Bĕlohlávek J, Dytrych V, Linhart A. Pulmonary embolism, part I: Epidemiology, risk factors and risk stratification, pathophysiology, clinical presentation, diagnosis and nonthrombotic pulmonary embolism. Exp Clin Cardiol . 2013;18(2):129-138. Kline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost . 2008;6(5):772-780. doi:10.1111/j.1538-7836.2008.02944.x Amesquita M, Cocchi MN, Donnino MW. Pulmonary embolism presenting as flank pain: a case series. J Emerg Med. 2012;42(5):e97-e100. doi:10.1016/j.jemermed.2009.02.005 Al-Ramadhan MA, Al-Janobi AA. The Great Mimicker: Pulmonary Embolism Presenting as Flank Pain in a Sickle Cell Disease Patient. Cureus . 2023;15(6):e39924. Published 2023 Jun 3. doi:10.7759/cureus.39924 Nazerian P, Vanni S, Volpicelli G, et al. Accuracy of point-of-care multiorgan ultrasonography for the diagnosis of pulmonary embolism. Chest. 2014;145(5):950-957. doi:10.1378/chest.13-1087 Nazerian P, Gigli C, Reissig A, et al. Retrospective analysis of the diagnostic accuracy of lung ultrasound for pulmonary embolism in patients with and without pleuritic chest pain. Ultrasound J . 2022;14(1):35. Published 2022 Aug 12. doi:10.1186/s13089-022-00285-3 Mathis G, Blank W, Reissig A, et al. Thoracic ultrasound for diagnosing pulmonary embolism: a prospective multicenter study of 352 patients. Chest. 2005;128(3):1531-1538. doi:10.1378/chest.128.3.1531 Mediratta A, Addetia K, Medvedofsky D, Gomberg-Maitland M, Mor-Avi V, Lang RM. Echocardiographic Diagnosis of Acute Pulmonary Embolism in Patients with McConnell's Sign. Echocardiography. 2016;33(5):696-702. doi:10.1111/echo.13142 Singh B, Parsaik AK, Agarwal D, Surana A, Mascarenhas SS, Chandra S. Diagnostic accuracy of pulmonary embolism rule-out criteria: a systematic review and meta-analysis. Ann Emerg Med. 2012;59(6):517-20.e204. doi:10.1016/j.annemergmed.2011.10.022 Centers for Disease Control and Prevention. "Deep Vein Thrombosis & Pulmonary Embolism." In: CDC Yellow Book 2024: Health Information for International Travel. Available at: https://wwwnc.cdc.gov/travel/yellowbook/2024/air-land-sea/deep-vein-thrombosis-and-pulmonary-embolism. Al-Nasser B. Influence of Tobacco Smoking on Perioperative Risk of Venous Thromboembolism. Turk J Anaesthesiol Reanim. 2020;48(1):11-16. doi:10.5152/TJAR.2019.08683 Pastori D, Cormaci VM, Marucci S, et al. A Comprehensive Review of Risk Factors for Venous Thromboembolism: From Epidemiology to Pathophysiology. Int J Mol Sci. 2023;24(4):3169. Published 2023 Feb 5. doi:10.3390/ijms24043169 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6315035","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":434481585,"identity":"c47b240f-7c62-460c-a487-5d646df6e222","order_by":0,"name":"Abdolghader Pakniyat","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABPUlEQVRIie2RMWvCQBTH33GQLjF2TJf6FZKlUKj4VXIE4pIWi0uHDpaDuGhmQwe/Qro4Ww508QMETqgg2MUhLiVIKL0zLYUmlo4d7sfd/eFxPx7vDkCh+I+YYMEKpiCXwAFNRiq2dvKL4vxQ0MNIKvivigBRXcYRpf5In1bOftkw5sMV7tx7N4bpvq6v9pOGgQGlO7/cZDnrWiTc2NFibuHRzO9qpmfT65DbAQZ8Fk3KbRL/wiQDhuLEA6xrdyQwHaEMOBKKhmtlpfGptOKXjVDepdLe0csBbx1TLKk4GSNxogGuBb5QfJtCxskxxT7M0mNutPCARaFHAn17Gw173A0wolWznHPxYmnOmuF8htadN5eM++04zXLeHPfpc7qrGF+CgiLZ4Tx1viqoV31fkhdR/F19+l1RKBQKheADHv96Id2p8jwAAAAASUVORK5CYII=","orcid":"","institution":"Al Zahra Pvt. Hospital Dubai","correspondingAuthor":true,"prefix":"","firstName":"Abdolghader","middleName":"","lastName":"Pakniyat","suffix":""},{"id":434481586,"identity":"07de7528-1c45-458a-b41c-7616fba7721a","order_by":1,"name":"Sabrina Berdouk","email":"","orcid":"","institution":"Al Zahra Pvt. Hospital Dubai","correspondingAuthor":false,"prefix":"","firstName":"Sabrina","middleName":"","lastName":"Berdouk","suffix":""}],"badges":[],"createdAt":"2025-03-26 19:49:28","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":true,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6315035/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6315035/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79587548,"identity":"58f2c1fb-1eb7-46d5-ad4d-f4be6a102432","added_by":"auto","created_at":"2025-03-31 12:41:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":366526,"visible":true,"origin":"","legend":"\u003cp\u003ePoint-of-care ultrasound (POCUS) using a phased-array probe on the left posterior thorax, demonstrating B-lines suggestive of pulmonary pathology. This finding contributed to the suspicion of pulmonary embolism (PE)-related infarction in a PERC-negative patient with isolated flank pain.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6315035/v1/5952f1d5c79fe52c1929d11c.png"},{"id":79587547,"identity":"86e545dc-f68a-4947-87a8-869abf1fe749","added_by":"auto","created_at":"2025-03-31 12:41:20","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1030273,"visible":true,"origin":"","legend":"\u003cp\u003e(A) CXR: Subtle opacity in the left lower lung field, raising suspicion for pulmonary pathology, (B, C, D) CTPA: Segmental and sub-segmental pulmonary emboli in the right lower pulmonary artery and left lateral-basal sub-segmental arteries, with associated pulmonary infarct, bibasal ground-glass opacities, and minimal left pleural fluid.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6315035/v1/3b96d705e46e02ea7f09fce1.png"},{"id":79588433,"identity":"87a65dc3-8d1c-442d-bdce-b96e34181085","added_by":"auto","created_at":"2025-03-31 12:49:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2099713,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6315035/v1/7c41ddad-a987-436d-9589-ee795e9eadd5.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eAtypical Presentation of Pulmonary Embolism: Flank Pain as the Sole Symptom in a PERC-Negative Patient–The Role of POCUS in Early Detection\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePulmonary embolism (PE) is a leading cause of cardiovascular morbidity and mortality, with an estimated incidence of 60\u0026ndash;70 cases per 100,000 individuals annually \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. It results from the obstruction of pulmonary arteries by thrombi, most commonly originating from deep vein thrombosis (DVT) in the lower extremities. PE presents with a broad spectrum of clinical manifestations, ranging from asymptomatic cases to sudden cardiac arrest. The classical triad of dyspnea, pleuritic chest pain, and hemoptysis is well recognized; however, a significant proportion of patients exhibit non-specific or atypical symptoms, leading to frequent misdiagnoses and delayed treatment \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAtypical presentations of PE include syncope, isolated cough, upper abdominal pain, and, as in this case, flank pain. Flank pain as the sole presenting symptom of PE is uncommon and often leads to misattribution to renal, musculoskeletal, or gastrointestinal etiologies. Studies show that up to 30% of PE cases present with atypical symptoms, increasing the likelihood of diagnostic challenges. Given the potential for fatal complications, including right heart failure and hemodynamic collapse, timely diagnosis and intervention are vital \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlthough risk stratification tools such as the Pulmonary Embolism Rule-Out Criteria (PERC) are extensively used in the emergency department (ED) due to their simplicity and reliability, clinicians must be cautious about their limitations \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. We present a case that illustrates these points: an atypical presentation of PE (flank pain as the sole symptom in a PERC-negative patient) in which POCUS played a critical role in early detection and management.\u003c/p\u003e"},{"header":"Case Presentation","content":"\u003cp\u003eA 39-year-old male with a history of smoking (10 pack-years) presented to the emergency department with a 12-hour history of sharp, left-sided flank pain without radiation rated 6/10 in intensity. The pain was slightly exacerbated by deep inspiration and changing position but was not associated with dyspnea, cough, fever, hemoptysis, or leg swelling. He had recently undertaken 11-hour flight four weeks prior but had no personal or family history of venous thromboembolism, recent surgery, malignancy, or chronic illness.\u003c/p\u003e \u003cp\u003eOn initial evaluation, his vital signs were stable: blood pressure 142/89 mmHg, heart rate 60 bpm, respiratory rate 16 breaths/min, oxygen saturation 98% on room air, and temperature 36\u0026deg;C. Physical examination revealed normal heart sounds with no murmurs. The respiratory assessment was unremarkable, with no wheezing or rales. His abdominal exam was normal, with no tenderness, guarding, or distention. His extremities showed no signs of edema or deep vein thrombosis.\u003c/p\u003e \u003cp\u003ePoint-of-care ultrasound (POCUS) ruled out hydronephrosis or nephrolithiasis and revealed localized B-lines in the 10th-11th intercostal space of the left posterior chest, suggestive of lung pathology. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGiven his stable hemodynamic status, an initial workup included an electrocardiogram (ECG), which demonstrated normal sinus rhythm without signs of right heart strain, normal finding on bedside echocardiography, normal bilateral Ultrasound scan of leg veins and Haziness in the left lower zone at the CP angle noted in a chest x-ray. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. A routine laboratory panel was within normal limits, but his D-dimer level was elevated at 1.8 mg/L (normal\u0026thinsp;\u0026lt;\u0026thinsp;0.5 mg/L), prompting further investigation.\u003c/p\u003e \u003cp\u003eTo further evaluate the possibility of PE, CT pulmonary angiography (CTPA) was performed. This revealed multiple filling defects in the segmental and subsegmental branches of the right lower pulmonary artery, reaching the posterior basal subsegmental branch. Additionally, occlusive filling defects were seen in the left lateral-basal subsegmental pulmonary arteries. The scan also showed heterogeneous ground-glass opacification in the left lower lobe, indicative of pulmonary infarction, with minimal left pleural fluid. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBased on these findings, a diagnosis of segmental PE with pulmonary infarction was established despite the patient being PERC-negative. He was promptly initiated on therapeutic anticoagulation with subcutaneous enoxaparin (Clexane) 80 mg. Pain management included intravenous paracetamol. The patient remained hemodynamically stable throughout his hospital course and was monitored closely for 24 hours. He was subsequently admitted under pulmonology care for further observation and discharged with oral anticoagulation therapy. At his 3-month follow-up, he was asymptomatic, with no recurrence of PE.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eDiagnosing PE can be particularly challenging when symptoms deviate from the typical presentation of dyspnea and pleuritic chest pain. In this case, flank pain was the primary complaint, a presentation reported in less than 5% of PE cases. The absence of common PE symptoms can lead to misdiagnosis, often resulting in an initial workup focused on renal or musculoskeletal causes rather than a thromboembolic process. Studies suggest that such atypical cases frequently result in delayed diagnosis and increased risk of complications \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Physicians should consider pulmonary embolism when diagnosing patients with isolated flank pain. Unexpected pulmonary findings on abdominal CT scans can suggest PE in the right clinical context \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Using integrated point-of-care lung ultrasound (POCUS) and assessing the lungs at the bedside, especially in cases with flank pain without obvious pathologies like hydronephrosis, may detect related lung pathology. This can lead to prompt investigation and diagnosis of PE in suspected cases.\u003c/p\u003e \u003cp\u003eOne possible explanation for the patient's presentation is pleural irritation due to pulmonary infarction, which can manifest as pain referred to the flank due to shared innervation of the diaphragm and lower thoracic structures \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Additionally, embolic obstruction of subsegmental pulmonary arteries has been associated with localized inflammation and infarction, as seen in the heterogeneous ground-glass opacification noted on CTPA. This correlation highlights the importance of imaging in atypical cases, particularly when clinical signs alone do not strongly indicate PE.\u003c/p\u003e \u003cp\u003ePOCUS played a crucial role in this case, demonstrating localized B-lines suggestive of pulmonary infarction. Lung ultrasound has been shown to have high diagnostic accuracy in PE, with a sensitivity of 81% and specificity of 83% when combined with clinical assessment. The use of POCUS in this patient guided further evaluation despite his PERC-negative status. Literature supports that multi-organ ultrasound assessment, incorporating lung, cardiac, and venous ultrasound, significantly improves diagnostic accuracy in suspected PE, studies linked B-lines to peripheral PE infarcts, demonstrating a specificity of 78% when evaluated in the appropriate clinical context \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAdditionally, cardiac POCUS findings, such as McConnell's sign (RV free wall hypokinesis), have been reported to have a specificity of 77% for PE, reinforcing its role in risk stratification [10]. Given the diagnostic limitations of PERC, as highlighted in a meta-analysis by Singh B et al. showing a 1.5% PE prevalence in PERC-negative patients, clinical suspicion should not be dismissed solely based on scoring criteria, particularly in high-risk individuals with risk factors such as malignancy, smoking, and recent travel \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis case highlights the role of prolonged travel and smoking as contributing risk factors for PE. Long-distance travel increases VTE risk, peaking within the first two weeks post-travel and normalizing by eight weeks .Despite being PERC-negative, this patient's history warranted further evaluation, demonstrating the limitations of PERC and Wells' criteria in atypical cases. A comprehensive clinical assessment incorporating history, risk factors, and imaging remains crucial for timely diagnosis and management \u003csup\u003e[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case emphasizes the importance of clinical vigilance for pulmonary embolism, even in patients presenting atypically with isolated flank pain. It demonstrates the diagnostic value of POCUS, especially in scenarios where standard clinical decision tools like PERC fail to capture underlying risks. Emergency clinicians should consider integrating multi-organ ultrasound into their routine evaluation of unexplained or atypical presentations of PE. Further research is warranted to refine clinical decision rules, incorporating the role of bedside ultrasound, to enhance timely diagnosis, reduce unnecessary radiation exposure, and ultimately improve patient outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003ePatient Consent Statement: Written informed consent was obtained from the patient for the publication of this case report, including all clinical details and relevant medical information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone Declared.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFinancial Disclosure\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eI would like to express my sincere appreciation to the Emergency Medicine team at \u0026hellip;. , as well as the Radiology department, the Pulmonologist, and all staff members for their invaluable assistance in managing this case.\u003c/p\u003e\n\u003cp\u003eData availability\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are not openly available due to reasons of privacy and sensitivity and are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAgnelli G, Becattini C. Acute pulmonary embolism. N Engl J Med. 2010 Jul 15;363(3):266-74. doi: 10.1056/NEJMra0907731. Epub 2010 Jun 30. PMID: 20592294.\u003c/li\u003e\n\u003cli\u003eAujesky D, Obrosky DS, Stone RA, et al. Derivation and validation of a prognostic model for pulmonary embolism. \u003cem\u003eAm J Respir Crit Care Med\u003c/em\u003e. 2005;172(8):1041-1046. doi:10.1164/rccm.200506-862OC\u003c/li\u003e\n\u003cli\u003eBĕlohl\u0026aacute;vek J, Dytrych V, Linhart A. Pulmonary embolism, part I: Epidemiology, risk factors and risk stratification, pathophysiology, clinical presentation, diagnosis and nonthrombotic pulmonary embolism. \u003cem\u003eExp Clin Cardiol\u003c/em\u003e. 2013;18(2):129-138.\u003c/li\u003e\n\u003cli\u003eKline JA, Courtney DM, Kabrhel C, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. \u003cem\u003eJ Thromb Haemost\u003c/em\u003e. 2008;6(5):772-780. doi:10.1111/j.1538-7836.2008.02944.x\u003c/li\u003e\n\u003cli\u003eAmesquita M, Cocchi MN, Donnino MW. Pulmonary embolism presenting as flank pain: a case series. J Emerg Med. 2012;42(5):e97-e100. doi:10.1016/j.jemermed.2009.02.005\u003c/li\u003e\n\u003cli\u003eAl-Ramadhan MA, Al-Janobi AA. The Great Mimicker: Pulmonary Embolism Presenting as Flank Pain in a Sickle Cell Disease Patient. \u003cem\u003eCureus\u003c/em\u003e. 2023;15(6):e39924. Published 2023 Jun 3. doi:10.7759/cureus.39924\u003c/li\u003e\n\u003cli\u003eNazerian P, Vanni S, Volpicelli G, et al. Accuracy of point-of-care multiorgan ultrasonography for the diagnosis of pulmonary embolism. Chest. 2014;145(5):950-957. doi:10.1378/chest.13-1087\u003c/li\u003e\n\u003cli\u003eNazerian P, Gigli C, Reissig A, \u003cem\u003eet al.\u003c/em\u003e Retrospective analysis of the diagnostic accuracy of lung ultrasound for pulmonary embolism in patients with and without pleuritic chest pain. \u003cem\u003eUltrasound J\u003c/em\u003e. 2022;14(1):35. Published 2022 Aug 12. doi:10.1186/s13089-022-00285-3\u003c/li\u003e\n\u003cli\u003eMathis G, Blank W, Reissig A, et al. Thoracic ultrasound for diagnosing pulmonary embolism: a prospective multicenter study of 352 patients. Chest. 2005;128(3):1531-1538. doi:10.1378/chest.128.3.1531\u003c/li\u003e\n\u003cli\u003eMediratta A, Addetia K, Medvedofsky D, Gomberg-Maitland M, Mor-Avi V, Lang RM. Echocardiographic Diagnosis of Acute Pulmonary Embolism in Patients with McConnell\u0026apos;s Sign. Echocardiography. 2016;33(5):696-702. doi:10.1111/echo.13142\u003c/li\u003e\n\u003cli\u003eSingh B, Parsaik AK, Agarwal D, Surana A, Mascarenhas SS, Chandra S. Diagnostic accuracy of pulmonary embolism rule-out criteria: a systematic review and meta-analysis. Ann Emerg Med. 2012;59(6):517-20.e204. doi:10.1016/j.annemergmed.2011.10.022\u003c/li\u003e\n\u003cli\u003eCenters for Disease Control and Prevention. \u0026quot;Deep Vein Thrombosis \u0026amp; Pulmonary Embolism.\u0026quot; In: \u003cem\u003eCDC Yellow Book 2024: Health Information for International Travel.\u003c/em\u003e Available at: https://wwwnc.cdc.gov/travel/yellowbook/2024/air-land-sea/deep-vein-thrombosis-and-pulmonary-embolism.\u003c/li\u003e\n\u003cli\u003eAl-Nasser B. Influence of Tobacco Smoking on Perioperative Risk of Venous Thromboembolism. Turk J Anaesthesiol Reanim. 2020;48(1):11-16. doi:10.5152/TJAR.2019.08683\u003c/li\u003e\n\u003cli\u003ePastori D, Cormaci VM, Marucci S, et al. A Comprehensive Review of Risk Factors for Venous Thromboembolism: From Epidemiology to Pathophysiology. Int J Mol Sci. 2023;24(4):3169. Published 2023 Feb 5. doi:10.3390/ijms24043169\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Al Zahra Pvt. Hospital Dubai","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Pulmonary embolism, flank pain, point-of-care ultrasound, PERC, D-dimer, CT pulmonary angiography","lastPublishedDoi":"10.21203/rs.3.rs-6315035/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6315035/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePulmonary embolism (PE) is a potentially life-threatening condition with diverse clinical presentations. While dyspnea and pleuritic chest pain are the hallmark symptoms, atypical presentations such as isolated flank pain can obscure timely diagnosis. We report a case of a 39-year-old male smoker who presented with left-sided flank pain exacerbated by deep inspiration. Despite meeting Pulmonary Embolism Rule-Out Criteria (PERC), the crucial role of lung point-of-care ultrasound (POCUS) in identifying localized B-lines and an elevated D-dimer prompted CT pulmonary angiography, confirming segmental PE. This case underscores the diagnostic utility of POCUS and highlights the limitations of PERC in atypical presentations.\u003c/p\u003e","manuscriptTitle":"Atypical Presentation of Pulmonary Embolism: Flank Pain as the Sole Symptom in a PERC-Negative Patient–The Role of POCUS in Early Detection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-31 12:33:15","doi":"10.21203/rs.3.rs-6315035/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e0ad7ff3-0ed6-49d5-855f-a001c144a812","owner":[],"postedDate":"March 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46432150,"name":"Critical Care \u0026 Emergency Medicine"}],"tags":[],"updatedAt":"2025-03-31T12:33:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-31 12:33:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6315035","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6315035","identity":"rs-6315035","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}