Pulmonary Embolism Presenting as Backache After Appendectomy: An Atypical Presentation of a Common Diagnosis

Abstract

Pulmonary embolism (PE) is a disease with diverse clinical manifestations, which lacks specificity but may be life-threatening. We describe a 39-year-old male who presented with acute PE complicated by pulmonary infarction, confirmed by computed tomography pulmonary angiography 2 weeks following laparoscopic appendectomy. His initial symptom was right lower-back pain. This case underscores the diagnostic challenge posed by an atypical presentation of PE, in which isolated back pain was the sole initial manifestation. Furthermore, we delineate the pathophysiologic mechanisms that may account for PE presenting initially as isolated back pain, knowledge that could expedite early recognition and guideline-directed anticoagulation.

Introduction

Pulmonary embolism (PE) is a form of venous thromboembolism that is common and sometimes fatal. ¹ The presentation of PE is variable, and sometimes atypical, which makes the diagnosis of PE difficult. Suspected PE should be evaluated and diagnosed as quickly as possible for timely targeted treatment, which can reduce the associated mortality and disability. Warfarin and direct oral anticoagulants (DOACs) are commonly used for the treatment of PE. ² DOACs have a lower risk of bleeding as reported. ³ In this case, following warfarin initiation, the patient developed an allergic rash and hepatic injury; these adverse effects resolved after the attending physician substituted rivaroxaban.

Case Presentation

A 39-year-old man was admitted to the emergency room for “chest distress with right-sided lower-back pain.” Chest distress appeared 2 days prior with right back dull ache and worsened with activity. Two weeks prior, the patient underwent a laparoscopic appendectomy that lasted for 5 hours because of an ectopic appendix. He took oral cefuroxime axetil for 10 days for anti-infection therapy. There were no clinical symptoms such as cough, hemoptysis, dyspnea, chest pain, palpitation, or syncope. Four hours before admission, the patient felt that the right back dull ache had developed into continuous sharp pain and was unable to maintain a supine position. Deep inspiration or cough can exacerbate the symptoms. In addition, the patient reported bilateral lower extremity swelling on the day after the operation; however, the surgical team elected neither to re-evaluate nor to intervene further. This patient denied symptoms of the urinary system such as frequent urination, urgency of urination, painful urination, or gross hematuria. Past medical history was unremarkable except for an umbilical hernia that resolved spontaneously of unknown etiology. Family history revealed no inherited thrombophilia or malignancy. The patient is an office worker without a history of tobacco, alcohol, or illicit drug use.

Initial vital signs showed blood pressure was 123/79 mmHg, heart rate was 92 bpm, respiratory rate was 20 breaths per minute, and SpO2 was 90%. Auscultation of the chest revealed decreased breath sounds in the lower lobes of both lungs, without other abnormalities. An electrocardiogram (ECG) revealed sinus rhythm. The white blood cell count was 12.63 ×10⁹/L (4.0-9.5 × 10⁹/L), and the neutrophil count was 10.46 × 10⁹/L (1.8-6.3 × 10⁹/L). The C-reactive protein (CRP) concentration was 62.46 mg/L (0-5 mg/L). The D-dimer level was 4.07 mg/L (0-0.55 mg/L). Myocardial enzyme screening, renal and liver function, and urine tests were normal. Abdominal computed tomography (CT) revealed that the appendix was absent, with a short striated dense shadow in the operative area and a slightly swollen adjacent peritoneum with increased size of the corresponding mesangial lymph nodes. No renal parenchymal abnormalities or urolithiasis were identified. The liver exhibited normal echotexture and contour, with no focal or diffuse pathology detected. Computed tomographic pulmonary angiography (CTPA) revealed multiple filling defects in the pulmonary artery with slight inflammation in the middle lobe of the right lung and the lower lobe of both lungs (Figure 1 ①-⑦). The ventilation/perfusion (V/Q) ratio indicated a V/Q mismatch in the medial and lateral segments of the right middle lobe and the upper lingual segment of the left upper lobe, suggesting PE. Therefore, the patient was diagnosed with low-risk PE. ¹

Figure 1.

Contrast-enhanced chest CT and CTPA were performed at admission and 4 months after discharge.

Further screening for thrombophilia risk factors, autoimmunity results revealed negative results for lupus anticoagulant, anticardiolipin, and anti-β2 glycoprotein I antibodies, but a weak positive results for anti-Jo-1 and anti-SSA antibodies. Positron emission tomography/computed tomography (PET-CT) excluded malignant tumors. Ultrasound of the blood vessels in the extremities suggested thrombosis in the right peroneal vein and the intermuscular vein of both lower limbs. Consequently, the patient’s backache and bilateral lower extremity swelling were relieved when he received a subcutaneous low molecular-weight heparin (LMWH) injection (7000 IU i.p. q12h) for 10 days after diagnosis of PE and bridging therapy with warfarin (3.25 mg p.o. q.d.) for anticoagulation therapy. Thus, the international normalized ratio was 1.97, and the D-dimer concentration was 1.96 mg/L (0-0.55 mg/L). However, 1 week after warfarin treatment, an erythematous rash occurred throughout the body with pruritus (Figure 2). The transaminase levels were more than 5 times higher than the upper limit of the normal range, and the uric acid levels were significantly elevated. The dermatology consultation yielded a diagnosis of allergic dermatitis and suggested loratadine (10 mg p.o. q.d.). Subsequently, the patient discontinued warfarin, and the attending physician initiated anticoagulation with rivaroxaban (20 mg p.o. q.d). After 1 week of rivaroxaban and loratadine, the patient was discharged with resolution of rash and back pain, and normalization of liver function.

Figure 2.

Comparison of the erythematous rash before and after treatment.

Follow-up

After 4 months of rivaroxaban, the right-sided back pain had resolved. Routine blood tests, serum chemistry, D-dimer and CRP were all within normal limits. Arteriovenous ultrasound of both lower limbs revealed no abnormalities. CTPA revealed no signs of PE in the main pulmonary artery, and there was no significant dilatation or stenosis in the pulmonary artery vessels. Patchy lesions were detected in the lower lobe of the right lung, along with a few inflammatory changes in the middle lobe of the right lung and the lower lobes of both lungs (Figure 1 ⑧-⑭).

Discussion

Venous thromboembolism (VTE), including pulmonary thromboembolism and deep venous thrombosis (DVT), is associated with high mortality.^{2 -4} The heterogeneous presentation of PE frequently overlaps with other cardiopulmonary conditions, increasing the risk of misdiagnosis. Chest pain, hemoptysis, syncope, dyspnea, and palpitation were typical but not specific clinical symptoms of PE.^4,5 Additionally, abdominal pain ⁶ and hoarseness of voice ⁷ were reported as atypical presentation of PE. Becattini et al. noted that renal area pain is a rare PE symptom; delayed recognition carries a high mortality risk, so vigilance is essential. ⁸ Acute nontraumatic renal area pain can be differentiated from multiple diseases (urinary system stones, kidney embolism, peritonitis, etc). In this case, abdominal CT suggested post-appendectomy changes without peritonitis, urinary stones, and abnormalities around the kidney area. Normal kidney function suggested no acute renal injury. CTPA and V/Q ratio confirmed the diagnosis of PE and pulmonary infarction in the lower wedges of both lungs. Pulmonary infarction is the necrosis of lung tissue caused by the occlusion of blood flow, which is a common complication of PE.^1,4 In approximately 10% of patients, small clots in distal (segmental or subsegmental) pulmonary arteries cause infarction, triggering local inflammation of lung and pleura that produces pleuritic pain and hemoptysis. ⁹ This patient’s right-sided lower-back pain likely reflected basal pulmonary infarction distal to the embolus. Owing to the right lower-lung infarction near the diaphragm, local pleural inflammation and direct pleural irritation can activate intercostal and spinal nerves, producing acute referred back pain.^6,10

Multiple risk factors for VTE could be traced, especially when the onset of symptoms was atypical. Vascular endothelial damage, blood stasis, and blood viscosity are the 3 major factors of thrombosis.^1,8 VTE is closely related to the long-time anesthesia ¹¹ and abdominal surgery. ⁴ LMWH is recommended for thrombosis prophylaxis (ETP), while extending the time of ETP can reduce the incidence of VTE and proximal DVT, without increasing the risk of major bleeding.^12,13 In this case, the patient underwent a 5-hour-long laparoscopic appendectomy 10 days prior due to acute appendicitis. On the day after the operation, there was persistent pain in the right shoulder joint and swelling in the backs of both lower limbs, which did not attract much attention. The pain in the right shoulder joint improved, but the swelling and pain in both lower limbs persisted without relief after discharge. The attending physician prescribed oral cefuroxime 250 mg twice daily for infection prophylaxis. What’s more, prolonged sitting or immobility slows down blood circulation in the lower limbs, leading to blood stasis in the veins, ¹⁴ like “Economy class syndrome,” “computer thrombosis,” or “mahjong syndrome.”^5,14,15 After discharge, he continued working, with prolonged sitting, which may have contributed to thrombosis.

In conclusion, we report a case in which right-sided low backache was the first clinical symptom of PE after appendectomy. The case underscores the need to regard such atypical presentations as possible PE and to pursue early diagnostic work-up and treatment.