Diagnostic Challenges in Spondylodiscitis After Endoscopic Retrograde Cholangiopancreatography Mimicking Malignancy and Radiculopathy

Introduction

Spondylodiscitis is a serious infection of the intervertebral disc and adjacent vertebrae that requires prompt recognition to prevent neurological deficits. Although most cases arise from hematogenous spread, iatrogenic causes after abdominal, vascular, and spinal procedures have also been described. ERCP is generally safe; however, transient bacteremia may occur and, rarely, may be followed by metastatic infection. Post-ERCP spondylodiscitis appears to be rare, with only isolated case reports in the literature.¹

Diagnostic delay may occur when clinicians become anchored to the earliest available explanation, a cognitive bias commonly described as diagnostic anchoring. In inflammatory biliary conditions, biochemical abnormalities such as increased CA 19–9, CA 15–3, and marked vitamin B12 elevation may strengthen that anchoring by mimicking malignancy.^2,3 In addition, patients with persistent lumbosacral pain after abdominal procedures may first present to pain clinics because the symptoms resemble common radiculopathy. In such settings, pain specialists may be among the first clinicians to suspect an occult spinal infection and redirect the workup toward dedicated spinal imaging.

We report a case of radiologically diagnosed L5-S1 spondylodiscitis identified after pain management reassessment in a patient with persistent pain following ERCP. The educational value of the case lies in the diagnostic delay, the misleading biochemical profile, and the importance of multidisciplinary re-evaluation when symptoms and inflammatory markers fail to improve as expected.

Case Presentation

A 57-year-old woman with diabetes mellitus and coronary artery disease underwent ERCP on 10 December 2025 for biliary sludge. The formal ERCP procedure report was not available in the accessible records; however, a subsequent outside-hospital computed tomography report described a catheter/stent-like structure within the common bile duct, suggesting biliary instrumentation and likely stent placement.

On 17 December 2025, the patient presented to another hospital with right upper quadrant pain and fever. According to the available hospital note, computed tomography showed prior cholecystectomy, a catheter-related appearance within the common bile duct and biliary tree, minimal fluid around the common bile duct stent with suspicion for abscess, and air within the biliary tract. These findings were clinically interpreted in the context of biliary infection/sepsis, and the patient received empirical antibiotic therapy. Exact agent and dose details from the outside treatment were not available in the records reviewed for this report.

Despite this treatment, severe low back pain radiating to the right leg persisted. The patient was first evaluated in the pain management clinic on 18 February 2026. She reported intractable pain with a visual analog scale score of 9/10. Electromyography demonstrated L5-S1 sensorimotor neuropathy. Laboratory evaluation during the clinical course showed persistent inflammation and misleading biochemical abnormalities, including CRP 75 mg/L at initial presentation, procalcitonin 0.6 ng/mL, vitamin B12 >2000 pg/mL without prior supplementation, CA 19–9 59.8 U/mL, CA 15–3 42 U/mL, and leukocytosis (Table 1). Because these findings coexisted with persistent pain after ERCP, the initial differential diagnosis included occult malignancy as well as biliary sepsis.

Table 1 Laboratory Findings During the Clinical Course

An initial sacroiliac magnetic resonance imaging study demonstrated extensive inflammatory edema in the right paravertebral soft tissues and gluteal muscles (Figures 1 and 2) but did not establish definite disc-space infection. Ongoing severe radicular pain, continued elevation of inflammatory markers at discharge, and insufficient clinical improvement prompted the pain management team to request repeat laboratory testing and dedicated lumbar magnetic resonance imaging. The lumbar study revealed aggressive L5-S1 spondylodiscitis with disc-space abnormality, adjacent endplate destruction/erosive change, epidural abscess causing foraminal compression, and associated psoas involvement (Figure 3).

Figure 1 Coronal sacroiliac MRI demonstrating extensive inflammatory involvement. Coronal T2-weighted sacroiliac MRI showing extensive inflammatory changes. Red arrows indicate paravertebral soft tissue inflammation (upper arrow), sacral region involvement (middle arrow), and associated gluteal muscle inflammatory edema (lower arrow).

Figure 2 Axial MRI demonstrating epidural and paravertebral involvement. Axial T2-weighted sacroiliac MRI demonstrating epidural and adjacent paravertebral soft tissue involvement. The red arrow indicates the region of inflammatory extension.

Figure 3 Multiplanar MRI findings of L5-S1 spondylodiscitis. Combined axial (left) and sagittal (right) T2-weighted lumbar MRI views demonstrate infection at the L5-S1 level. In the axial image, the red arrow indicates epidural/paravertebral inflammatory involvement. In the sagittal image, the red arrow highlights L5-S1 disc-space infection with adjacent vertebral body marrow edema. The sagittal image was cropped to remove timestamps for patient confidentiality.

The patient was rehospitalized and treated with 6 weeks of intravenous antibiotics. Blood cultures were not obtained, and spinal biopsy was not performed; therefore, microbiological confirmation was not available. Management was guided by the clinical course and radiological findings. After treatment, inflammatory markers normalized and the patient’s pain resolved completely.

Discussion

This case illustrates several clinically important points. First, severe inflammatory states may create a biochemical picture that mimics malignancy. CA 19–9 can rise during acute cholangitis and other biliary inflammatory conditions, while vitamin B12 may become markedly elevated because the liver is its principal storage site and hepatobiliary inflammation may increase its release into the circulation.^2,3 These abnormalities should therefore be interpreted cautiously in the acute inflammatory setting and should not be viewed in isolation as evidence of neoplasia.

Second, the case demonstrates diagnostic anchoring and the consequences of non-specific early imaging. The initial sacroiliac MRI showed substantial inflammatory change but did not answer the key clinical question. Because the patient’s pain pattern remained radicular and inflammatory markers remained elevated, pain management reassessment redirected the workup toward dedicated lumbar imaging, which revealed the true pathology. This sequence is educational because persistent pain after an invasive biliary procedure is easily attributed to musculoskeletal or reactive causes unless the overall timeline is reconsidered.

Third, the association with ERCP should be interpreted cautiously but remains clinically meaningful. We have intentionally framed this as spondylodiscitis occurring after ERCP in the context of biliary infection rather than as microbiologically proven procedure-caused infection. The available chronology supports a plausible pathway of transient bacteremia and hematogenous seeding: ERCP on 10 December 2025, documented febrile biliary illness with suspicious computed tomography findings on 17 December 2025, and subsequent persistent spinal pain culminating in radiological diagnosis. Similar post-biliary-infection spinal complications have been reported, although they are rare.^1,4

The principal limitations are the absence of blood cultures, lack of spinal biopsy, incomplete outside-hospital treatment documentation, and unavailable formal ERCP report. These limitations reduce etiological certainty and should be acknowledged explicitly. Nevertheless, the clinico-radiological picture, the evolution of symptoms, and complete response to prolonged intravenous therapy support the working diagnosis of pyogenic spondylodiscitis.^4,5 In everyday practice, not every patient is diagnosed under ideal microbiological conditions; this case therefore remains relevant as a report of diagnostic delay, multidisciplinary recognition, and practical clinical decision-making.

Conclusion

Spondylodiscitis should be considered in patients with persistent back pain, radiculopathy, and systemic inflammation after ERCP or biliary infection. Marked vitamin B12 elevation and mildly increased tumor markers may be reactive rather than neoplastic in this setting. When symptoms persist despite initial treatment and early imaging is non-specific, dedicated spinal magnetic resonance imaging and multidisciplinary reassessment are essential to reduce diagnostic delay and prevent complications.