The problem is rooted in the biology and anatomy of these tumours. Brush cytology and forceps biopsy taken during ERCP sample only a small fraction of the stricture, and desmoplastic stroma often surrounds sparse malignant cells, so malignant strictures can yield false negatives. Serum carbohydrate antigen 19-9, the most widely used blood marker, is also unreliable in this setting: cholestasis itself, the bile-flow obstruction that brings patients to endoscopy in the first place, can push CA19-9 concentrations above the usual 44 U/mL cutoff even when no cancer is present. The result is a diagnostic limbo in which patients undergo repeated procedures, delayed referrals and, in the worst cases, missed opportunities for resection.

A study published in eGastroenterology by Rojo and colleagues at the First Hospital of Jilin University proposes a strikingly simple way to extract more information from a procedure patients already undergo: sequence the bile. Bile collected during routine ERCP is ordinarily treated as waste, but it bathes the tumour and is rich in cell-free DNA, fragments of genetic material shed by dying cells. Because malignant cells in the ductal epithelium and pancreas release their DNA directly into this fluid, bile offers a far more concentrated and anatomically relevant source of tumour DNA than peripheral blood, where pancreatobiliary cancer DNA is heavily diluted.

The technical elegance of the approach lies in its economy. Rather than deep sequencing, the team used ultra-low-pass whole-genome sequencing, or ULP-WGS, reading the bile cell-free DNA at roughly 0.2× genomic coverage from as little as 2 nanograms of starting material. At such shallow depth, individual bases cannot be reliably called, but the method does something arguably more useful: it reveals large-scale copy-number alterations, the gains and losses of whole chromosome arms that are hallmarks of cancer genomes. Using the open-source ichorCNA pipeline, the researchers computed a tumour fraction, the estimated proportion of cell-free DNA derived from tumour, with a threshold of 10 per cent or more indicating detectable circulating tumour DNA. Reducing sequencing depth from the conventional 30–50× used in clinical whole-genome sequencing to 0.2× was estimated to cut sequencing costs by approximately 130- to 215-fold, a difference that could make the test scalable in routine practice.

The prospective cohort comprised 95 patients undergoing their first ERCP for a biliary stricture that was radiologically suspicious for malignancy. At the outset, pathological assessment classified 26 strictures as malignant and 69 as indeterminate. Over follow-up of up to 12 months, 45 of the initially indeterminate cases were confirmed malignant and 24 proved benign, giving a final malignant cohort of 40 cholangiocarcinomas and 31 pancreatic ductal adenocarcinomas. This design mirrors the real clinical dilemma, since the patients who matter most are precisely those in whom the first pathological evaluation fails to settle the question.

The performance figures are encouraging on both ends of the spectrum. Among patients already diagnosed with malignancy at the first ERCP, bile ULP-WGS detected tumour DNA in 73 per cent of cases, including 82 per cent of cholangiocarcinomas and 56 per cent of pancreatic cancers. More importantly, in the initially indeterminate strictures later confirmed as malignant, sensitivity was 51 per cent, while 23 of the 24 ultimately benign cases tested negative, corresponding to a specificity of 96 per cent. By comparison, CA19-9 at the prespecified threshold of 44 U/mL achieved only 53 per cent specificity in evaluable benign cases, underscoring how poorly the conventional marker performs in the obstructed, inflamed patients who need clarity most.

The most clinically compelling finding concerns timing. In the 23 patients whose malignancy was not established at the first ERCP but whose bile tested positive, tumour DNA was detected a median of 38 days before the conventional diagnosis was made. In seven patients the genomic signal preceded diagnosis by more than 100 days, and in one case by an extraordinary 499 days. For cancers in which every week of delay can shift a patient from resectable to unresectable disease, a lead time measured in months could translate directly into surgical candidacy and survival. The researchers also compared their shallow approach with a targeted next-generation sequencing assay of 52 genes, dubbed Bilemut, which detected mutations in 94.7 per cent of evaluable malignant strictures and remained more sensitive overall. ULP-WGS, however, required less DNA and delivered genome-wide copy-number information that targeted mutation panels cannot capture, suggesting the two methods are complementary rather than competing.

Beyond detecting cancer, the copy-number profiles carried information about where the tumour had arisen. The bile-derived alterations reproduced genomic patterns previously described in pancreatobiliary tumour tissue, including recurrent losses of chromosome arms 9p, 17p and 18q and gains of 7p, 7q, 8q and 19q. A supervised classifier built on 50 copy-number regions distinguished cholangiocarcinoma from pancreatic ductal adenocarcinoma with 86.4 per cent accuracy in the reference cohort and 85.0 per cent in a separate validation cohort. Loss of 1p was enriched in pancreatic cancer, whereas 9p loss occurred more frequently in cholangiocarcinoma. This matters because the two tumours demand different management, from neoadjuvant strategies to surgical planning, and tissue-of-origin assignment from a liquid biopsy could guide decisions even before a formal histological diagnosis exists.

The sequencing data also appeared to carry prognostic weight. Neither tumour fraction alone nor targeted tumour mutational burden alone significantly stratified overall survival, but the combination did. Patients who were both tumour-fraction positive and carried mutations in at least three genes had a median overall survival of 5.1 months, compared with 13.7 months among the remaining patients. After adjustment for initial management, CA19-9 and carcinoembryonic antigen, this combined genomic profile remained independently associated with poorer survival, with an adjusted hazard ratio of 2.51 and a 95 per cent confidence interval of 1.22 to 5.14. If validated, such a signature could help clinicians identify patients whose disease course is likely to be aggressive and for whom early referral to palliative or intensified protocols might be appropriate.

The authors are careful about the limits of their test. A negative bile ULP-WGS result is not sensitive enough to exclude malignancy, and the method should not replace histopathology, which remains the diagnostic gold standard. Its most promising role is as a complementary test after an inconclusive first ERCP: a positive result could justify accelerated repeat sampling, cholangioscopy with directed biopsy, endoscopic ultrasound-guided tissue acquisition or closer multidisciplinary surveillance, while sparing patients with negative results some of the cascade of repeat procedures. The study also has constraints that temper enthusiasm. It was conducted at a single centre, the cohort was modest, the ultimately benign group was small, and the cholangiocarcinoma-versus-pancreatic-cancer classifier requires external validation before it can inform real-world decisions. Prospective multicentre studies must now determine whether bile genomics can genuinely shorten diagnostic delays, reduce the number of invasive repeat procedures and, ultimately, improve outcomes for patients caught in the diagnostic grey zone of the biliary stricture. What the current work establishes, however, is that a fluid routinely discarded at the end of every ERCP contains a readable, cost-effective genomic record of the tumours it touches, and that reading it may move pancreatobiliary cancer diagnosis weeks or even months earlier.

Subject of Research: Ultra-low-pass whole-genome sequencing of bile cell-free DNA for detecting and classifying malignant biliary strictures

Article Title: Bile genome sequencing may accelerate diagnosis of malignant biliary strictures

Article References: Bile genome sequencing may accelerate diagnosis of malignant biliary strictures. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: bile cell-free DNA, ultra-low-pass whole-genome sequencing, biliary strictures, cholangiocarcinoma, pancreatic ductal adenocarcinoma, ERCP, copy-number alterations, tumour fraction, liquid biopsy, CA19-9, early cancer diagnosis, eGastroenterology

The research, led by Belarmino Gonçalves of the Portuguese Oncology Institute of Porto and Thiago Franchi Nunes of Interventix in Campo Grande, Brazil, brought together ten tertiary referral centers across South America and Europe. Between January 2018 and July 2025, the investigators analyzed 68 diagnostic percutaneous transhepatic cholangioscopy, or PTCS, procedures performed in patients whose cross-sectional imaging and prior endoscopic evaluation had been nondiagnostic, or whose anatomy made standard endoscopic access impossible. Crucially, cases performed primarily to treat gallstones were excluded, isolating a cohort in which the sole purpose of the camera voyage into the ducts was to determine whether cancer was present.

The technique itself is a remarkable feat of interventional radiology. Using ultrasound and fluoroscopic guidance, physicians thread a needle through the liver into the bile ducts and establish a percutaneous tract, typically secured with a 10 to 12 French introducer sheath. Through that sheath, flexible cholangioscopes, single-operator platforms, or single-use ultra-slim endoscopes measuring roughly 2.8 to 3.5 millimeters in outer diameter are advanced directly into the biliary tree. Saline irrigation clears the field, allowing the operator to inspect the duct lining in real time — something computed tomography and magnetic resonance cholangiopancreatography fundamentally cannot do, since they offer only indirect views of the biliary mucosa. Some centers perform the cholangioscopic inspection in the same session when tract and sheath conditions permit; others prefer a staged approach roughly 48 to 72 hours later to allow decompression and reduce infection risk in patients with cholangitis or complex anatomy.

During each procedure, operators recorded two kinds of optical judgments before any tissue results were known. The first was a global impression — a binary real-time call of benign versus malignant that integrated everything seen during the examination. The second was a checklist of five predefined visual criteria: tumor vessels appearing as tortuous neovessels, hypervascular mucosa, nodular or polypoid masses, papillary projections, and infiltrative lesions marked by irregular mucosa and loss of normal duct architecture. When recorded images or videos were available, blinded investigators independently reviewed the material against the checklist, with disagreements resolved by consensus, adding a layer of methodological rigor to what has historically been a subjective art.

The results against the gold standard of histopathology were striking. Malignancy was ultimately confirmed in 57 of the 68 procedures, reflecting the referral-enriched, high-risk nature of the population. Against that benchmark, the operator’s global impression achieved 84.2 percent sensitivity, 90.9 percent specificity, and 85.3 percent accuracy. Most notable was the positive predictive value of 98.0 percent: when an experienced operator called a lesion malignant on direct visualization, that call was almost always right. The negative predictive value of 52.6 percent, by contrast, shows that a benign-appearing duct cannot safely rule out cancer — tissue sampling remains essential. The authors caution that these predictive values must be interpreted in light of the unusually high cancer prevalence in this cohort.

Among the individual visual criteria, two emerged as the most trustworthy warning signs. An infiltrative appearance showed 90.9 percent specificity and was strongly associated with malignant histopathology, carrying an odds ratio of 13.75 and a positive predictive value of 97.1 percent. Tumor vessels were also significantly linked to cancer, with an odds ratio of 4.57. Hypervascular mucosa, by comparison, offered little discriminatory power. The researchers then explored combined decision rules: using the permissive rule of tumor vessels or infiltrative appearance raised sensitivity to 84.2 percent at moderate specificity, while the restrictive rule requiring both features achieved 100 percent specificity — a powerful rule-in finding when tissue is scarce — albeit with sensitivity dropping to 36.8 percent. These PTCS-specific heuristics remain hypothesis-generating and await prospective validation.

Safety data were equally informative. Adverse events occurred in 10 of 68 procedures, or 14.7 percent, graded using the modified CIRSE classification system. Two events were grade I, five were grade II, and three were grade IV — the latter all infectious complications requiring intensive care-level support such as vasopressors or ventilation, rather than mechanical injury from the instruments themselves. The predominance of low-grade complications underscores the importance of standardized antibiotic prophylaxis, careful biliary decompression, controlled irrigation strategies, and structured post-procedure monitoring for anyone undergoing antegrade cholangioscopy.

The study’s context matters. In patients with surgically altered anatomy — bilioenteric anastomoses or Roux-en-Y reconstructions accounted for nearly a third of the cohort — conventional endoscopic retrograde cholangiopancreatography is often impossible or has already failed. Traditional blind or fluoroscopy-guided biopsies perform poorly for infiltrative, flat, or submucosal tumors, frequently returning nondiagnostic or discordant samples. Prior meta-analyses have shown that cholangioscopy-guided targeted biopsy outperforms fluoroscopy-guided sampling for indeterminate strictures, and consensus guidelines now frame cholangioscopy as a problem-solving tool. What has been missing, the authors argue, is multicenter real-world evidence about how the percutaneous, antegrade version of the technique performs across diverse devices, operators, and health systems — a gap this Brazil-and-Europe network directly addresses.

The investigators are candid about the limitations. The retrospective design limits control of confounding and standardization, and partial verification bias is possible. The high prevalence of malignancy limits generalizability to lower-risk populations, and procedural heterogeneity — different scopes, sheath sizes, sedation protocols, and timing — reflects the reality of a varied referral network but complicates interpretation. Confidence intervals around some analyses were wide, and inter-observer reproducibility was not formally assessed. Still, the single-session design, which avoided within-patient clustering, and the combination of operator impression with structured criteria strengthen the findings considerably.

Looking ahead, the authors call for prospective validation of PTCS-specific optical reporting frameworks, standardized documentation of procedural variables such as tract maturation and irrigation strategy, and quantification of how cholangioscopic findings actually change patient management. Emerging technologies, including standardized image annotation and artificial intelligence-assisted pattern recognition, could sharpen interobserver agreement and refine the visual criteria tailored to percutaneous referral populations. For now, the message for patients with mysterious bile duct blockages is encouraging: a camera threaded through the liver, guided by a trained eye and a disciplined checklist, can bring clarity where scans and standard endoscopy leave only doubt — with a safety profile that is, in most cases, reassuringly benign.

Subject of Research: Diagnostic performance and safety of percutaneous transhepatic cholangioscopy for complex, indeterminate biliary lesions

Article Title: Percutaneous transhepatic cholangioscopy for complex biliary lesions: multicenter real-world diagnostic performance and safety study

Article References: Gonçalves, B., Nunes, T. F., Leitão, L., de Oliveira Leite, T. F., Stefanini, F. S., Fornazari, V. A. V., De Santi, G. F., Pazinato, L. V., Szejnfeld, D., Mosconi, C., Ierardi, A. M., Sousa, M. J., Dezman, R., Krokidis, M., & Hatzidakis, A. (2026). Percutaneous transhepatic cholangioscopy for complex biliary lesions: multicenter real-world diagnostic performance and safety study. CVIR Oncology, 2(1), Article 14. https://doi.org/10.1007/s44343-026-00045-3

Image Credits: AI Generated

DOI: 10.1007/s44343-026-00045-3

Keywords: percutaneous transhepatic cholangioscopy, biliary strictures, cholangiocarcinoma, indeterminate biliary lesions, targeted biopsy, interventional radiology, diagnostic accuracy, adverse events, multicenter study, bile duct cancer, Percutaneous, transhepatic