Pan-intestinal capsule endoscopy (PCE) enables non-invasive assessment of the small bowel and colon and has been investigated as a first-line diagnostic alternative to colonoscopy in patients with suspected mid- or lower gastrointestinal bleeding (MLGIB). This study aimed to assess the concordance between PCE and colonoscopy for detecting and characterizing colonic lesions, and to evaluate the influence of colonic transit time (CTT) on diagnostic agreement.

This was a post-hoc analysis of data from a prospective single-center clinical trial. Consecutive patients with suspected MLGIB underwent same-day PCE and colonoscopy. Only complete examinations were included. Concordance between techniques was evaluated for detection of any lesion, vascular lesions, polyps, and polyp size categories (<6 mm, 6–10 mm, >10 mm) using Cohen’s Kappa (κ). Sensitivity analyses stratified patients by CTT: ≤60 vs >60 min, ≤90 vs >90 min, and ≤120 vs >120min.

Of 100 enrolled patients, 76 had complete PCE examinations (median age 67 years; 60.5% women), and 80.3% presented with occult bleeding. Adequate bowel preparation was achieved in 77.6% of PCEs and 84.2% of colonoscopies.

Overall, PCE demonstrated moderate agreement with colonoscopy for detecting any colorectal lesion (κ=0.45, p<0.001). Agreement was also moderate for vascular lesions (κ=0.56, p<0.001) and polyps (κ=0.51, p<0.001). Polyp size classification showed substantial concordance (κ=0.69, p<0.001).

CTT strongly influenced global diagnostic agreement. For any lesion, concordance was non-significant for rapid CTT (≤60 and ≤90 min). Agreement improved to fair for CTT≤120 min (κ=0.384, p=0.025) and reached moderate levels for CTT>120 min (κ=0.50, p=0.002).

Detection of vascular lesions was comparatively stable across all CTT categories, with moderate-to-substantial agreement at every threshold (κ=0.577, p=0.008 for ≤60 min; κ=0.578, p=0.002 for ≤90 min; κ=0.635, p<0.001 for ≤120 min).

In contrast, polyp detection showed a marked dependence on CTT. Concordance increased from fair at ≤60 min (κ=0.40, p=0.049) to moderate for >60 min (κ=0.55, p<0.001) and >90 min (κ=0.56, p<0.001). For ≤120 min agreement remained moderate (κ=0.46, p=0.006), again increasing for >120 min (κ=0.56, p<0.001).

Similarly, polyp size classification was unreliable for rapid transit (≤90 min: p=0.273) but became almost perfect for >90 min (κ=0.824, p<0.001) and >120 min (κ=0.805, p<0.001).

PCE showed moderate-to-substantial agreement with colonoscopy for the detection of colorectal lesions. Diagnostic performace was significantly influenced by CTT. While vascular lesion detection remained stable across all CTT categories, rapid CTT (<90minutes) was associated with an increased risk of false negatives, especially for polypoid lesions. In such cases, repeat examination, closer follow-up, or alternative diagnostic strategies should be considered.