Evaluating the Diagnostic Accuracy of Combined CT and MRI Imaging in Detecting Lymph Node Metastasis in Colorectal Cancer
Submission: 05 December 2025 | Acceptance: 29 December 2025 | Publication: 23 January 2026
Amna Fareed, Mazhar Iqbal, Syed Shafqatullah, Resham Ali, Naeem Khan, Sarkhail Ahmed Sayar, Uroosa Shadani, Raja Jawad Ali , Ali Muhammad
Jinnah Post Graduate Medical Center
Abstract
Background: Lymph node metastasis is a major prognostic determinant in colorectal cancer, directly influencing surgical strategies and the use of adjuvant therapy. While CT and MRI are widely applied in preoperative staging, there is limited evidence assessing the combined diagnostic accuracy of these modalities for nodal evaluation.
Objective: To assess the diagnostic performance of combined CT and MRI in detecting lymph node metastases in colorectal cancer, using histopathology as the gold standard.
Methods: This cross-sectional study included patients with colorectal cancer who underwent preoperative CT and MRI, followed by surgical resection at [JPMC] between January and June 2025. Imaging was interpreted using standardized radiologic criteria and compared against histopathological findings of resected lymph nodes. Diagnostic indices, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy, were calculated.
Results: Histopathology confirmed nodal metastases in 57.9 % (22/38) of colon cancer patients and 57.1 % (20/35) of rectal cancer patients. For colon cancer (CT only), the sensitivity, specificity, PPV, NPV, and accuracy were 68.2 %, 68.8 %, 75.0 %, 61.1 %, and 68.4 %, respectively. For rectal cancer (CT + MRI), these were 85.0 %, 80.0 %, 85.0 %, 80.0 %, and 82.9 %, respectively. Mean lymph node counts on imaging were 5.8 ± 2.1 for colon cancer and 6.4 ± 2.3 for rectal cancer, compared with 14.2 ± 3.9 and 13.7 ± 3.6, respectively, on histopathology. Micrometastases <5 mm were detected only by histology.
Conclusion: Combining CT with MRI improves diagnostic sensitivity for nodal metastasis detection in rectal cancer compared with CT alone for colon cancer. Histopathology remains the definitive reference, particularly for small-volume disease.
Keywords: Colorectal cancer, lymph node metastasis, CT, MRI, diagnostic accuracy, preoperative imaging.