Role of diffusion-weighted magnetic resonance imaging in detection of lymph node metastasis in rectal cancer

Rectal cancer is the most prevalent gastrointestinal tumor. Early diagnosis, accurate staging as well as early treatment are the keys for improving the five-year survival rate. The objective of this research is to assess the effectiveness of diffusion-weighted MRI (DWI) in identifying lymph nodes and distinguishing between benign and metastatic nodes throughout the first stage of primary rectal cancer. The study showed that mean ADC value was significantly higher in mucinous carcinoma (1.72 ± 0.36 × 10–3 mm2/sec) than that in non-mucinous carcinoma (0.981 ± 0.276 × 10–3 mm2/sec) with a cutoff value of (1.3 × 10–3) mm2/s which was the precise value to produce high sensitivity, specificity and accuracy of 93%, 94%, and 94%, respectively. ADC analysis showed either intermediate or low signal in 49 (70%) and high signal in 21 (30%) L.Ns. Mean ADC value showed a significant reduction in malignant L.Ns (1.01 ± 0.54 × 10–3 mm2/sec) compared to benign L.Ns (1.51 ± 0.51 × 10–3 mm2/sec), AUC of 0.674 (P = 0.008) and a cutoff value of 0.987 × 10–3 mm2/s with sensitivity, specificity and accuracy of 44.4%, 91.2% and 67.5%, respectively. The mean L.N /tumor ratio was 1.65 ± 0.73 in benign L.Ns and 1.06 ± 0.37 in malignant L.Ns. In rectal cancer, there was a significant difference between benign and malignant L.Ns regarding diffusion result, L.Ns size, shape, and margin. The study demonstrated the effectiveness of DWI in diagnosing lymph node metastasis in colorectal cancer; true diffusion restriction was significantly noted in malignant L.Ns compared to benign L.Ns. Mean ADC value showed a significant reduction in malignant L.Ns compared to benign L.Ns. L.N/tumor ratio showed a significant reduction in malignant L.Ns compared to benign L.Ns.