Differential diagnosis of solitary rectal ulcer syndrome and early rectal cancer via endorectal ultrasound: a retrospective matched case-control study.

BACKGROUND

Solitary rectal ulcer syndrome (SRUS) is a rare chronic rectal disease with nonspecific symptoms and endoscopic findings that overlap with rectal cancer, leading to misdiagnosis in up to 64%. Biopsy is often limited by insufficient depth. Data on the use of endorectal ultrasound (ERUS) for differentiating SRUS from early rectal cancer (ERC) are scarce. Thus, this study aims to identify ERUS features that differentiate SRUS from ERC (T1 and T2 stages).

METHODS

Twenty-nine patients who were pathologically diagnosed with SRUS between 2015 and 2024 were enrolled, whereas ERC patients were randomly selected at a 1:1 ratio and matched based on sex and lesion-to-anal verge distance. The ERUS features and clinical information of the two groups were compared via t tests, Wilcoxon rank sum tests or chi-square tests. Predictive factors for SRUS were analyzed via univariable and multivariable logistic regression. Diagnostic performance was assessed using ROC curves.

RESULTS

SRUS patients were younger and presented with constipation more frequently than ERC patients did (P < 0.001 and P = 0.013, respectively). Compared with ERC lesions, SRUS lesions were more frequently located in the anterior rectal wall (44.83% vs. 13.79%, P = 0.044), were longer (median: 37 mm vs. 26 mm, P = 0.002), and had greater rectal circumferential involvement (41.38% vs. 13.79%, P = 0.019). Similarly, rectal wall thickening with preserved layer stratification and anarchic vascularization were more frequently observed in the SRUS group (79.31% vs. 13.79% and 96.55% vs. 65.52%, respectively; both P < 0.05). Multivariable logistic regression revealed that age (OR:0.87; 95% CI:0.78-0.97; P = 0.014), rectal wall thickening with preserved layer stratification (OR: <0.001, 95% CI: 0.00-0.36, P = 0.015) and > 50% circumferential involvement (OR: 97.04, 95% CI: 1.32-7,134.40, P = 0.037) were independent factors for differentiating between SRUS and ERC. The area under the curve (AUC) was 0.815, 0.638, 0.828, and 0.933 for age, circumferential involvement, layer stratification, and their combination, respectively, in the diagnosis of SRUS.

CONCLUSION

ERUS features, including anterior wall location, longer lesions, > 50% circumferential involvement, rectal wall thickening with preserved layer stratification, and anarchic vascularization, are typical ERUS findings of SRUS. Younger patient age, preserved layer stratification and > 50% circumferential involvement are particularly valuable for differential diagnosis between SRUS and ERC.