Purpose To determine the detailed computed tomography angiography (CTA) features of isolated superior mesenteric artery dissection (ISMAD), aiming to improve the current understanding of ISMAD. Materials and methods We retrospectively analyzed 57 patients with confirmed diagnoses of ISMAD with CTA from June 2011 to June 2018 in our hospital. The superior mesenteric artery (SMA) angle, entry site of dissection, and features of both false and true lumen were analyzed individually. Results In general, middle-aged men with atherosclerosis (42.1%), hypertension (35.3%), or long-term smoking (33.3%) were the main populations. 80.7% of patients can be discharged successfully after conservative treatment. 87% of patients had a right (or almost right) SMA angle, and the entry site of dissection in 90% of patients occurred in the curved segment of the SMA. As a polymorphic disease, we can use the coded CTA features to delineate individual cases, including cases beyond the presenting classification systems. The diameter of the true lumen is the only different CTA feature between the conservative treatment group and the interventional treatment group (p = 0.000). The re-entry site (p = 0.501), thrombosis in the false lumen (p = 0.135), the distance between the entry site of dissection and SMA root (p = 0.133), and SMA branch involvement (p = 0.322) had no difference between the 2 groups. Conclusions Based on CTA analysis, the bending area, especially in the SMA with right or nearly right SMA angle, is the most vulnerable anatomical region for the occurrence of ISMAD. The diameter of true lumen is the determined CTA feature for the decision of treatment. CTA should be recommended as a standardized diagnostic and classification tool for ISMAD.