Radiological features are suggestive of organized rectus sheath hematoma. The well defined lentiform shape of the hematoma is suggestive of intrafascial hemorrhage. The anterior wall of rectus sheath at the infraumbilical level is composed of the aponeurosis of the external oblique and the anterior lamina of the aponeurosis of the internal oblique muscles, the latter is intimately related to the rectus muscle and encloses it along with the posterior lamina of the internal oblique muscle. Since the fluid collection is anterior to the right rectus muscle with biconvex shape and separable from the rectus muscles as well as the internal oblique aponeurosis, the anatomic site of hemorrhage is likely inside the right external oblique aponeurosis. 

Superiorly, the hematoma is arrested at the level of the umbilicus. Inferiorly, it is arrested at the anatomical region of the arcuate line, below which all three abdominal wall muscle aponeuroses of the rectus sheath join anterior to the rectus abdominis muscles. This region is supplied through perforator branches from the deep inferior epigastric artery, which are likely to be the source of bleeding.

The etiology here is iatrogenic after abdominal wall surgery (abdominoplasty). Other causes of rectus sheath/muscle hematoma include anticoagulation therapy, coagulopathies, trauma, and vascular disorders.