Pseudoaneurysms of the middle rectal artery are rare. When encountered, these have the potential for significant morbidity and mortality due to bleeding and potential rupture. Endovascular embolization is a feasible option in the management of these pseudoaneurysms. The present report describes a case of a 43-year-old male presenting with hemorrhagic shock secondary to lower gastrointestinal bleeding one day after undergoing excision of an external perineal condyloma, incision and drainage of a perirectal abscess, and biopsy of a perianal mass. Angiographic imaging revealed a right middle rectal artery pseudoaneurysm. Selective embolization of the right middle rectal artery and bilateral superior rectal arteries was successfully performed. At the two-week post-embolization follow-up, hemoglobin was stable, and the patient reported normal bowel movements with no episodes of bleeding per rectum.

OBJECTIVE: Lateral lymph node (LLN) metastasis is one of the leading causes of local recurrence in patients with lower rectal cancer. Unfortunately, no diagnostic biomarkers are currently available that can predict LLN metastasis preoperatively. Accordingly, we investigated the relationship between the middle rectal artery (MRA) identified by contrast-enhanced magnetic resonance imaging (ceMRI) and LLN metastases.
METHODS: Data from 102 patients with lower rectal cancer who underwent surgery, and were evaluated by preoperative ceMRI, between 2008 and 2016 were reviewed retrospectively. Two expert radiologists evaluated the MRA findings. The diagnostic performance of MRA for LLN metastasis was evaluated by a multivariate analysis with conventional clinicopathological factors.
RESULTS: The MRA was detected in 67 patients (65.7%), including 32 (31.4%) with bilateral MRA and 35 (34.3%) with unilateral MRA. The tumor size, presence of the MRA, and clinical LLN status were significantly correlated with LLN metastasis. A multivariate analysis demonstrated that the presence of MRA (P = 0.045) and clinical LLN status (P = 0.001) were independent predictive factors for LLN metastasis. Furthermore, the sensitivity and negative predictive value of MRA for LLN metastasis were 95% and 97.1%, respectively.
CONCLUSIONS: We successfully demonstrated that MRAs could be clearly detected by ceMRI, and the presence of MRA robustly predicted LLN metastasis in patients with lower rectal cancer, highlighting its clinical significance in the selection of more appropriate treatment strategies.
BACKGROUND: Trial registration number: retrospectively registered 2126 Trial registration date of registration: August 23, 2019.

The middle rectal artery is a very important anatomical structure in rectal cancer surgery. It is the only vessel that penetrates through the proper rectal fascia into the pelvic cavity, and therefore threatens the integrity of total mesorectal excision. Moreover, it is very closely related to the lateral lymphatic drainage root. The definition of the middle rectal artery is ambiguous, and different frequencies, origins, and trajectories have been reported in various papers. The frequency of the middle rectal artery is reported to range from 12 to 97 %. Traditionally, the middle rectal artery is described as an artery that penetrates the pelvic plexus from the lateral side along with the lateral ligament; the frequency of this lateral type of middle rectal artery ranges from 20 to 30 %. However, the reports that describe higher frequency values also consider another type of middle rectal artery, which penetrates the neuro-vascular bundle from the antero-lateral direction; this antero-lateral type of middle rectal artery tends to be a small vessel, and frequently forms a common trunk with the prostatic artery. With advancements in endoscopic surgery, the knowledge of the precise anatomy of this structure is becoming more crucial for optimal rectal cancer surgery.