A Retzius shunt between the ileocecal vein and inferior vena cava is rare. To avoid major hemorrhage due to shunt injury, it is essential to evaluate vascular abnormalities on preoperative imaging and to confirm anatomic structures in detail during the operation.

A 71-year-old woman with diabetes and asthma developed anaemia.

She was diagnosed with cecal cancer by endoscopy and found to have a venous malformation forming a Retzius shunt from the ileocecal vein to the inferior vena cava on computed tomography.

Laparoscopic ileocecal resection was performed. Colonic mobilization and resection of the ileocecal vessels were performed while minimizing traction on the shunt. After confirming the anatomy, the Retzius shunt was resected without complications.

The patient experienced an unremarkable postoperative clinical course without complications.

This case involved a rare vascular anomaly associated with colorectal cancer, characterized by an abnormal blood vessel connecting the inferior vena cava and mesenteric veins. When abnormal vessels are detected on preoperative abdominal computed tomography, a Retzius shunt should be considered. Detailed review of the imaging, careful surgical manipulation to avoid shunt damage, and thorough anatomical verification, are important to perform a safe operation.

A coexisting short-circuit from the inferior mesenteric vein (IMV) to the inferior vena cava, known as a Retzius shunt, and arteriovenous malformation (AVM) of the inferior mesentery are extremely rare conditions. We encountered a case of rectal cancer with coexisting Retzius shunt and inferior mesenteric AVM successfully treated with laparoscopic surgery. Contrast computed tomography (CT) in a 62-year-old man with rectal cancer showed multiple dilated veins at the mesenterium of the descending sigmoid colon. These dilated veins were connected between the IMV and the left renal vein. A diagnosis of Retzius shunt was made, and laparoscopic low anterior resection with lymph node dissection was performed. A pathological examination of the colonic mesenterium revealed AVM communicating with the dilated IMV and Retzius shunt. The preoperative evaluation of aberrant vessels by three-dimensional CT is particularly useful for patients with vascular malformations to ensure safe laparoscopic surgery.

Three-dimensional (3D) modelling technology translates the patient-specific anatomical information derived from two-dimensional radiological images into virtual or physical 3D models, which more closely resemble the complex environment encountered during surgery. It has been successfully applied to surgical planning and navigation, as well as surgical training and patient education in several surgical specialties, but its uptake lags behind in colorectal surgery. Rectal cancer surgery poses specific challenges due to the complex anatomy of the pelvis, which is difficult to comprehend and visualise.

To review the current and emerging applications of the 3D models, both virtual and physical, in rectal cancer surgery.

Medline/PubMed, Embase and Scopus databases were searched using the keywords "rectal surgery", "colorectal surgery", "three-dimensional", "3D", "modelling", "3D printing", "surgical planning", "surgical navigation", "surgical education", "patient education" to identify the eligible full-text studies published in English between 2001 and 2020. Reference list from each article was manually reviewed to identify additional relevant papers. The conference abstracts, animal and cadaveric studies and studies describing 3D pelvimetry or radiotherapy planning were excluded. Data were extracted from the retrieved manuscripts and summarised in a descriptive way. The manuscript was prepared and revised in accordance with PRISMA 2009 checklist.

Sixteen studies, including 9 feasibility studies, were included in the systematic review. The studies were classified into four categories: feasibility of the use of 3D modelling technology in rectal cancer surgery, preoperative planning and intraoperative navigation, surgical education and surgical device design. Thirteen studies used virtual models, one 3D printed model and 2 both types of models. The construction of virtual and physical models depicting the normal pelvic anatomy and rectal cancer, was shown to be feasible. Within the clinical context, 3D models were used to identify vascular anomalies, for surgical planning and navigation in lateral pelvic wall lymph node dissection and in management of recurrent rectal cancer. Both physical and virtual 3D models were found to be valuable in surgical education, with a preference for 3D printed models. The main limitations of the current technology identified in the studies were related to the restrictions of the segmentation process and the lack of 3D printing materials that could mimic the soft and deformable tissues.

3D modelling technology has potential to be utilised in multiple aspects of rectal cancer surgery, however, it is still at the experimental stage of application in this setting.