The sigmoid arteries are two to four branches of the inferior mesenteric artery that descend through the sigmoid mesocolon to supply the sigmoid colon. They anastomose with each other and with the left colic artery above and the superior rectal artery below, forming the arcade of sigmoid arteries in the mesentery. The critical point of Sudeck, between the last sigmoid artery and the superior rectal artery, is a zone of potentially poor collateral supply.
The sigmoid arteries and their territory are the most common site of diverticular disease complications including haemorrhage, perforation, and abscess formation. Sigmoid colon carcinoma requires adequate proximal vascular ligation of the inferior mesenteric artery for adequate lymph node harvest. The point of Sudeck's critical zone between the last sigmoid branch and the superior rectal artery determines the safe level for bowel division and anastomosis in left-sided colorectal surgery: division too close to this watershed risks anastomotic ischaemia.
Rupture of penetrating vasa recta at the neck of sigmoid diverticula causes painless massive lower gastrointestinal bleeding in the sigmoid artery territory, managed with colonoscopic haemostasis, angiographic embolisation, or surgical resection in refractory cases.
The watershed zone between the last sigmoid branch and the superior rectal artery is at risk during sigmoid or rectal resection when the inferior mesenteric artery is ligated high and sigmoid branches are also divided, potentially leaving an ischaemic anastomosis requiring intraoperative Doppler assessment.
