Griffiths' point at the splenic flexure and Sudeck's point at the rectosigmoid junction
Mnemonic
Two watersheds, both named:
- Splenic flexure (Griffiths’ point) - between the superior and inferior mesenteric territories
- Rectosigmoid junction (Sudeck’s point) - between the inferior mesenteric and superior rectal territories
“The flexures are the fragile points.”
These are the least well collateralised segments, so they are the first to suffer in hypoperfusion, giving ischaemic colitis with left sided abdominal pain and bloody diarrhoea, and thumbprinting from mucosal oedema on the abdominal radiograph.
The marginal artery of Drummond provides the collateral along the mesenteric border, and where it is well developed the watershed is protected; where it is deficient, which is common at Griffiths’ point, ischaemia follows.
The rectum is relatively protected because it has a triple supply from the superior, middle and inferior rectal arteries, which is why rectal ischaemia is rare.
Expansion
- Griffiths’ point - the splenic flexure, at the junction of the superior and inferior mesenteric territories (middle colic meeting left colic)
- Sudeck’s point - the rectosigmoid junction, between the last sigmoid artery and the superior rectal artery
The marginal artery is discontinuous or narrow in these regions in a substantial minority of people, so a fall in perfusion pressure, hypotension, cardiac failure, aortic surgery, produces mucosal ischaemia here first.
The classic presentation of ischaemic colitis is left-sided abdominal pain with bloody diarrhoea in an older patient, with thumbprinting on plain radiography from submucosal oedema.
Note the contrast with acute mesenteric ischaemia, which usually involves the superior mesenteric artery, affects the small bowel, and is far more lethal.