GI Endoscopy · 4 min read
Colonic Watersheds: Griffith, Sudeck, and Where to Read Next
This URL is the map. Colon ischemia is the clinical page. Griffith and Sudeck have their own anatomy pages. Do not treat Drummond as a watershed.
A colonic watershed is the far edge of two arterial territories. Griffith's point is the splenic flexure (SMA/IMA). Sudeck's point is the last sigmoid to superior rectal junction. The clinical syndrome is colon ischemia. The named points are anatomy. This page only points.
Experienced teaching points
Clinical Pearls
- Griffith is SMA meeting IMA at the splenic flexure. Clinical: left-colon ischemia after hypotension.
- Sudeck is last sigmoid to superior rectal. Anatomy lives at /sudecks-point/, not at /sudeck-point/.
- Drummond is the marginal arcade, not a watershed. Arc of Riolan is a central SMA-IMA collateral, often fat in chronic SMA or IMA occlusion.
- Isolated right-colon ischemia is a different, worse pattern. That argument is on the colon ischemia page and the AMI differentiator.
Clinical Bottom Line
| URL | What it is for |
|---|---|
| /ischemic-colitis/ | Canonical colon-ischemia page. ACG 2015. When to CTA, when to operate, isolated right colon. |
| /griffith-point-colon/ | Griffith anatomy (splenic flexure, SMA/IMA). Drummond stays the arcade here. |
| /sudecks-point/ | Sudeck anatomy (last sigmoid to superior rectal). |
| /sudeck-point/ | AMI versus colon ischemia. Different permalink on purpose. Do not 301 it onto Sudeck anatomy. |
What is a colonic watershed?
It is the distal overlap of two named arteries, the first mucosa to fade when flow falls. Two matter in the colon:
- Griffith's point at the splenic flexure: left branch of the middle colic (SMA) meeting the ascending left colic (IMA).
- Sudeck's point at the rectosigmoid: lowest sigmoid branch meeting the superior rectal artery.
The marginal artery of Drummond is the running arcade that can bail both junctions out if it is complete. It is not itself a watershed. The arc of Riolan is a more central SMA-IMA channel; a fat arc of Riolan is a clue to chronic occlusive disease, not a third watershed name.
About 5% of people have a thin or absent Drummond connection at the splenic flexure. Those colons infarct first when blood pressure drops. That is why Griffith shows up on colon-ischemia lists. Detail and the CT/endoscopy stills live on the colon ischemia page.
Why does this URL still exist?
WordPress shipped a combined anatomy stub here. Griffith, Sudeck, AMI versus colon ischemia, and the clinical syndrome each already have a permalink. Expanding this URL into a fifth full article would compete with those four. Keeping the slug as a map is the honest use of an existing address.
ACG 2015 (Brandt, PMID 25584722) remains the colon-ischemia guideline. Isolated right-colon ischemia needs CTA and a vascular surgeon in the room, not a watershed lecture. That split is on the AMI page.
Selected references
- Brandt LJ, Feuerstadt P, Longstreth GF, Boley SJ. ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and management of colon ischemia. Am J Gastroenterol. 2015;110:18-44.
- Henry Vandyke Carter. Gray's Anatomy 20th ed. 1918, plate 537 (IMA). Public domain.
Last reviewed September 20, 2026. Written for clinicians who searched watershed colon and need the named points without a third copy of the ischemia article.
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