Jejunum
Ileum
Terminal ileum
Cecum
Appendix
Right colon
Transverse colon
Left colon
Sigmoid colon
Rectum
Anus
One front door to evidence‑based IBD Surgical care.
IBDology — the study of all aspects of surgery for IBD.
New evidence takes ~17 years to reach the bedside. We're aiming a laser at that gap.
IBDology exists to collapse the distance between publication and practice. We focus AI like a laser beam — pairing the latest IBD-surgery publications with “deep and narrow,” queryable large language models — to put the newest evidence into the hands of providers and patients faster.
Frequently Asked Questions
Quick, plain-language answers to the questions we hear most.
I'm new to IBD — where should a student, PA, nurse, or resident start?
Start with the Primer — a plain-language, few-minute orientation written for clinicians new to IBD. It explains the difference between ulcerative colitis, Crohn's disease, and IBD-unclassified, decodes the acronyms you'll meet here (IPAA / J-pouch, PSC, NSQIP, perianal Crohn's), and shows where surgery fits, with optional deep dives for more advanced readers.
What do the acronyms IPAA, IBD-U, PSC, and NSQIP mean?
IPAA (ileal pouch–anal anastomosis, or “J-pouch”) is the operation that removes the colon and rectum and builds an internal pouch so stool still passes normally. IBD-U (IBD-unclassified) is colitis that isn't clearly ulcerative colitis or Crohn's. PSC (primary sclerosing cholangitis) is a bile-duct disease that overlaps with IBD and raises cancer risk. NSQIP is a national surgical-quality database centers use to benchmark outcomes. The Primer defines these and more in context.
What is IBDology?
IBDology is the front door to a family of inflammatory bowel disease (IBD) resources from the Holubar Lab. It points you to the right site for your need — whether you are a clinician looking for evidence and quality data, or a patient looking for plain-language education.
Which sites are for patients and which are for providers?
Patient sites include Pouchy (J-pouch), Crohnz (Crohn's), and pCrohns (perianal Crohn's). Provider/clinician sites include Pouchology (pouch literature) and Crohnsology (Crohn's evidence). The consortia — iPouch, iCrohnz, and NSQIP IBD — serve clinicians and researchers.
I have a J-pouch (IPAA). Where should I start?
Patients and families should start at pouchy.org for friendly, plain-language education. Clinicians and researchers can search the pouch literature at pouchology.org.
I have Crohn's disease. Which site is for me?
For intestinal Crohn's, patients should visit crohnz.org; if you have perianal disease (fistulas, abscesses, setons), see pcrohns.org. Clinicians can use crohnsology.org for the evidence base.
What is IBD-PSC?
IBD-PSC is inflammatory bowel disease together with primary sclerosing cholangitis, a liver condition. The overlap changes surveillance, colorectal cancer risk, transplant considerations, and pouch decisions. Learn more at ibdpsc.org.
Who runs these sites?
They are produced by the Holubar Lab, led by Stefan D. Holubar, MD, MS, Professor of Surgery in the Department of Colon & Rectal Surgery at Cleveland Clinic. The sites are educational and do not replace advice from your own care team.
IBD Primer — a quick orientation
A plain-language orientation for clinicians new to inflammatory bowel disease — medical students, PAs, nurses, residents, fellows, and early-career staff. It gets you oriented in a few minutes; it is not a substitute for a textbook. Hover or tap any dotted term for a plain-language definition.
IBD is chronic, immune-driven inflammation of the gut. It comes in two main forms — ulcerative colitis and Crohn's disease — with a middle ground when the two can't be told apart. Medicines control most disease; surgery enters when medicines fail or complications develop. These sites help you reach the right evidence or patient resource quickly.
- Ulcerative colitis (UC)
- Continuous inflammation limited to the colon and rectum. Because the disease lives in the colon, removing the colon — often building a J-pouch — can be curative.1
- Crohn's disease (CD)
- Patchy, full-thickness inflammation that can occur anywhere from mouth to anus. Surgery treats complications (strictures, fistulas, abscesses) but is not curative, so operations aim to spare bowel.2
- IBD-unclassified (IBD-U)
- Colitis that isn't clearly UC or Crohn's. The uncertainty matters most when deciding whether a J-pouch is safe.3
- IPAA / “J-pouch”
- The restorative operation for UC: after the colon and rectum come out, the small intestine is folded into an internal pouch and joined to the anus, so stool still passes normally — no permanent bag.
- Colectomy & proctocolectomy
- Removing the colon (colectomy) or the colon and rectum together (proctocolectomy) — the step before a J-pouch or a permanent ileostomy.
- IBD-PSC
- IBD together with primary sclerosing cholangitis, a scarring disease of the bile ducts. The overlap raises colorectal-cancer risk and changes surveillance.4,5
- Perianal Crohn's
- Crohn's around the anus — fistulas, abscesses, and draining setons — managed very differently from disease inside the bowel.
- NSQIP & consortia
- Multi-center collaborations (NSQIP IBD, iPouch, iCrohnz) that pool surgical data across hospitals to benchmark and improve outcomes.
Most patients are managed medically — biologics and other drugs. Surgery is considered when medicines can't control the disease, when a complication develops (obstruction, abscess, fistula, bleeding), or when precancerous change is found on surveillance. In UC, surgery can be curative; in Crohn's, it manages complications while preserving bowel.1,2,6
Which site do I need?Every topic has a provider resource and a patient resource. For J-pouch / UC surgery, clinicians use Pouchology and patients use Pouchy. For Crohn's, clinicians use Crohnsology; patients use Crohnz (intestinal) or pCrohns (perianal). The quality collaboratives — iPouch, iCrohnz, and NSQIP IBD — are for clinicians and researchers. Return to the hub map to choose.
Going deeper — for advanced providersWhy IBD-unclassified complicates the J-pouch decision Advanced
A J-pouch is the standard restorative option for ulcerative colitis, but it fares worse in Crohn's disease, where fistulas and pouch inflammation are more common and pouch failure is higher.7,8 When the diagnosis is IBD-unclassified, the team is effectively betting on which disease will declare itself later.
Many centers still offer a pouch in IBD-U with careful counseling, since a substantial share behave like UC.3 This is exactly the grey zone ibdunclassified.org is built to unpack.
How PSC shifts cancer surveillance and risk Advanced
PSC is one of the strongest risk multipliers for colorectal cancer in IBD.4 Guidelines recommend annual colonoscopic surveillance from the time of PSC diagnosis — not the usual 8-to-10-year interval — and the risk persists even after a J-pouch, so pouch surveillance continues too.5,9,10
PSC also raises bile-duct cancer risk and can progress to liver transplant, which interacts with the timing of colorectal surgery. See ibdpsc.org for the full picture.
Staged IPAA: 2-stage vs 3-stage, in brief Advanced
Building a J-pouch is often split across operations to lower the risk of a leak (a staged approach).11,12 A 2-stage approach makes the pouch plus a temporary ileostomy, then closes the ileostomy later. A 3-stage approach starts with a colectomy alone — useful when a patient is acutely ill, malnourished, or on high-dose steroids — and builds the pouch at a second operation once they've recovered.
Choosing the number of stages is a core pouch-surgery decision; the evidence lives at pouchology.org, with patient-facing explanations at pouchy.org.
About IBDology
IBDology is the hub for a family of inflammatory bowel disease resources from the Holubar Lab, led by Stefan D. Holubar, MD, MS, Professor of Surgery, Department of Colon & Rectal Surgery, Cleveland Clinic, Cleveland, Ohio. Each site translates the best available evidence into resources for either clinicians or patients — from the iPouch and NSQIP IBD quality consortia to plain-language guides for living with a J‑pouch or Crohn's disease.
Some content may be AI-assisted and reviewed by the lab. These sites are educational and are not a substitute for professional medical advice.
Support & community
Trusted, independent organizations and communities for people living with inflammatory bowel disease, an ostomy, or a J‑pouch — and for their families.
External resources are independent of the Holubar Lab; listing does not imply endorsement. Always verify with your own care team.
The 100 most-cited IBD papers of all time
The most-cited inflammatory bowel disease papers ever published, ranked by total citations. These are the landmark studies — epidemiology, genetics, the microbiome, and the trials that defined modern IBD care.
Method: Pool ranked by OpenAlex cited_by_count (all citing sources). Candidate pool: Top 700 most-cited works under the OpenAlex IBD, ulcerative-colitis, and Crohn's-disease concepts (relevance score >= 0.3), with a PubMed ID and year. Citation counts: OpenAlex (all citing sources). Generated: 2026-06-29. Counts are dynamic and rise over time.
The 100 most-disruptive IBD papers of all time
Disruptiveness is not the same as popularity. The CD5 disruption index (Funk & Owen-Smith 2017; Wu, Wang & Evans 2019) measures whether a paper eclipsed the work before it — later papers cite it instead of its predecessors (+1, disruptive) versus alongside them (−1, consolidating). These IBD papers reshaped their field the most.
Method: CD_5 (5-year forward window) over the PubMed-indexed pool via the NIH iCite citation graph (Funk & Owen-Smith 2017; Wu, Wang & Evans 2019). Eligible: published <= 2021 (full window), >= 3 references, >= 100 citations. Formula: CD5 = (ni − nj) / (ni + nj + nk), in [−1, +1]. Citation graph: NIH iCite. Generated: 2026-06-29.