MRI-based standard may predict outcomes in perianal Crohn's
The TopCLASS definition identifies healing based on three criteria.
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02/02/2026
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by Doug Brunk
Results from a small multicenter study suggest that a strict MRI-based definition of radiological healing may help predict long-term outcomes for patients with perianal fistulizing Crohn’s disease, a difficult-to-treat complication of inflammatory bowel disease.
For study known as VALIDATE-PERIANAL, presented by Sami Samaan, MD, a research fellow in the Deepak Lab and Research Group at Washington University School of Medicine in St. Louis, at the 2026 Crohn’s & Colitis Congress®, a partnership of AGA and the Crohn’s & Colitis Foundation, held in Las Vegas, evaluated whether a consensus-based MRI definition developed by an international group of experts known as the TopCLASS consortium could be reliably applied in real-world clinical settings and whether it correlated with improved patient outcomes.
According to Dr. Samaan, previous research has shown that clinical closure of perianal fistulas does not always reflect true healing beneath the surface. MRI studies have demonstrated that persistent inflammation may remain even when fistulas appear closed on physical exam, increasing the risk of recurrence. However, until now, there has been no standardized MRI definition of what constitutes true radiological healing.
The TopCLASS definition identifies healing based on three criteria: absence of T2 hyperintensity on MRI, a completely fibrotic fistula tract, and lack of contrast enhancement when contrast is used. Experts reached a 95% consensus on this definition.
To test it, researchers conducted a retrospective, multicenter study from 2021 to 2023 using data from Washington University in St. Louis, St. Mark’s Hospital in London, and Amsterdam University Medical Center, the Netherlands. Out of 977 patients screened, 40 met inclusion criteria after having MRIs locally reported as healed. Independent expert radiologists then re-reviewed the scans using the TopCLASS criteria.
Only 14 patients met the strict definition of radiological healing, highlighting how difficult the endpoint is to achieve. However, outcomes among these patients were markedly better: 93% achieved sustained clinical remission for at least one year, compared with 78% of those who did not meet the criteria for radiological healing. Fistular recurrence at one year was also less frequent in the radiologically healed group (7% vs. 22%).
Secondary outcomes also favored the radiologically healed group over the non-healed group, including lower rates of fistula-related antibiotic use (7% vs. 22%, respectively), seton placement (7% vs. 15%), proctectomy (7% vs. 11%), return to operating room (30% vs. 7%), defunctioning stoma (0% vs. 15%), and hospitalizations (7% vs. 19%).
The study found excellent inter-reader reliability, with agreement exceeding 95%. “This means that our definition was objective, easy to use, and highly reproducible across different sectors,” Dr. Samaan said.
He acknowledged limitations of the study, including its small sample size, retrospective design, and lack of comparison with data on quality of life.
“For future directions, we have ongoing funded work to validate this definition in a larger retrospective and prospective cohort,” Dr. Samaan said. “We're also incorporating radiomics and AI in collaboration with biomedical engineers to better understand fistula healing response on MRI.”
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The guidelines emphasize four-hour gastric emptying studies over two-hour testing. How do you see this affecting diagnostic workflows in practice?
Dr. Staller: Moving to a four-hour solid-meal scintigraphy will actually simplify decision-making. The two-hour reads miss a meaningful proportion of delayed emptying; standardizing on four hours reduces false negatives and the “maybe gastroparesis” purgatory that leads to repeat testing. Practically, it means closer coordination with nuclear medicine (longer slots, consistent standardized meal), updating order sets to default to a four-hour protocol, and educating front-line teams so patients arrive appropriately prepped. The payoff is fewer equivocal studies and more confident treatment plans.
Metoclopramide and erythromycin are the only agents conditionally recommended for initial therapy. How does this align with what is being currently prescribed?
Dr. Staller: This largely mirrors real-world practice. Metoclopramide remains the only FDA-approved prokinetic for gastroparesis, and short “pulsed” erythromycin courses are familiar to many of us—recognizing tachyphylaxis limits durability. Our recommendation is “conditional” because the underlying evidence is modest and patient responses are heterogeneous, but it formalizes what many clinicians already do: start with metoclopramide (lowest effective dose, limited duration, counsel on neurologic adverse effects) and reserve erythromycin for targeted use (exacerbations, bridging).
Several agents, including domperidone and prucalopride, received recommendations against first-line use. How will that influence discussions with patients who ask about these therapies?
Dr. Staller: Two points I share with patients: evidence and access/safety. For domperidone, the data quality is mixed, and US access is through an FDA IND mechanism; you’re committing patients to EKG monitoring and a non-trivial administrative lift. For prucalopride, the gastroparesis-specific evidence isn’t strong enough yet to justify first-line use. So, our stance is not “never,” it’s just “not first.” If someone fails or cannot tolerate initial therapy, we can revisit these options through shared decision-making, setting expectations about benefit, monitoring, and off-label use. The guideline language helps clinicians have a transparent, evidence-based conversation at the first visit.
The guidelines suggest reserving procedures like G-POEM and gastric electrical stimulation for refractory cases. In your practice, how do you decide when a patient is “refractory” to medical therapy?
Dr. Staller: I define “refractory” with three anchors.
1. Adequate trials of foundational care: dietary optimization and glycemic control; an antiemetic; and at least one prokinetic at appropriate dose/duration (with intolerance documented if stopped early).
2. Persistent, function-limiting symptoms: ongoing nausea/vomiting, weight loss, dehydration, ER visits/hospitalizations, or malnutrition despite the above—ideally tracked with a validated instrument (e.g., GCSI) plus nutritional metrics.
3. Objective correlation: delayed emptying on a standardized 4-hour solid-meal study that aligns with the clinical picture (and medications that slow emptying addressed).
At that point, referral to a center with procedural expertise for G-POEM or consideration of gastric electrical stimulation becomes appropriate, with multidisciplinary evaluation (GI, nutrition, psychology, and, when needed, surgery).
What role do you see dietary modification and glycemic control playing alongside pharmacologic therapy in light of these recommendations?
Dr. Staller: They’re the bedrock. A small-particle, lower-fat, calorie-dense diet—often leaning on nutrient-rich liquids—can meaningfully reduce symptom burden. Partnering with dietitians early pays dividends. For diabetes, tighter glycemic control can improve gastric emptying and symptoms; I explicitly review medications that can slow emptying (e.g., opioids; consider timing/necessity of GLP-1 receptor agonists) and encourage continuous glucose monitor-informed adjustments. Pharmacotherapy sits on top of those pillars; without them, medications will likely underperform.
The guideline notes “considerable unmet need” in gastroparesis treatment. Where do you think future therapies or research are most urgently needed?
Dr. Staller: I see three major areas.
1. Truly durable prokinetics: agents that improve emptying and symptoms over months, with better safety than legacy options (e.g., next-gen motilin/ghrelin agonists, better-studied 5-HT4 strategies).
2. Endotyping and biomarkers: we need to stop treating all gastroparesis as one disease. Clinical, physiologic, and microbiome/omic signatures that predict who benefits from which therapy (drug vs G-POEM vs GES) would transform care.
3. Patient-centered trials: larger, longer RCTs that prioritize validated symptom and quality-of-life outcomes, include nutritional endpoints, and reflect real-world medication confounders.
Our guideline intentionally highlights these gaps to hopefully catalyze better trials and smarter referral pathways.
Dr. Staller is with the Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston.