Can Crohn’s Disease Be Misdiagnosed?

Crohn’s disease is misdiagnosed often enough that researchers have spent decades studying the problem. In one multicenter study, women with Crohn’s faced nearly four times the odds of initial misdiagnosis compared to men, and the median time from first symptoms to a correct diagnosis stretched past a year for female patients. The reasons are varied: Crohn’s shares symptoms with dozens of other conditions, its hallmark features on biopsy are not always present, and the disease can affect any part of the digestive tract, making its presentation wildly inconsistent from one person to the next.

Why Crohn’s Is Difficult to Diagnose Correctly

There is no single test that definitively confirms Crohn’s disease. Diagnosis relies on a combination of clinical symptoms, blood work, stool tests, imaging, endoscopy, and biopsy findings. A textbook case might involve a young adult with chronic diarrhea, abdominal pain concentrated in the lower right side, weight loss, and biopsy showing granulomas (small clusters of immune cells). But many patients do not present this way. Some have upper GI involvement, some have only perianal disease, some present with nothing more than fatigue and iron-deficiency anemia for months before anything else surfaces.

Granulomas, often described as a hallmark of Crohn’s, illustrate the problem. They are far from universal. One retrospective analysis found that detection rates depend heavily on where the biopsy is taken, the size of the specimen, and how many pieces of tissue the endoscopist collects. When five or more specimens were taken, granuloma detection reached about 68%, but smaller or fewer biopsies produced significantly lower rates.¹ Sites in the terminal ileum and colon yielded more granulomas than the rectum, and the detection rate was actually higher in mild-to-moderate disease than in severe disease. That last finding is counterintuitive and means that patients with the most obvious endoscopic damage may paradoxically lack the histological feature clinicians are looking for.¹ Other useful pathological features include deep fissures, a patchy inflammatory pattern, and confluent linear ulcers, but even these are not always reliably observed.²

The IBS Mix-Up

The single most common early misdiagnosis for Crohn’s disease is irritable bowel syndrome.³ The overlap is obvious: both cause abdominal pain, bloating, and changes in bowel habits. IBS is far more prevalent, so when a patient shows up with these complaints and no alarming red flags like bloody stool or significant weight loss, many clinicians reasonably start with the more common explanation. The trouble is that early Crohn’s can look exactly like IBS, especially when the disease is limited to the small bowel where standard colonoscopy may not reach.

Research has shown that a prodromal phase of IBS-like symptoms may actually extend the time it takes to get a Crohn’s diagnosis. Patients with celiac disease and Crohn’s disease both experience this phenomenon, where what looks like functional gut trouble delays recognition of an underlying inflammatory or structural problem.⁴ Interestingly, this effect was not seen in ulcerative colitis, likely because UC tends to present with more obvious bloody diarrhea that prompts earlier investigation.

Crohn’s Disease Versus Ulcerative Colitis

Even once a clinician suspects inflammatory bowel disease, distinguishing Crohn’s from ulcerative colitis is not always straightforward. About 5 to 15% of IBD patients initially receive a label of “IBD unclassified” because their features overlap. The two diseases can produce similar symptoms like diarrhea, urgency, and abdominal cramping, and both cause visible inflammation on colonoscopy. The classic teaching is that UC involves continuous inflammation starting at the rectum and extending proximally, while Crohn’s produces patchy “skip lesions” that can appear anywhere from mouth to anus. In practice, the distinction is not always clean.

Endoscopic ultrasound offers one way to tease them apart. In active ulcerative colitis, the innermost mucosal layer of the bowel wall thickens significantly while the deeper layers stay relatively normal. In active Crohn’s, the opposite pattern appears: the deeper submucosal layer swells while the mucosa stays closer to normal. One study found that combining wall-layer measurements with the presence of nearby lymph nodes yielded a sensitivity above 90% for distinguishing active UC from active Crohn’s.⁵ This technique is not widely used, though, and the distinction gets harder when disease is in remission or when Crohn’s happens to affect only the colon.

Infectious Look-Alikes

Some infections produce gut inflammation that is nearly indistinguishable from Crohn’s, and getting the diagnosis wrong in this scenario can be dangerous.

Intestinal tuberculosis is the most notorious mimic, particularly in parts of the world where TB is common. Both diseases cause ulcers, strictures, and granulomas in the gut, and both tend to favor the ileocecal region. The misdiagnosis rate between these two conditions has been reported at 50 to 70%.⁶ Certain endoscopic clues help: Crohn’s tends to produce longitudinal ulcers and aphthous ulcers, while TB more often causes transverse ulcers. On imaging, Crohn’s favors long-segment involvement with skip lesions, whereas TB tends to show contiguous involvement of the ileocecal area and necrotic lymph nodes. But the only truly exclusive findings for TB are caseation necrosis on biopsy, a positive acid-fast bacillus smear or culture, and necrotic lymph nodes on cross-sectional imaging.⁷ Without those, clinicians are often making a judgment call.

Other infections pose similar risks. Acute terminal ileitis caused by bacteria like Yersinia can be mistaken for early Crohn’s, and is sometimes discovered incidentally during surgery for suspected appendicitis. In a long-term follow-up study, about 6% of patients initially diagnosed with acute terminal ileitis went on to develop Crohn’s disease over a median of 13 years, and none of those who developed Crohn’s had tested positive for Yersinia.⁸ That finding suggests some patients labeled with acute ileitis may have had unrecognized Crohn’s all along.

Parasitic infections present another dangerous overlap. A systematic review of case reports from high-income countries found that parasitic colitis was misdiagnosed in about 69% of cases, with three-quarters of those misdiagnoses being IBD. When patients with strongyloidiasis or amoebiasis were then treated with corticosteroids (standard therapy for IBD flares), outcomes were often severe. Among strongyloidiasis patients who received corticosteroids, 89% developed major complications or died, compared to 17% of those who did not receive them.⁹

Drug-Induced Inflammation That Mimics Crohn’s

Nonsteroidal anti-inflammatory drugs like ibuprofen, naproxen, and meloxicam can cause ulcers and inflammation in the small bowel that look remarkably like Crohn’s disease on endoscopy. The terminal ileum, which is the same location Crohn’s most commonly affects, is a frequent site for NSAID-related damage. Even inflammatory markers that clinicians use to support a Crohn’s diagnosis, like elevated C-reactive protein and fecal calprotectin, can spike from NSAID enteropathy alone.¹⁰

On biopsy, NSAID enteropathy can be genuinely hard to tell apart from Crohn’s.¹¹ The critical difference is that NSAID damage resolves after stopping the drug, whereas Crohn’s does not. A thorough medication history is the simplest tool for avoiding this particular trap. NSAIDs also complicate the picture in another way: a meta-analysis found that using NSAIDs at the time of diagnosis was a risk factor for delayed Crohn’s diagnosis, possibly because the drugs mask or muddy the symptom picture.¹²

Gender Gaps and Diagnostic Delay

Women wait longer for a Crohn’s diagnosis than men. In a multicenter observational study, the median time from symptom onset to diagnosis was about 12.6 months for women compared to 4.5 months for men, and women had nearly four times the odds of initial misdiagnosis.¹³ The reasons are complex, but they likely include a tendency to attribute women’s abdominal symptoms to gynecological conditions, functional disorders, or stress.

Disease location matters too. Crohn’s confined to the ileum (the end of the small intestine) is associated with delayed diagnosis, likely because the ileum is harder to visualize and ileal-only disease may not produce the bloody diarrhea that triggers urgent investigation.¹² Smoking at the time of diagnosis was also flagged as a risk factor for delay in the same meta-analysis, though the mechanism is less clear.

When It Happens to Children

Pediatric Crohn’s presents its own diagnostic challenges. Children may not articulate their symptoms the way adults do, and the disease can initially manifest as growth failure, delayed puberty, or unexplained anemia rather than classic GI complaints. In some documented cases, adolescents with Crohn’s-related weight loss and food avoidance were initially diagnosed with anorexia nervosa, sometimes for extended periods before the underlying inflammatory disease was recognized.¹⁴

The stakes of diagnostic delay in children are particularly high. A study of pediatric IBD patients found that delayed diagnosis of Crohn’s was associated with a 2.5-fold higher rate of strictures and internal fistulas, and every additional month of delay was associated with a measurable decrease in height-for-age. Abdominal pain without other red flags was the symptom most strongly associated with delayed diagnosis in this population.¹⁵ For growing children, months of uncontrolled inflammation can have effects on stature that may not be fully recoverable.

Less Common Mimics Worth Knowing About

Several rarer conditions can produce bowel inflammation that closely resembles Crohn’s.

Behçet’s disease, a systemic vasculitis, can cause deep intestinal ulcers, fistulas, and extra-intestinal symptoms like joint pain and skin lesions that overlap heavily with Crohn’s. Telling them apart can be extremely difficult based on intestinal and pathological findings alone.¹⁶ Behçet’s tends to involve oral and genital ulcers and eye inflammation, but these are not always present at the time of initial GI presentation.

Cancer immunotherapy drugs known as checkpoint inhibitors can trigger colitis that shares many features with both Crohn’s and ulcerative colitis. The colitis caused by anti-CTLA-4 agents typically looks more like UC with continuous superficial inflammation, but it can occasionally produce fistulas and abscesses reminiscent of Crohn’s.¹⁷ As the use of these drugs expands in oncology, this mimic is becoming more common.

In young children, especially infants who develop inflammatory bowel disease symptoms in the first year or two of life, rare genetic (monogenic) disorders can be the true cause. These patients may show endoscopic and biopsy features that look exactly like Crohn’s or UC but are actually driven by a single-gene defect affecting immune function.¹⁸ Genetic testing has become increasingly important for very early onset IBD for exactly this reason: the treatment approach for a monogenic immune disorder is fundamentally different from standard IBD therapy.

Segmental colitis associated with diverticulosis (SCAD) can also create confusion. In one cohort, about 16% of patients initially diagnosed with SCAD were later reclassified as having IBD over a median follow-up of roughly 19 months. Of those, a subset turned out to have Crohn’s disease specifically.¹⁹

How Stool Tests and Imaging Help Sort Things Out

Fecal calprotectin, a protein released by inflamed gut tissue, has become one of the most useful screening tools for distinguishing inflammatory conditions from functional ones like IBS. A meta-analysis confirmed it is a reliable test for separating IBD from IBS.²⁰ Commercially available calprotectin kits have shown overall accuracy ranging from about 76% to 97% for distinguishing IBD from IBS or other types of colitis, depending on the specific kit used.²¹

The test is highly sensitive but not perfectly specific. In one study of patients referred for abdominal pain, elevated fecal calprotectin caught 100% of significant findings on colonoscopy, but its specificity was only about 44%, meaning many patients with elevated levels had no major disease.²² In practical terms, a normal calprotectin result makes IBD very unlikely, but an elevated one does not guarantee it. NSAID use, infections, and other inflammatory conditions can all push calprotectin up.

Capsule endoscopy, where you swallow a tiny camera that photographs the entire small bowel, has proven especially valuable for Crohn’s involving the small intestine, which conventional colonoscopy may not reach. A meta-analysis found that capsule endoscopy had a better diagnostic yield than older small bowel imaging techniques, though it performed comparably to CT and MR enterography.²³ Newer panenteric capsule systems that image the entire gut have shown specificity advantages over MR enterography, particularly in the proximal small bowel, a region where Crohn’s is easily missed by other methods.²⁴

Artificial Intelligence in Crohn’s Diagnosis

AI-assisted analysis of colonoscopy images is an active research area that may eventually reduce misdiagnosis. Systems trained on endoscopic images have been able to differentiate UC from Crohn’s with accuracy above 90%, and to separate IBD from non-IBD conditions with roughly 72% accuracy.²⁵ The lower accuracy for the IBD-versus-non-IBD distinction probably reflects the sheer variety of conditions that can mimic IBD endoscopically.

AI models are also being developed to tackle the Crohn’s-versus-tuberculosis problem. A systematic review of studies using AI for this distinction found accuracy ranging from about 70% to 100%, though all studies to date relied on retrospective data, and real-world performance in clinical settings remains to be proven.²⁶ The technology is promising but still at the point where it would assist rather than replace a gastroenterologist’s clinical judgment. One scenario where it could help most is in settings where the TB-versus-Crohn’s question comes up frequently and experienced specialists are scarce.

What Happens When the Wrong Diagnosis Sticks

The consequences of Crohn’s misdiagnosis fall into two broad categories: harm from missing the real diagnosis, and harm from treating the wrong disease.

When Crohn’s is missed and labeled as IBS or another benign condition, the disease progresses unchecked. Inflammation damages the bowel wall, which can lead to strictures (narrowing), fistulas (abnormal connections between organs), and abscesses. In children, as noted earlier, the cost includes impaired growth. In adults, delayed treatment often means that by the time the correct diagnosis arrives, the disease has progressed to a stage requiring surgery rather than medication alone.

The reverse error, where an infection is mistakenly labeled as Crohn’s and treated with immunosuppressive drugs, can be life-threatening. Beyond the parasitic infection data described earlier, there are case reports of fungal infections worsened dramatically by immunosuppressive therapy given for presumed Crohn’s. One documented case involved paracoccidioidomycosis, a fungal infection endemic to Latin America, which was misdiagnosed as Crohn’s. The immunosuppressive treatment reactivated and spread the infection, significantly increasing the risk of complications and death.²⁷ These cases are individually rare, but they reveal a pattern: the drugs that control Crohn’s suppress the immune system, and suppressing the immune system when the actual problem is an infection you haven’t identified is a recipe for disaster.