Flares & ER
Every Crohn's patient learns to live with symptoms, but most are never taught what those symptoms actually mean. Abdominal pain, diarrhea, blood in the stool, bloating: these are listed in every Crohn's disease overview, yet few resources explain why the specific character of each symptom matters. Where your pain is located, what your stool looks like, and how your symptoms change over time all carry clinical information about your disease location, behavior, and severity. This guide breaks down the major Crohn's symptoms one by one, explains what each can indicate, and provides practical thresholds for when a change warrants a call to your gastroenterologist (GI).
Abdominal Pain: Location Tells a Story
The location of your Crohn's disease pain is one of the most diagnostically useful signals your body provides. Crohn's can affect any part of the gastrointestinal tract from mouth to rectum, but the terminal ileum is involved in the majority of cases. This means the most common pain pattern is cramping or steady aching in the lower right abdomen, roughly where the appendix sits. This lower right quadrant pain reflects inflammation at the ileocecal valve, the junction between the small and large intestine.
If your pain is more central or around the navel, inflammation may be affecting higher segments of the small intestine. Diffuse abdominal pain spread across multiple regions can suggest more extensive disease involving both the small and large bowel. Left-sided or lower abdominal pain, while less typical, can indicate Crohn's colitis, where inflammation is concentrated in the colon.
The quality of pain matters too. Crampy pain that comes in waves and improves after a bowel movement is common with active inflammation. Steady, worsening pain that does not let up, especially when accompanied by vomiting or abdominal distention, can signal a bowel obstruction caused by a stricture, a narrowed section of intestine from scar tissue. Severe, constant pain with abdominal rigidity is a warning sign of perforation or abscess and requires immediate medical attention.
When to call your GI about pain: Contact your gastroenterologist if you develop a new pain location, if your usual pain changes in character from crampy to constant, or if pain is accompanied by fever, vomiting, or inability to pass gas. Seek emergency care for severe pain that steadily worsens, high fever above 102°F, or signs of dehydration.
Diarrhea: What the Stool Itself Reveals
Diarrhea is among the most common Crohn's symptoms, but the character of your stool varies based on where your disease is active. Understanding these differences can help you and your GI team assess what is happening between scopes.
When Crohn's affects the small intestine, specifically the ileum, diarrhea tends to be large-volume and watery. Inflammation in the ileum disrupts the absorption of water and bile salts, resulting in loose, often urgent stools without much visible blood. When disease is concentrated in the colon, stools are typically smaller in volume but more frequent, and they are more likely to contain visible blood, mucus, or pus. The color of blood in the stool also carries information: bright red blood typically indicates bleeding from the lower colon or rectum, while darker or black stools can suggest bleeding higher in the GI tract.
Stool frequency varies widely. Some patients deal with three to four loose stools a day during mild flares, while severe disease can mean 20 or more bowel movements in a day, including overnight urgency that disrupts sleep. Nocturnal diarrhea, waking at night specifically to have a bowel movement, is a clinical red flag that distinguishes inflammatory bowel disease from many functional conditions like irritable bowel syndrome.
When to call your GI about diarrhea: Report a significant increase in stool frequency over your baseline, any new appearance of blood or mucus, nocturnal diarrhea that is new for you, or diarrhea severe enough to cause signs of dehydration such as dizziness, dry mouth, or dark urine.
Blood and Mucus in the Stool
Seeing blood in your stool is alarming, but it is a recognized feature of Crohn's disease, especially when the colon is involved. Hemorrhage is far more common in colonic Crohn's than in isolated small bowel disease, with studies showing that approximately 85% of significant bleeding events in Crohn's originate from the colon. The bleeding source is typically a deep ulcer, most often in the left colon.
Bright red blood on the surface of stool or on toilet paper usually indicates inflammation or ulceration in the lower colon or rectum. Blood mixed into the stool suggests a source higher in the colon. Black, tarry stools may point to upper GI bleeding, though iron supplements and bismuth-containing medications can also cause dark stools.
Mucus in the stool is another common finding. The inflamed intestinal lining overproduces mucus as a protective response, and it often appears as a clear or yellowish gel coating the stool. Some mucus with a bowel movement is normal for anyone, but a noticeable increase in mucus production, especially combined with other changing symptoms, can indicate rising inflammation.
When to call your GI about blood or mucus: Any new onset of blood in stool warrants a call. If you already have occasional bleeding, report a noticeable increase in volume or frequency, blood that appears darker than usual, or bleeding accompanied by lightheadedness, fatigue, or rapid heart rate, which may indicate anemia from chronic blood loss.
Bloating and Gas: More Than a Dietary Issue
Many Crohn's patients attribute bloating and excess gas to something they ate, but persistent bloating can carry clinical significance. Two mechanisms specific to Crohn's disease drive bloating beyond ordinary dietary intolerance.
The first is stricturing disease. As inflammation heals, scar tissue can narrow the intestinal lumen, creating a stricture that partially blocks the passage of stool and gas. A 2022 review found that 7 in 10 Crohn's patients will develop strictures within 10 years of diagnosis. Early stricture symptoms often look like bloating: distention after meals, cramping, and audible gurgling sounds from the abdomen. As a stricture progresses, symptoms can escalate to nausea, vomiting, and inability to pass gas.
The second mechanism is small intestinal bacterial overgrowth (SIBO). SIBO is roughly 10 times more common in Crohn's patients than in the general population. In SIBO, bacteria proliferate in the small intestine and ferment food earlier in the digestive process than normal, producing excess hydrogen or methane gas. The result is bloating, abdominal pain, and either diarrhea or constipation depending on the predominant gas type. Hydrogen-predominant SIBO tends to cause diarrhea, while methane-predominant overgrowth is more commonly associated with constipation.
When to call your GI about bloating: Report bloating that is new, progressive, or consistently occurs after meals, especially if accompanied by cramping, vomiting, or reduced stool output. These symptoms may indicate a developing stricture that needs evaluation.
Constipation: The Overlooked Crohn's Symptom
Constipation is rarely mentioned in popular Crohn's disease resources, which creates a confusing experience for the many patients who deal with it. Because Crohn's is associated with diarrhea in most public-facing content, patients experiencing constipation sometimes question whether their symptoms are even related to their disease. They are.
Constipation in Crohn's can occur for several reasons. The most clinically significant is a stricture proximal to the rectum: if a narrowed segment of intestine is slowing transit, stool backs up behind it. Medications used to treat Crohn's, including certain antidiarrheal agents and opioid-based pain medications, can also contribute. And as noted above, methane-predominant SIBO can shift the dominant bowel pattern toward constipation.
Some patients alternate between diarrhea and constipation, which can indicate variable disease activity or a partial stricture that intermittently obstructs. This alternating pattern is worth documenting carefully because it gives your GI information about how your disease is behaving over time.
When to call your GI about constipation: Report constipation that is new, especially if it comes with bloating, cramping after meals, or vomiting. If you have not had a bowel movement in several days and are experiencing abdominal distention or pain, contact your provider promptly, as these may be signs of an obstruction.
Building a Symptom Record That Helps Your GI
Individual symptoms are useful data points, but patterns over time are what help your GI team make treatment decisions. A single episode of blood in the stool during a flare is different from gradually increasing blood over several weeks. A day of bloating after a large meal is different from daily postprandial distention that is getting worse.
The most useful symptom log for your GI tracks a few specific things daily: pain location and character, stool frequency and consistency, presence of blood or mucus, and any bloating or gas patterns. This does not need to be elaborate. Brief daily entries create a timeline that can reveal trends invisible in a single office visit, especially changes that develop slowly enough to feel normal until you look back at the record.
Log your symptoms daily with Aidy, especially pain location and stool changes, to build a pattern your GI can use to assess your disease activity and location between scopes.