Crohn’s disease is a type of inflammatory bowel disease (IBD), characterized by chronic inflammation that can affect any part of the digestive tract. While its most recognized symptom is persistent diarrhea, the disease process is complex and can paradoxically lead to constipation. Constipation is defined as having fewer than three bowel movements per week or experiencing hard, difficult-to-pass stools. This symptom demands careful attention in the context of IBD.
The Counterintuitive Symptom
The expectation of diarrhea stems from inflammation causing rapid intestinal transit and poor water absorption. However, this generalized understanding can lead to constipation being overlooked. Constipation may occur when inflammation is localized to the lower colon, known as proctitis, which affects the rectum’s function. The resulting inflammation can impede the body’s normal signals for evacuation, leading to stool retention.
Systemic effects of the disease can also contribute to slower gut motility without localized inflammation. Small intestinal bacterial overgrowth (SIBO) is common in Crohn’s and produces methane gas that slows the movement of material through the intestines. This downstream effect of the disease process creates reduced bowel function that manifests as constipation.
Mechanical Causes of Blockage
The most serious causes of constipation stem from structural changes within the bowel. Chronic cycles of inflammation and healing lead to scar tissue deposition, a process called fibrosis, which narrows the intestine’s internal diameter. This narrowing is referred to as a stricture, which physically restricts the passage of stool and digestive contents.
Strictures are a common complication; up to 70% of people with Crohn’s disease may develop one within a decade of diagnosis. A severe stricture can progress to a partial or complete bowel obstruction, which is a medical emergency. Symptoms often include cramping, abdominal distension, nausea, and an inability to pass gas or stool.
Prior abdominal surgeries, often necessary to manage complicated Crohn’s disease, can introduce another mechanical risk: adhesions. Adhesions are bands of internal scar tissue that form between organs or the intestine and the abdominal wall, frequently occurring after any abdominal procedure. These fibrous bands can twist, kink, or compress sections of the intestine. The resulting compression creates a functional blockage that slows or stops stool transit, mimicking a stricture’s symptoms.
Medication and Lifestyle Triggers
Several systemic and behavioral factors common in Crohn’s management can significantly slow gut motility. Pain management is a frequent concern, and certain medications prescribed for disease-related pain can cause constipation. Opioid pain relievers, such as morphine or oxycodone, reduce propulsive peristaltic waves in the colon. This mechanism substantially increases the risk of opioid-induced constipation, a condition where the gut essentially becomes paralyzed.
Iron supplements, often prescribed to manage anemia resulting from chronic blood loss or malabsorption, are another common pharmaceutical culprit. People often make precautionary dietary adjustments that inadvertently trigger constipation. Many patients deliberately avoid high-fiber foods or follow a low-residue diet, fearing the bulk will cause pain or lead to a blockage. However, fiber is necessary to provide the volume needed for healthy bowel movements.
Some individuals reduce fluid intake to limit bathroom visits, which leads to dehydration. Low fluid levels cause the body to absorb more water from the stool, resulting in hard, dry fecal matter that is difficult to pass. Another contributing factor is pelvic floor dysfunction, a condition where chronic straining from prior diarrhea or pain avoidance leads to impaired coordination of the pelvic muscles needed for evacuation. This muscular incoordination creates a functional obstruction, making it difficult to fully empty the bowels.
Diagnosis and Treatment Approaches
When a person with Crohn’s disease reports constipation, the immediate focus is to determine the underlying cause and rule out a mechanical obstruction. Diagnostic imaging, such as a CT scan or Magnetic Resonance Enterography (MRE), is necessary to visualize the bowel lumen and identify any strictures or signs of bowel wall thickening. These studies help distinguish between functional constipation and a structural blockage.
If a mechanical obstruction is ruled out, treatment focuses on lifestyle and non-structural interventions. Patients are typically advised to increase their fluid intake and may be guided to cautiously incorporate soluble fiber, which is gentler than insoluble fiber, into their diet. Osmotic laxatives, such as polyethylene glycol, are often the first-line treatment, as they work by drawing water into the colon to soften the stool.
When the constipation is linked to inflammation, anti-inflammatory medications used to treat the underlying Crohn’s disease are the primary therapeutic approach, as controlling the inflammation should resolve the associated functional issues. For cases linked to pelvic floor dysfunction, specialized biofeedback therapy is an effective treatment to retrain the coordination of the pelvic muscles. If a severe stricture is confirmed, the treatment pathway may involve endoscopic balloon dilation to stretch the narrowed segment or, in more advanced cases, surgical resection to remove the diseased section of the intestine.