Inflammatory bowel disease (Crohn disease): Clinical sciences

Inflammatory bowel disease, or IBD for short, is a condition characterized by chronic gastrointestinal tract inflammation that can be subdivided into Crohn Disease and Ulcerative Colitis. Crohn Disease, or CD, can affect any part of the GI tract, mouth to anus, and is characterized by transmural skip lesions, which can lead to abdominal pain, diarrhea, fatigue and fever. Management is based on the severity of disease and it can be categorized as mild to moderate, moderate to severe, or severe.

Now, when evaluating a person with suspected CD, you should first perform an ABCDE assessment to determine if they are stable or unstable. They might present with signs of shock like tachycardia and hypotension. Because of the high mortality-risk in these individuals, it is essential to hospitalize them, obtain intravenous access, and start them on IV fluids. Once they are stable, you should determine the cause of their instability, which can be small bowel obstruction, or SBO for short, or sepsis.

Alright, individuals with SBO typically report severe nausea, vomiting, and the absence of flatus, while physical exam might reveal a distended abdomen and high pitched, tinkling, bowel sounds. An abdominal X-ray will show dilated loops of small bowel with air-fluid levels.

Now, when it comes to individuals with sepsis, which often occurs from an abscess, they might report fever, fatigue, localized pain and sometimes a mass in the perianal area. On a physical exam, you might be able to palpate an abdominal or perianal mass, but sometimes you’ll need to use a CT or MRI of the abdomen and pelvis to detect the abscess.

As for the treatment, all unstable individuals should be hospitalized, get IV antibiotics and a surgery consultation for laparoscopy or abscess drainage. Additionally, for an SBO, you should place a nasogastric tube for suction.

Ok, let’s switch gears and talk about stable individuals. The first step is to obtain a focused history and physical exam. History typically reveals postprandial abdominal pain, usually in the right lower quadrant, and non-bloody diarrhea. However, if the disease is in the colon, the patient might report bloody diarrhea. Additionally, they may report fatigue, weight loss, and fever, as well as extraintestinal manifestations such as joint or eye pain, skin findings like tender red spots that indicate erythema nodosum and painful ulcerations associated with pyoderma gangrenosum.

Now, since CD is transmural inflammation, some individuals develop penetrating and stricturing disease. This can lead to complications such as strictures, fistulas, phlegmon, or abscesses. If there are complications, a physical exam usually reveals a tender abdomen and sometimes a palpable abdominal or perianal mass, from stricture or an abscess. Additionally, a skin exam might reveal fistula tracts.

Alright, to differentiate IBD from other diagnoses with similar presentations, such as Irritable Bowel Syndrome or C.difficile colitis, you should obtain stool laboratory studies. Fecal calprotectin is a marker of colon inflammation. Since IBS does not cause colon inflammation, having a positive fecal calprotectin would increase our suspicion for IBD. Similarly, negative stool studies for infectious microbiology help rule out C.difficile colitis. Next, you should check blood work, which may reveal anemia, dehydration, malnutrition, and elevated inflammatory markers such as ESR and CRP.

If the H&P, stool study, and lab findings suggest IBD, the next step is to confirm the diagnosis with an ileocolonoscopy with biopsy. You may observe discontinuous deep linear serpiginous ulcerations, which usually skip the rectum but commonly involve the ileum and cecum. Typical biopsy findings of CD include transmural chronic inflammation with granulomas.

In addition to endoscopy, a person with suspected CD should have a magnetic resonance enteroscopy, or MRE for short, to evaluate their small bowel. An MRE can reveal bowel thickening from strictures, organ connections from fistulas, and mesenteric fibrofatty proliferation, also called creeping fat. Finally, if they have symptoms such as colicky abdominal pain with nausea, vomiting, or anorexia, an esophagogastroduodenoscopy, or EGD, should be used to check for upper gastrointestinal involvement.

Once you’ve confirmed the diagnosis of CD, you should determine its severity based on signs and symptoms such as abdominal pain, presence of bloody diarrhea, nausea, vomiting, weight loss, anemia, presence of complications, and how much CD impacts quality of life. Using these findings, CD can be subdivided into three main categories: mild to moderate, moderate to severe, and severe.