context: Crohn's disease causes inflammation in part of your digestive system. Crohn's can affect any part of it, but most often it affects your small intestine and colon. Crohn's and another disease, called ulcerative colitis, belong to a group of diseases known as inflammatory bowel disease. There's no cure, but treatment can ease your symptoms and help you enjoy a full, active life. People with Crohn's disease can have severe symptoms followed by periods of no symptoms that can last for weeks or years. The symptoms depend on where the disease happens and how severe it is. You might notice: Chronic diarrhea, often bloody and containing mucus or pus Weight loss Fever Abdominal pain and tenderness Feeling of a mass or fullness in the abdomen Rectal bleeding Crohn's causes two types of complications: Local, which affect just the intestines Systemic, which affect your whole body. You might hear them called extraintestinal complications. Local complications of Crohn's include: Abscess: This pocket of pus happens from bacterial infection. It can form on the walls of your intestines and bulge out. Or you might get one near your anus that looks like a boil. You'd notice swelling, tenderness, pain, and fever. Bile salt diarrhea: Crohn's disease most often affects the ileum, the lower end of your intestine. This part usually absorbs bile acids, which your body creates to help it absorb fat. If your body can't process the fat, you could get this type of diarrhea. Fissure: This is a painful tear in the lining of the anus. It can cause bleeding during bowel movements. Fistula: Sores or ulcers can turn into openings called fistulas that connect two parts of your intestine. They can also tunnel into nearby tissues, like the bladder, vagina, and skin. Malabsorption and malnutrition: Crohn's affects your small intestine, the part of your body that absorbs nutrients from food. After you've had it for a long time, your body may no longer be able make the most of what you do eat. Small intestinal bacterial overgrowth ( SIBO): Your gut is full of bacteria that help you break down food. When this happens higher up in your digestive tract than normal, you can get gas, bloating, belly pain, and diarrhea. Strictures: These narrowed, thickened areas of your intestines result from the inflammation that comes with Crohn's. They can be mild or severe, depending on how much of your intestine is blocked. Symptoms include cramping, abdominal pain, and bloating. Systemic complications include: Arthritis: Joint inflammation, which leads to pain, swelling, and a lack of flexibility, is the most common complication. There are three types of arthritis that sometimes come with Crohn's: Peripheral: This type affects large joints in your arms and legs, like your elbows, knees, wrists, and ankles. Axial: This type affects your spine or lower back (the doctor will call it your sacroiliac joint). Ankylosing spondylitis: This more serious type of spinal arthritis is rare among people with Crohn's, but it can happen. It can also lead to inflammation in your eyes, lungs, and heart valves. Skin problems: These are the second most common systemic complication. Those most often linked to Crohn's disease include: Erythema nodosum: These small, tender, red nodules usually show up on your shins, ankles, and sometimes your arms. Pyoderma gangrenosum: These pus-filled sores often follow an injury or other skin trauma. They often appear on your legs but can show up anywhere. Skin tags: These small flaps of skin are common in people with Crohn's, especially around the anus or hemorrhoids. Mouth ulcers: You might hear them called canker sores. They form between your gum and lower lip or along the sides and bottom of your tongue. Bone loss: Medications like steroids can lead to bone loss, a condition known as osteoporosis. They can: Stop your body from absorbing calcium, which your body needs to build bone Make your body get rid of calcium when you pee Boost production of cells that break down bone Lower the number of cells that help form bones Lower your body's output of estrogen. Estrogen also helps build bone. The proteins that cause inflammation change the pace at which old bone is removed and new is formed. Vitamin D deficiency. If your body can't absorb vitamin D because of Crohn's damage to the small intestine or part of your small intestine has been removed, you're less likely to be able to absorb calcium and make bone. Eye problems: Over time, the inflammation in Crohn's, or sometimes the other complications that come with it, can affect your eyes. Common conditions include: Episcleritis: Inflammation of the area just below the conjunctiva (the clear tissue that covers the inside of your eyelids and the white of your eye) is the most common complication of Crohn's. It can affect one eye or both. You'll notice pain, itching, burning, and intense redness, but it won't hurt your vision. Scleritis: This condition causes a constant pain that gets worse when you move your eyes. Uveitis: This is a painful inflammation of the uvea, the middle layer of your eye. It can cause blurry vision, light sensitivity, and redness. Kidney problems: These organs can be affected by Crohn's because they play a role in processing waste and are located near your intestines. Potential issues include: Kidney stones: They're a common problem with Crohn's. A salt called oxalate gets absorbed into your kidneys and can turn into stones. Uric acid stones: These kidney stones form because your body can't absorb all the uric acid it makes. Hydronephrosis: This happens when the ileum (where the small intestine meets the large) swells from Crohn's and puts pressure on your ureter, the tube that carries urine from your kidney to your bladder. When urine can't drain like it should, your kidney swells and scar tissue can form. Fistulas: In addition to forming within your intestines, fistulas can also form between the intestine and other organs, like the bladder or ureter. Liver problems: Your liver processes everything you eat and drink. It can get inflamed as a result of Crohn's treatment or the disease itself. You're only likely to notice low energy and fatigue unless you develop a more serious problem. Among the most common issues: Fatty liver disease: When your body doesn't process fats as well, they can build up in your liver. Steroids can help. Gallstones: When Crohn's affects the ileum (where your small intestine meets the large intestine), it can't process bile salts, which help cholesterol dissolve. The cholesterol can form into stones that block the opening between the liver and the bile duct. Hepatitis: Chronic, long-term liver inflammation can result from Crohn's disease itself. Pancreatitis: Inflammation of the pancreas can result from both gallstones and medications. It can cause pain, nausea, vomiting, and fever. Physical development problems: Crohn's can start at any age. When kids get Crohn's, parents are likely to notice: Growth failure: Kids with Crohn's are likely to be shorter and weigh less than those without. They may stop getting taller before symptoms start. Delayed puberty: Kids with Crohn's are likely to start puberty later. The cause of Crohn's disease is unknown. It has often been thought of as an autoimmune disease, but research suggests that the chronic inflammation may not be due to the immune system attacking the body itself, but rather a result of the immune system attacking a harmless virus, bacteria, or food in the gut. A few things can make you more likely to get Crohn's disease: Genetics: Crohn's disease is often inherited. About 20% of people with Crohn's disease may have a close relative with either Crohn's or ulcerative colitis. In addition, Ashkenazi Jews are at greater risk for the disease. Age: While Crohn's disease can affect people of all ages, it's primarily an illness of the young. Most people are diagnosed before age 30, but the disease can happen in people in their 50s, 60s, 70s, or even later in life. Smoking: This is the one risk factor that's easy to control. Smoking can make Crohn's more severe and raise the odds that you'll need surgery. Medications: nonsteroidal anti-inflammatory drugs like ibuprofen, naproxen, and similar medications don't cause Crohn's disease, but they can lead to inflammation of the bowels that makes it worse. The world around you: People who live in urban areas or industrialized countries are more likely to get Crohn's. Diet: if you eat a lot of high-fat or processed foods, your odds of Crohn's could go up. Infections: Bacteria linked to Crohn's include Mycobacterium avium paratuberculosism, which causes a similar condition in cattle, and a type of E. coli. Doctors use many tests to distinguish Crohn's disease from other conditions like ulcerative colitis. First, your doctor will review your medical history and talk about your symptoms. Your doctor might want to do some lab tests, like: Blood tests, including blood counts Stool samples to rule out infections as the cause of diarrhea Imaging tests or endoscopy: Your doctor might send you to a specialist called a gastroenterologist to get one of these: Balloon-assisted enteroscopy: This test uses balloons that inflate and deflate to pull a flexible tube called an endoscope through your small intestine. A tiny camera on one end gives a view of the inside of your guts. Capsule endoscopy : You'll swallow a tiny, pill-sized camera to give the doctor a closer look at your small intestine. Colonoscopy or sigmoidoscopy: These give the doctor a clear picture of your intestines and let them take a tissue sample to study. Computed tomography ( CT) scan: This test uses X-rays to make detailed images of your internal organs. Magnetic resonance imaging ( MRI): This shows your doctor a clear picture of the inside of your body without using radiation. Upper endoscopy: The doctor does this to see your esophagus, stomach, and first part of the small intestine, called the duodenum. With Crohn's disease, you have periods of symptoms that can last for days, weeks, or months, followed by periods of remission when you have no symptoms. Remissions can last days, weeks, or years. Things that worsen Crohn's disease include: Infections (including the common cold) Cigarette smoking Certain anti-inflammatory drugs (such as aspirin and ibuprofen) Though treatments can't cure Crohn's disease, they can help most people lead normal lives. Medication Crohn's disease is treated primarily with medications, including: Anti-inflammatory drugs. Examples include mesalamine ( Asacol, Lialda, Pentasa), olsalazine ( Dipentum), and sulfasalazine ( Azulfidine). Side effects include upset stomach, headache, nausea, diarrhea, and rash. Corticosteroids, a more powerful type of anti-inflammatory drug. Examples include budesonide ( Entocort) and prednisone or methylprednisolone ( Solu- Medrol). If you take these for a long time, side effects can be severe and may include bone thinning, muscle loss, skin problems, and a higher risk of infection. Entocort has fewer side effects. Immune system modifiers such as azathioprine ( Imuran) and methotrexate ( Rheumatrex). It can take up to 6 months for these drugs to work. These drugs cause a higher risk of infections that can be life-threatening. Antibiotics such as ciprofloxacin ( Cipro), metronidazole ( Flagyl), and others. Flagyl can cause a metallic taste in the mouth, nausea, and tingling or numbness of the hands and feet. Cipro can cause nausea and tears in the Achilles tendon. Drugs for diarrhea. Biologic medicines, such as adalimumab ( Humira), adalimumab-atto ( Amjevita), certolizumab pegol ( Cimzia), infliximab ( Remicade), infliximab-abda ( Renflexis), infliximab-dyyb ( Inflectra), natalizumab ( Tysabri), ustekinumab ( Stelara), and vedolizumab ( Entyvio). Once you start treatment, your doctor will check to see how well it works within several weeks. You'll continue until you reach remission. When that happens, your doctor may prescribe what he calls "maintenance therapy" to keep your symptoms at bay. If you don't get better, you'll need more aggressive treatment. Your doctor may suggest you take nutritional supplements, too. Surgery About 66% to 75% of people with Crohn's disease will need surgery. Surgery is done to treat complications of the disease or when medications don't help. Common procedures include: Anastomosis: Your surgeon removes the diseased part of the bowel and joins the two healthy ends together. This surgery can allow many people to remain symptom-free for years, but it isn't a cure. Crohn's disease often comes back at the site of the anastomosis. Ileostomy: You might need this if your rectum is diseased and the doctor can't use it for an anastomosis. This procedure connects your intestine to the skin of your torso. The result is an opening in the skin that can collect waste products in a special pouch that you empty. While foods don't appear to cause Crohn's disease, soft, bland foods may cause less discomfort than spicy or high-fiber foods when the disease is active. Most doctors try to be flexible in planning the diets of their Crohn's disease patients. You might also try an elimination diet, which can help you figure out which foods trigger Crohn's symptoms. You'll remove things from your diet one at a time to and see what happens. Work with your doctor or a dietitian to make sure you don't miss out on any nutrients while you're doing it.