Short bowel syndrome – causes, symptoms, diagnosis, treatment, pathology

Short bowel syndrome – causes, symptoms, diagnosis, treatment, pathology

In short bowel syndrome, bowel is another
word for the intestines. It’s a condition that occurs when either
the small intestine and/or the large intestine become physically shorter when a portion is
removed by surgery, or functionally shorter, when a portion is damaged in a way that makes
it nonfunctional. This can lead to poor absorption of water
and vital nutrients from food. Normally, digestion begins when food is chewed
and travels into the stomach where it’s dissolved by stomach acid, enzymes, and physical
churning. Then, it’s sent to the first portion of
the small intestine, which is called the duodenum. This is where more enzymes are added from
the pancreas to digest macronutrients, including proteins, carbohydrates, and fats, while bile
is added from the liver and gallbladder to help absorb fats. It’s also where the absorption of some minerals
like calcium, iron, and magnesium begins. The next section is called the jejunum, and
it has long projections on its surface, giving it a large surface area for absorption. It plays the biggest role in the digestion
and absorption of most nutrients, including the breakdown-products of macronutrients,
zinc, water-soluble vitamins, and fat soluble vitamins, namely A, D, E, and K. The third section is called the ileum, and
it has tight intercellular junctions, allowing it to efficiently absorb fluid and begin concentrating
the intestinal contents. Unlike the jejunum, the ileum is also capable
of undergoing structural and functional adaptations to compensate for the jejunum if needed. The final portion is called the terminal ileum,
and it absorbs vitamin B12 and bile salts which are recycled. It ends with the ileocecal valve, which prevents
intestinal contents from going into the large intestine too quickly and the backward flow
of material. The large intestine functions to absorb water,
electrolytes like sodium and potassium, short-chain fatty acids, and bacteria within it produce
vitamin K. Since each part of the small intestine has
a specialized function, as does the large intestine, the manifestations of short bowel
syndrome depend on which portion is no longer functioning normally. Diarrhea can result from intestinal contents
moving too quickly or from food intolerances due to loss of certain enzymes. This can lead to life-threatening dehydration. An inability to absorb certain vitamins and
minerals can lead to a large range of signs and symptoms, while malabsorption of macronutrients
leads to malnutrition and weight loss. Short bowel syndrome can be present at birth,
but typically occurs when part of the small bowel is removed during surgery. Common conditions requiring this include necrotizing
enterocolitis in babies, and Crohn’s disease in adults. Any condition that injures the small intestine
and makes part of it nonfunctional can cause the condition even if the intestinal length
is normal. Diagnosis includes the medical history, lab
tests looking for nutritional or electrolyte deficiencies or a resulting anemia, imaging
such as an abdominal X-ray, barium studies, or MRI, and endoscopy of the upper and lower
intestines. Treatment depends on the symptoms. Mild cases may require dietary adjustments
with slowly increasing food and water intake, supplements, and diarrhea medications. Severe cases may include total parenteral
nutrition, or TPN, which provides intravenous nutrition and fluids, and an eventual small
bowel transplant. All right, as a quick recap…Short bowel
syndrome occurs when either the small intestine and/or the large intestine become physically
or functionally shorter. This leads to malabsorption of water and nutrients,
and can cause a wide variety of symptoms depending on the section of bowel involved. Diagnosis depends on the medical history,
lab tests, and abdominal imaging, while treatment may include dietary adjustments, diarrhea
medications, and TPN.

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