The small intestine is the long, coiled tube that connects the stomach to the large intestine. It has three parts — the duodenum, the jejunum, and the ileum — and it is where most of the nutrients from food are absorbed into the body. When tissue is removed from the small intestine, a pathologist examines it under a microscope and describes what they see in your pathology report.
This page brings together our guides to conditions found in the small intestine. The articles are grouped by type to help you find the one that matches your diagnosis. Some conditions are cancerous, some are precancerous (not cancer, but a change that can increase the risk of cancer over time), and many are caused by inflammation. Select any article below to learn more.
Cancers of the small intestine
These diagnoses are tumors of the small intestine that are cancerous or have the potential to behave like cancer. Some develop at a spot called the ampulla, where ducts from the liver and pancreas drain into the duodenum. The articles explain how each type is diagnosed and what the details in your pathology report mean.
Adenocarcinoma of the small intestine
Adenocarcinoma is the most common type of cancer in the small intestine. It develops from the gland-forming cells of the lining. This article explains how it is diagnosed and what the details in your pathology report mean.
You may find this helpful if your report says adenocarcinoma of the small intestine, duodenum, jejunum, or ileum.
Ampullary adenocarcinoma is a cancer that develops at the ampulla, where the bile and pancreatic ducts enter the duodenum. This article explains how it is diagnosed and what your report describes.
You may find this helpful if your report mentions ampullary adenocarcinoma, or a cancer of the ampulla of Vater.
Nonampullary adenocarcinoma of the duodenum
Nonampullary adenocarcinoma is a cancer that develops in the duodenum but away from the ampulla. This article explains how it is diagnosed and what your report describes.
You may find this helpful if your report mentions a nonampullary adenocarcinoma of the duodenum.
Well differentiated neuroendocrine tumor
A well differentiated neuroendocrine tumor is a slow-growing tumor that develops from hormone-producing cells in the small intestine. This article explains how it is diagnosed and what your pathology report describes.
You may find this helpful if your report mentions a well differentiated neuroendocrine tumor or a carcinoid tumor of the small intestine.
Precancerous changes
These diagnoses describe noncancerous growths, called adenomas, that develop in the lining of the small intestine. An adenoma is not cancer, but it can slowly change into cancer over time, so adenomas are usually removed. The articles explain what each diagnosis means.
A duodenal adenoma is a precancerous polyp that develops in the duodenum, the first part of the small intestine. This article explains what this diagnosis means and how it is treated.
You may find this helpful if your report mentions a duodenal adenoma.
A nonampullary duodenal adenoma is a precancerous polyp that develops in the duodenum but away from the ampulla. This article explains what this diagnosis means.
You may find this helpful if your report mentions a nonampullary duodenal adenoma.
An ampullary adenoma is a precancerous polyp that develops at the ampulla, where the bile and pancreatic ducts enter the duodenum. This article explains what this diagnosis means.
You may find this helpful if your report mentions an ampullary adenoma, or an adenoma of the ampulla of Vater.
Inflammatory conditions
These diagnoses describe inflammation of the lining of the small intestine. They are not cancer. The articles explain what each diagnosis means and what a pathologist looks for.
Active enteritis means there are signs of ongoing inflammation in the lining of the small intestine. This article explains what this diagnosis means and what a pathologist looks for.
You may find this helpful if your report mentions active enteritis.
Chronic enteritis means there are signs of long-lasting inflammation in the lining of the small intestine. This article explains what this diagnosis means and what may cause it.
You may find this helpful if your report mentions chronic enteritis.
Chronic active enteritis means the lining of the small intestine shows both long-lasting and ongoing inflammation. This article explains what this diagnosis means and what may cause it.
You may find this helpful if your report mentions chronic active enteritis.
Chronic active ileitis means the ileum, the last part of the small intestine, shows both long-lasting and ongoing inflammation. This article explains what this diagnosis means.
You may find this helpful if your report mentions chronic active ileitis, which can be a sign of Crohn’s disease.
Peptic duodenitis is inflammation of the duodenum caused by stomach acid. This article explains what this diagnosis means and what a pathologist looks for.
You may find this helpful if your report mentions peptic duodenitis.
Celiac disease is a condition in which the immune system reacts to gluten and damages the lining of the small intestine. This article explains what a pathologist sees in celiac disease.
You may find this helpful if your report mentions celiac disease, or changes such as villous blunting or increased intraepithelial lymphocytes.
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