Fatty Stool (Steatorrhea) / Greasy Feces Causes

Stool is composed of water, microbes like bacteria, waste substances, enzymes, fiber as well as small amounts of nutrients such as carbohydrates, fat and protein. The fat within the stool does not usually make it oily or greasy. When there is greasiness evident in the stool then there may be some problem with fat digestion and absorption within the gut.  The greasiness of the stool is only a sign of an underlying problem and it is important that the cause is investigated and treated appropriately.

What is steatorrhea?

Steatorrhea is the medical term for abnormally large amounts of fat in the stool. Sometimes the stool may not obviously greasy and steatorrhea is only detected upon conducting laboratory investigations. At other times steatorrhea may be noticed by its tendency to float and for being very bulky although these characteristics of fatty stool may not always be present. Mucus that is mixed with the stool is not steatorrhea although the same conditions could cause fatty stools and mucus in the stool.

The are a number of different causes of steatorrhea. Some of these conditions may be temporary and steatorrhea is short lived. It resolves when the underlying condition is treated or once it resolves on its own. At other times steatorrhea may occur for the long term as the causative condition is chronic. With the latter, especially where it is progressive, the steatorrhea may worsen over time until the greasiness is pronounced and difficult to miss. Apart from diseases, steatorrhea can also occur with the use of certain medication.

Why does stool turn fatty?

Fat in food is usually broken down chemically by bile and digestive enzymes in the gut. Bile is produced by the liver and stored in emulsifies fats making it into smaller globules. Then digestive enzymes known as lipases break down fat in order for it to be absorbed into the body where it is then processed. Most of these nutrients like fat are not wasted. Only a small amount is lost in the stool.

However, if these dietary fats are not digested and absorbed then it travels down the gut to eventually mix with the stool and be passed out with it during defecation. There are three reasons why stool may be fatty:

  • Lack of digestive enzymes to break down fat.
  • Inability to absorb fats.
  • Rapid movement of fats through the bowels which hampers normal digestion and absorption.

Causes of Fatty Stool

The causes of steatorrhea are discussed below according to the area where the problem exists. The gallbladder, pancreas and bowels (especially small intestine) are the main organs for the digestion and absorption of fats. Therefore if these organs are not functioning as normal or diseases the fats may remain in the bowel and pass out with stool. The presence of other symptoms may provide an indication of the underlying cause. However, it is often necessary to conduct further diagnostic investigations to confirm the exact causative condition.

Gallbladder Problems

Bile released from the gallbladder plays an important role in fat digestion. By emulsifying the fats, bile ensures that the fat-digesting enzymes can act on it efficiently. Only when the fats are digested can it be absorbed and therefore removed from the gut.

  • Gallstones are tiny hard masses that form from bile. These stones can block the gallbladder duct or bile ducts and prevent bile from being passed out into the duodenum of the small intestine. Therefore the dietary fats cannot be emulsified.
  • Cholangitis is inflammation of the bile duct which may be due to injury to the duct or infection. The inflammation causes narrowing of the duct and a total blockage may occur with a gallstone that is obstructed within it.
  • Other gallbladder and bile duct disorders include:
    Cholecystitis – inflamed gallbladder.
    Gallbladder cancer.

Pancreas Problems

The pancreas is the main organ to secrete the powerful digestive enzymes needed for fat breakdown. These enzymes, known as lipases, are inactive until it is needed. Any problem with the pancreas where the enzymes are not released will therefore lead to steatorrhea.

  • Pancreatitis is inflammation of the pancreas that can be acute or chronic. It is often associated with alcohol misuse. The enzymes within the pancreas may be prematurely activated leading to tissue injury and inflammation.
  • Pancreatic exocrine insufficiency is a condition where there is insufficient digestive enzymes that are normally secreted from the pancreas thereby impairing digestion. Apart from pancreatitis, it may also be caused by pancreas surgery and disorders like cystic fibrosis.
  • Other conditions:
    Pancreatic cancer

Bowel Problems

Nutrients that are sufficiently digested are absorbed through the walls of the bowels, mainly in the small intestine. Failure of these nutrients to be absorbed means that it will remain in the bowels, mix with stool and is eventually passed out with feces.

  • Inflammatory bowel disease (IBD) is an autoimmune condition where the gut wall becomes inflamed. In one type of IBD known as Crohn’s disease the inflammation can occur anywhere in the gut. The inflammation hampers absorption.
  • Celiac disease is a condition where the immune system reacts to the presence of wheat protein (gluten) in the gut. This leads to inflammation which hampers the intestine’s ability to absorb nutrients.
  • Irritable bowel syndrome (IBS) with diarrhea is a functional bowel disorder where the movement through the bowels are faster than normal. This rapid transit time prevents normal digestion and absorption.
  • Other conditions:
    Diarrhea for any reason.
    Short bowel syndrome


Certain medication can lead to steatorrhea for various reasons. In most instances the disruption in fat digestion and absorption is not intended and occurs as a side effect. However, sometimes this disruption is part of the mechanism of the specific drug.

  • Laxatives can increase bowel motility and if used in excess this can reach a point where normal digestion and absorption is disturbed to the point that steatorrhea occurs.
  • Weight loss drugs that block fat absorption usually by inhibiting enzymes that break down the fats. As a result the dietary fat is passed out in the stool. Example of this type of drug is any medication containing orlistat.

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