Common Reasons for Stool Changes After Surgery

Pain or cramps in stomach
MarsBars/Getty Images

After surgery you may notice changes in your stool in the days and weeks following surgery. It is absolutely normal to experience a change in your bowel habits, especially in the first few days following surgery, and most changes are not serious. Surgery often causes a major change in your diet, your stress level and your medication regimen. Any and all of these can result in a change in your regular bathroom pattern that typically resolves as your recovery progresses.

It is important to be aware that some stool changes can be a sign of a problem after surgery.


Diarrhea is defined as 4-6 watery/loose stools per day. This can be caused by the change in diet prior to surgery, a change in diet after surgery, medications provided for surgery, or even an increase in the amount of fluids you drink or receive in an IV. Diarrhea should be concerning if it associated with moderate to severe cramping, a foul odor to the stool, fever, vomiting or pain. Diarrhea that lasts more than a day during the first few days of recovery should be reported to the surgeon.

Clostridium difficile, commonly known as C. Diff, is a bacteria that lives in the digestive tract and can become too plentiful in people who have taken or are currently taking antibiotics. This overgrowth can be a serious condition that leads to foul smelling and often painful cramping. For that reason, diarrhea should not be ignored after a procedure, as most surgery patients receive antibiotics. A stool culture can be performed to see if bacteria overgrowth is present.


Pain medications, particularly opioids such as hydrocodone, oxycodone, morphine, Dilaudid, or Fentanyl, can cause constipation. Many patients also eat less when they have had surgery, or eat things that are outside of their normal diet. Many surgeons recommend a stool softener to prevent constipation after surgery, and if prevention does not work, a gentle laxative to treat constipation. Increasing dietary fiber by eating fruits and vegetables, increasing water intake and increasing physical activity in the form of walking can help relieve constipation.

Severe constipation, which is defined as constipation that is causing pain or less than two bowel movements a week, may require multiple medications in order to find relief. Do not use an enema if you had surgery on your rectum, colon or digestive tract without talking to your surgeon.

Black, Dark, or Tarry Stool

Dark stool, or stool that looks black in color, is not normal after surgery and often indicates bleeding in the upper part of the digestive tract. Tarry, sticky looking stool is also not normal. Both of these types of stool can indicate blood in the stool and should be reported to your surgeon unless you were told to expect this after surgery. The vast majority of surgeries do not cause blood to be seen in the stool, and it is not considered normal after a procedure.

Dark stool can be caused by medications, particularly iron supplements, charcoal, and Pepto-Bismol. Black foods, such as licorice, can result in black stool as well. A simple test called an occult stool test can be performed to determine if blood is present or if the change is due to another cause.

If you are experiencing black or tarry stool it is essential to seek treatment.

Less Frequent Stool

Less frequent stool doesn't necessarily mean constipation. If you were told to refrain from food prior to surgery, or you are eating very little after surgery, you can expect to go to the bathroom less than you might normally. You should expect an increase in the number of times per week you use the bathroom when you are eating more regularly, but you should also be aware that you may be seeing the early signs of constipation.

Clay Colored Stool

White or clay colored stool is often a sign of significant liver disease or liver failure. Very light colored stool should be reported to the doctor immediately unless you have recently had a barium as part of a test to examine your digestive tract. Overuse of antacids and a milk only diet (infants) can also result in white stool. Seek treatment for white or clay-colored stools unless there is a clear explanation for the lack of color in the stool.

Green Stool

Green stool is typically caused by eating green foods such as spinach, broccoli, or kale. Green food dyes, such as those found in brightly colored foods such as Jell-O, are often to blame for green stool. Stool that is very dark green, which may be difficult to differentiate from black stool, is still considered normal. If you are unsure if the stool is dark green versus black in color, smear a scant amount of stool on a piece of paper and it will be easier to tell.

Rapid transit times, meaning the amount of time from eating food until having a bowel movement containing that food is short, can also lead to green stools.

Red Stool

Red stool, not to be confused with dark or tarry stool is most often the result of diet. Beets, cranberries, tomatoes and brightly colored foods including candy and Jell-O can cause dramatic red stool that is, in reality, perfectly normal.

Red stool can also indicate bleeding at the very end of the digestive tract, such as the bleeding seen with hemorrhoids. This type of bleeding is more often noted on the toilet paper rather than on the stool itself and is often improved with the use of a stool softener to prevent straining. When in doubt, seek treatment for red stools.

Blue/Purple/Yellow/Orange Stool

Like many other unusual stool colors, these colors are typically the result of food dyes found in brightly colored foods or brightly colored fruits and vegetables. In some cases, yellow/orange stool can indicate high-fat content in the stool and may indicate that the pancreas is not able to do its part in helping the body to digest food.

Stool Colors That Are Concerning

Most changes in stool color are not medical issues. The colors that might indicate a serious issue are red, black (and/or tarry), and white. Other colors are generally the result of diet but may become more pronounced if the individual has diarrhea or a "rapid transit time" which means that food moves from the mouth and through the body very quickly and may not be fully digested. Rapid transit time is often seen in sick children and adults who are experiencing diarrhea, so those with diarrhea are much more likely to see partially digested foods and bright and unusually colored stool.

If you are a parent and think your child with an upset tummy may have food-related changes in their stool due to brightly colored food or beverages, consider changing from red food/drink to blue or green.

A Word From Verywell

Changes in stool color can be alarming, but they are often the result of food dyes that are common in processed foods. If your stool is an unusual color, and you are feeling well, consider changing what you are eating to see if the stool color changes. If you are having bowel movements that are unusual colors and feeling unwell, you should seek medical attention.

View Article Sources