Understanding Stool Changes After Surgery

After surgery, you may notice some changes in your stool. It is normal for your bathroom habits to change, especially in the first few days following surgery. Most changes are not serious.

If you have had surgery, you may have made major changes to your diet. Surgery can also affect your stress level and your medication routines. These changes can lead to a different bathroom pattern. Usually, these changes resolve as you recover.

This article will discuss some common stool changes that can happen after surgery. It will also explain which changes are likely to go away on their own and which ones may need medical attention.

Verywell / Hilary Allison


Diarrhea is defined as three or more loose stools per day. Diarrhea can happen if your diet or medicines changed before or after surgery. Diarrhea can also happen the amount of fluid in your body changes, either because you are drinking more, or you received intravenous (IV) fluids in a vein.

It's a good idea to talk to your healthcare provider if you have diarrhea, especially if you also have moderate to severe cramping, a foul odor to the stool, fever, vomiting, or pain. 

Clostridioides difficile (sometimes called C. diff) is a type of bacteria that live in the digestive tract. If you have taken or are still taking antibiotics, these bacteria could build up in your body. Too much C. diff can lead to foul-smelling stools and painful cramping. If left untreated, it can lead to serious health issues.

For that reason, it's best not to ignore diarrhea after your surgery, especially if you are taking antibiotics. To check for bacteria, your doctor may want to perform a stool culture.

Diarrhea lasting for more than 24 hours during the first few days of recovery should be reported to your surgeon immediately.


Going to the bathroom less often doesn't necessarily mean you are constipated. Constipation means you're having fewer than three bowel movements in a week. You may also be constipated if your stools are dry or hard.

Some pain medications can cause constipation, such as the opioids hydrocodone, oxycodone, morphine, and fentanyl.

You could also become constipated if you eat less or eat different things than you normally eat. When your eating habits return to normal, your bathroom habits should, too.

To keep you from becoming constipated, your doctor may recommend a stool softener, a medication that adds water to stools and makes them easier to pass. If prevention doesn't work, a gentle laxative may help.

You might try boosting the fiber in your diet by eating fruits and vegetables. It's also a good idea to drink more water and to move as much as possible. Some people find walking helpful.

Constipation is considered severe if it causes pain, or if you have fewer than two bowel movements in a week. If you have severe constipation, you may need more than one medication to treat the problem.

If you had surgery on your rectum, colon, or digestive tract, don't use an enema without talking to your surgeon.

Call your surgeon if you have not had a bowel movement or passed gas for more than five days. (Passing gas is a sign that your bowel movements are starting to return to normal.)

Also, if you have pain, fever, vomiting, or unusually foul-smelling stools, it's very important to talk to your healthcare team right away.

Black or Tarry Stool

Stool that is black or looks like tar may have blood in it. Most of the time, stools of this color are not considered normal after surgery. Dark stool can be caused by medications such as iron supplements, charcoal, and Pepto-Bismol. Black foods, such as licorice, can also make stools black.

To find out what's causing a black stool, your doctor can perform an fecal occult blood test.

If you have black or tarry stools, it is important to seek medical care even if you have no other symptoms.

Healthy and Unhealthy Stools
 Verywell / Gary Ferster

Clay-Colored Stool

Your stool may be white or clay-colored if you had barium, a chalky liquid, as part of a medical test. Very light stools can also happen if you have taken antacids. Some babies on milk-only diets also have very light stools.

If your stool is white, very light, or clay-colored, it's a good idea to talk to your doctor about it. Stools with little color can sometimes be a sign of a liver condition. Some liver conditions can be dangerous if left untreated.

Call your surgeon if you have white or clay-colored stools and there is no clear explanation for the lack of color.

Green Stool

Green stool is often caused by eating green foods such as spinach, broccoli, or kale. Green food dyes, such as those found in Jell-O, are often to blame for green stool. If you eat something green and it passes quickly through your body, the green color may be more noticeable.

Stool that is very dark green (almost black) is still considered normal. If you are not sure if the stool is dark green or black, smear a tiny amount on a piece of paper.

Red Stool

Red stool is most often the result of diet. Beets, cranberries, tomatoes, and brightly colored foods such as candy and Jell-O can cause red stool. If you've eaten something bright red, a red stool is normal.

If you want to be sure red stool is related to something you ate, you could cut out that particular food to see if the stool color changes.

You may also notice bright red blood in your stool if you have a health condition affecting the end of the digestive tract, such as hemorrhoids, swollen veins in the rectum or anus. Hemorrhoids are often caused by constipation and straining to pass stool.

This bleeding may show up on toilet paper rather than on the stool itself. If you notice this kind of red in your stool, you may want to try a stool softener to keep you from straining.

Bright red stool is sometimes a sign of a serious health condition such as colorectal cancer. For that reason, it's important to talk to your healthcare provider if you notice red in your stool, on toilet paper, or in the toilet.

Call your surgeon if you experience rectal pain, rectal bleeding, lightheadedness, high fever, nausea, or vomiting.

Other Stool Colors

Most changes in stool color are not medical issues.

Food dyes or brightly colored fruits and vegetables can change the color of your stool. In some cases, yellow/orange stool can be a sign of 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.

"Rapid transit time" is also a common culprit. Rapid transit time means food moves through the body quickly and may not be fully digested. Diarrhea can cause rapid transit times and visible color changes in stool.


Surgery can change how often you go to the bathroom. Most of the time, your body will return to its usual patterns in several days. But if you experience diarrhea for longer than 24 hours or constipation for longer than five days, it's important to check in with your doctor. If you have cramping, fever, vomiting, or pain, don't wait to talk to your healthcare team.

Surgery can also change the color of your stool. After surgery, the most important stool colors to notice are black, red, and white. If you see these color changes, talk to your surgeon to find out whether there is cause for concern.

A Word From Verywell

Changes in stool patterns can be stressful, especially after surgery. Some changes are normal and will resolve as you recover. Others may be a sign that a problem is developing. It's always okay to talk to the people on your healthcare team about what's happening after surgery.

Frequently Asked Questions

  • What causes constipation after surgery?

    Constipation after surgery can be caused by certain pain medications, such as opioids. It can also be caused by a change in eating habits, physical inactivity, and anesthesia.

  • What causes black stool?

    Black stool is usually caused by eating certain foods like black licorice, or from taking medications such as iron supplements, charcoal, and Pepto-Bismol. However, it can also indicate bleeding in the upper digestive tract, and it is not normal to see black stool after surgery. You should contact your surgeon or healthcare provider, even if there are no other symptoms.

  • Does anesthesia cause constipation?

    Yes, anesthesia can cause constipation after surgery. When under anesthesia, muscles are paralyzed and intestinal tract movement stops.

21 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Health Utah. Constipation After Surgery is Normal.

  2. Finnerty CC, Mabvuure NT, Ali A, Kozar RA, Herndon DN. The surgically induced stress response. JPEN J Parenter Enteral Nutr. 2013;37(5_suppl):21S-29S. doi. 10.1586/17474124.2014.911659

  3. American College of Surgeons. Medication and Surgery: Before Your Operation.

  4. MedlinePlus. Diarrhea.

  5. Haran JP, Hayward G, Skinner S, et al. Factors influencing the development of antibiotic associated diarrhea in ED patients discharged home: risk of administering IV antibiotics. Am J Emerg Med. 2014;32(10):1195-1199. doi. 10.1016/j.ajem.2014.07.015

  6. University of Michigan Health. Clostridium Difficile Colitis.

  7. John Hopkins Medicine. Constipation.

  8. Müller-Lissner S, Bassotti G, Coffin B, et al. Opioid-induced constipation and bowel dysfunction: a clinical guideline. Pain Med. Published online December 29, 2016:pnw255. doi. 10.1093/pm/pnw255

  9. Harvard Health Publishing. Don't bomb the bowel with laxatives.

  10. MedlinePlus. Constipation.

  11. American Family of Physicans. Management of Constiptation in Older Adults.

  12. MedlinePlus. Black or tarry schools.

  13. John Hopkins Medicine. Barium Swallow.

  14. Tufts Medical Center. Magnesium, Antacids, Oral.

  15. Mount Sinai. Stools - pale or clay - colored.

  16. Rocky Mountain Hospital for Children. Green Poop.

  17. Sutter Health. Blood in Your Stool.

  18. UpToDate. Patient Education: Blood in the stool (rectial bleeding) in adults (Beyond the Basics).

  19. American Cancer Society. Colorectal Cancer Signs and Symptoms.

  20. UC San Diego Health. End Results: What color is your poop and other pressing fecal matters.

  21. Lee TH, Lee JS. Ramosetron might be useful for treating diabetic diarrhea with a rapid small bowel transit time. Korean J Intern Med. 2013;28(1):106. doi. 10.3904/kjim.2013.28.1.106

Additional Reading

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.