Kidney stones do not directly cause diarrhea. The pain from a kidney stone can trigger digestive upset, including loose stools, in some people. But diarrhea is not a standard symptom of kidney stones themselves. If you have a kidney stone and diarrhea, it is more likely related to the pain, an infection, or another separate issue.
What Causes Diarrhea During a Kidney Stone Episode?
The link between kidney stones and diarrhea is indirect. The intense pain from a kidney stone, known as renal colic, can stimulate the vagus nerve. This nerve connects your brain to your digestive system. When it gets overstimulated, it can speed up bowel movements and cause diarrhea or nausea.
Another common cause is a urinary tract infection (UTI) that happens with the stone. The CDC reports that UTIs can cause gastrointestinal symptoms in some people. If the stone blocks urine flow, bacteria can build up and cause an infection. That infection may lead to diarrhea along with fever and chills.
Pain medications are another factor. Many people take ibuprofen, naproxen, or stronger prescription painkillers for kidney stone pain. Some of these drugs can irritate the stomach and cause loose stools. Opioid pain medications in particular are known for causing constipation in most people, but they can cause diarrhea in others.
Can Kidney Stones Cause Diarrhea? What the Research Shows
Research published in the Journal of Endourology has looked at how kidney stones affect the digestive system. The studies found that nausea and vomiting are common during stone passage, but diarrhea is not listed as a primary symptom. In one survey of kidney stone patients, less than 10% reported diarrhea as part of their experience.
There is a separate condition called enteric hyperoxaluria that connects the gut and kidneys. This happens when someone has a bowel disease like Crohn’s disease or has had gastric bypass surgery. In these cases, the gut absorbs too much oxalate, which can lead to kidney stones. But the diarrhea comes from the bowel disease, not the stone itself.
Some people report diarrhea right before or after passing a stone. This is widely claimed in patient forums, but strong clinical evidence is limited. It may be the body’s response to the stress of passing a stone rather than a direct effect.
How to Tell If the Diarrhea Is from Your Kidney Stone or Something Else
If you have a known kidney stone and develop diarrhea, ask yourself a few questions. Did the diarrhea start at the same time as the pain? Is it mild and going away as the pain fades? If yes, it is likely related to the pain response or medication.
If the diarrhea is severe, bloody, or lasts more than 24 hours, it is probably not from the kidney stone. Look for other signs like fever, chills, or vomiting. These could mean you have a kidney infection, which needs medical attention quickly. The National Institute of Diabetes and Digestive and Kidney Diseases warns that a kidney infection can become serious if not treated.
Also check if you have recently changed your diet or started a new medication. Many people drink more water and cranberry juice during a stone episode, which can loosen stools. Some antibiotics for UTIs also cause diarrhea as a side effect.
| Symptom | Likely from Kidney Stone | Likely from Other Cause |
|---|---|---|
| Sharp back or side pain | Yes | No |
| Nausea or vomiting | Yes, common | Possible |
| Diarrhea alone | Unlikely | More likely |
| Diarrhea with fever | Possible infection | Yes, infection |
| Blood in urine | Yes | Possible |
What Actually Helps When Kidney Stone Pain Causes Digestive Upset
If the diarrhea is mild and linked to pain, treating the stone pain often resolves the digestive symptoms. Over-the-counter pain relievers like acetaminophen are less likely to upset the stomach than ibuprofen or naproxen. Ask your doctor which pain medication is safest for you during a stone episode.
Stay hydrated but avoid sugary drinks. Water is best. Sports drinks can make diarrhea worse because of the sugar content. The American Urological Association recommends drinking enough water to produce clear urine, which helps both the stone and the digestive system.
If you are taking antibiotics for a UTI with your stone, do not stop them even if you get diarrhea. Call your doctor instead. They may be able to switch you to a different antibiotic that causes fewer stomach issues. Probiotics can sometimes help with antibiotic-related diarrhea, but check with your doctor first.
Common Misconceptions About Kidney Stones and Diarrhea
One common myth is that passing a kidney stone always causes diarrhea. This is not true. Most people pass stones without any change in their bowel movements. The idea likely comes from the fact that both kidney stones and diarrhea are unpleasant, so people assume they happen together.
Another misconception is that diarrhea means the stone is about to pass. There is no evidence that diarrhea signals the end of a stone episode. The stone passes through the urinary tract, not the digestive tract. They are separate systems that share some nerve connections but do not directly affect each other.
Some people believe that drinking more water will flush out the stone and stop the diarrhea. While staying hydrated is important, it will not directly stop diarrhea. If the diarrhea is from an infection or medication, more water alone will not fix it. You need to address the underlying cause.
When to See a Doctor for Kidney Stones and Diarrhea
You should see a doctor if you have kidney stone symptoms and diarrhea that lasts more than 24 hours. Also go if you have a fever over 101°F, chills, or vomiting. These signs suggest an infection that needs treatment. The CDC reports that kidney infections can lead to sepsis if not treated promptly.
If the diarrhea is bloody or you feel dizzy or faint, seek emergency care. Dehydration from diarrhea can make kidney stone symptoms worse. It can also make it harder for your body to fight an infection. Older adults and people with chronic conditions like diabetes are at higher risk for complications.
Call your doctor if the diarrhea starts after you begin a new medication for the stone. They can tell you if it is a common side effect and whether you should stop the drug. Never stop a prescribed medication without talking to your doctor first.
What to Avoid When You Have Kidney Stones and Diarrhea
Avoid taking more than the recommended dose of pain medication. Some people try to double up on ibuprofen to stop the pain, but this can damage the kidneys and make diarrhea worse. Stick to the dose on the label or what your doctor prescribed.
Do not take antidiarrheal medications without asking a doctor first. Drugs like loperamide (Imodium) can slow down the gut, which might be fine for simple diarrhea. But if the diarrhea is from an infection, stopping it too quickly can trap bacteria in your system. The FDA has warned about serious side effects from using these drugs when they are not needed.
Avoid foods that irritate the gut. Spicy foods, fried foods, and dairy can make diarrhea worse. Stick to bland foods like rice, bananas, and toast until the digestive symptoms settle. This is sometimes called the BRAT diet and is safe for short-term use.
Frequently Asked Questions
Can a kidney stone cause diarrhea and vomiting?
Vomiting is a common symptom of kidney stone pain, but diarrhea is less common. Both can happen together if the pain triggers a strong vagus nerve response.
Does diarrhea mean my kidney stone is passing?
No, diarrhea does not mean the stone is passing. The stone moves through the urinary tract, not the digestive system, so there is no direct connection.
Can kidney stone medication cause diarrhea?
Yes, some pain relievers and antibiotics used for kidney stones can cause diarrhea as a side effect. Check with your doctor if you suspect your medication is the cause.
Should I go to the ER for kidney stone pain and diarrhea?
Go to the ER if you have a fever over 101°F, bloody diarrhea, or severe pain that medication does not help. These could be signs of a serious infection.
