How Crohn’s Disease Can Affect Kidney Health

While kidney complications are not always front of mind for people living with inflammatory bowel disease (IBD), they are more common than in the general population.

Many of these complications are preventable — or at least manageable — by recognizing risks early and taking steps to protect kidney health in the long run.

People with Crohn’s disease face a higher risk of developing kidney stones, especially calcium oxalate stones. This tends to be the most prevalent kidney-related concern Crohn’s disease patients encounter, according to Alan Moss, MD, the chief scientific officer at the Crohn’s & Colitis Foundation and a professor of gastroenterology at Boston University.

“Kidney stones are common in Crohn’s disease because diarrhea, dehydration, and difficulty absorbing fat and certain nutrients change the chemistry of the urine, which makes stone-forming substances like oxalate and uric acid more likely to crystallize,” Dr. Moss says.

When inflammation from Crohn’s interferes with fat absorption in the gut, unabsorbed fat binds to calcium. Normally, calcium would bind to oxalate and help remove it from your body. But when calcium is “used up” by fat, oxalate is left free to be absorbed into your bloodstream. From there, it travels to your kidneys, where it can crystallize and form stones, says Kirk Campbell, MD, the president of the National Kidney Foundation and chief of the renal division at the Hospital of the University of Pennsylvania in Philadelphia.

Crohn’s can also reduce helpful gut bacteria that degrade oxalate, leaving more oxalate free for absorption, says Fionnuala Cormack, MD, a professor of clinical practice in the division of nephrology at the University of Washington in Seattle, where she cares for patients with kidney stones at the UW Medical Center Northwest Kidney Stone Center.

Dehydration is most likely during a Crohn’s disease flare or after bowel surgery, Moss says, noting that AKI is a frequent cause of a hospital readmission post-op.

Dehydration can also contribute to certain types of kidney stones. “Diarrhea makes urine more concentrated and acidic, both of which increase the risk of uric acid stone formation,” Dr. Campbell says.

Everyone with a Crohn’s diagnosis should pay attention to hydration, especially during a flare or in hot weather, Moss says. Make sure you’re drinking electrolyte-containing fluids and not just plain water if you’re losing a lot of fluid from diarrhea or vomiting.

“A simple rule of thumb is to aim for steady fluid intake across the day, watch for signs of dehydration such as dark urine, dizziness, or reduced urine output, and ask your healthcare team for personalized guidance on when to add oral rehydration solutions or sports drinks,” he says.

Some of the medications used to manage Crohn’s disease require monitoring for possible kidney-related side effects.

Despite the low risk, it’s standard practice for your doctor to monitor kidney function with periodic blood and urine tests if you’re on 5-ASAs or other potentially kidney-active therapies long-term. They’ll also repeat or widen testing if they notice any concerning changes, Moss says.

NSAIDs Although they’re not used to treat Crohn’s itself, nonsteroidal anti-inflammatory drugs like ibuprofen are sometimes taken for pain — and can pose risks, Campbell says. “They can reduce kidney blood flow and contribute to acute kidney injury or worsening chronic kidney disease, especially when someone is already dehydrated.”

Moss adds that NSAIDs can also worsen gut inflammation, especially if you take them in higher doses, making them a double concern for Crohn’s patients.

Biologics Advanced therapies like biologics are not strongly linked to kidney damage, but very rare complications tied to kidney damage have been reported.

“It is still important for clinicians to review other kidney risk factors, monitor labs periodically, and investigate any new changes in kidney function while a patient is on these therapies,” Moss says.

While it’s relatively uncommon, in more severe cases of Crohn’s disease, Moss says “fistulas or severe inflammation can sometimes involve or press on the tubes that drain the kidneys or connect to the bladder.”

“This is one of the clearest settings in which the gut-kidney axis likely matters,” Campbell says, pointing to chronic gut inflammation, imbalance of intestinal bacteria, and increased intestinal permeability driving the conditions for glomerulonephritis.

“It’s a rare complication of Crohn’s disease and is becoming less common with the development of better medications to treat Crohn's,” Cormack says, noting most people will never develop serious kidney problems beyond kidney stones.

Protecting kidney health in Crohn’s disease comes down to a few priorities: hydration, nutrition, monitoring, and disease control. Expert tips include:

Stay hydrated. Aim to drink liquids steadily throughout the day — to around 10 to 13 cups, says Cormack. If you’re losing a lot of fluid, like during a flare, electrolyte drinks may help more than water alone, says Moss.

Get regular checkups. Simple blood and urine tests can catch kidney issues early, even before you notice symptoms. Your IBD team will include routine monitoring as part of long-term Crohn’s care, Cormack says.

Keep your Crohn’s under control. “Good disease control lowers the risk of dehydration, surgery-related complications, and rare inflammation-driven kidney disease,” says Campbell.

Be careful with pain relievers. Avoid frequent or unsupervised use of NSAIDs like ibuprofen, which can stress both your gut and kidneys, especially if you’re already dehydrated or experiencing a flare, says Cormack.

• Crohn’s disease can affect kidney health through dehydration, malabsorption, inflammation, and certain medications and their side effects.
• Most people will not develop severe kidney problems, though kidney stones, especially calcium oxalate stones, are one of the most common extraintestinal complications in people with Crohn’s disease.
• Many kidney-related issues are preventable with the right steps, including staying hydrated, monitoring kidney function through blood and urine tests, and adjusting your diet.