What Causes Stones in the Pancreas?

Pancreatic stones form when calcium-rich deposits build up inside the ducts of the pancreas, almost always as a consequence of chronic pancreatitis. The stones are primarily made of calcium carbonate mixed with proteins and phosphates, and they develop gradually as repeated bouts of inflammation change the chemistry of pancreatic juice. Alcohol use is the single most recognized driver, but the causes turn out to be surprisingly varied, ranging from genetic predispositions and metabolic disorders to smoking and even tropical geography.

What the Stones Are Actually Made Of

Unlike kidney stones, which are commonly built from calcium oxalate, pancreatic stones are dominated by calcium carbonate. Detailed structural analyses have shown that these stones consist of calcium carbonate as their major component, along with phosphates and protein content, and may also contain aragonite, a specific crystal form of calcium carbonate.¹ The protein embedded in the stones includes remnants of a pancreatic secretory protein called lithostathine, which plays a complicated role in stone formation discussed below. Infrared spectroscopy of these stones reveals organic bands corresponding to protein amides, confirming that they are not pure mineral but a mix of biological and mineral material.

Understanding the composition matters because it shapes how stones are treated. Calcium carbonate is relatively brittle compared to some other biological stones, which is one reason shock-wave lithotripsy can be effective at shattering them. The protein matrix, however, can make certain stones tougher and stickier, sometimes anchoring them firmly to the duct wall.

The Central Role of Chronic Pancreatitis

Pancreatic stones rarely appear in a healthy pancreas. In the vast majority of cases, they are a downstream consequence of chronic pancreatitis, a condition in which the gland becomes progressively inflamed and scarred. One large multicentre study of 1,500 patients with chronic pancreatitis found that about 60% had calcifications visible on imaging.² Pancreatic stones are common in adults with chronic pancreatitis, occurring in up to 60% of all patients and up to 90% of those with alcohol-related disease.³

The mechanism works roughly like this. Chronic inflammation damages the cells lining the pancreatic ducts. Damaged ducts produce juice with an altered balance of proteins and bicarbonate, which normally keep calcium dissolved. When that balance tips, calcium precipitates out and begins forming tiny plugs of protein and calcium. Over time, these plugs mineralize into hard stones. The process feeds on itself: stones block the duct, the blockage worsens inflammation, and more stones form in the stagnant fluid upstream.

The Lithostathine Puzzle

The pancreas normally secretes a protein called lithostathine (also known as Reg protein or pancreatic stone protein) into its juice. As its name implies, lithostathine was originally believed to prevent stone formation by inhibiting the growth and nucleation of calcium carbonate crystals.⁴ The thinking was straightforward: if the pancreas makes a stone-blocking protein, then stones form when that protein is deficient or overwhelmed.

The reality is murkier. Later research revealed that lithostathine is unlikely to be a physiologically relevant stone inhibitor and may actually contribute to stone formation.⁵ In certain conditions, the protein can undergo a structural change, essentially transforming from a soluble molecule into an insoluble fibrillar form that acts as a scaffold for calcium carbonate crystals. So the very protein that was supposed to protect the ducts may seed the stones instead. This flip from protective to harmful likely depends on the local environment inside the duct, including pH, calcium concentration, and the degree of tissue damage.

Alcohol and Smoking

Alcohol is the most frequently cited cause of chronic pancreatitis in Western countries, and by extension, the most common reason people develop pancreatic stones. Heavy, prolonged drinking damages the pancreatic acinar cells and changes the composition of pancreatic secretions, making them more viscous and protein-rich. That sets the stage for the protein plugs described above. In the 1,500-patient multicentre study, alcoholic aetiology was independently associated with calcifications, with roughly 1.8 times the odds compared to non-alcoholic causes.²

Smoking is an independent accelerator that often gets overlooked. A study tracking CT findings in chronic pancreatitis patients found that continued smoking was a strong predictor of worsening calcification. In multivariate analysis, smokers had roughly ten times the odds of seeing their calcifications progress compared to non-smokers. Heavy smokers, those going through a pack or more a day, had dramatically higher odds still.⁶ The amount smoked mattered in a dose-dependent way: light smokers saw their calcification odds rise, but heavy smokers faced a far steeper increase. Because many heavy drinkers also smoke, the two habits compound each other.

Genetic Susceptibility

Not everyone who drinks heavily develops chronic pancreatitis, and not everyone with chronic pancreatitis forms stones. Genetics help explain the variation. The strongest genetic risk factors involve variations in genes called PRSS1, SPINK1, CFTR, and to a lesser extent CTRC and CASR.⁷ These genes encode proteins involved in regulating digestive enzymes inside the pancreas. When the regulation fails, enzymes activate prematurely and start digesting the gland from the inside, triggering inflammation.

What research increasingly shows is that a single genetic variant rarely causes pancreatitis on its own. Most patients with recurrent or chronic pancreatitis carry multiple variants, sometimes in the same gene, sometimes across different genes, often coupled with environmental stressors like alcohol or smoking.⁷ This “multiple hits” model explains why two people with the same drinking history can have very different outcomes: one might carry two susceptibility variants that lower the threshold for chronic pancreatitis, while the other does not.

The CFTR gene is the same one mutated in cystic fibrosis, and certain milder CFTR variants increase the risk of pancreatitis without causing full-blown cystic fibrosis. Cystic fibrosis-related pancreatitis tends to be more common in individuals with milder forms of CF who still have some pancreatic function.³

Metabolic and Anatomical Triggers

Elevated blood calcium, most often caused by an overactive parathyroid gland, is a recognized metabolic risk factor. Hypercalcemia may predispose pancreatic acinar cells to abnormally sustained calcium levels inside the cell, which triggers premature activation of digestive enzymes and pancreatitis.⁸ At the same time, excess calcium in the pancreatic juice makes precipitation into calcium carbonate crystals more likely. The metabolic insult and the stone-forming chemistry reinforce each other.

Anatomy can also contribute. Pancreas divisum is a congenital variant in which the two embryonic halves of the pancreas fail to fuse properly, leaving the majority of pancreatic juice draining through a smaller-than-usual duct. Over a ten-year period, one multi-centre study documented patients with both pancreas divisum and dorsal duct stones in the setting of chronic pancreatitis.⁹ The narrow outflow creates higher pressure and slower drainage, conditions that favor both chronic pancreatitis and stone formation. Pancreas divisum is not rare, showing up in a meaningful fraction of the general population, but only a small subset of those individuals ever develop pancreatitis or stones. As with the genetic variants, the anatomy seems to lower the threshold rather than guarantee problems.

Tropical Pancreatitis

In developing countries across the tropics, a distinctive form of chronic non-alcoholic pancreatitis produces some of the largest and densest pancreatic stones seen anywhere. Tropical chronic pancreatitis strikes younger people, often in their teens or twenties, and progresses aggressively toward diabetes and severe pancreatic insufficiency.¹⁰ Large intraductal calculi are a hallmark of the diagnosis, and the stones often fill the main pancreatic duct extensively.

Earlier theories blamed malnutrition or toxins from cassava, a dietary staple in some affected regions. Those explanations have largely been disproven. Current thinking emphasizes genetic risk factors, with variants in SPINK1, cathepsin B, chymotrypsin C, CFTR, and carboxypeptidase A1 predicting risk of tropical calcific pancreatitis.¹¹ Some researchers have also explored whether micronutrient deficiency and oxidative stress play a role, but that work is still evolving. The disease’s clinical picture has shifted over recent decades: it now appears in somewhat older patients with less severe initial symptoms, possibly because of improvements in nutrition and earlier detection through imaging.

Consequences Beyond Pain

The most immediate problem pancreatic stones cause is pain. Stones mechanically irritate the duct lining and block the flow of pancreatic juice, creating pressure that produces severe, recurrent abdominal pain. Over time, the obstruction and ongoing inflammation destroy the functional tissue of the pancreas. Two major consequences follow.

First, the exocrine function of the gland deteriorates. The pancreas can no longer produce enough digestive enzymes, leading to poor fat absorption and greasy, foul-smelling stools, a condition called steatorrhoea. Second, the endocrine function suffers as the insulin-producing islet cells are damaged by the surrounding fibrosis. In tropical pancreatitis, the condition called fibrocalculous pancreatic diabetes affects young individuals and runs an aggressive course toward diabetes, calculi, and exocrine failure.¹²

There is also a cancer connection. Long-standing chronic pancreatitis with stones has been linked to an elevated risk of pancreatic cancer. Clinicopathologic studies have documented cases where pancreatic cancer was diagnosed years after the initial discovery of stones, with stones found embedded within the tumor and signs of prolonged chronic inflammation throughout the surrounding tissue.¹³ In tropical calcific pancreatitis, the estimated relative risk of pancreatic cancer compared to the general population has been reported as strikingly high.¹⁴ Whether the stones themselves drive the cancer or whether both are products of the same chronic inflammatory process is debated, but the association is strong enough to warrant long-term surveillance.

Autoimmune Pancreatitis and Calcification

Autoimmune pancreatitis is a distinct condition driven by the immune system rather than alcohol or genetics, and it typically responds to steroid therapy. Stones are not its hallmark. In the 1,500-patient multicentre study, autoimmune pancreatitis was negatively associated with calcifications, meaning these patients were far less likely to have stones than those with other causes.² However, a subset of autoimmune pancreatitis patients do develop severe calcification over time, and when they do, the pancreas can end up looking and functioning much like advanced chronic pancreatitis from any other cause.¹⁵ About 18% of autoimmune pancreatitis patients in one study developed severe calcification. This is a reminder that regardless of what initiates the inflammation, chronic damage to the pancreas can eventually produce stones.

When Children Develop Pancreatic Stones

Pancreatic stones are uncommon in children, but they do occur, particularly in the setting of chronic pancreatitis. In one study of 75 pediatric patients with idiopathic chronic pancreatitis in China, 60% had evidence of pancreatic ductal stones.³ In children, the causes lean heavily toward genetic factors and structural abnormalities rather than alcohol. Hereditary pancreatitis caused by PRSS1 mutations can begin in early childhood and lead to stone formation by the teenage years. Cystic fibrosis-related pancreatitis is another route, especially in children who have enough residual pancreatic function to produce juice that can stagnate and calcify. In tropical regions, the juvenile onset of tropical pancreatitis remains a significant cause of stones in young people.

How Pancreatic Stones Are Removed

Removing stones matters because they perpetuate the cycle of obstruction, pain, and tissue destruction. The first-line approach for many patients is extracorporeal shock wave lithotripsy, or ESWL, which uses focused sound waves to shatter stones from outside the body. The fragments are then extracted or allowed to pass during an endoscopic procedure. In one large series of over 1,000 patients, ESWL achieved complete duct clearance in about three-quarters of cases and partial clearance in most of the rest, with short-term pain relief in roughly 84% of patients.¹⁶ An earlier study similarly described ESWL as a safe and effective method for breaking up pancreatic stones and reducing duct obstruction.¹⁷

When stones are too large, too numerous, or too deeply embedded for ESWL and endoscopy to handle, surgery becomes an option. The Frey procedure, a hybrid operation that combines partial removal of the pancreatic head with drainage of the main duct, has been conceptualized specifically around the pathophysiology of chronic pancreatitis with stones.¹⁸ By opening the duct and clearing it while removing the most diseased tissue, the procedure aims to relieve obstruction and slow further damage. Other surgical options range from simpler duct-drainage procedures to more extensive resections depending on the extent and location of disease.

One frustration in managing pancreatic stones is recurrence. Even after successful clearance, stones can come back if the underlying chronic pancreatitis continues. This is particularly true when the original cause, whether alcohol, smoking, or a metabolic condition, remains unaddressed. Quitting alcohol and tobacco does not reverse existing damage, but it substantially slows the progression of calcification and reduces the likelihood that cleared ducts will fill with new stones.

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