Kidney stones and diverticulitis both cause intense abdominal pain that can send you to the emergency room, but they originate from entirely different organs and require different treatments. Kidney stones form in the urinary tract, while diverticulitis is an inflammation of small pouches in the colon wall. The distinction matters because treating one as though it were the other can waste precious time or lead to complications. While a doctor with imaging tools can usually tell them apart quickly, understanding the differences in pain patterns, accompanying symptoms, and risk profiles can help you communicate more effectively in an urgent care setting and recognize when something needs immediate attention.
Where the Pain Starts and Where It Travels
The single most useful clue for telling these conditions apart is the location and movement of the pain. Kidney stone pain typically begins in the flank, the area between your lower ribs and your hip on one side of your back. As the stone moves through the ureter toward the bladder, the pain often migrates downward into the lower abdomen and groin on the same side. This traveling quality is distinctive. The pain comes in waves, sometimes called renal colic, with intense peaks that ease off before surging again. You might feel fine for a few minutes and then be doubled over.
Diverticulitis pain behaves differently. It tends to settle in the lower left abdomen and stay put. The left side is most common because diverticulitis overwhelmingly affects the sigmoid colon, which sits in the lower left part of your belly. The pain usually builds gradually over a day or two rather than striking suddenly, and it stays constant rather than arriving in waves. Pressing on the tender area typically makes diverticulitis pain worse, while kidney stone pain does not respond much to external pressure because the problem is deep inside the urinary tract, not in the abdominal wall.
That said, right-sided diverticulitis does occur and can confuse the picture. A case report of a 59-year-old man who arrived at the emergency department with acute right lower quadrant pain illustrates the problem: his symptoms initially looked like appendicitis or possibly a kidney stone, but imaging revealed right-sided diverticulitis instead.1PubMed Central. Right-Sided Diverticulitis: A Rare Cause of Right-Sided Abdominal Pain Right-sided diverticulitis is uncommon in Western populations but more frequent in people of Asian descent, so the classic “left side means diverticulitis” rule has real exceptions.
Accompanying Symptoms That Help Narrow It Down
Beyond pain location, each condition tends to travel with a different set of secondary symptoms. Kidney stones are primarily a urinary problem, so you should watch for changes in urination: blood in the urine (which can look pink, red, or brown), a frequent urgent need to urinate, burning or stinging when you go, and urine that looks cloudy or smells unusually strong. Nausea and vomiting are common during the worst pain waves, but fever is not typical with an uncomplicated stone. If you do develop a fever alongside kidney stone symptoms, that can signal a urinary tract infection or an obstructed infected kidney, which is a medical emergency.
Diverticulitis, because it involves the colon, tends to come with digestive symptoms. Changes in bowel habits are a strong clue: constipation is more common than diarrhea, though some people experience either. Bloating and gas often accompany the abdominal tenderness. Unlike kidney stones, diverticulitis frequently causes a low-grade fever and a general feeling of being unwell, almost flu-like, because the body is fighting localized inflammation or infection in the colon wall. Nausea can occur with diverticulitis too, but the urinary symptoms that accompany kidney stones are typically absent.
A quick mental checklist: if your pain is sided, comes in waves, and you notice anything unusual about your urine, kidney stones are more likely. If your pain is steady, sits in the lower left belly, and you have a mild fever with changes in your bowel habits, diverticulitis moves up the list. Neither checklist is foolproof, which is why imaging usually settles the question.
Why These Two Conditions Get Confused
The overlap between kidney stones and diverticulitis is not just theoretical. Emergency departments deal with this diagnostic ambiguity regularly. In a study of patients who came in with suspected renal colic, CT scans revealed that about 13 percent had some other diagnosis entirely, and diverticulitis was among the most common alternative findings.2PubMed Central. Ultrasound vs. Computed Tomography for Severity of Hydronephrosis and Its Importance in Renal Colic That means roughly one in eight people who showed up thinking they had a kidney stone actually had something else going on, with diverticulitis being one of the culprits.
The anatomy explains a lot of this confusion. The left ureter runs very close to the sigmoid colon. When a stone gets stuck in the lower ureter, the pain it generates can feel almost identical to inflammation in the nearby sigmoid. Referred pain, where the brain misinterprets signals from one organ as coming from a neighboring area, compounds the issue. A stone lodged near the bladder can produce lower abdominal discomfort that feels more like a bowel problem than a urinary one, and inflamed diverticula pressing against the ureter can mimic kidney stone symptoms.
Age also muddies the waters. Both conditions become more common as people get older. By age 60, a large proportion of people have diverticula in their colon, and kidney stone incidence rises with age too. So in an older adult presenting with left-sided abdominal pain, both diagnoses are genuinely plausible, and the clinical picture alone may not be enough to distinguish them without imaging.
How Doctors Sort It Out
The workhorse for both diagnoses is the CT scan. A non-contrast CT, meaning no dye is injected into the veins, is the gold standard for detecting kidney stones because stones show up as bright white spots against the surrounding tissue. That same scan can also reveal signs of diverticulitis, such as thickening of the colon wall, fat stranding around the inflamed area, and the presence of diverticula. A study comparing non-contrast CT to contrast-enhanced CT for diagnosing acute diverticulitis found that non-contrast scans achieved an accuracy of about 90 percent, which was statistically non-inferior to contrast-enhanced scans at 92 percent.3PubMed Central. Comparison of Non-Contrast CT vs. Contrast-Enhanced CT with Both Intravenous and Rectal Contrast Application for Diagnosis of Acute Colonic Diverticulitis: A Multireader, Retrospective Single-Center Study The practical upside is that the same non-contrast CT scan ordered to look for kidney stones can often catch diverticulitis at the same time.
There is a caveat, though. The same study showed that non-contrast CT was less sensitive for detecting complications of diverticulitis, specifically perforations and abscesses, compared to contrast-enhanced scans.3PubMed Central. Comparison of Non-Contrast CT vs. Contrast-Enhanced CT with Both Intravenous and Rectal Contrast Application for Diagnosis of Acute Colonic Diverticulitis: A Multireader, Retrospective Single-Center Study If the initial non-contrast scan raises concern about complicated diverticulitis, your doctor may order a follow-up scan with contrast to get a clearer picture of whether an abscess or perforation is present. Perforation of a diverticulum can result from ongoing inflammation, infection, or reduced blood flow to the colon wall.4PubMed Central. Diverticulitis With Microperforation – Section: Discussion
Urine tests provide another piece of the puzzle. A urinalysis that shows blood, even microscopic amounts invisible to the naked eye, pushes the diagnosis toward kidney stones. White blood cells in the urine suggest infection in the urinary tract. Blood tests looking at white blood cell counts and inflammatory markers like C-reactive protein tend to be elevated in diverticulitis because of the infectious or inflammatory process in the colon, whereas uncomplicated kidney stones typically do not provoke the same systemic immune response.
Ultrasound plays a supporting role but is more useful for kidney stones than for diverticulitis. It can detect hydronephrosis, the swelling of the kidney caused by a backed-up stone, which gives indirect evidence that a stone is present. Ultrasound is not great at directly visualizing the stone or at evaluating the colon for diverticulitis, so CT remains the tool of choice when the diagnosis is uncertain.
Pain Management Is Different for Each
If you end up in an emergency department, how your pain is treated can depend on which condition is suspected. For kidney stone pain, evidence supports using anti-inflammatory medications like ibuprofen or ketorolac as the first-line approach. A Cochrane review covering 20 trials and over 1,600 patients found that both NSAIDs and opioids significantly relieve renal colic pain, but opioids cause more side effects.5PubMed Central. Renal Calculi: Emergency Department Diagnosis And Treatment A separate randomized trial found that combining an NSAID (ketorolac) with morphine provided better pain relief than either drug alone, which is a strategy some emergency physicians use for severe renal colic.
Diverticulitis pain management takes a different route. Because the problem is inflammation and often infection in the colon, treatment focuses on antibiotics for moderate to severe cases and bowel rest, meaning a temporary shift to clear liquids or a very bland diet to take pressure off the inflamed colon. Over-the-counter pain relievers can help with discomfort, but NSAIDs are used more cautiously in diverticulitis because some research has suggested they may increase the risk of perforation in people with active colonic inflammation. Acetaminophen is generally preferred for mild diverticulitis pain, with stronger medications reserved for more complicated cases.
Smaller kidney stones, those under about five millimeters, often pass on their own with adequate hydration and pain control. The misery is real but temporary. Larger stones may need intervention: shock wave lithotripsy to break them into smaller fragments, or a procedure called ureteroscopy where a thin scope is passed up through the bladder to retrieve or fragment the stone. Diverticulitis, if uncomplicated, usually resolves with antibiotics over a week or two. Complicated cases involving abscess, perforation, or fistula may require drainage procedures or surgery.
Who Gets Each Condition
Risk factors for kidney stones and diverticulitis overlap in some areas but diverge in others. Both conditions are more common in people who eat a Western-style diet high in processed food, red meat, and salt, and both are influenced by hydration habits. But the specifics differ enough to be worth understanding if you are trying to prevent recurrence of either one.
For kidney stones, diet plays a particularly well-documented role. Research comparing different dietary patterns found that vegetarian and low-meat diets were associated with substantially lower risk of stone formation compared to high-meat diets. People who followed a DASH-style eating pattern, which emphasizes fruits, vegetables, and whole grains while limiting sodium and red meat, had roughly 40 to 45 percent lower risk of developing kidney stones compared to people eating a standard American diet.6PubMed Central. Risk of Kidney Stones: Influence of Dietary Factors, Dietary Patterns, and Vegetarian–Vegan Diets High fruit intake showed an inverse association with stone risk, and both red meat and poultry were linked to increased stone events.6PubMed Central. Risk of Kidney Stones: Influence of Dietary Factors, Dietary Patterns, and Vegetarian–Vegan Diets Dehydration is the other major risk factor: concentrated urine allows minerals to crystallize into stones more easily.
Diverticulitis risk is driven more by structural changes in the colon wall that accumulate with age, combined with lifestyle factors. Low fiber intake is the classic risk factor, though recent research has added nuance to that picture. Obesity, smoking, lack of physical activity, and heavy use of NSAIDs or corticosteroids all increase the chance that existing diverticula will become inflamed. Family history plays a role in both conditions, but especially in diverticular disease, where genetic factors influence the structure and resilience of the colon wall.
Gender patterns differ too. Kidney stones are roughly twice as common in men as in women, though the gap has been narrowing in recent decades, possibly because of dietary shifts. Diverticulitis affects men and women at roughly similar rates, though men are slightly more likely to develop it at younger ages while women see higher rates after menopause.
When to Go to the Emergency Room
Both conditions can be managed at home in their mildest forms, but both have red-flag scenarios that require urgent medical attention. For kidney stones, get emergency care if you have a fever along with flank pain and urinary symptoms, because this combination may indicate an infected obstructed kidney, a condition called pyonephrosis or urosepsis, which can become life-threatening within hours. Uncontrollable pain that does not respond to over-the-counter medication, complete inability to urinate, or persistent vomiting that prevents you from staying hydrated are also reasons to go in.
For diverticulitis, the danger signs include high fever, severe abdominal pain that is getting worse rather than better, signs of peritonitis like a rigid abdomen that hurts when you release pressure after pressing on it, and blood in the stool. These can indicate that a diverticulum has perforated, allowing bacteria to spill into the abdominal cavity. Perforation is a surgical emergency.
If you are genuinely unsure which condition you are dealing with, err on the side of being evaluated. The study mentioned earlier, which found that about 13 percent of patients with suspected kidney stones actually had different diagnoses, underscores that self-diagnosis is unreliable when it comes to abdominal pain.2PubMed Central. Ultrasound vs. Computed Tomography for Severity of Hydronephrosis and Its Importance in Renal Colic Some of those alternative diagnoses required additional management that would not have happened without imaging.
The Gut Microbiome and Kidney Stones
One area of research that blurs the boundary between kidney and gut health involves the gut microbiome. A systematic review and meta-analysis found that people with kidney stones have a measurably different gut bacteria profile compared to people without stones. Specifically, stone formers had higher levels of Bacteroides and Escherichia-Shigella and lower levels of Prevotella_9 in their intestines.7PubMed Central. Gut microbiota in patients with kidney stones: a systematic review and meta-analysis The analysis also found that genes involved in oxalate degradation were altered in stone patients, which matters because oxalate is a key ingredient in the most common type of kidney stone.
This is still early-stage science, and nobody is prescribing specific probiotics to prevent kidney stones based on it yet. But the finding is interesting because it suggests the colon and the kidneys are more connected than we traditionally thought. The colon is where dietary oxalate is either broken down by gut bacteria or absorbed into the bloodstream and eventually filtered by the kidneys. If the wrong bacterial community dominates your gut, more oxalate reaches your kidneys, and your stone risk goes up. People who have had portions of their colon removed, for instance after complicated diverticulitis requiring surgery, sometimes develop more kidney stones afterward, possibly because they lose some of the colonic surface area where oxalate-degrading bacteria reside. The two conditions, while distinct in their acute presentations, share an unexpected piece of biological real estate in the gut.