Dozens of conditions can produce flank pain, nausea, and urinary symptoms that look and feel almost identical to a kidney stone. When researchers reviewed CT scans ordered specifically to find kidney stones in emergency patients with flank or back pain, roughly one in eleven turned up a non-stone diagnosis instead, and more than half of those alternative findings were classified as acutely important. The overlap is not just academic: some of the mimics, including abdominal aortic aneurysm and ovarian torsion, can become life-threatening if they are mistaken for a stone and treated with pain medication alone.
Vascular Emergencies That Look Like Stones
Two vascular conditions deserve special attention because they share the sudden-onset, severe flank pain that defines kidney stone attacks and because missing them can be fatal.
An abdominal aortic aneurysm (AAA) that is expanding or leaking commonly sends pain radiating into the flank and groin, the same distribution as a stone passing through the ureter. In a review of 134 patients who came to the emergency room with symptomatic AAAs over a ten-year period, 24 were initially misdiagnosed with kidney stones.1PubMed. Symptomatic abdominal aortic aneurysm misdiagnosed as nephroureterolithiasis The patients most at risk for this mix-up tend to be older men with cardiovascular risk factors, but the pain pattern alone does not reliably distinguish the two. AAA becomes especially dangerous when it ruptures, so any older adult with sudden flank pain and risk factors for vascular disease should be evaluated for an aneurysm before everyone settles on a stone diagnosis.
Renal infarction, where a blood clot blocks the artery supplying the kidney, is rarer but even more commonly mistaken for a stone. A case-control study comparing renal infarction patients to ureteral stone patients in the emergency department found that emergency clinicians never initially suspected renal infarction in any of the infarction cases. The most common first diagnosis given to those patients was ureteral stone, accounting for about 40% of the initial impressions.2PubMed. Clinical differentiation between acute renal infarction and acute ureteral stone in the emergency department There are subtle differences: renal infarction patients more often describe diffuse abdominal pain rather than classic flank-to-groin radiation, and they tend to have underlying conditions like atrial fibrillation or recent vascular procedures that predispose to clotting. But when someone with a history of kidney stones shows up with what feels like another episode, a renal infarct can easily hide behind that assumption. Case reports have documented patients with recurrent nephrolithiasis who were treated for yet another stone before imaging revealed a clot-driven infarct instead.3PubMed Central. Renal Artery Thrombosis Leading to Renal Infarct in a Patient With Recurrent Nephrolithiasis
Gynecological Conditions in Women
Ovarian torsion is one of the most dangerous mimics of kidney stone pain in women. When an ovary twists on its blood supply, it causes sudden, severe pain on one side of the abdomen or flank, often with nausea and vomiting. The overlap with a stone attack is close enough that published case reports describe patients who were initially worked up for ureteral stones before ovarian torsion was discovered. In one such case, a woman presenting with abdominal pain, nausea, and vomiting was first suspected of having a ureteral stone or appendicitis. She was ultimately found to have a torsed ovary with a dermoid cyst, and the delay cost her the ovary and fallopian tube.4PubMed. Ovarian torsion masquerading as a ureteral stone
The lesson clinicians draw from these cases is blunt: gynecologic emergencies need to stay on the list for any woman with acute abdominal or flank pain, even when a urinary stone seems like the obvious answer.5PubMed Central. Torsion of ovarian dermoid cyst mimicking obstructing urinary tract stone Ovarian cysts that rupture can produce a similar picture, with sudden one-sided pain that can radiate toward the back. Ectopic pregnancy is another consideration in women of childbearing age, since it can cause sharp lower abdominal or flank pain along with light-headedness if there is internal bleeding. A pregnancy test is a fast way to narrow the possibilities, but it has to be ordered in the first place, and the stone narrative can be convincing enough that it gets skipped.
Gastrointestinal Conditions That Overlap
Appendicitis is probably the gastrointestinal mimic most people have heard of. The appendix sits close to the right kidney and ureter, and when it becomes inflamed, the pain can settle in the right flank rather than the classic lower-right-abdomen location. Clinicians list appendicitis alongside aortic aneurysm and ovarian torsion as one of the potentially life-threatening conditions that must be excluded in a patient presenting with what looks like renal colic.5PubMed Central. Torsion of ovarian dermoid cyst mimicking obstructing urinary tract stone The distinguishing features are not always obvious. Appendicitis tends to cause pain that starts vaguely around the navel and migrates, fever that climbs over hours, and tenderness that worsens with pressure on the right lower abdomen. But atypical presentations are common, especially when the appendix sits in an unusual position behind the colon or near the kidney.
Diverticulitis, particularly of the small bowel, is a less well-known mimic. Small bowel diverticulitis is uncommon enough that it tends to get overlooked in the emergency department. Case series describe patients whose symptoms mimicked more familiar conditions, including kidney stones, before imaging revealed the true diagnosis.6SpringerLink / Emerg Radiol. Small bowel diverticulitis: an often overlooked cause of acute abdomen Colonic diverticulitis, which is far more common, usually produces left-sided pain and is less easily confused with right-sided renal colic, though left-sided stones can blur that line.
Pancreatitis, cholecystitis (gallbladder inflammation), and bowel obstruction can also produce pain that radiates to the flank or back. These conditions generally come with additional features like jaundice, bloating, or pain worsened by eating, but in the acute phase, when someone is doubled over in pain and vomiting, the clinical picture can look a lot like a stone.
Urological Problems That Are Not Stones
Not every urinary-system problem that causes flank pain involves a stone. A few conditions originate in the same anatomical neighborhood and produce nearly identical symptoms through different mechanisms.
Acute pyelonephritis, a kidney infection, causes flank pain and can be accompanied by blood in the urine, both features shared with stones. The usual distinguishing clue is fever, which stones rarely cause on their own. However, imaging is not always helpful early on. Ultrasound, which is often the first test ordered, shows normal findings in up to 80% of patients with pyelonephritis.7Synapse (KAMJE). Ultrasonography of acute flank pain: a focus on renal stones and acute pyelonephritis That means a negative ultrasound does not rule out infection, and a patient who actually has pyelonephritis could be sent home with a stone diagnosis if fever is subtle or absent early in the course.
Ureteropelvic junction (UPJ) obstruction is a structural narrowing where the kidney’s drainage system meets the ureter. It can produce classic renal colic with episodes of severe, cramping flank pain, sometimes triggered by drinking a lot of fluid. The pain pattern can be identical to a stone passing through the same area, and the condition often goes undiagnosed until imaging is done during one of these painful episodes.8PubMed Central. Ureteropelvic Junction Obstruction in Adults Some people with UPJ obstruction get told repeatedly that they have kidney stones before the structural problem is finally identified.
Nutcracker syndrome is an uncommon condition where the left renal vein gets compressed between two major blood vessels. It can cause left flank pain and blood in the urine, a combination that easily suggests a stone. In children and adolescents, it is an especially important consideration because kidney stones are less common in younger age groups, yet the diagnosis is frequently missed.9PubMed Central. A Rare Cause of Abdominal and Flank Pain in Children: Nutcracker Syndrome In the pediatric population, the condition sometimes resolves on its own as the child grows, but in adults it may require intervention.
Retroperitoneal and Medication-Related Causes
The retroperitoneum, the space behind the abdominal cavity where the kidneys sit, can be the source of pain that mimics stones even when the kidneys themselves are fine.
Retroperitoneal fibrosis is a condition where abnormal fibrous tissue forms around the structures in the retroperitoneum, including the ureters. It can compress or encase the ureters, producing flank pain and sometimes hydronephrosis (swelling of the kidney from backed-up urine), both of which look like what a stone might cause. While it is sometimes idiopathic, retroperitoneal fibrosis has been linked to a range of medications. A study mining the French pharmacovigilance database identified 73 cases associated with suspect drugs, and the strongest associations were with ergot-derived medications. Beyond those, drugs used in cardiology (beta-blockers, statins, antiplatelet agents) and neuropsychiatry (certain sedatives, antiepileptics, antipsychotics, and antidepressants) also showed significant associations.10PubMed. Drug-induced retroperitoneal fibrosis: a case/non-case study in the French PharmacoVigilance Database The median age in that cohort was 60, and about two-thirds of affected patients were men. The condition tends to develop gradually, so the pain is usually chronic and dull rather than the sudden, sharp colic of a stone, but the overlap in location and associated urinary symptoms can still lead to initial confusion.
Spontaneous renal hemorrhage, sometimes called Wunderlich syndrome, is a dramatic and rare cause of sudden flank pain. The kidney bleeds into the surrounding retroperitoneal space without any trauma. It can occur in people with underlying kidney tumors, vascular malformations, or blood-thinning medications, and occasionally in otherwise healthy young adults. The sudden onset and severity of the pain closely mimic a large stone, and the correct diagnosis usually requires CT imaging.
Musculoskeletal and Nerve-Related Pain
Not every condition that mimics kidney stone pain originates inside the abdomen. The flank region is served by nerves that also supply muscles, ribs, and the spine, which creates opportunities for musculoskeletal problems to produce pain in the same area.
A herniated disc in the thoracic or upper lumbar spine can compress a nerve root and send shooting or aching pain around to the flank. The pain may come and go, worsen with certain movements, and feel deep enough to be mistaken for something happening inside the abdomen. Herpes zoster (shingles) reactivation along a thoracic dermatome can also produce severe, band-like flank pain before any rash appears. In the pre-rash phase, which can last days, the pain alone is sometimes worked up as a possible kidney stone. Once the characteristic blistering rash appears, the diagnosis becomes obvious, but the initial days can be confusing.
Muscle strains in the lower back or oblique muscles, costochondritis involving the lower ribs, and even rib fractures can all produce pain that patients localize to the flank. These tend to be positional, meaning the pain changes with movement, breathing, or pressing on the area, while true renal colic is usually not affected by body position. But that distinction is not always reliable in practice, particularly when someone is anxious and bracing against pain.
Why Hematuria Does Not Settle the Question
One of the most common assumptions, both among patients and in clinical practice, is that blood in the urine confirms a kidney stone. The reality is more nuanced and cuts both ways: blood in the urine can come from non-stone conditions, and its absence does not rule stones out.
When researchers studied the sensitivity of microscopic blood in the urine for detecting stones, they found it was around 77% overall, meaning roughly one in four stone patients did not have detectable blood in their urine at the time of testing.11PubMed Central. Hematuria: Is it useful in predicting renal or ureteral stones in patient presenting to emergency department with flank pain? The sensitivity varied depending on stone location: it was higher (around 85%) for stones in the ureter but lower (around 55%) for stones still in the kidney. A separate study looking at ureteral stones found similar figures and noted that sensitivity actually dropped in patients with more severe obstruction and hydronephrosis.12PubMed Central. A Comparison of Urolithiasis in the Presence and Absence of Microscopic Hematuria in the Emergency Department That is counterintuitive: you might expect the most obstructing stones to produce the most blood, but complete blockage can actually prevent blood-tinged urine from reaching the bladder, so the urine sample comes back clean.
On the other side, many of the mimics discussed in this article, including renal infarction, pyelonephritis, nutcracker syndrome, and even some gynecological conditions, can produce blood in the urine on their own. So the presence of hematuria cannot confirm a stone, and its absence cannot exclude one. This is why a non-contrast CT scan remains the most reliable tool for sorting out what is actually going on. That scan found an acutely important alternative diagnosis in roughly 3-6% of patients who came in looking like they had stones.13PubMed. Prevalence and clinical importance of alternative causes of symptoms using a renal colic computed tomography protocol in patients with flank or back pain and absence of pyuria
When Pain Recurrence Itself Changes the Picture
People who have had kidney stones before tend to assume that any similar pain is another stone. That assumption is understandable but carries risk. An interesting finding from research on renal colic severity is that patients experiencing their first episode report significantly higher pain scores than those who have been through it multiple times, and there is actually a negative correlation between the number of past episodes and pain intensity reported during the current one.14PubMed Central. Correlation of Severity of Renal Colic With Clinical, Laboratory, and Radiological Parameters That may reflect a kind of perceptual recalibration or anatomical adaptation, but it also means that a recurrent stone patient who presents with unusually severe pain deserves extra scrutiny. If the pain is markedly worse than their typical stone episodes, it could signal that something else is happening, such as a renal infarct or vascular event, rather than just another stone.
This is precisely the trap documented in the renal infarction case reports: a patient with known stone disease comes in with flank pain, and everyone, including the patient, assumes it is the same old problem. The history of stones becomes a cognitive anchor that delays consideration of alternatives.
Drug-Seeking Behavior and Functional Pain
Kidney stone pain has a particular reputation in emergency medicine because it is one of the conditions most commonly cited in drug-seeking behavior. The classic presentation used to involve a patient claiming radiolucent stones (which would not show up on X-ray) and an allergy to contrast dye (which would prevent the confirmatory imaging). As CT scanning replaced older imaging methods, those strategies shifted. Case reports have documented patients with incidental pelvic calcifications on CT who used those findings to support claims of ongoing stone pain in order to receive narcotic medications.15PubMed Central. Drug-seeking behavior in urolithiasis in the noncontrast computed tomography era: 2 cases
This creates an uncomfortable dynamic for people who genuinely have severe pain from a non-stone cause that imaging cannot explain. Chronic flank pain without an identifiable structural source does exist and can be debilitating. Conditions like loin pain hematuria syndrome produce real, severe kidney-area pain with blood in the urine but no stone, infection, or other detectable cause. Patients with these conditions sometimes face skepticism in emergency settings precisely because the drug-seeking narrative is so familiar to clinicians. The takeaway is not that unexplained flank pain is always suspicious but that the range of conditions causing real pain in this area is wider than most people realize, and neither patients nor clinicians benefit from anchoring too quickly on the stone diagnosis or on skepticism.
When to Push for More Investigation
If you have been told you have a kidney stone but something about the situation feels off, there are practical signals worth paying attention to. Fever above 101°F with flank pain points toward infection rather than a simple stone, and an infected obstructed kidney is a urological emergency. Pain that does not come in waves, which is the hallmark colicky pattern of a stone, and instead remains constant and severe may suggest infarction, torsion, or hemorrhage. In women, pain associated with a missed menstrual period, unusual vaginal bleeding, or dizziness raises the possibility of an ectopic pregnancy or ovarian problem. Patients over 60 with new-onset flank pain and any history of heart disease, atrial fibrillation, or vascular surgery should have vascular causes considered early. And anyone on blood thinners who develops sudden flank pain should be evaluated for bleeding rather than assumed to have a stone.
The underlying reality is that the kidney stone diagnosis is often correct. Stones are common, and the pain they produce is distinctive enough that experienced clinicians get it right most of the time. But “most of the time” leaves a meaningful minority where the pain is coming from something else, and some of those alternatives demand urgent treatment that pain medication and time will not provide.