Ureteral Stone
A ureteral stone is a solid crystalline deposit that has lodged within the ureter, the muscular tube carrying urine from the kidney to the bladder. Most ureteral stones originate in the kidney and travel down until they become stuck at one of the ureter’s natural narrowings. Ureteral stones classically cause sudden, severe waves of flank or back pain (renal colic), often with radiation to the abdomen, groin, testicle, or labia, and are frequently accompanied by blood in the urine, nausea, and vomiting. Small stones often pass on their own with hydration and pain control; larger stones or those causing complications may require procedures such as ureteroscopy with laser lithotripsy or shock wave lithotripsy. When ureteral stones are combined with infection or significant obstruction, urgent evaluation is essential.
What is it?
The ureter is a muscular tube, about 25 to 30 centimeters long in adults, that carries urine from the kidney to the bladder. A ureteral stone is a solid crystalline deposit that has traveled from the kidney into the ureter and become lodged, disrupting the normal flow of urine. When a stone becomes stuck, the ureter contracts around it in an attempt to move it along, and the urine backs up above the stone, causing distention of the renal pelvis and calyces (hydronephrosis). This combination of ureteral spasm and increased pressure produces the classic pain of renal colic.
Ureteral stones typically lodge at one of three natural narrowings of the ureter. The first is the ureteropelvic junction (UPJ), where the renal pelvis narrows to become the ureter. The second is where the ureter crosses over the iliac vessels as it passes into the pelvis. The third—and by far the most common location where stones become symptomatic—is the ureterovesical junction (UVJ), where the ureter enters the bladder. Stones at the UVJ often cause urinary urgency, frequency, and painful urination in addition to flank pain, and can sometimes be mistaken for a urinary tract infection.
The likelihood that a ureteral stone will pass spontaneously depends primarily on its size and location. Small stones (typically less than 5 mm) have a high likelihood of passing on their own—generally more than 60–80% for stones less than 4–5 mm. Larger stones (typically greater than 5 mm) have progressively lower rates of spontaneous passage as size increases, and stones larger than about 7–8 mm rarely pass on their own. Stones closer to the bladder (distal ureteral stones) are more likely to pass than stones higher in the ureter.
The composition of ureteral stones varies. Most stones are made of calcium oxalate, either alone or in combination with calcium phosphate; these stones typically appear bright on CT and X-ray. Uric acid stones are less common and are notable because they may not appear on standard X-rays (though they are visible on CT), and they can sometimes be dissolved with medical therapy. Struvite stones are associated with certain urinary tract infections. Cystine stones are rare and occur in patients with cystinuria, an inherited condition. Knowing the stone composition—typically determined by analyzing a stone that has passed or been removed—helps guide long-term prevention strategies.
Ureteral stones classically cause sudden, severe pain that develops over minutes to an hour or two. The pain of renal colic is often described as one of the most severe pains a person can experience, comparable to childbirth or major trauma. Pain typically starts in the flank or back on the affected side and can radiate to the abdomen, groin, testicle, or labia, depending on the stone’s location within the ureter. As the stone moves lower, the pain often shifts. Patients with renal colic are typically restless and cannot find a comfortable position—an important distinction from conditions like appendicitis, in which patients tend to lie very still. Nausea and vomiting are extremely common. Blood in the urine (visible or microscopic) is present in most patients, though its absence does not rule out a stone.
Complications can include obstruction leading to hydronephrosis (and, if prolonged, damage to the kidney), infection above the stone (which can be severe and can lead to sepsis), and, in patients with only one functioning kidney, acute kidney injury from bilateral or solitary-kidney obstruction. Infected obstruction—a stone blocking urine drainage in a patient with a urinary tract infection—is a urologic emergency because it can rapidly progress to sepsis.
Diagnosis is based on clinical presentation, imaging, and laboratory testing. Non-contrast CT (often called CT KUB, for kidneys, ureters, and bladder) is the primary imaging test in adults and is highly sensitive, detecting the vast majority of ureteral stones and providing detailed information about their size, location, density, and any obstruction. CT can also identify alternative diagnoses when the presentation is atypical. Ultrasound is often preferred as the initial test in pregnant women (to avoid radiation), in children, and in patients with recurrent stones who need repeat imaging. Ultrasound can identify hydronephrosis and larger stones, particularly at the UPJ and UVJ, but is less sensitive than CT for smaller mid-ureteral stones. Abdominal X-ray (KUB) can identify radiopaque stones but misses radiolucent stones such as those made of pure uric acid.
Laboratory testing typically includes urinalysis (usually shows blood, often shows crystals, and may show signs of infection), urine culture (particularly when infection is suspected), complete blood count (elevated white blood cells may suggest infection), kidney function (creatinine and estimated glomerular filtration rate), and, in selected patients, uric acid and calcium levels. Metabolic evaluation with 24-hour urine studies is recommended for patients with recurrent stones or specific risk factors and helps identify contributing factors such as high urine calcium, low urine citrate, high urine oxalate, high urine uric acid, or low urine volume.
Stone analysis, when a stone is retrieved (either passed spontaneously or removed surgically), provides critical information about the stone type and guides long-term prevention.
Important to Know
Management of ureteral stones is guided by the stone’s size and location, whether infection or significant obstruction is present, kidney function, whether the patient has a single functioning kidney, patient-specific factors, and preferences. Care is typically coordinated by emergency medicine clinicians (in acute presentations), urologists, and, in selected circumstances, interventional radiologists, nephrologists, and other specialists.
The first priority is adequate pain control and evaluation for complications. Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally the first-line treatment for renal colic when kidney function is preserved and no contraindications exist; they are typically more effective than opioids for this specific pain and have fewer side effects. Common choices include ketorolac (given by injection) and ibuprofen (given by mouth). Opioids may be added or used when NSAIDs are contraindicated or inadequate. Antiemetics are given for nausea and vomiting. Intravenous fluids are used when patients are dehydrated from vomiting, but aggressive hydration does not appear to significantly increase stone passage rates.
For small stones (typically less than 5 mm) in patients without infection, severe obstruction, or intractable pain, observation with pain control, hydration, and, in some cases, medical expulsive therapy (with an alpha-blocker medication such as tamsulosin) is a reasonable approach. Medical expulsive therapy may help facilitate passage of larger distal ureteral stones (particularly those 5–10 mm at the UVJ) though the evidence for smaller stones is more limited. Patients are typically followed with clinical assessment and, when needed, follow-up imaging (often ultrasound to minimize radiation) to confirm stone passage.
For stones that do not pass, are too large to pass, or that require urgent intervention, several treatment options exist.
Ureteroscopy with laser lithotripsy has become one of the most common approaches for ureteral stones. A thin scope is passed through the urethra and bladder up the ureter to the stone, and a laser (typically holmium or, more recently, thulium) is used to fragment the stone into small pieces that can be removed or that will pass. Success rates are high, and the procedure can be used for stones throughout the ureter. A ureteral stent (a thin flexible tube left in the ureter for a period of days to weeks) is often placed after the procedure to allow the ureter to heal and to prevent obstruction from swelling. Stents can cause discomfort, urinary symptoms, and other side effects that patients should be aware of.
Shock wave lithotripsy (SWL) uses external focused shock waves to fragment the stone into smaller pieces that can pass on their own. It is a completely non-invasive treatment that does not require insertion of instruments into the body. SWL works best for stones in the kidney and upper ureter, and is less effective for large stones or stones in the lower ureter. Multiple sessions may be required for larger stones.
Percutaneous approaches (such as percutaneous nephrolithotomy) are typically reserved for larger stones located in the kidney rather than the ureter but may be used in specific circumstances.
Urgent drainage (with a ureteral stent placed by a urologist through cystoscopy, or a percutaneous nephrostomy placed by an interventional radiologist through the back) is essential in several situations. These include infected obstruction (a urologic emergency because of the risk of sepsis), severe pain not controlled by other measures, significantly impaired kidney function (particularly with bilateral obstruction or in a solitary kidney), and other complications. Drainage relieves the obstruction and allows infection to be treated, with definitive stone treatment typically deferred until infection is controlled and the patient is stable.
For patients with a first stone episode, basic metabolic evaluation (a metabolic panel including calcium, phosphorus, and uric acid; urinalysis; and, when available, stone analysis) is generally recommended. For patients with recurrent stones, high-risk features, or first stones in specific populations (children, patients with bilateral stones, or others), more detailed metabolic evaluation with 24-hour urine studies is recommended and can identify targetable metabolic abnormalities.
Preventive strategies are important because stone recurrence is common—roughly half of patients will develop another stone within 5 to 10 years without preventive measures. Core strategies include increased fluid intake (aiming for at least 2 to 2.5 liters of urine output per day for most patients, sometimes more), dietary modifications tailored to the stone type and metabolic findings (such as moderate reduction in sodium and animal protein intake, adequate but not excessive calcium intake from food, and reduced intake of oxalate-rich foods for calcium oxalate stone formers), and, in selected patients, medications. Common preventive medications include thiazide diuretics for hypercalciuria, potassium citrate for hypocitraturia or uric acid stones (by raising urinary citrate and pH), and allopurinol for hyperuricosuria or uric acid stones.
For patients with underlying conditions (such as hyperparathyroidism, cystinuria, primary hyperoxaluria, or specific gastrointestinal conditions), treatment of the underlying condition is important.
For pregnant patients with ureteral stones, management is individualized and typically emphasizes conservative approaches when possible. Most stones can be managed with hydration and pain control, though certain pain medications are avoided in pregnancy. When intervention is needed, ureteroscopy or ureteral stent placement is generally preferred. Shock wave lithotripsy is avoided during pregnancy. Coordination with obstetrics and, when appropriate, maternal-fetal medicine is essential.
For patients with a solitary functioning kidney and a ureteral stone, the threshold for intervention is generally lower because any obstruction affects overall kidney function.
Long-term follow-up may include periodic imaging (typically ultrasound or low-dose CT), assessment for new stone formation, and reinforcement of preventive strategies. Patients with recurrent stones or specific risk factors benefit from care coordinated by urologists or nephrologists with expertise in stone prevention.
Care is typically coordinated by urologists and, when needed, nephrologists, primary care clinicians, and other specialists. Imaging and laboratory findings are interpreted alongside the patient’s symptoms, examination, past medical history, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding the diagnosis, the specific stone type when known, the rationale for the treatment plan, the importance of preventive measures (particularly hydration and dietary modifications), what to expect from procedures and stents, warning signs of complications or recurrent stones, and, when relevant, treatment of underlying conditions all contribute to better outcomes.
Red flag symptoms include severe flank or back pain not controlled by medications, high fever with chills (which combined with obstruction is a urologic emergency), signs of sepsis (severe illness, low blood pressure, rapid heart rate, confusion), significant decrease or absence of urine output (particularly in a solitary kidney), significant blood in the urine with clots or difficulty urinating, severe nausea and vomiting with dehydration, severe abdominal pain, or rapid clinical deterioration. These warrant immediate emergency evaluation, as they may indicate obstructed infection, severe obstruction, or other serious complications.