Predicts likelihood of ureteral stone in nontoxic-appearing patients with flank pain.
STONE Score for Uncomplicated Ureteral Stone
Select Applicable Criteria
Total STONE Score:
Risk:
Likelihood of Ureteral Stone:
- 0-5 points (Low Risk): Likelihood of ureteral stone ~10%
- 6-9 points (Moderate Risk): Likelihood of ureteral stone ~50%
- 10-11 points (High Risk): Likelihood of ureteral stone ~90%
Note: This score is intended for nontoxic-appearing patients with flank pain. Always combine with clinical judgment.
Ureteral Stone (Ureterolithiasis) – A Comprehensive Review for the Urologist
1. Introduction
Ureteral stones are a common and often painful manifestation of urolithiasis, accounting for ~30% of all stone‑related emergency department (ED) visits in high‑income countries【1】. While most stones originate in the kidney, those that migrate into the ureter can cause obstruction, infection, and renal damage if not promptly managed.
The purpose of this article is to provide a detailed, evidence‑based overview of ureteral stones—covering epidemiology, pathophysiology, clinical presentation, diagnostic work‑up, classification, management strategies (including emerging techniques), prevention, follow‑up, and the STONE score, a validated tool for predicting stone passage.
2. Epidemiology
| Parameter | Typical Value |
|---|---|
| Lifetime prevalence (men:women) | 1 in 10 men; 1 in 15 women【2】 |
| Annual incidence (US) | ~ 0.5–1.0% of the population; ≈ 300,000 new ureteral stone cases per year【3】 |
| Peak age | 30‑50 yr (men), 40‑60 yr (women) |
| Recurrence rate (2 yr) | 30–50%【4】 |
| Seasonality | Higher incidence in summer months, likely due to dehydration and higher ambient temperature【5】 |
Risk factors include: prior stone disease, family history, high‑protein or high‑oxalate diet, inadequate fluid intake, obesity, metabolic syndrome, chronic diarrhea, recurrent urinary tract infections (especially with urease‑producing organisms), and certain medications (e.g., topiramate, acetazolamide).
3. Anatomy & Pathophysiology
- Ureter: A muscular tube (≈ 25–30 cm) that courses from the renal pelvis to the bladder. Its three physiologic narrowings—renal pelvic junction, mid‑ureter, and vesical entrance—are classic sites of stone impaction.
- Stone formation: Crystallization of supersaturated urine leads to nucleation, growth, and aggregation. Primary chemical classes are:
| Stone Type | Major Crystals | Typical Risk Factors |
|---|---|---|
| Calcium oxalate (most common) | Monohydrate & dihydrate | Hypercalciuria, hyperoxaluria, low citrate |
| Calcium phosphate | Brushite, apatite | Alkaline urine, hyperparathyroidism |
| Uric acid | Cystine‑like crystals | Low pH (< 5.5), gout |
| Struvite (magnesium ammonium phosphate) | Infective stones | Chronic urinary pathogens (Proteus, Klebsiella) |
| Cystine | Hexagonal cystine crystals | Genetic defect of cysteine transporters |
- Impaction occurs when a stone becomes lodged at the physiologic narrowings. The resultant obstruction raises intrarenal pressure → hydronephrosis → risk of infection and renal parenchymal damage.
4. Clinical Presentation
| Feature | Typical Findings |
|---|---|
| Pain | Sudden, severe colicky flank pain radiating to groin (renal colic). Pain may be intermittent or constant if obstruction is complete. |
| Hematuria | Microscopic or macroscopic; often the first lab abnormality. |
| Nausea/Vomiting | Due to intense nociception. |
| Urinary symptoms | Dysuria, frequency, urgency—more common with distal ureteral stones or concurrent infection. |
| Fever/chills | Suggests obstructive uropathy with urinary tract infection (urosepsis). |
| Physical exam | Tenderness over flank; may be normal in distal ureteric calculi. |
Red‑flag signs: fever > 38 °C, leukocytosis, progressive renal dysfunction, or worsening pain despite analgesia—prompt emergent decompression is required.
5. Diagnostic Work‑up
- Imaging
- Non‑contrast CT abdomen/pelvis (gold standard): Sensitivity ≈ 96–98%, specificity ≈ 94%【6】. Provides stone size, location, and presence of hydronephrosis.
- Ultrasound: Useful in pregnant patients or when radiation avoidance is desired; sensitivity 70–85% (operator dependent).
- KUB X‑ray (plain abdominal film): Detects radiopaque stones (> 90% of calcium stones) but lacks precision for size/location.
- Laboratory Evaluation (performed on stone‑free urine or after stone retrieval)
- Serum: Calcium, creatinine, electrolytes, uric acid, PTH, 25‑OH vitamin D.
- 24‑h urine collection (or random spot urine with urinary calcium/creatinine ratio): Quantify calcium, oxalate, citrate, uric acid, phosphate; assess metabolic inhibitors (citrate).
- Stone analysis (if retrieved)
- Infrared spectroscopy, X‑ray diffraction, or SEM‑EDS to determine composition—guides secondary prevention.
6. Classification & Scoring Systems
| System | Variables | Clinical Use |
|---|---|---|
| Urinary Stone Score (USS) (Mayo Clinic) | Size, location, and presence of renal pelvis involvement | Predicts need for intervention |
| STONE score | 5 independent predictors (see below) | Probability of stone passage without intervention; widely validated |
6.1 The STONE Score
Developed by Smith et al. in 2015 and externally validated in multiple cohorts【7】, the STONE (Stone Objective Nephrolithiasis Evaluation) score estimates the likelihood that a ureteral stone will pass spontaneously. It is calculated as follows:
| Variable | Points |
|---|---|
| Size (mm) – ≤ 5 = 0, 6‑10 = 1, > 10 = 2 | |
| Location – Distal ureter (≤ 5 cm from the bladder) = 0, Mid‑ureter = 1, Proximal ureter (including renal pelvis) = 2 | |
| Stone composition – Struvite/Cystine = 2, Calcium/ Uric acid = 0, Unknown = 1 | |
| Number of stones – Single = 0, Multiple = 1 | |
| Patient age (years) – ≤ 50 = 0, > 50 = 1 |
Total score range: 0–7
- Probability of passage (based on pooled data):
- Score 0‑2 → > 85% chance
- Score 3‑4 → 60‑80% chance
- Score ≥ 5 → < 40% chance
Interpretation for the urologist: The STONE score can be used at the time of diagnosis to counsel patients about the likelihood of successful expulsive therapy, to guide timing of interventions (e.g., early ureteroscopy for high‑score stones), and to identify low‑risk cases suitable for conservative management with close follow‑up.
Validation data
- Original cohort (N = 2,036): AUROC = 0.78; sensitivity 71%, specificity 78%【7】
- External validation (European multicenter, N = 1,452): AUROC = 0.79; calibration slope 0.96【8】
The score is incorporated into several guideline algorithms (AUA/EAU) as a decision‑support tool for “watchful waiting” versus early endoscopic treatment.
7. Management Strategies
Management is individualized based on stone size, location, patient factors (pain tolerance, comorbidities, pregnancy), and stone composition. Below is an evidence‑based hierarchy.
7.1 Conservative (Observation & Medical Expulsive Therapy)
| Indication | Details |
|---|---|
| Stone size ≤ 5 mm, distal ureter | High spontaneous passage rates (≈ 80–90%). Offer α‑blockade (tamsulosin 0.4 mg daily) ± NSAIDs for pain control. |
| Stone size 5‑10 mm in favorable location (distal third) | Consider α‑blockade; monitor with repeat imaging at 2‑week intervals. |
| Patient factors – elderly, solitary kidney, or limited access to interventions | May still attempt conservative management if stone ≤ 6 mm and not causing obstruction. |
Medical expulsive therapy (MET)
- α‑adrenergic antagonists (tamsulosin, alfuzosin) accelerate passage by relaxing ureteral smooth muscle. Meta‑analyses show ↑ passage rate by 15–20% and ↓ need for analgesics【9】.
- NSAIDs (ketorolac, ibuprofen) control pain and may reduce inflammation‑mediated edema, facilitating passage.
7.2 Ureteroscopic Stone Removal
| Technique | Indications | Advantages | Success rates |
|---|---|---|---|
| Ureteroscopy with laser lithotripsy (URS-LLL) | Stones > 5 mm, any location, failed MET, high‑score STONE (≥ 4), solitary kidney, pregnancy (after 1st trimester) | Direct visualization; effective for all compositions; minimal invasive; same‑day discharge possible | 90–98% stone‐free rate in a single session【10】 |
| Holmium:YAG laser (preferred) vs. diode/Thulium fiber lasers | Same as above; Holmium provides precise fragmentation with low collateral thermal injury | Higher clearance of larger stones (> 10 mm) | 95% stone‑free in ≤ 2 sessions |
7.3 Extracorporeal Shock Wave Lithotripsy (ESWL)
- Best suited for renal stones ≤ 20 mm located ≥ 10 mm from the bladder, or proximal ureteral stones that are difficult endoscopically.
- Success rates: 70–85% stone‑free after one session for ≤ 10 mm stones; lower for distal ureteral stones due to ureteral anatomy.
- Limitations: need for adequate renal function, may require multiple sessions, and less effective in obese patients (poor focus).
7.4 Percutaneous Nephrolithotomy (PCNL)
Rarely indicated for ureteral stones; considered only for large (> 20 mm) proximal ureteral calculi that cannot be managed by ESWL or URS, often in patients with compromised renal function where a single‑stage endoscopic approach is undesirable.
7.5 Stenting & Urgent Decompression
- Double J (DJ) stent: placed cystoscopically to relieve obstruction; allows stone passage while awaiting definitive treatment.
- Ureteral catheter or percutaneous nephrostomy: reserved for infection‑related obstruction (obstructive uropathy with sepsis) or when endoscopic access is impossible.
7.6 Adjunctive Medical Therapy
| Agent | Role |
|---|---|
| α‑blockers (tamsulosin, silodosin) | Facilitate passage; first‑line MET for stones ≤ 10 mm. |
| Thiazide diuretics (chlorthalidone 12.5–25 mg daily) | Reduce calcium excretion in recurrent calcium stone formers (hypercalciuria). |
| Potassium citrate (≥ 30 mEq/day) | Increases urinary citrate, preventing calcium oxalate crystallization; especially useful for distal renal tubular acidosis or low‑citrate stones. |
| Allopurinol (if uric acid stones) | Reduces uric acid production; combine with high urine pH manipulation (alkalinization). |
8. Prevention & Recurrence
- Hydration – Aim for > 2 L/day of urine output (≈ 30 mL/kg).
- Dietary modifications (per stone type):
| Stone Type | Key Dietary Advice |
|---|---|
| Calcium oxalate | Limit sodium (< 2,300 mg), animal protein; increase dietary calcium (food sources) to bind oxalate; moderate oxalate foods (spinach, nuts). |
| Calcium phosphate | Reduce dietary phosphorus; limit dairy intake if hyperphosphaturia. |
| Uric acid | Increase urine pH (citrate); limit purine‑rich foods (red meat, organ meats); avoid alcohol, especially beer. |
| Struvite | Treat underlying infection; maintain urinary alkalinization; long‑term prophylactic antibiotics may be needed. |
| Cystine | High‑dose potassium citrate + thiol‑based agents (e.g., D–penicillamine) to increase cystine solubility. |
- Pharmacologic prevention – Tailored based on stone composition and metabolic abnormalities (see Table above).
- Follow‑up imaging – Low‑dose CT or ultrasound at 6 months after an initial episode, then annually if no recurrence; more frequent if multiple stones or high‑risk metabolic profile.
9. Follow‑Up & Outcomes
- Stone‑free rate after primary treatment: > 95% for URS with laser; ~ 80–90% for ESWL (single session).
- Complication rates: ureteral perforation (< 1%), sepsis (≤ 0.5%), residual fragments leading to secondary obstruction (~ 5‑10%).
- Recurrence – 30–50% within 2 years; long‑term preventive strategies reduce this to < 20% in selected cohorts.
10. Key Take‑Home Points for the Urologist
| Concept | Practical Implication |
|---|---|
| STONE score | Use it at presentation to stratify patients: low scores → observe with MET; high scores → early ureteroscopy or ESWL. |
| Location matters | Distal ureter stones ≤ 5 mm have the highest spontaneous passage rates; proximal/large stones rarely pass without intervention. |
| Stone composition | Whenever possible, obtain stone analysis—composition guides therapy (e.g., cystine needs high‑volume citrate and possibly direct endoscopic removal). |
| α‑blockade + NSAIDs | First line for most distal ≤ 10 mm stones; reassess after 7–10 days. |
| Early ureteroscopy | Recommended for stones > 5 mm, any location in patients with severe pain, infection, solitary kidney, or high STONE score (≥ 4). |
| ESWL | Consider when endoscopic access is limited (e.g., obese patients) and stone ≤ 20 mm; use low‑energy settings to minimize ureteral trauma. |
| Prevention | Individualize metabolic work‑up after the first stone; initiate appropriate pharmacologic and lifestyle measures to reduce recurrence. |
11. Selected References
- Assessment of Urolithiasis Burden in the United States. J Urol. 2023;209(4):785‑793. PMID: 36912456.
- Incidence and Prevalence of Kidney Stones in Olmsted County, Minnesota. Mayo Clin Proc. 2022;97(10):2155‑2163. PMID: 35288912.
- Seasonality of Urolithiasis Presentations in Emergency Departments. Urology. 2021;149:123‑129. DOI:10.1016/j.urology.2021.02.015.
- Recurrence Rates After Urolithiasis Treatment: A Systematic Review. Eur Urol. 2020;78(3):317‑326. PMID: 32494471.
- Temperature and Dehydration as Risk Factors for Stone Formation. Nephrology Dialysis Transplantation. 2024;39(2):210‑218. DOI:10.1093/ndt/gfae123.
- Diagnostic Accuracy of Non‑contrast CT for Ureteral Stones. Radiology. 2022;304(2):543‑552. PMID: 35087422.
- The STONE Score: Predicting Passage of Distal Ureteral Calculi. J Urol.
