What is Urinary Stone Passage?
A urinary stone passage (also called renal colic when painful) occurs when a stone that has formed in the kidneys, ureters, bladder, or urethra starts to move through the urinary tract and is expelled in the urine. Most stones are composed of calcium oxalate, but they can also be made of uric acid, cystine, struvite, or other compounds. The passage itself is often painful because the stone can temporarily block the narrow ureter, stretching the smooth‑muscle wall and causing intense spasms.
While many small stones (< 5 mm) pass spontaneously within a few days to weeks, larger stones may become lodged, require medical intervention, or lead to complications such as infection or kidney damage.
Common Causes
Urinary stones develop when the balance between substances that form crystals and those that dissolve them is disturbed. The following conditions increase the likelihood of stone formation and therefore of stone passage:
- Dehydration – Low fluid intake concentrates urine, allowing crystals to stick together.
- Hypercalciuria – Excess calcium in the urine, often due to dietary excess, hyperparathyroidism, or genetic disorders.
- Hyperoxaluria – High oxalate levels from foods (spinach, nuts) or intestinal disorders that increase absorption.
- Uric acid excess – Seen in gout, high‑purine diets, or metabolic syndrome, leading to uric acid stones.
- Infection‑related stones (struvite) – Chronic urinary tract infections with urease‑producing bacteria create alkaline urine and magnesium‑ammonium‑phosphate stones.
- Cystinuria – An inherited defect in amino‑acid transport that causes cystine stones.
- Obesity and metabolic syndrome – Associated with lower urine pH and higher calcium, oxalate, and uric acid excretion.
- Medications – Certain diuretics, calcium‑based antacids, vitamin D supplements, and topiramate can raise stone risk.
- Gastrointestinal disorders – Inflammatory bowel disease, short bowel syndrome, or bariatric surgery alter absorption, increasing calcium and oxalate loss.
- Family history / genetics – A first‑degree relative with stones raises personal risk 2–3‑fold.
Associated Symptoms
Stone passage is often preceded or accompanied by a characteristic set of symptoms:
- Severe, colicky flank pain that may radiate to the groin or lower abdomen.
- Hematuria (pink, red, or brown urine) due to irritation of the urinary lining.
- Frequent urination or an urgent need to urinate, especially when the stone reaches the bladder.
- Painful urination (dysuria) once the stone is in the lower tract.
- Nausea and vomiting – common because the visceral pain shares pathways with the gastrointestinal tract.
- Lower back or abdominal tenderness.
- Fever or chills – a sign that infection may be present (see “Emergency Warning Signs”).
- Cloudy or foul‑smelling urine indicating possible infection.
When to See a Doctor
Most small stones pass without the need for invasive treatment, but prompt medical evaluation is essential when any of the following occur:
- Persistent pain that does not improve after 48 hours of hydration and analgesia.
- Fever ≥ 38 °C (100.4 °F) or chills – possible urinary infection.
- Blood in the urine that does not lessen after a few days.
- Inability to pass urine (urinary retention) or a sudden decrease in urine output.
- Severe vomiting or inability to keep fluids down, leading to dehydration.
- History of kidney disease, immunosuppression, or pregnancy.
- Sudden onset of severe side‑pain after known stone passage – could indicate another stone or a complication.
Diagnosis
Evaluation typically follows a stepwise approach:
1. Medical History & Physical Exam
- Details about pain pattern, timing, previous stones, diet, fluid intake, medications, and family history.
- Physical exam focusing on flank tenderness, abdominal exam, and evaluation for signs of infection.
2. Laboratory Tests
- Urinalysis – looks for blood, crystals, infection, and pH.
- Serum chemistry – calcium, phosphate, uric acid, creatinine, and electrolytes to assess kidney function and metabolic contributors.
3. Imaging Studies
- Non‑contrast CT scan (gold standard) – detects stones as small as 1‑2 mm and determines location.
- Ultrasound – preferred in pregnancy or when radiation avoidance is essential; can detect hydronephrosis and larger stones.
- Plain abdominal X‑ray (KUB) – useful for radiopaque stones but less sensitive.
4. Stone Analysis
If the patient expels a stone, sending it to a laboratory for composition analysis helps tailor prevention strategies.
Treatment Options
Treatment is individualized based on stone size, location, composition, and the patient’s overall health.
Conservative (Home) Management
- Increased fluid intake – Aim for >2 L (about 8–10 glasses) of water daily to dilute urine.
- Medication for pain – NSAIDs (ibuprofen 400‑600 mg every 6 h) are first‑line; opioids may be required for severe pain.
- Alpha‑blockers (tamsulosin) – Relax ureteral smooth muscle, increasing passage rates for stones < 10 mm (shown effective in multiple RCTs1).
- Citrate supplementation – Potassium citrate can help prevent calcium stones and may aid passage.
- Heat and movement – Warm packs on the flank and gentle walking may reduce spasm.
Medical Interventions
- Extracorporeal Shock Wave Lithotripsy (ESWL) – Uses focused sound waves to break larger stones into fragments that can pass.
- Ureteroscopy with laser lithotripsy – A thin scope is passed through the urethra and bladder into the ureter to fragment and retrieve the stone.
- Percutaneous Nephrolithotomy (PCNL) – Recommended for very large (>2 cm) or complex stones; a small incision creates a tract directly into the kidney.
- Insertion of a ureteral stent – Keeps the ureter open if swelling or obstruction occurs.
Management of Complications
- Antibiotics for concurrent urinary tract infection (UTI).
- Hospitalization for severe pain, uncontrolled vomiting, or renal impairment.
Prevention Tips
Preventing future stones involves lifestyle changes and, when indicated, targeted medical therapy.
Hydration
- Drink enough fluids to produce at least 2.5 L of urine per day (≈2 L of water + other beverages).
- Spread fluid intake throughout the day; avoid large gaps without water.
Dietary Modifications
- Calcium – 1,000–1,200 mg/day from food (not supplements) is protective.
- Oxalate‑rich foods – Limit excessive spinach, rhubarb, nuts, and chocolate if you form calcium oxalate stones.
- Sodium – Keep < 2,300 mg/day; high salt increases calcium excretion.
- Animal protein – Moderate intake; excessive protein raises uric acid and calcium loss.
- Limit sugary drinks – Especially those with high fructose corn syrup.
- Citrus fruits – Lemon or orange juice (rich in citrate) can help prevent stone formation.
Medical Prevention
- Thiazide diuretics for hypercalciuria.
- Allopurinol for recurrent uric acid stones.
- Potassium citrate to raise urinary pH and inhibit calcium stone formation.
- Regular follow‑up labs (24‑hour urine studies) to tailor therapy.
Lifestyle
- Maintain a healthy weight (BMI < 25) – obesity raises stone risk.
- Exercise regularly to improve overall metabolism.
- Avoid prolonged immobilization after surgery or injury, which can increase calcium loss from bone.
Emergency Warning Signs
If you experience any of the following, seek emergency medical care immediately (call 911 or go to the nearest emergency department):
- Fever ≥ 38 °C (100.4 °F) with chills or shaking.
- Severe pain that is not relieved by prescribed analgesics.
- Inability to pass urine or a sudden decrease in urine output.
- Persistent vomiting that prevents you from staying hydrated.
- Blood in the urine accompanied by dizziness, fainting, or rapid heartbeat.
- Swelling of the abdomen or flank indicating possible blockage or infection.
References
- Silverman, D.J., et al. "Alpha‑blockers for ureteral stone passage: a systematic review and meta‑analysis." J Urol. 2022;207(3): 650‑658. DOI:10.1016/j.juro.2021.11.014.
- Mayo Clinic. “Kidney stones – symptoms and causes.” Updated 2023. https://www.mayoclinic.org
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). “Kidney Stones.” 2022. https://www.niddk.nih.gov
- American Urological Association. “Clinical Guidelines for the Management of Kidney Stones.” 2023. https://www.auanet.org
- World Health Organization. “Water, Sanitation and Health – Guidelines for Drinking‑water Quality.” 2021.