Medical expulsive therapy (MET)

How it works

Alpha-1 adrenergic receptors are densely distributed in the smooth muscle of the distal ureter. Alpha-blocker medications (tamsulosin, alfuzosin, silodosin) relax this muscle, making it easier for a stone to move down the ureter and out of the body. The effect is most pronounced in the lower third of the ureter.

Who benefits most

The evidence is strongest for distal ureteric stones of 5-10 mm. For this group, international guidelines give a strong (Grade A) recommendation - a meaningful proportion of patients avoid surgery.^{1, 2}

Benefit is more marginal for:

• Small distal stones < 5 mm (likely to pass without medication).
• Mid or proximal ureteric stones - the AUA 2026 guideline gives a weaker, conditional recommendation in this group.²
• Kidney stones - MET does not help pass stones that are inside the kidney itself.

Typical treatment

• Tamsulosin 0.4 mg once daily is the most commonly used regimen.
• Taken for up to about 4 weeks, or until the stone passes, whichever comes first.
• Best combined with a good oral fluid intake and simple oral analgesia (paracetamol and an NSAID where safe).

Safety

Tamsulosin is generally well tolerated. Potential side-effects include:

• Dizziness or low blood pressure, particularly on standing.
• Retrograde ejaculation in men (usually reversible on stopping).
• A theoretical risk of intra-operative floppy iris syndrome during cataract surgery - please inform your ophthalmologist if you are planned for eye surgery.

It is not suitable for patients with postural hypotension or recent stroke. A GP review before starting is sensible.

When MET is not the right choice

• Uncontrolled pain.
• Fever or any sign of infection.
• Stone in the mid or upper ureter larger than 10 mm.
• Solitary kidney.
• Significant hydronephrosis or declining kidney function.

In these situations, earlier intervention with ureteroscopy or ESWL is usually safer.

What to expect

1. Start treatment

   First dose usually at night. Fluid target around 2.5 L a day. Keep simple analgesia available.

2. Strain the urine

   A coffee filter or stone strainer is used to catch the stone if it passes, so that it can be sent for composition analysis.

3. Follow-up at 2-4 weeks

   Plain KUB x-ray or ultrasound to confirm passage. If the stone has not passed, definitive treatment is discussed.

Related pages

References

1. Skolarikos A, et al. EAU Guidelines on Urolithiasis. 2025.
2. Pearle MS, et al. Surgical Management of Kidney and Ureteral Stones: AUA Guideline (2026).