Medical expulsive therapy (MET) for kidney (renal) stones

• Medical Expulsive Therapy (MET) - use of medical therapies to facilitate the passage of the stone
  
  (1,2,3,4) - stones <4 mm have a 95% chance of spontaneous passage within 40 days (5)
  • useful in cases where there is no obvious reason for immediate surgical removal
  • medical options include calcium-channel blockers (eg, nifedipine) or alpha-blockers (eg, tamsulosin)
  • small, less than 5-mm distal ureteral stones, will most likely spontaneously pass within 4 weeks, without the need for urologic intervention (1)
  • for 5-10mm stones, MET may increase the passage rate by 30%. With smaller stones, it may reduce transit time and symptoms (2) possible side effects include postural hypotension and retrograde ejaculation
    
    • best evidence is for alpha-blockers (tamsulosin 400 microgram once a day)
    • medical expulsive therapy with α-blockers, such as tamsulosin 400 mcg once daily (off label indication), for 1 month may accelerate spontaneous passage of distal stones, particularly those >5 mm (5) -
• a corticosteroid such as prednisolone is occasionally added when an alpha-blocker is used (but should not be given as monotherapy) (3)
  • though a review stated that "..wiith regard to MET, we support use of tamsulosin for medical expulsive therapy in appropriate patients due to the favorable side effect profile and the evidence for decreased time to stone passage. At this time we do not feel there is sufficient evidence to recommend addition of corticosteroid therapy..." (4)

Reference:

• Singh A et al. A systematic review of medical therapy to facilitate passage of ureteral calculi. Ann Emerg Med. 2007;50:552-63.
• Fan B et al. Can tamsulosin facilitate expulsion of ureteral stones? A meta-analysis of randomized controlled trials. Int J Urol. 2013 Aug;20(8):818-30.
• Seitz C, Liatsikos E, Porpiglia F, et al; Medical therapy to facilitate the passage of stones: what is the evidence? Eur Urol. 2009 Sep;56(3):455-71.
• Xu H et al. Kidney stones: an update on current pharmacological management and future directions. Expert Opin Pharmacother. 2013 Mar;14(4):435-47
• Wilcox CR et al. Kidney stone disease: an update on its management in primary care. BJGP 2020; 70: 205–206.