Introduction:
Alpha-1 receptors are present in the human ureter, particularly in the distal ureter. Alpha-blockers lead to an increase in release rates of distal ureteral stones. It further decreases the time to expulsion and the need for analgesics (pain-relievers) during the stone passage. Alpha-blockers also help in the passage of stones in patients undergoing shock wave lithotripsy (a procedure used to break up stones by shock waves in the kidney and parts of the ureter) and relieve ureteral stent-related symptoms.
Recent studies in endoscopic stone management have helped in the treatment of kidney stones using minimally invasive techniques and increased success rates, and decreased treatment-related morbidity. Other recent advances include
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Shock wave lithotripsy or SWL (a procedure used to break up stones by shock waves).
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Ureteroscopy (a procedure to remove kidney stones involving a small telescope, called a ureteroscope, through the urethra and bladder up the ureter to the point where the stone is located).
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Percutaneous nephrolithotomy (minimally-invasive procedure to remove stones from the kidney by making a small puncture wound through the skin).
These approaches are less invasive than traditional open-surgical approaches. However, they are risky and expensive.
How Common Are Kidney Stones?
Kidney stones are a commonly occurring and expanding problem in the United States. It was recently documented that around 11 percent of males and seven percent of females will be diagnosed with at least one kidney stone during their lifetime. The recurrence rate is around 50 percent within five years.
Risk factors associated with kidney stones include
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Male gender.
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Gout (a type of arthritis caused by extra uric acid in the body forming crystals in the joints).
Noncontrast computed tomography (CT) scan is usually used for confirming the diagnosis and estimating the stone size. The most common symptom of kidney stones is pain as the stone attempts to pass through the ureter. Kidney stones are usually asymptomatic while growing and might take several months to grow to a detectable size.
What Are Alpha-1-Adrenergic Receptors?
Alpha-1-adrenergic receptors are present in the entire human ureter. The physiologic response to the antagonism of these receptors leads to
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Reduced force of contraction.
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Reduced peristaltic (wave-like muscle contractions that move food through the digestive tract) frequency.
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Increased fluid bolus volume transported down the ureter.
These responses are influenced by α-blockers to help in the passage of the ureteral stone.
What Is the Role of Alpha Blockers in Ureteral Stones?
Alpha-blockers, also known as alpha-1 antagonists, act by preventing the stimulation of adrenergic agonists, such as Norepinephrine, which regulate the diameter of small arteries, veins, and the urinary system.
This increased urinary system dilation helps kidney stones pass more quickly out of the body. Alpha-blockers can be used for benign prostatic hyperplasia (age-associated prostate gland enlargement that can lead to difficulty in urination) and hypertension. The off-label use includes the management of kidney stones.
Alpha-blockers help in the following:
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Increase the expulsion rate of distal ureteral stones.
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Reducing the time to stone passage.
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Decrease the amount of pain medication needed during passage stones.
They should be used as first-line therapy in any appropriate candidate on an observation protocol during the passage of a distal ureteral stone. Successful treatment has also been shown with calcium channel blockers with or without steroids and nonsteroidal anti-inflammatory drugs (NSAIDs).
Additionally, alpha-adrenergic receptor antagonists also help during the conservative treatment of mid and proximal ureteral stones and after surgical intervention of renal stones.
What Are the Factors That Affect the Treatment of Kidney Stones?
Treatment of kidney stones depends on the following factors:
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Stone size.
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Symptoms.
For stones less than five millimeters with little to no pain, the treatment involves waiting for the stone to pass spontaneously. Management for larger and more painful stones includes shock wave lithotripsy, surgical removal, ureteroscopy, and pharmacologic therapy.
What Is Medical Expulsive Therapy (MET)?
Traditionally pharmacologic therapy was used for symptomatic relief or for preventing the recurrence of kidney stones. However, some studies recommend the use of medications to help in the passage of stones and decrease the time it takes to pass the stone spontaneously.
This is known as medical expulsive therapy (MET). Alpha-blockers are used as a part of this therapy. Medical expulsive therapy can be used as monotherapy, with additional pharmacologic therapy or post-lithotripsy.
The primary agents that have been used in medical expulsive therapy include
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Calcium channel blockers.
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Steroids.
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Nonsteroidal anti-inflammatory drugs (NSAIDs).
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Alpha-adrenergic receptor antagonists.
Alpha-blockers are also useful in the combination treatment of both ureteral and renal stones with shock wave lithotripsy. They are also useful in treating the pain associated with double-J ureteral stents and other urinary symptoms.
However, a detailed investigation is required to define the role of alpha-blockers in the treatment of proximal ureteral and renal stones and to increase the potential mechanisms of renal stone clearance after the intervention of surgical stones.
They are used as the first-line therapy in any appropriate candidate on an observation protocol during the passage of a distal ureteral stone because of the following reasons.
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High success rates.
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Excellent safety profile.
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Low side effect profile.
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Ease of use.
According to the American Urological Association (AUA), guidelines for urolithiasis (kidney stones) management involve stone prevention with diet and medications.
Dietary recommendations include:
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Drinking plenty of water.
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Limiting sodium intake.
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Reducing consumption of animal protein.
For conservative management of urolithiasis, alpha-blockers with nonsteroidal anti-inflammatory drugs are recommended as it facilitates the passage of debris from lithotripsy and medical expulsive therapy (without lithotripsy) for uncomplicated stones.
There is no recommendation on the choice of alpha-blocker. Alpha-blockers are also recommended to help relieve stent discomfort and to facilitate the passage of stone fragments following shock wave lithotripsy.
What Is the Dosage of Alpha-Blockers Prescribed for Treating Ureteral Stones?
Tamsulosin 0.4 milligrams once a day is an alpha-blocker usually used for stone treatment.
Alpha-blockers are usually well tolerated and may be used to prevent a recurrence. If medical expulsive therapy is continued for more than three months should be reassessed for the progression of stone formation and other causes of renal colic.
Conclusion:
Studies support the use of alpha-blockers post-lithotripsy for shortening time to the passage and reducing renal colic, increasing clearance rate, which is most beneficial for stones greater than ten millimeters in diameter located in the mid-upper calyx, renal pelvis, or mid-upper ureter.
Current studies also recommend alpha-blockers as medical expulsive therapy without lithotripsy for increasing the passage and time to passage of symptomatic ureteral stones less than ten millimeters in diameter. Additionally, long-term alpha-blocker use may be a viable method to prevent stone recurrence.
