What are the chances of spontaneous passage of renal calculi (kidney stones)?

From the Guidelines

Spontaneous passage of renal calculi (kidney stones) is possible, with approximately 68% of stones ≤5 mm passing spontaneously, and 47% of stones between 5-10 mm passing spontaneously, as reported in the 2007 guideline for the management of ureteral calculi 1. To facilitate spontaneous passage, patients should increase fluid intake to at least 2-3 liters daily to maintain dilute urine.

• Alpha-blockers like tamsulosin (0.4mg daily) can be prescribed for 4 weeks to relax ureter muscles and improve passage rates by 29% (CI: 20% to 37%) 1.
• Pain management typically includes NSAIDs such as ibuprofen (600-800mg every 6-8 hours) or naproxen (500mg twice daily), with opioids reserved for severe pain.
• Patients should strain their urine to collect passed stones for analysis.
• Medical attention is necessary for fever, severe uncontrolled pain, vomiting, or inability to urinate.
• If the stone hasn't passed within 4-6 weeks, or if complications develop, urological intervention may be required.
• Stones pass more readily when patients remain physically active rather than bedridden, as gravity and movement can assist the stone's progression through the urinary tract. It is essential to note that patients with ureteral stones >10 mm will likely require surgical treatment, and spontaneous passage (with or without medical therapy) is not recommended for large stones 1.
• Patients should be counseled on the attendant risks of medical expulsive therapy (MET) including associated drug side effects and should be informed that it is administered for an “off label” use 1.
• Patients who elect for an attempt at spontaneous passage or MET should have well-controlled pain, no clinical evidence of sepsis, and adequate renal functional reserve 1.

From the Research

Spontaneous Passage of Renal Calculi

The chances of spontaneous passage of renal calculi (kidney stones) depend on various factors, including the size and location of the stone.

• According to 2, the lifetime risk of passing a stone is 8-10%, with men being twice as likely to develop stones as women.
• Alpha-blocker medication, such as tamsulosin, can facilitate spontaneous passing of a stone 2, 3, 4.
• Studies have shown that alpha-blockers may improve clearance of stone fragments after shock wave lithotripsy (SWL) 3, 4.
• The use of alpha-blockers as adjuvant medical expulsive therapy may result in improved stone clearance, less need for auxiliary treatments, fewer major adverse events, and a reduced stone clearance time compared to usual care alone 4.

Predicting Spontaneous Stone Passage

Several factors can predict spontaneous stone passage, including:

• Stone size: smaller stones are more likely to pass spontaneously 5
• Stone location: stones in the lower pole of the kidney are less likely to pass spontaneously 5
• White blood cell (WBC) and neutrophil counts: increased concentrations of WBCs and neutrophils at the time of the acute phase of a renal colic were associated with increased likelihood of spontaneous passage 6
• Patient's previous experience with stone passage: patients who have passed larger stones are less likely to choose observation over surgery 5

Treatment Options

Treatment options for renal calculi include:

• Observation: active surveillance of patients with asymptomatic renal calculi is an acceptable option 5
• Shock wave lithotripsy (SWL): a non-invasive treatment that uses shock waves to break up the stone into smaller pieces that can pass spontaneously 3, 4
• Ureteroscopy (URS): a minimally invasive treatment that uses a small scope to remove the stone from the ureter 5
• Percutaneous nephrolithotomy (PCNL): a minimally invasive treatment that uses a small scope to remove the stone from the kidney 2