Kidney Stone Treatment Calculator

The Kidney Stone Treatment Calculator estimates the likelihood of spontaneous stone passage probability and recommends the most appropriate first-line treatment based on stone size, location, and clinical risk factors. This tool helps clinicians and informed patients determine whether conservative management, medical expulsive therapy, or procedural intervention is required. Whether you are assessing a small distal ureteral stone or a large renal stone, this calculator provides evidence-based guidance aligned with AUA/EAU guidelines.

Maximum diameter measured on imaging (1-50 mm).
Anatomical location in the urinary tract.
5
Patient-reported pain level on a standard scale.
Baseline kidney function assessment.
Signs of UTI or sepsis.
Radiologic evidence of blockage.

How Spontaneous Passage Probability Is Calculated

The spontaneous passage probability estimates the chance a stone will leave the urinary tract without medical intervention. This calculation relies primarily on stone size, as larger stones naturally pass less frequently than smaller ones. Location is also a critical factor; stones located in the distal ureter have a higher likelihood of passing compared to those in the kidney or proximal ureter.

Clinical risk factors are then applied to adjust this baseline probability. Factors such as severe pain (level 8 or higher), partial obstruction of the urinary tract, or impaired renal function all reduce the likelihood of natural passage. The result is a percentage bounded between 10% and 95% to provide a realistic clinical expectation based on AUA and EAU observational studies.

What Your Spontaneous Passage Probability Means

Understanding your probability score helps determine the appropriate level of medical intervention. High probabilities suggest that the body may naturally resolve the issue, whereas lower probabilities often indicate the need for procedural assistance to prevent complications.

Clinical Scenarios

  • High Probability (≥70%): Typically associated with stones ≤5 mm. Conservative management with hydration and analgesics is usually recommended.
  • Moderate Probability (40%–69%): Often seen in stones 6–10 mm. Medical expulsive therapy (e.g., tamsulosin) is frequently prescribed to facilitate passage.
  • Low Probability (<40%): Common for stones >10 mm. Procedural intervention such as lithotripsy or ureteroscopy is generally required.

Related Calculators

Calculation logic verified using publicly available standards.

View our Accuracy & Reliability Framework →