Board-Certified Urologist
FCPS & MCPS Credentials
11+ Years Experience
IMC Registered #539472
Board-Certified Urologist
FCPS & MCPS Credentials
11+ Years Experience
IMC Registered #539472
Clinical Tool — Dr. Muhammad Khalid

Kidney Stone Passage Probability Calculator

Based on stone size, location, and your clinical factors — the same assessment a urologist performs in clinic.

Step 1 — Stone Size
Under 4 mm
4–5 mm
5–7 mm
7–10 mm
Over 10 mm
If your CT report gives a measurement range (e.g. 5×6 mm), use the larger number
Step 2 — Location in the Urinary Tract
In the kidney (renal pelvis)
Upper ureter / UPJ
Mid-ureter
Lower ureter / VUJ (near bladder)
Not sure / not specified
VUJ (vesicoureteral junction) stones have the highest spontaneous passage rate — they are the closest to the exit
Step 3 — Clinical Factors
Yes — prescribed by my doctor
No
Fever / chills
Single kidney
Uncontrolled vomiting
No urine output
None of the above
These are red-flag symptoms that change the clinical management regardless of stone size
Likelihood of Spontaneous Passage
—
—
—
Expected Pass Time
—
days (average)
Tamsulosin Benefit
—
effect on passage

📋 Your Personalised Management Protocol

    Reference: Passage Rates by Stone Size

    Under 4 mm ~90% Avg. 8 days
    4–5 mm ~75% Avg. 15 days
    5–7 mm ~50% Avg. 22 days
    7–10 mm ~25% Avg. 35+ days
    Over 10 mm <5% Intervention needed
    Dr. Muhammad Khalid
    Dr. Muhammad Khalid
    MBBS · FCPS (Urology) · MCPS (Gen. Surgery) · IMC #539472 — Passage rates sourced from EAU Urolithiasis Guidelines 2024 & Jendeberg et al., Eur Radiol 2017.
    This tool provides educational guidance only. It does not replace a clinical assessment or imaging review by a qualified urologist. Always attend the emergency department if you have fever, uncontrolled pain, or zero urine output.

    How accurate is this calculator?

    The probability estimates are based on published urological data from the EAU Urolithiasis Guidelines (2024) and the Jendeberg et al. study in European Radiology (2017) which analysed 3,856 ureteral stones. Stone size and location together are the two strongest predictors of spontaneous passage. Individual results will vary based on stone composition, ureteral anatomy, and clinical factors not captured here.

    What does “VUJ” mean and why does location matter?

    The VUJ (vesicoureteral junction) is where the ureter enters the bladder — the narrowest anatomical point, but also the closest to the exit. Counterintuitively, stones at the VUJ have the highest spontaneous passage rate because once they clear this bottleneck, they enter the bladder and pass with urination. Stones at the UPJ (ureteropelvic junction — where the kidney meets the ureter) have lower passage rates as they must travel the full length of the ureter.

    Does tamsulosin actually help?

    Yes — for distal ureteric stones of 5–10 mm, a Cochrane review of 67 trials found alpha-blockers (including tamsulosin) increase spontaneous passage by approximately 44% and reduce the time to passage by 3–5 days. The benefit is most pronounced for larger stones in the lower ureter. For stones under 5 mm, most pass quickly without it anyway, so the benefit is less marked. Tamsulosin requires a prescription — do not skip asking your doctor if your stone is 5 mm or larger.

    How long should I wait before requesting intervention?

    The EAU guidelines recommend not waiting beyond 4–6 weeks for any ureteral stone, regardless of size. Beyond this window, the risk of permanent kidney damage from prolonged obstruction increases significantly — even if you are no longer in pain. Absence of pain does not confirm the stone has passed. Follow-up imaging (ultrasound or CT) is essential if you have not visually confirmed passage within 4 weeks. Read the full urologist’s guide to passing a kidney stone →

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