Ottawa Kidney Stone Rule (Modified Flexner)

Apply the modified Ottawa/Flexner kidney stone rule to identify low-risk patients who do not require immediate CT imaging. Low-risk criteria include: age below 75, no prior renal stones requiring intervention, no fever, and limited pain on arrival. High-risk features warrant immediate CT KUB.

Weight
Height
Clinical Guidance

BMI is a screening measure of body size, not a direct measure of body fat. The standard WHO categories are underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

BMI can overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Interpret it alongside waist circumference and clinical context rather than as a standalone diagnosis.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.
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How to Use

Enter the values for the scenario you are assessing. Apply the modified Ottawa/Flexner kidney stone rule to identify low-risk patients who do not require immediate CT imaging. Low-risk criteria include: age below 75, no prior renal stones requiring intervention, no fever, and limited pain on arrival. High-risk features warrant immediate CT KUB. Use the ottawa stone rule result to inform your calculation.

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Frequently Asked Questions