Limit Computed Tomography (CT) Scanning in Suspected Renal Colic

Validation of a Decision Rule to Limit CT Scanning in Suspected Renal Colic

Computed tomography (CT) scanning is overused, expensive, and causes cancer. CT scan utilization in the U.S. has increased from an estimated 3 million CTs in 1980 to 62 million per year in 2007. From 2000 through 2006, Medicare spending on imaging more than doubled to $13.8 billion with advanced imaging such as CT scanning largely responsible. CT represents only 11% of radiologic examinations but is responsible for two-thirds of the ionizing radiation associated with medical imaging in the U.S. Recent estimates suggest that there will be 12.5 cancer deaths for every 10,000 CT scans. Renal colic is a common, non-life-threatening condition for which CT is overused. As many as 12% of people will have a kidney stone in their lifetime, and more than one million per year will present to the emergency department (ED). CT is now a first line test for renal colic, and is very accurate. However, 98% of kidney stones 5mm or smaller will pass spontaneously, and CT rarely alters management. A decision rule is needed to determine which patients with suspected renal colic require CT. While the signs and symptoms of renal colic have been shown to be predictable, no rule has yet been rigorously derived or validated to guide CT imaging in renal colic. A subset of patients with suspected renal colic may have a more serious diagnosis or a kidney stone that will require intervention; however the investigators maintain that clinical criteria, point of care ultrasound and plain radiography (when appropriate), will provide a more comparatively effective and safer approach by appropriately limiting imaging.

Study Aim: The specific aim of this study is to prospectively validate the previously derived decision rule for obtaining a Flank Pain Protocol (FPP) CT scan in suspected renal colic.

The investigators will integrate the derived clinical decision rule from the ongoing retrospective analysis with gestalt clinician pre-test probability, point of care ultrasound, and plain radiography (when appropriate) to prospectively and observationally test the rule at two distinct clinical settings. CT results and 90-day follow-up will be used to determine predefined outcomes.

Study Hypothesis: Prospective observational testing of a clinical decision rule, combined with point of care ultrasound and plain radiography when appropriate, will categorize >85% of patients who will require intervention, validating a decision rule to avoid unnecessary CT.

This amendment comes from recent evidence and work at our institution to develop an "ultra-low dose" CT scan protocol (ULDCT) with an effective radiation dose close to that of a plain film of the abdomen (KUB), or near 1mSv (compared to 8.5mSv in current practice). While we expect the ULDCT to be better than a KUB at localizing and characterizing kidney stones, what is unknown is how the loss in resolution with an ultra-low dose CT protocol might affect this localization and characterization of stones relative to a regular dose CT (current protocol), as well as the ability to find alternate diagnoses. Incorporating this additional imaging study in a subgroup of patients during the observational phase will allow us to determine test characteristics of the ULDCT that will allow incorporation into the prospective phase. This will hopefully provide excellent evidence about how to implement an ultra-low dose CT scan in practice, ultimately leading to a dramatic reduction in radiation exposure for a large number of patients at Yale and other sites.

We filed an amendment 11-15-2011. This amendment comes from recent evidence and work at our institution to develop an "ultra-low dose" CT scan protocol (ULDCT) with an effective radiation dose close to that of a plain film of the abdomen (KUB), or near 1mSv (compared to 8.5mSv in current practice). While we expect the ULDCT to be better than a KUB at localizing and characterizing kidney stones, what is unknown is how the loss in resolution with an ultra-low dose CT protocol might affect this localization and characterization of stones relative to a regular dose CT (current protocol), as well as the ability to find alternate diagnoses. Incorporating this additional imaging study in a subgroup of patients during the observational phase will allow us to determine test characteristics of the ULDCT that will allow incorporation into the prospective phase. This will hopefully provide excellent evidence about how to implement an ultra-low dose CT scan in practice, ultimately leading to a dramatic reduction in radiation exposure for a large number of patients at Yale and other sites.

This amendment comes from recent evidence and work at our institution to develop an "ultra-low dose" CT scan protocol (ULDCT) with an effective radiation dose close to that of a plain film of the abdomen (KUB), or near 1mSv (compared to 8.5mSv in current practice). While we expect the ULDCT to be better than a KUB at localizing and characterizing kidney stones, what is unknown is how the loss in resolution with an ultra-low dose CT protocol might affect this localization and characterization of stones relative to a regular dose CT (current protocol), as well as the ability to find alternate diagnoses. Incorporating this additional imaging study in a subgroup of patients during the observational phase will allow us to determine test characteristics of the ULDCT that will allow incorporation into the prospective phase. This will hopefully provide excellent evidence about how to implement an ultra-low dose CT scan in practice, ultimately leading to a dramatic reduction in radiation exposure for a large number of patients at Yale and other sites.

Future Direction: Ultimately the investigators intend to implement the validated decision rule at both study sites to evaluate further the feasibility, physician acceptance and comparative effectiveness of our rule. Using standard dissemination techniques and integration of the rule into the computerized physician order entry (CPOE) system at our institutions the investigators will determine the actual reduction in the number of FPP CT scans ordered, clinical outcomes based on 90-day follow up, survey of physician acceptance of the rule as well as an comparative effective analysis. The investigators will submit an application at a later date nearing the end of our projected enrollment for this study.

Inclusion Criteria:

• Patients who present to the adult YNHH ED and Shoreline Medical Center SMC ED who are

  • 18 years or older,
  • renal colic is suspected upon presentation to the ED suggested by flank pain, back pain, abdominal pain, and/or hematuria, and
  • the physician intends to order a CT FPP study for suspicion of a kidney stone. Members of all ethnic and racial groups are eligible.

Exclusion Criteria:

• Patients will be excluded for any one of the following reasons: patients that are

  • pregnant
  • prisoners
  • unable or unwilling to consent (including non-English speaking) and
  • with a history or physical evidence of recent trauma.