Feasibility and Impact of a Decision Rule for Imaging of Emergency Department Patients With Suspected Kidney Stone

Patients that a clinician deems a CT Flank Pain Protocol for suspected kidney stone is
warranted based on their usual practice will be eligible for enrollment. Clinicians will be
encouraged to page the Research Associate (RA) prior to ordering the CT, and an automatic
page will go out for all CT flank pain protocols that are ordered via EPIC. RAs will
approach eligible subjects for written informed consent. Subjects who are incapable or
unwilling to provide informed consent, including non-English speaking patients will be
excluded.

Following written informed consent, eligibility for the S.T.O.N.E. score will be determined.

Subjects that consent to enrollment but have exclusion criteria will be enrolled
observationally to determine the performance of the S.T.O.N.E. score and outcomes in these
groups, but will not be eligible for alternate imaging pathways.

Subjects who do not have any of the above exclusion criteria will be placed in one of three
groups based on the S.T.O.N.E. score (which may be supplemented by gestalt clinician
pre-test probability and/or point-of-care ultrasound for hydronephrosis). The groups are
low, moderate, or high and correspond to the likelihood of the patient having a kidney stone
as described in results from phases I and II.Subjects in the "high" likelihood of stone
group will be eligible to get either ULDCT or "expectant management". The choice will be
determined by the primary clinician in conjunction with the patient. If ULDCT is elected,
the scan will be read diagnostically by the radiologist and the clinician will treat the
patient based on these results. If the expectant management option is chosen, no CT will be
done during the ED visit and they will be treated as if they have a kidney stone. We will
attempt to contact these patients at ~1 week after their ED visit, and they will also have
the option to contact our study team. If symptoms are persistent for a week or more,
subjects may of course pursue further clinical care with the clinician of their choice and
this will not be billed to the study.

Subjects in the "moderate" likelihood of stone group will be given the option to receive
either a standard dose CT or ULDCT. Again, the decision of which imaging option to choose
will be made by the primary clinician in conjunction with the patient.

In the "low" likelihood of stone group the RA will present the data from the stone score to
the physician and explain that patient is unlikely to have a kidney stone and they will be
advised that probability of a stone is very low and that alternate imaging choices may be
warranted. If they still choose to order a CT Flank Pain Protocol they will be asked to
provide reasoning and the patient will receive a regular dose CT Flank Pain Protocol.

All subjects will be followed during their ED course and follow-up care (records in EPIC),
with an attempt to contact the patient at ~90 days after the initial ED visit. Outcomes will
include the number of eligible patients that receive regular dose CT, ULDCT, or the
expectant management option. Radiation dose received will be measured with comparison of
both the expected radiation dose if regular CT had been performed in all eligible patients
and using a before and after model from phases I and II. We will also follow all patients to
determine the prevalence and timing of diagnosis and/or intervention for kidney stone or
other pathology. We will qualitatively compare the prevalence of alternative causes of
symptoms and incidental findings (and follow-up) for regular and low dose CTs.

Inclusion Criteria:

- Patients 18 or older who present to the adult YNHH ED, Saint Raphael Campus ED or SMC
ED in whom renal colic is suspected upon presentation, 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:

- Exclusion Criteria Patients will be excluded for any one of the following reasons:
patients that are

1. pregnant

2. prisoners

3. unable or unwilling to consent (including non-English speaking)

4. with a history or physical evidence of recent trauma

5. renal colic not suspected by clinician

Patients with the following will not be eligible for alternate imaging, but will be
enrolled observationally:

1. evidence of infection (leucocytes in urine, fever)

2. pre-existing renal disease (including creatinine 1.5 or greater)

3. prior urologic intervention

4. active malignancy (within last 6 months)