STONE PLUS - a Tool for Renal Colic

STONE Plus Byte


STONE PLUS: Evaluation of Emergency Department Patients With Suspected Renal Colic, Using a Clinical Prediction Tool Combined With Point-of-Care Limited Ultrasonography

Annals of Emergency Medicine April 2016 - Pubmed Link


Emergency Medicine Literature of Note Review


Take Home Points

1. Hydronephrosis on POCUS increased likelihood of ureterolithiasis as diagnosis in low and moderate STONE score groups, but did not help in the high STONE score group.

2. Hydronephrosis improved prediction of need for intervention in low STONE score group, but only weak improvement in moderate or high STONE groups.

3. You can still miss important alternative diagnoses even if the patient has hydronephrosis.


Background

Pain from kidney stones is a common reason for presenting to the emergency department. Sometimes the diagnosis is easy, but there are other pathologies that can masquerade as renal colic. CT is performed in 70% of patient with a diagnosis of ureterolithiasis. This can pick up alternate diagnoses but at the cost of time and radiation. Ideally, there would be a clinical prediction rule that could diagnose those likely to have an uncomplicated symptomatic stone and unlikely to have alternate findings. The STONE score (previously described here) is an acronym that looks at clinical features of the patient and presentation to provide a risk that this presentation is caused by a stone. STONE score = sex (points for being male), timing (points for acute), origin (points for nonblack race), nausea (points if present), erythrocytes (points for hematuria). So how does ultrasound fit in? This study wants to know if adding ultrasound to this score makes it more accurate at predicting who has a kidney stone and also if it can predict who will require an intervention.


Question

Does the finding of hydronephrosis (sometimes abbreviated as hydro from here on out) on point of care ultrasound (POCUS) improve STONE score for identifying patients with ureteral stones as the cause for current symptoms?

Can hydronephrosis on ultrasound identify people who need urologic intervention for their stones?


Population

2 sites - a large urban academic center and a freestanding suburban ED.

Inclusion

  • Adults

  • All patients undergoing CT abd/pelvis for flank pain or suspected renal colic


Exclusion

  • Refused/unable to consent

  • Pregnant

  • Prisoners

  • Non-English speaking


Who did the scans?

Emergency medicine attending physicians, resident physicians, or midlevel providers

No additional ultrasound training


Design

Prospectively enrolled, not blinded, not randomized, no control

Primary Outcome was to see symptomatic stones and alternate findings on CT

Symptomatic stones were considered in the ureter only OR if report said “signs of a passed stone”

Alternate findings = if determined to be cause of pain, required intervention (abx, admission, operation)

Secondary outcome was need for urologic intervention - determined by 90 day follow up


Intervention

Research assistants would be paged anytime a noncontrast CT abdomen/pelvis was ordered

All patients received point of care limited ultrasonography (PLUS) prior to CT

Interpreted at bedside, degree of hydronephrosis conveyed to research assistant

Patients followed up at 90 days for any urological intervention


The Scan

Curvilinear probe

Curvi probe


Determined if no, mild, moderate, or severe hydro

Renal stones noted

Ureteral jets noted but not required part of scan


Learn how to ultrasound for hydronephrosis - 5minsono


Results

Patients

835 patients

  • 52.9% dx with stone on CT

  • 6.5% (54 patients) had important alternate findings


Primary Outcome

Renal PLUS for diagnosis of symptomatic ureterolithiasis

65% sensitive

75% specific

If moderate or greater hydronephrosis

44% sensitive

93% specific.


If moderate or low STONE score - adding the finding of hydronephrosis increased chance of stone as diagnosis.

If high STONE score - adding hydro did not change accuracy much (in fact, for the most part, it worsened)

STONE table 1


Secondary Outcome

People with hydro were more likely to require intervention, OR 3.5 if moderate or greater hydro, OR 2.7 if any hydro.

Only 10% of those with no hydro needed intervention compared to 22.8% of those with any hydro.

STONE table 2

Note LRs are not that big. Only one above 10 is low stone score with moderate or greater hydro (for both making the diagnosis and requiring intervention).


Those with hydro were more likely to have stone > 5mm, Any hydro OR 3.9, mod or greater hydro OR 5.1.

Moderate or greater hydro was 86% specific for urologic intervention.

Patients who required alternate intervention even when they had hydro, 2 who had high score (pyelo, appe). 3/5 appendicitis they saw had hydro. 25% of pyelo/UTI had hydro.

Overall, 11 of the 54 (20.4%) of the acutely important alternate findings had hydronephrosis.


Also, the authors created an algorithm:

  1. if low STONE + no hydro → unlikely stone, pursue other diagnosis

  2. If low STONE + hydro OR moderate STONE + mild hydro → more likely, get reduced dose CT to confirm

  3. If moderate STONE and severe hydro OR high STONE score (regardless of US) → likely ureteral stone, consider trial of passage without additional imaging

They estimate that you could save 34% of the CTs done in this study by this protocol with only 1% would have missed diagnosis.


Limitations

Well trained ultrasonologists

Patients who did not receive CT were not included - limited sample to patients in whom practitioners felt CT was necessary (perhaps because of suspected alternate diagnoses).

Results show only a small percentage of population helped by ultrasound - mostly when you found hydro in those whom you did not suspect to have a stone based on their STONE score. Does this mean that people we don't think have a kidney stone need a renal POCUS, but people that we are convinced have renal stones do not need one??


Take Home Points

1. Hydronephrosis on POCUS increased likelihood of ureterolithiasis as diagnosis in low and moderate STONE score groups, but did not help in the high STONE score group.

2. Hydronephrosis improved prediction of need for intervention in low STONE score group, but only weak improvement in moderate or high STONE groups.

3. You can still miss important alternative diagnoses even if the patient has hydronephrosis.


Our score

3 Probes


Published on 03/13/17 02:00 AM
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