24 hour Observation through Novel Stone Observation Pathway within Emergency Department Predicts Success of Outpatient Medical Expulsive Therapy
Meredith C. Wasserman, MD MS, Siddharth Marthi, BS, David W. Sobel, MD, Edmond Godbout, PA, Chris Tucci, MS RN, Gyan Pareek, MD MS.
Brown University, Providence, RI.
BACKGROUND: The incidence of nephrolithiasis continues to increase and safe emergency department management of acute renal colic is critical to patient outcomes. With the understanding that the majority of ureteral stones will pass spontaneously with outpatient medical expulsive therapy (MET), achieving pain control and treating associated symptoms to allow for safe discharge is paramount. In 2016 we developed a novel stone observation pathway (SOP) within our institution's Clinical Decision Unit (CDU) for patients with acute renal colic to have up to 24 hours of observation with the goal of a safe discharge on MET without requiring hospital admission or urologic consultation. The purpose of this study is to evaluate the safety and efficacy of the 24 hour observation model through a SOP for patients with acute renal colic. METHODS: A retrospective review of all patients admitted to the CDU utilizing the SOP from January 2016 to November 2019 was performed. Patients with ureterolithiasis were excluded from admission to the CDU if any single criteria from Table 1 was met. Patient characteristics, axial imaging, and follow up information were analyzed. Of note, it was assumed if a patient did not follow up with a urologist, they did not undergo surgical intervention for their ureteral stone. MET was considered successful if the patient did not return to the emergency department. Urologic consultation was not required during observation, however the urologist on call was alerted to patients with acute kidney injury, severe hydronephrosis, or calculi >10mm. RESULTS: 189 patients were diagnosed with uncomplicated ureterolithiasis and admitted via the SOP to the CDU (Table 2). The mean stone size was 4.6mm (SD +/- 1.9mm). 148/189 (78%) patients were discharged within the 24 hour observation period and 42 patients were admitted for operative intervention (22%). 17 patients discharged from the unit returned to the emergency department for recurrent renal colic (9%) and 8 of these required admission for operative intervention (53%). 85 patients discharged from the unit followed up with a urologist (57%) and 30 of these patients ultimately required surgical intervention (22%). There were no readmissions for infection or sepsis. CONCLUSIONS: 24 hour observation and discharge from a CDU in the emergency department using a SOP predicts success of outpatient MET. The protocol is both effective (<10% readmission rate) and safe (0% readmission for UTI/pyelonephritis). Additionally, by avoiding admission to a urology service for observation, the urologist can focus efforts on more acute surgical consultation and management. Partnership between the divisions of urology and emergency medicine is critical for the success of the SOP. Future research will evaluate the cost savings of this protocol as well as low follow-up rate (57.4%) as an area for quality improvement. 
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