Madeleine Carroll, MS4
The Article: J.M. Fields et al. “The ability of renal ultrasound and ureteral jet evaluation to predict 30-day outcomes in patients with suspected nephrolithiasis.” American Journal of Emergency Medicine 33 (2015) 1402–1406.
The Idea: Renal colic caused by a ureteral stone is a common reason for presentation to the Emergency Department. These patients frequently undergo CT imaging in the ED to assess stone size and location, the idea being that smaller, more distally located stones will pass on their own, whereas larger stones are more likely to require urologic intervention. The downside of course is that CT imaging is expensive, often requires waiting additional hours in the ED, and exposes patients to ionizing radiation. Ultrasound, on the other hand, is cheap, fast, and does not expose patients to ionizing radiation. While ultrasound cannot identify stone size or location, it can easily identify hydronephrosis secondary to ureteral obstruction. Previous studies have shown that an ultrasound-first approach to patients with suspected ureteral stones reduces CT usage, and that in the absence of hydronephrosis visualized on ultrasound, only 1% of patients with ureteral stones require urologic interventions. Ultrasound is also used in these patients to assess ureteral jets of urine flowing into the bladder, which has been shown to be asymmetric in cases of obstructive ureterolithiasis. The purpose of this study is to determine if renal and bladder ultrasound alone in patients with suspected ureterolithiasis can predict the need for hospitalization and/or urologic intervention.
The Study: This was a prospective, observational study using a convenience sample of patients who presented to a single ED with symptoms of renal colic between 2008 and 2011. A total of 77 patients were enrolled and underwent point of care ultrasound examination of the bilateral kidneys and the bladder. These examinations were performed by seven emergency physicians who met the 2008 American College of Emergency Physician's Emergency Ultrasound Guidelines with at least 25 renal studies and underwent a training for assessment of ureteral jets. The physicians performing the ultrasound examinations were blinded to the laboratory and radiology data of enrolled patients and were not otherwise involved in the clinical care of these patients. The patients were followed up 30 days after their initial ED visit by phone and review of medical records to determine if they had been hospitalized during that time period. The authors hypothesized that in patients with suspected nephrolithiasis, the severity of hydronephrosis and a decreased or absent ureteral jet on the side of the patient’s pain would be associated with an increased need for hospitalization within 30 days.
Inclusion Criteria: Adult patients with symptoms consistent with renal colic.
Exclusion Criteria: Presence of ureteral stent or PCN, history of ESRD or renal transplant, pregnancy, and patients in whom the most likely cause of their symptoms was not nephrolithiasis.
The Results: Of the 77 patients enrolled in this study, 13 (17%) required hospital admission (10 were admitted during the initial ED visit and 3 within 72 hours of the initial ED visit). Of those 13 admissions, 8 were for intractable pain and 5 were for evidence of infection. Inpatient urologic intervention occurred in 7 patients. Regarding the rest of the patients, 23 (29%) visualized a stone pass at home and 61 (79%) reported resolution of symptoms. Renal ultrasound to evaluate for hydronephrosis was performed in all patients and identified no hydronephrosis in 28, mild hydronephrosis in 38, moderate hydronephrosis in 11, and severe hydronephrosis in none. Of those patients with no hydronephrosis, 0% (0/28) were admitted, as compared to 24% (9/38) of patients with mild hydronephrosis and 36% (4/11) of patients with moderate hydronephrosis, P<0.1. Overall, the identification of any hydronephrosis on bedside ultrasound was found to be 100% sensitive and 44% specific for predicting the need for hospitalization within 30 days. Ultrasound evaluation of ureteral jets occurred in all but 7 (9%) of patients, in whom an empty bladder precluded the evaluation. No significant difference in admission rate was found between patients with a decreased or absent ipsilateral ureteral jet as compared to patients with normal ureteral jets.
Limitations:
· Patients were only able to be enrolled when research personnel were available.
· Nephro/ureterolithiasis was not definitively proven in all cases, leaving the results open to misclassification bias.
· Four patients were lost to follow up and may have required hospitalization within 30 days.
· No patients with severe hydronephrosis were identified.
· Ureteral jet evaluation occurred for 3 minutes, but some data suggests that a longer period of observation and/or fluid bolus prior to observation improves this exam.
· Patients in whom the leading diagnosis was something other than nephrolithiasis were excluded, meaning that sicker patients with potentially serious alternative diagnoses which may have been missed on bedside renal and bladder ultrasound were not included, which may have biased the results.
The Takeaway: Patients who present to the ED with renal colic who are found to have no hydronephrosis on bedside ultrasound are very unlikely to require hospitalization for pain, infection, or urologic intervention. Patients with moderate hydronephrosis are more likely to require hospitalization than patients with mild hydronephrosis. The addition of 3 minute bedside ureteral jet evaluation does not significantly contribute to the prediction of patient outcomes.