Natalia Hernandez

Ultrasonography Significantly Overestimates Stone Size When Compared to Low-dose, Noncontrast Computed Tomography

OBJECTIVE To evaluate the differences between low-dose noncontrast computed tomography (NCCT) and renal ultrasound (US) in the identification and measurement of urinary calculi. MATERIALS AND METHODS A retrospective review was conducted at 3 institutions of patients evaluated for flank pain with both renal US and NCCT, within 1 day of one another, from 2012 to 2015. Stone presence and size were compared between imaging modalities. Stone size was determined by largest measured diameter. Stones were grouped into size categories (≤5 mm, 5.1-10 mm, and >10 mm) based on NCCT and compared with US. Statistical analysis was performed using 2-sided t tests. RESULTS One hundred fifty-five patients received both a renal US and NCCT within 1 day. In 79 patients (51.0%), both US and NCCT identified a stone for size comparison. Fifty-eight patients (37.4%) had a stone visualized on NCCT but not on US, and 2 patients (1.3%) had a stone documented on US but not seen on NCCT. The average NCCT size of the stones missed on US was 4.5 mm. When comparing the average largest stone diameter for US (9.1 mm) vs NCCT (6.9 mm), US overestimated stone size by 2.2 mm (P < .001). US overestimated stone size by 84.6% for stones ≤5 mm, 27.1% for stones 5.1-10 mm, and 3.0% for stones >10 mm. CONCLUSION US significantly overestimated stone size and this was most pronounced for small (≤5 mm) stones. The potential for systematic overestimation of stone size with standard US techniques should be taken into consideration when evaluating endourologic treatment options.

Compliance with American Urological Association Guidelines for Post-Percutaneous Nephrolithotomy Antibiotics Does Not Appear to Increase Rates of Infection

PURPOSE We compared infection rates after percutaneous nephrolithotomy in a group of patients without a history of infection or struvite calculi who received 24 hours or less of antibiotics postoperatively (ie compliance with AUA guidelines) vs a group that received 5 to 7 days of antibiotics postoperatively. MATERIALS AND METHODS We retrospectively reviewed the records of consecutive percutaneous nephrolithotomy procedures in patients without a history of urinary tract infection. Group 1 received 24 hours or less of antibiotics postoperatively and group 2 received a mean of 6 days of antibiotics postoperatively. RESULTS A total of 52 patients in group 1 (24 hours or less of antibiotics) and 30 in group 2 (mean 6 days of antibiotics) met study inclusion criteria. In 5 group 1 patients (9.6%) fever developed within 72 hours of percutaneous nephrolithotomy but none demonstrated bacteriuria or bacteremia on cultures. No patient in group 1 was treated for urinary tract infection on postoperative days 3 to 14. In 4 group 2 patients (13.3%) fever developed within 72 hours of percutaneous nephrolithotomy. A single patient showed bacteriuria (less than 10,000 cfu mixed gram-positive bacteria) on culture while no patient demonstrated bacteremia. No patient in group 2 was treated for urinary tract infection on postoperative days 3 to 14. There was no difference in stone-free rates or the need for additional procedures between the 2 groups. CONCLUSIONS In this pilot series compliance with AUA guidelines for antibiotic prophylaxis did not result in higher rates of infection than in a comparable group of 30 patients who received approximately 6 days of antibiotics postoperatively.

Is Hydronephrosis on Ultrasound Predictive of Ureterolithiasis in Patients with Renal Colic

PURPOSE Renal ultrasound accurately identifies hydronephrosis but it is less sensitive than computerized tomography for the detection of ureterolithiasis. We investigated whether the presence of hydronephrosis on ultrasound was associated with a ureteral stone in patients who underwent both ultrasound and computerized tomography during the evaluation of acute renal colic. MATERIALS AND METHODS We retrospectively reviewed the records of patients from 3 institutions who were evaluated for acute renal colic by both ultrasound and computerized tomography between 2012 and 2015. Patients were included in analysis if ultrasound and computerized tomography were performed on the same day. The presence of ureterolithiasis, stone location and hydronephrosis was reviewed and compared between imaging modalities. RESULTS Ureteral stones were present in 85 of 144 patients. Ultrasound identified hydronephrosis in 89.8% of patients and a ureteral stone in 25.9%. Computerized tomography identified hydronephrosis in 91.8% of patients and a ureteral stone in 98.8%. In 75.0% of cases the presence or absence of hydronephrosis on ultrasound correctly predicted the presence or absence of a ureteral stone on computerized tomography. Hydronephrosis on ultrasound had a positive predictive value of 0.77 for the presence of a ureteral stone and a negative predictive value of 0.71 for the absence of a ureteral stone. CONCLUSIONS Hydronephrosis on ultrasound did not accurately predict the presence or absence of a ureteral stone on computerized tomography in 25.0% of the patients in this study. Ultrasound is an important tool for evaluating hydronephrosis associated with renal colic but patients may benefit from other studies to confirm the presence or absence of ureteral stones.

Cessation of Ureteral Colic Does Not Necessarily Mean that a Ureteral Stone Has Been Expelled

Purpose: We evaluated whether cessation of renal colic is consistent with an expelled ureteral stone or whether imaging may be indicated even in the absence of symptoms. Materials and Methods: We performed a retrospective study of patients who presented to our institution with acute renal colic and ureteral stone, and were subsequently evaluated at a followup visit where they reported complete cessation of pain for at least 72 hours. Results: Study inclusion criteria were met by 52 patients, who reported no pain for at least 72 hours at the time of the followup visit. A persistent ureteral stone was demonstrated in 14 of the 52 patients (26%) although they denied any associated symptoms. Multivariate logistic regression did not show an association between stone size or location and the likelihood of passage in this cohort. Conclusions: Cessation of pain was associated with ureteral stone passage in almost 75% of this study cohort but 26% of patients still had persistent ureteral stones. We recommend routine followup imaging in all patients with ureteral stones to document stone passage and avoid the risks of silent ureteral obstruction.

MP01-05 CAN A STONE OBSTRUCTING THE URETER CEASE TO CAUSE PAIN?

INTRODUCTION AND OBJECTIVES: Follow-up imaging is recommended as follow up for patients who present to the emergency department with ureteral stones and colic, but it often omitted if patients report cessation of pain. The purpose of this study was to update a previous report of how often a patient’s ureteral colic will cease despite still having a stone obstructing the ureter. METHODS: Fifty-three patients evaluated in an emergency department for ureteral colic and diagnosed with an obstructing ureteral stone who subsequently had follow-up in the urology clinic were retrospective evaluated. Patients who described the cessation of pain 72 hours prior to their office visit and who had follow up imaging were included in the study. RESULTS: Fifty-three (53) patients were included in the study. Mean patient age was 49.7 years (SD 15.3), gender distribution was 36% female:64% male, and mean time between visits was 27.4 days (SD 37.5). All patients (100%) reported having no pain for at least 72 hours prior to follow-up appointment, while 12/53 patients (22.6%) still demonstrated an obstructing ureteral stone on follow up imaging. Mean stone axial diameter was not different for patients who had passed their stones versus those who had not (4.9 mm versus 5 mm, p1⁄4NS). CONCLUSIONS: In this study of 53 patients,?22%?of patients with ureteral stones?whose?pain completely ceased still had obstructing stones lodged in the ureter?on follow up imaging. ?This demonstrates that in the short term, one cannot confidently assume that cessation of pain signifies stone passage.