Advanced imaging in stone management

Temporal trends in incidence of kidney stones among children: a 25-year population based study

PURPOSE

We conducted a population based pediatric study to determine the incidence of symptomatic kidney stones during a 25-year period and to identify factors related to variation in stone incidence during this period.

MATERIALS AND METHODS

The Rochester Epidemiology Project was used to identify all patients younger than 18 years who were diagnosed with kidney stones in Olmsted County, Minnesota from 1984 to 2008. Medical records were reviewed to validate first time symptomatic stone formers with identification of age appropriate symptoms plus stone confirmation by imaging or passage. The incidence of symptomatic stones by age, gender and study period was compared. Clinical characteristics of incident stone formers were described.

RESULTS

A total of 207 children received a diagnostic code for kidney stones, of whom 84 (41%) were validated as incident stone formers. The incidence rate increased 4% per calendar year (p = 0.01) throughout the 25-year period. This finding was due to a 6% yearly increased incidence in children 12 to 17 years old (p = 0.02 for age × calendar year interaction) with an increase from 13 per 100,000 person-years between 1984 and 1990 to 36 per 100,000 person-years between 2003 and 2008. Computerized tomography identified the stone in 6% of adolescent stone formers (1 of 18) from 1984 to 1996 vs 76% (34 of 45) from 1997 to 2008. The incidence of spontaneous stone passage in adolescents did not increase significantly between these 2 periods (16 vs 18 per 100,000 person-years, p = 0.30).

CONCLUSIONS

The incidence of kidney stones increased dramatically among adolescents in the general population during a 25-year period. The exact cause of this finding remains to be determined.

Imaging evaluation in the patient with renal stone disease

Numerous imaging modalities are available for the evaluation of patients with renal stone disease. The study of choice is dependent on the clinical scenario and the indication for imaging. Additional factors such as patient age and pregnancy status will influence the radiographic study that is chosen. Currently available technologies for the evaluation of urolithiasis include plain abdominal radiography, ultrasound, intravenous pyelogram, computed tomography, and magnetic resonance imaging. This article reviews the indications, advantages, and disadvantages of each study in the evaluation of patients with known or suspected stone disease.

Detection of urolithiasis using low-dose CT--a noise simulation study

How does an acquisition at reduced doses using automatic tube current modulation techniques compare to the normal standard dose CT? Does it affect the sensitivity for detection of calcifications? CT raw data of 54 patients with suspected urolithiasis acquired with automatic tube current modulation techniques were used for image noise simulations with 100%, 50% and 25% dose simulated. Data were analyzed by independent readers with regard to the presence of urolithiasis, stone location, size, density and differential diagnoses. The mean effective dose per standard examination/50%/25% simulation was 7.3 mSv/3.8 mSv/1.9 mSv. Sensitivities/specificities for detection of urolithiasis were calculated for all dose simulations and resulted in 0.94/0.98 in the 50% dose level group and 0.82/0.97 in the 25% dose level group. Low-dose CT with tube current modulation can be used as a standard procedure for the evaluation of patients with suspected acute renal colic.

The role of emergency ultrasound for evaluating acute pyelonephritis in the ED

BACKGROUND

Controversy remains over the imaging method of choice for evaluating acute pyelonephritis (APN) in the emergency department (ED).

OBJECTIVE

The aim of the study was to determine the efficacy of ultrasound in the diagnosis and management of patients presented to the ED with APN.

METHODS

This was a retrospective study of prospectively collected data. A cohort of ED patients diagnosed as APN were prospectively registered, and their medical records were then retrospectively reviewed for the presence of complications (admitted >14 days, admission to intensive care unit, or received invasive procedures), significant abnormalities (hydronephrosis, polycystic kidney diseases, renal abscess, emphysematous pyelonephritis), and mild abnormalities (cysts, stones, swelling).

RESULTS

The study included 243 patients. Most of the patients received one or more renal imaging studies (n = 206) and 39.5% of which were considered abnormal. The rates of significant abnormalities on different imaging methods were Kidney-ureter-bladder (KUB), 16.3%; emergency ultrasound (EUS), 39.6%; combination of KUB and EUS, 56.6%; and computed tomography, 58.8%. Factors contributed to complicated APN were elderly, male, a history of preexisting renal diseases, current use of catheters, previous renal calculi, and diabetes mellitus. Significant abnormalities can be identified by EUS in 61% of patients with complicated APN. In fact, the presence of significant sonographic abnormalities effectively diverted 34.3% of patients to receive surgical interventions (percutaneous nephrostomy, abscess aspiration, ureteroscopic stone manipulation, lithotripsy, or nephrectomy).

CONCLUSION

Structural abnormalities are not uncommon in ED patients with APN. Early assessment of these patients with EUS is likely to have a great impact on their diagnosis and management.

Diagnostic performance of low-dose CT for the detection of urolithiasis: a meta-analysis

OBJECTIVE

The objective of our study was to perform a meta-analysis to evaluate the diagnostic performance of low-dose CT for the diagnosis of urolithiasis (seven studies, 1,061 patients).

MATERIALS AND METHODS

The medical literature from 1995 to 2007 was searched using PubMed, Medline, and Cochrane Library databases for articles on studies that used low-dose CT (< 3 mSv dose applied for the entire CT examination) as a diagnostic test for the detection of urolithiasis. Prospective and retrospective studies were included if they separately reported the rate of true-positive, true-negative, false-positive, and false-negative diagnoses of urolithiasis from low-dose CT compared with the positive and negative rates of normal-dose CT or a combination of diagnostic tests. Two readers assessed the quality of the studies.

RESULTS

The pooled sensitivity and specificity of low-dose CT for the diagnosis of urolithiasis were 0.966 (95% CI, 0.950-0.978) and 0.949 (95% CI, 0.920-0.970), respectively.

CONCLUSION

The results of this meta-analysis suggest that a low-dose CT protocol can be used as the initial imaging technique in the workup of patients with suspected urolithiasis.

Role of Helical Nonenhanced Computed Tomography in the Evaluation of Acute Flank Pain

OBJECTIVE

To evaluate the role of helical nonenhanced computed tomography (NECT) in the diagnosis of acute flank pain.

METHODS

Seventy-five consecutive patients were analysed retrospectively for profile, loin pain, urine analysis and NECT findings. Diagnostic accuracy of NECT for urolithiaisis was calculated. The value of combined microhaematuria and NECT in the diagnosis of flank pain was also highlighted. The potential for identifying phleboliths and alternative diagnoses on NECT was also explored.

RESULTS

There were 46 males and 29 females with an average age of 42.2 years. Forty-four patients presented with acute left flank pain. NECT carries a sensitivity and specificity of 96% for the diagnosis of stone disease. Combined with microhaematuria, NECT has 100% accuracy in picking up urinary tract stones.

CONCLUSION

NECT is the first imaging investigation of choice for the evaluation of patients presenting to the emergency department with flank pain and suspected renal colic.