Detection of ureteral calculi in patients with suspected renal colic: value of reformatted noncontrast helical CT

Does the kidney actually swell during an acute urinary tract obstruction?

BACKGROUND

The appearance of renal swelling during an acute obstruction of the urinary tract could be caused by hydronephrosis or an increase of the parenchymal volume. To the best of our knowledge no studies have been performed regarding renal parenchymal volume change during an acute urinary tract obstruction.

PURPOSE

To investigate the change in renal parenchymal volume during an acute urinary tract obstruction and to correlate any such volume change to the degree of secondary signs of obstruction.

MATERIAL AND METHODS

In total, 20 patients with obstructive ureterolithiasis were retrospectively and randomly included. Two observers measured the parenchymal volume of the obstructed and the contralateral kidney in CT examinations before, during, and after obstruction. Hydronephrosis, hydroureter, perirenal stranding, and thickening of the renal fascia were graded and correlated to volume change.

RESULTS

A decreased volume was noted after obstruction in the obstructed kidneys (-24%) (P < 0.0001) and in the contralateral kidneys (-5%) (P = 0.0110) with a positive correlation of change in volume (P = 0.011). The volume of the obstructed kidneys was larger than the contralateral kidneys during obstruction (P < 0.0001) but not after obstruction (P = 0.559). No significant difference in volume was found before compared to after obstruction. Secondary signs of obstruction did not correlate to volume change.

CONCLUSION

The parenchymal volume increases in the obstructed kidneys as well as in the contralateral kidneys during obstruction. The increase in volume was larger in the obstructed kidneys compared to the contralateral kidneys. After obstruction the kidneys regained their original volume. Secondary signs did not correlate to volume change.

Hematuria as a Sign of Kidney Stone Disease Evaluated Using Computed Tomography: A Review

Kidney stone is a common cause of acute pain in the abdomen in patients presenting to casualty. Being present in roughly 12% of the world's population makes it the most prevalent pathology of the urinary system. The ureters, kidneys, and bladder frequently develop calculi, resulting in hematuria. The most effective imaging technique for evaluating calculi is unenhanced helical computed tomography. The population, intervention, control, and outcomes (PICO)-formatted question was used to generate methodological medical subject heading (MeSH) phrases, which increased the search strategy's sensitivity in finding research. Some of these names ("hematuria") included "renal calculi" (MeSH) and "cone-beam computed tomography" (MeSH). Studies that satisfied these requirements were subjected to critical evaluation. The merits of the listed studies were evaluated using a unique quality assessment scale. The most accurate imaging diagnostic test for people with hematuria is multidetector computed tomography. If a patient over 40 presents with microscopic hematuria, a non-contrast computed tomography or ultrasound study should be performed, and if gross hematuria is observed, cystoscopy should be added. Pre- and post-contrast computed tomography scans and cystoscopy should be carried out on elderly patients.

'Negative Ureteroscopy' for Stone Disease: Evidence from a Systematic Review

PURPOSE OF REVIEW

While ureteroscopy (URS) is a common procedure for ureteric stones, this window between diagnosis and treatment leaves the possibility for a 'negative', 'stoneless' or 'diagnostic' URS. We perform a systematic review to look at the rate of 'negative ureteroscopy' and risk factors associated with it.

RECENT FINDINGS

From a total of 3599 articles and 68 abstracts, 4 studies (1336 patients) were selected. The negative URS rate varied from 4 to 14%. Common predictors seem to be female gender, small stones, radiolucent stones and distal ureteric stones. Although infrequent, negative ureteroscopy should be avoided in patients with ureteric stones by performing a low-dose CT scan on the day of surgery. This should especially be performed for females and those with smaller, radiolucent or distal ureteric stones.

Predicting the stone composition of children preoperatively by Hounsfield unit detection on non-contrast computed tomography

INTRODUCTION

Many studies have been performed on adult patients to reveal the relationship between Hounsfield unit (HU) value and composition of stone, but none have focused on childhood.

OBJECTIVE

We aimed to predict stone composition by HU properties in pre-intervention non-contrast computed tomography (NCCT) in children. This could help to orient patients towards more successful interventions.

MATERIALS AND METHODS

Data of 94 children, whose pre-intervention NCCT and post-interventional stone analysis were available were included. Stones were grouped into three groups: calcium oxalate (CaOx), cystine, and struvite. Besides spot urine PH value, core HU, periphery HU, and Hounsfield density (HUD) values were measured and groups were compared statistically.

RESULTS

The mean age of patients was 7 ± 4 (2-17) years and the female/male ratio was 51/43. The mean stone size was 11.7 ± 5 (4-24) mm. There were 50, 38, and 6 patients in the CaOx, cystine, and struvite groups, respectively. The median values for core HU, periphery HU, and mean HU in the CaOx group were significantly higher than the corresponding median values in the cystine and struvite groups. Significant median HUD difference was seen only between the CaOx and cystine groups. No difference was seen between the cystine and struvite groups in terms of HU parameters. To distinguish these groups, mean spot urine PH values were compared and were found to be higher in the struvite group than the cystine group (Table).

DISCUSSION

The retrospective nature and small number of patients in some groups are limitations of this study, which also does not include all stone compositions. Our cystine stone rate was higher than childhood stone composition distribution in the literature. This is because our center is a reference center in a region with high recurrence rates of cystine stones. In fact, high numbers of cystine stones helped us to compare them with calcium stones more accurately and became an advantage for this study.

CONCLUSIONS

NCCT at diagnosis can provide some information for determination of stone composition. While CaOx stones can be discriminated from cystine and struvite stones using HU parameters, a simple spot urine pH assessment must be added to distinguish cystine stones from struvite stones.

Defining the Rate of Negative Ureteroscopy in the General Population Treated for Upper Tract Urinary Stone Disease

INTRODUCTION

Ureteroscopy is increasingly used to treat upper tract urinary stone disease. A negative ureteroscopy is a ureteroscopy performed with the intent of removing a kidney or ureteral stone, but in which ultimately no stone is removed. Negative ureteroscopy may occur when the stone is found to have already passed, or the presumed stone is found to be outside of the collecting system. We sought to determine the rate of negative ureteroscopy in a large population-based sample as well as factors associated with its use.

PATIENTS AND METHODS

We examined nonpublic data from the Office of Statewide Health Planning and Development (OSHPD) Database for all patients in California undergoing outpatient surgery from 2010 to 2012. We identified all patients with an International Classification of Diseases, Ninth Revision (ICD-9) diagnosis code for upper tract urinary stone disease, who underwent a ureteroscopic procedure. After excluding patients undergoing second look procedures or who had diagnosis codes for separate urologic pathology, the negative ureteroscopy rate was defined as the proportion of those ureteroscopy cases coded as a diagnostic ureteroscopy. We fit logistic regression models to evaluate patient factors associated with negative ureteroscopy.

RESULTS

During the years 2010 to 2012, 20,236 eligible patients underwent ureteroscopic procedures for upper tract stone disease. Of these, 1287 patients underwent diagnostic ureteroscopy and 19,039 underwent ureteroscopy with stone removal accounting for a negative ureteroscopy rate of 6.3%. The odds of receipt of a negative ureteroscopy rate were higher in females compared to males (odds ratio [OR] 1.41, 95% confidence interval [CI] 1.25, 1.58) and lower in self-pay patients compared with insured patients (OR = 0.55, 95% CI 0.33, 0.91).

CONCLUSIONS

Negative ureteroscopy is common, occurring in nearly 1 in 16 procedures to treat urinary stone disease.

Low-Dose (10%) Computed Tomography May Be Inferior to Standard-Dose CT in the Evaluation of Acute Renal Colic in the Emergency Room Setting

Introduction: Noncontrast CT is the standard of care to evaluate nephrolithiasis. We evaluated the performance of low-dose CT (LDCT) scan for evaluation of renal colic in the emergency room (ER).

Materials and Methods: Patients visiting the ER with suspected nephrolithiasis received a standard-dose CT (SDCT) and an LDCT. Two urologists read the LDCTs and later they read SDCTs. Stone information was recorded on a diagram of the renal system. Findings on SDCTs and LDCTs were correlated through side-by-side comparison of the diagrams. Later, the two urologists adjudicated all nonconcordance between SDCTs and LDCTs in an unblinded manner.

Results: Twenty-seven patients were included. SDCTs revealed 27 stones in 18 patients. Mean stone size was 3.81 mm. LDCTs revealed 27 stones in 18 patients with a mean stone size of 4.7 mm (p = 0.23). Overall sensitivity and specificity of LDCTs were 70% and 39%, respectively. There were eight false-positive and eight false-negative stones. All the false-positive stones on LDCTs were placed in the ureter, in which all of the corresponding SDCTs were visible calcifications outside the ureter. Of the eight false-negative stones on LDCTs, seven were visible calcifications on the SDCTs and the eighth stone was 1 mm and was not visible.

Conclusion: LDCT may not perform well in the evaluation of suspected nephrolithiasis in the acute setting. LDCT scan accurately demonstrates calcifications; however, accurate placement of calcifications in or out of the urinary tract may be diminished due to impaired resolution of soft tissue structures.

CT-Based Determination of Ureteral Stone Volume: A Predictor of Spontaneous Passage

INTRODUCTION AND OBJECTIVES

Which ureteral stone can pass spontaneously? It is hard to answer this question exactly. The size and location of the stone are the most important predictors. However, there is still a considerable gray zone that needs to be clarified. We try to identify the role of stone volume (SV) in the prediction of spontaneous passage (SP).

MATERIALS AND METHODS

Seventy-eight patients with a solitary ureteral stone were retrospectively evaluated. Ureter SV measurements were taken in three planes and were calculated using the following formula: V = (X) × (Y) × (Z) × 0.52. SVs, and the longest diameters (LDs) were compared between patients who passed stones spontaneously and those who needed intervention.

RESULTS

The SVs and LDs were significantly lower in patients who passed stones spontaneously than in patients who required intervention (41.2 ± 35.5 vs 128.1 ± 91.1 mm(3), p = 0.001; 5.7 ± 1.8 vs 7.4 ± 1.7 mm, p = 0.001). The optimum cutoff values were 7.0 mm and 52.6 mm(3) for the LD and SV, respectively. For those stones of ≤7 mm, the volumes of the stones that could and could not pass did not differ significantly. However, the volume of the stones >7.0 mm that could pass was significantly higher than of those that could not. SP was 30.6% for stones >7 mm; however, when we removed the stones >52.6 mm(3), SP increased to 75% for stones higher than 7 mm (p = 0.001).

CONCLUSIONS

To classify ureteral stones using only one parameter such as stone diameter may lead to heterogeneity within the group. SV may be used in addition to size to determine a more definite homogeneous group to predict SP more precisely.

The comparison of ultrasound and non-contrast helical computerized tomography for children nephrolithiasis detection

AIMS

Nephrolithiasis is less common in children than adults, but its diagnosis and management in children may be more perplexing. In this article, we compare two imaging ultrasound (US) and non-contrast helical computerized tomography (CT) for diagnosis of nephrolithiasis.

SUBJECTS AND METHODS

A total of 20 children who diagnosed as nephrolithiasis by US were imaged simultaneously by non-contrast helical CT. Their history like as family history in first and second degree relatives and urine analysis for hematuria and urine randomly calcium to creatinine ratio was obtained. All data analyzed by χ(2) and Mann-Whitney U-test in SPSS 16 and P < 0.05 was considered to be significant.

RESULTS

Out of 20 cases, only 5 cases diagnosed as nephrlithiasis by US were confirmed by CT method 2 out of 20 cases had another extrarenal origin for their complaint who diagnosed wrongly as nephrolithiasis by US. Stone size based of US that was confirmed by CT method was larger 4.6 ± 1.5 (minimum 3 max 6 mm) than non-confirmed ones 2.3 ± 0.7 mm (P 0.002). Hematuria occurred more in correct diagnosed compared with misdiagnosed (P 0.005). Positive family history and urine calcium ratio was not differed between two groups.

CONCLUSIONS

Non contrast helical CT is essential to confirm of nephrolithiasis and other extrarenal origin of complaints, which diagnosed wrongly as nephrolithiasis in children. Stone size and presence of hematuria are two major factors for right diagnosis of nephrolithiasis as US method but Urine calcium excretion ratio or positive family history cannot be predictive as this study.

Investigating the clinical significance of twinkling artifacts in patients with urolithiasis smaller than 5 mm

PURPOSE

Our aim was to evaluate the effectiveness of twinkling artifacts (TA) in detecting calculi <5 mm in diameter in patients with renal colic pain who had undergone urinary grayscale ultrasonography (US) and computed tomography (CT) imaging assays.

MATERIALS AND METHODS

In this retrospective study, a total of 76 calculi <5 mm detected in 60 patients were evaluated. Whole data were established using an ultrasound (US) probe at frequencies 1.5-4.5 MHz and noncontrast CT. In US, echogenicity and posterior-shadow (PS) parameters were evaluated and compared with color-Doppler ultrasonography (CDUS) and CT signs.

RESULTS

The mean size of measured calculi was 3.9 ± 0.8 mm (range 2-5 mm). The calculus localization rates detected by CT imaging were as follows: kidneys (n = 61, 80.3 %), proximal ureter (n = 4, 5.3 %), middle ureter (n = 3, 3.9 %) and distal ureter (n = 8, 10.5 %). CT detected the calculus in all 76 cases. There was a statistically significant difference in US-CT and CDUS-CT comparisons (p < 0.001 and p = 0.023, respectively); however, no difference was found when comparing both US methods with CT (p = 0.083).

CONCLUSIONS

TA can be regarded as a significant marker of urolithiasis, and co-operative usage of Doppler and grayscale methods can yield satisfactory results comparable with CT.

Renal scintigraphy in the acute care setting

Renal scintigraphy is a powerful imaging method that provides both functional and anatomic information, which is particularly useful in the acute care setting. In our institution, for the past 2 decades, we have used a 25-minute renal diuretic protocol, technetium-99m ((99m)Tc) mercaptoacetyltriglycine with simultaneous intravenous injection of furosemide, for all ages and indications, including both native and transplant kidneys. As such, this protocol has been widely used in the workup of acutely ill patients. In this setting, there are common clinical entities which affect patients with native and transplant kidneys. In adult patients with native kidneys one of the most frequent reasons for emergency room visits is renal colic due to urolithiasis. Although unenhanced computed tomography is useful to assess the anatomy in cases of renal colic, it does not provide functional information. Time zero furosemide renal scintigraphy can do both and we have shown that it can effectively stratify patients with renal colic. To this end, 4 characteristic patterns of scintirenography have been identified, standardized, and consistently applied: no obstruction, partial obstruction (mild vs high grade), complete obstruction, and stunned (postdecompressed) kidney. With the extensive use of this protocol over the past 2 decades, a pattern of "regional parenchymal dysfunction" indicative of acute pyelonephritis has also been delineated. This information has proved to be useful for patients presenting with urinary tract infection and suspected pyelonephritis, as well as for patients who were referred for workup of renal colic but were found to have acute pyelonephritis instead. In instances of abdominal trauma, renal scintigraphy is uniquely suited to identify urine leaks. This is also true in cases of suspected leak following renal transplant or from other iatrogenic/postsurgical causes. Patients presenting with acute renal failure can be evaluated with renal scintigraphy. A scintigraphic pattern of "relative preservation of flow as compared to function" has been identified as indicative of acute tubular necrosis, which is distinct from other potential causes of acute renal failure, such as nephrotoxicity and in the case of renal transplants, rejection.

Noncontrast multidetector CT of the kidneys: utility of 2D MPR and 3D rendering to elucidate genitourinary pathology

To encourage routine use of 2D multiplanar reconstructions (MRPs) and 3D renderings when interpreting noncontrast computed tomography (CT) of the kidney, as this practice can unveil findings related to the kidney or its vasculature that are not apparent on axial sections. Inspecting the kidneys or characterizing CT findings with both axial sections and MPRs may facilitate identification of vascular and neoplastic pathology.

Thick curved planar reformation of unenhanced multislice computed tomography demonstrating urolithiasis

OBJECTIVES

To determine what slice thickness provides optimal curved planar reformation (CPR) images of the urinary tract.

METHODS

A total of 75 consecutive patients with acute flank pain were included in a retrospective pilot study and underwent unenhanced multislice computed tomography (MSCT) (collimation 3.75 mm, pitch 6, reconstruction increment 3 mm, working voltage 120 kV, and tube current 100 mA) with CPR reconstruction of the urinary tract. CPRs with differing slice thicknesses of 3-20 mm at 1-mm increments to reformat each ureter were assessed in each patient separately. Two radiologists and a urologist evaluated the quality of the reformatted images by judging each ureter in terms of the delineation of all its parts using a 5-point scale (insufficient, poor, moderate, good, and excellent).

RESULTS

Of the 75 patients in our cohort, 52 (69%) had urolithiasis. CPR images could be made of all ureters in all patients. Good to excellent image quality was found in the CPRs performed with a slice thickness of 8-12 mm: 27.7% at 8 mm, 14.3% at 9 mm, 26.9% at 10 mm, 12.6% at 11 mm, and 18.5% at 12 mm. Thus, a slice thickness of 8-12 mm determined a cumulative likelihood of 96.7% to demonstrate the ureter totally.

CONCLUSIONS

The results of our study have shown that CPR is a feasible and quick useful tool. CPRs of the urinary tract with a slice thickness of 8-12 mm are best for good delineation of the whole ureter.

Differentiation of urinary stone and vascular calcifications on non-contrast CT images: an initial experience using computer aided diagnosis

The purpose of this study was to develop methods for the differentiation of urinary stones and vascular calcifications using computer-aided diagnosis (CAD) of non-contrast computed tomography (CT) images. From May 2003 to February 2004, 56 patients that underwent a pre-contrast CT examination and subsequently diagnosed as ureter stones were included in the study. Fifty-nine ureter stones and 53 vascular calcifications on pre-contrast CT images of the patients were evaluated. The shapes of the lesions including disperseness, convex hull depth, and lobulation count were analyzed for patients with ureter stones and vascular calcifications. In addition, the internal textures including edge density, skewness, difference histogram variation (DHV), and the gray-level co-occurrence matrix moment were also evaluated for the patients. For evaluation of the diagnostic accuracy of the shape and texture features, an artificial neural network (ANN) and receiver operating characteristics curve (ROC) analyses were performed. Of the several shape factors, disperseness showed a statistical difference between ureter stones and vascular calcifications (p < 0.05). For the internal texture features, skewness and DHV showed statistical differences between ureter stones and vascular calcifications (p < 0.05). The performance of the ANN was evaluated by examining the area under the ROC curves (AUC, A (z)). The A (z) value was 0.85 for the shape parameters and 0.88 for the texture parameters. In this study, several parameters regarding shape and internal texture were statistically different between ureter stones and vascular calcifications. The use of CAD would make it possible to differentiate ureter stones from vascular calcifications by a comparison of these parameters.

Evaluation of patients with suspected ureteral calculi using sonography as an initial diagnostic tool: how can we improve diagnostic accuracy?

OBJECTIVE

The purpose of this study was to evaluate the usefulness of sonography as an initial diagnostic tool in patients with suspected ureterolithiasis.

METHODS

We performed a prospective study of 318 patients with suspected ureteral stones over a 14-month period. All patients underwent sonography after fasting for 8 hours and bladder filling. If no cause of the flank pain was found by sonography, computed tomography or intravenous urography was performed immediately to confirm the absence of ureteral stones.

RESULTS

We found urolithiasis with sonography in 291 of 296 patients with confirmed urolithiasis. The 5 remaining cases were identified after non-contrast-enhanced computed tomography (n = 3), intravenous urography (n = 1), or the passage of a stone (n = 1, pregnant patient). We detected 313 calculi in the 291 patients with sonography as follows: 307 ureteral calculi in 285 patients, 5 urinary bladder calculi that were probably passed from the ureter in 5 patients, and 1 urethral calculus. The locations of the 313 calculi in the 291 patients with a sonographic diagnosis were as follows: 21 were in the ureteropelvic junction, 96 in the proximal half of the ureter, 69 in the distal half of the ureter, 121 in the ureterovesical junction, 5 in the urinary bladder, and 1 in the urethra. Hydronephrosis was seen in 200 of the 291 patients with calculi identified by sonography (68.7%). Twinkling artifacts helped confirm the presence of tiny calculi in 184 of the 214 calculi (86%).

CONCLUSIONS

Sonography can be used as an initial diagnostic tool in patients with suspected ureterolithiasis.

Characterization of human renal stones with MDCT: advantage of dual energy and limitations due to respiratory motion

OBJECTIVE

Our aim was to determine, using CT attenuation values, the chemical composition of 241 human renal stones placed in a jelly phantom and to analyze the influence of respiratory motion on the classification.

MATERIALS AND METHODS

The stones were placed in a jelly simulating the X-ray attenuation of the kidneys. A dynamic platform was used to apply to the phantom free-breathing motion (sinusoidal motion in z-axis) and motion due to lack of maintenance of a breath-hold (5 mm x s(-1) in z-axis). Determination of the chemical composition was performed with mean CT attenuation values obtained at 80 and 120 kV and with dual-energy CT attenuation values.

RESULTS

Two hundred forty-one human urinary stones were classified into six groups: uric acid, cystine, struvite, weddellite (calcium oxalate dihydrate), whewellite (calcium oxalate monohydrate), and brushite. With no motion, the use of dual energy enabled differentiation of all of the types of stones with statistically significant differences. Uric acid (-20 +/- 22 H), cystine (106 +/- 19 H), struvite (271 +/- 16 H), weddellite (323 +/- 5 H), brushite (415 +/- 30 H), and whewellite (510 +/- 17 H) were identified as distinct groups. Motion-induced mean CT attenuation values were significantly different from those obtained with no motion. With motion, dual-energy CT attenuation values did not allow differentiation of all stone types.

CONCLUSION

Dual-energy CT attenuation values can be used to predict the chemical composition of stones in vitro. However, when slight motion is applied to renal stones during image acquisition, the values become significantly different from those obtained with no motion. Consequently, confusion arises in differentiating stone types. A perfect breath-hold has to be performed for in vivo use of attenuation value to discern stone type.

Non-Enhanced Spiral CT Versus Excretory Urography in Acute Renal Colic

Objective: To evaluate the usefulness of non-enhanced spiral CT (NECT) and compare it with that of excretory urography (EU) in patients with acute flank pain.

Methods: Ninety five patients presenting with acute flank pain underwent both NECT and EU. Both techniques were used to determine the presence, size, and location of urinary stone, and the presence or absence of secondary signs was also evaluated. The existence of ureteral stone was confirmed by its removal or spontaneous passage during follow-up. The absence of a stone was determined on the basis of the clinical and radiological evidence.

Result: Seventy eight of the 95 patients had one or more ureteral stones and 17 had no stones. CT depicted 79 of 83 calculi in the 78 patients with a stone and no calculus in all seventeen without a stone. The sensitivity and specificity of NECT were 95% and 100%, respectively. EU disclosed 73 calculi in the 78patients with a stone and no calculus in fifteen of the seventeen without a stone, with sensitivity and specificity 89% and 88% respectively.

Conclusion: For the evaluation of patients with acute flank pain, NECT is an excellent modality with high sensitivity and specificity. In near future it may replace EU.

Plain abdominal radiography with transabdominal native tissue harmonic imaging ultrasonography vs unenhanced computed tomography in renal colic

OBJECTIVE

To compare plain film kidney, ureter and bladder radiography (KUB) with transabdominal native tissue harmonic imaging ultrasonography (NTHI-US) vs unenhanced computed tomography (CT) for the diagnosis of urinary calculi in patients with acute flank pain.

PATIENTS AND METHODS

In all, 112 patients who presented to the urological department with clinical suspicion of ureteric calculi were included. These patients had KUB with NTHI-US and unenhanced CT. Of the 112 patients, 14 were lost to follow-up and therefore excluded. For the remaining 98 patients (53 men, 45 women; mean age 43.3 years, range: 19-74) the KUB with NTHI-US findings were compared with the CT findings, which served as the 'gold standard'.

RESULTS

In all, 75 patients were confirmed to have ureteric calculi. KUB with transabdominal NTHI-US detected 72 of the 75 patients with calculi (sensitivity 96%, specificity 91%, and accuracy 95%). Unenhanced CT detected urolithiasis in all 75 patients (sensitivity, specificity and accuracy of 100%). Both techniques showed further extra-urinary pathologies.

CONCLUSION

This prospective study shows that CT is the most accurate technique for detecting urolithiasis. However, KUB with transabdominal NTHI-US is an alternative to unenhanced CT with comparable results.

Unenhanced MDCT in Patients with Suspected Urinary Stone Disease: Do Coronal Reformations Improve Diagnostic Performance?

OBJECTIVE

The objectives of our study were to assess whether coronal reformations improve the diagnostic performance of MDCT in patients with acute flank pain and suspected urinary stone disease; and to determine if performing such reformations from 3-mm-thick sections is sufficient or if it is necessary to perform reformations from thinner sections.

MATERIALS AND METHODS

We included 147 consecutive patients (72 women and 75 men; mean age +/- SD, 58 +/- 18.1 years) with suspected urinary stone disease who underwent unenhanced MDCT. Scans were obtained with a 4 x 1 mm collimation and were reconstructed with a section thickness of 1.25 and 3 mm. We compared the diagnostic yield of 3-mm axial sections with that of coronal reformations reconstructed from 1.25- and 3-mm axial sections. Imaging data were evaluated in random order by two radiologists. The significance of the difference between the axial sections and coronal multiplanar reformations (MPRs) was tested for the number, size, and location of uroliths and for the presence of alternative diagnoses. The time required for review by both observers was recorded.

RESULTS

We found uroliths in 72 patients. There was no difference between 3-mm axial sections and coronal reformations from 1.25-mm sections with regard to the number of detected stones (n = 264 for both protocols), whereas coronal reformations from 3-mm sections revealed significantly fewer calcifications (n = 255, p = 0.016). Coronal reformations did not improve the localization of calcifications. Review time, however, was significantly shorter for coronal reformations than for axial sections (p = 0.001); however, coronal reformations were less sensitive than axial sections for the detection of additional findings suggestive of alternative diagnoses in 16 (30%) of 53 patients.

CONCLUSION

Coronal reformations from MDCT do not improve urinary stone detection but may reduce evaluation time; however, there is the danger of missing additional findings. Coronal reformations reconstructed from thick (i.e., 3-5 mm) axial sections may result in reduced detection of small stones and should therefore be avoided.

Value of 3-dimensional transrectal/transvaginal sonography in diagnosis of distal ureteral calculi

OBJECTIVE

In a prospective study, the feasibility of 3-dimensional (3D) transrectal/transvaginal sonography in comparison with transabdominal sonography and intravenous urography (IVU) in identifying distal ureteral calculi was evaluated.

METHODS

Sixty-two patients in the urologic clinic with clinical suspicion of distal ureteral calculi were included. The patients consisted of 44 men and 18 women with a mean age +/- SD of 44 +/- 17 years. These patients underwent 3D transrectal/transvaginal sonography, transabdominal sonography with IVU, and, finally, ureterorenoscopy.

RESULTS

Fifty-nine patients were confirmed to have distal ureteral calculi on the basis of urologic intervention (ureterorenoscopy). Three patients had a spontaneous stone passage immediately after imaging completion. The median size of the calculi was 3.7 +/- 2.00 mm. Transabdominal sonography detected 34 of the 62 patients with calculi (sensitivity, 55%). The median size of the calculi was calculated as 5.0 +/- 2.4 mm. The examination time was 6.5 +/- 2.7 minutes. Intravenous urography detected 44 of the 62 patients with ureterolithiasis (sensitivity, 71%). Herein, the median stone size was measured as 3.9 +/- 1.9 mm, and the examination time was 38 +/- 17 minutes. The combination of transabdominal sonography and IVU in visualization of ureterolithiasis raised the sensitivity to 81% (50 of 62 patients). Three-dimensional transrectal/transvaginal sonography showed ureterolithiasis in all 62 patients confirmed to have distal ureteral calculi (sensitivity and specificity, 100%). The median size of the calculi was calculated as 4.4 +/- 2.2 mm, and the examination took 1.9 +/- 0.6 minutes.

CONCLUSIONS

The data in our prospective study show that transrectal/transvaginal sonography with 3D image assessment is superior to IVU and abdominal sonography for diagnosing distal ureteral calculi.

Definição do nível da junção ureterovesical pela tomografia computadorizada

OBJETIVO: Definir o nível da implantação ureteral na bexiga através da tomografia computadorizada. MATERIAIS E MÉTODOS: Através de tomografia computadorizada da pelve com contraste endovenoso de 46 pacientes (31 homens e 15 mulheres) com idade entre 18 e 45 anos, com pelo menos um dos ureteres contrastado pelo contraste excretado, medimos as distâncias do meato ureteral até o teto acetabular e a borda superior da sínfise púbica, além do volume da bexiga. Utilizamos o teste t de Student para avaliar se houve diferenças estatísticas entre grupos. RESULTADOS: O nível da implantação ureteral na bexiga foi, em média, 10,6 ± 8,1 mm abaixo do teto acetabular e, em média, 29,7 ± 9,5 mm acima da borda superior da sínfise púbica. Nos pacientes com volume de repleção vesical menor que 200 ml e maior ou igual a 200 ml os níveis da implantação ureteral na bexiga foram, em média, 11,6 ± 7,3 mm e 10,2 ± 8,4 mm abaixo do teto acetabular (p = 0,61) e, em média, 28,3 ± 7,3 mm e 30,3 ± 10,2 mm acima da borda superior da sínfise púbica (p = 0,52), respectivamente, e nos pacientes do sexo masculino e feminino foram, em média, 11,8 ± 8,0 mm e 8,3 ± 8,0 mm abaixo do teto acetabular (p = 0,17) e, em média, 27,7 ± 9,2 mm e 33,9 ± 8,8 mm acima da borda superior da sínfise púbica (p = 0,34), respectivamente. CONCLUSÃO: Calcificações localizadas abaixo de 3 cm do teto acetabular e abaixo de 1,5 cm acima da borda superior da sínfise púbica provavelmente não representam cálculos ureterais. O grau de repleção vesical e o sexo não interferem significativamente na posição do meato ureteral.

Tomografia computadorizada sem contraste intravenoso no abdome agudo: quando e por que usar

A tomografia computadorizada sem contraste intravenoso tem sido freqüentemente proposta na avaliação inicial de pacientes com suspeita de abdome agudo, ocupando o espaço de outros métodos diagnósticos. Os autores apresentam uma revisão bibliográfica dos principais aspectos e eficácia da tomografia computadorizada sem contraste intravenoso no diagnóstico de apendicite aguda, cólica nefrética, diverticulite, pancreatite aguda, apendicite epiplóica, pneumoperitônio e obstrução intestinal. Discutem quais as vantagens e limitações desta técnica de exame, bem como seus aspectos práticos.

Functional renal imaging: nonvascular renal disease

Functional renal imaging-a fast-growing field of MR-imaging-applies different sequence types to gather information about the kidneys other than morphology and angiography. This update article presents the current status of different functional imaging approaches and presents current and potential clinical applications. Apart from conventional in-phase and opposed-phase imaging, which already yields information about the tissue composition, BOLD (blood-oxygenation level dependent) sequences, DWI (diffusion-weighted imaging) sequences, perfusion measurements, and dedicated contrast agents are used.

[Imaging techniques and their impact in treatment management of patients with acute flank pain]

The purpose of this overview is to provide a general summary of the imaging techniques applied at the Vienna Hospital for the investigation of acute flank pain and the diagnosis of stone disease and the evaluation of their efficacy and impact on therapy management. The number of publications on the issue of "intravenous urography (IVU) vs computed tomography (CT)" is abundant; in recent years, advocates of CT make up the majority. In the Department of Urology at the Vienna Hospital, conventional techniques such as ultrasound and IVU besides UHCT still play an important role. This overview presents the advantages and disadvantages of the various imaging techniques for diagnosis of stone disease and evaluates their significance regarding therapy management of patients with acute flank pain.

Is fluid ingestion really necessary during ultrasonography for detecting ureteral stones? A prospective randomized study

OBJECTIVE

Ultrasonographic evaluation of ureteral stones is usually performed after fluid ingestion for filling the bladder to visualize the ureterovesical junction better. We hypothesized that water ingestion may decrease the imaging quality of ultrasonography for detecting ureter stones. In our prospective randomized study, the accuracy of ultrasonography for detecting ureteral stones performed with or without fluid intake were evaluated.

METHODS

The study population comprised 150 consecutive patients thought to have ureteral stones who underwent ultrasonography. Patients were divided into 2 groups. Group A patients ingested 500 mL of water to distend the bladder before ultrasonographic examination. Group B patients were restricted from drinking any water at least 4 hours before the procedure.

RESULTS

Ultrasonography showed 35 (67.30%) of 52 stones in group A and 68 (93.15%) of 73 stones in group B. The difference of detection rates between the 2 groups was statistically significant (P < .001). The greatest improvement in detection rates was noted in the middle ureter stones. The evaluated sensitivity and specificity rates for group A were 67% and 82%, respectively, and those for group B were 93% and 94%. When the 2 methods were compared, total accuracy of ultrasonography increased from 71% in group A to 93% in group B.

CONCLUSIONS

This prospective randomized study showed that the diagnostic accuracy of ultrasonography for detection of middle ureteral stones increased significantly when performed without any water ingestion before the procedure. We recommend that patients thought to have ureteral stones should be first examined without any fluid ingestion.

Unenhanced Multi–Detector Row CT in Patients Suspected of Having Urinary Stone Disease: Effect of Section Width on Diagnosis

PURPOSE

To assess prospectively the effect of section width in multi-detector row computed tomographic (CT) evaluation of patients with acute flank pain who are suspected of having or known to have urinary stone disease.

MATERIALS AND METHODS

This study was approved by the ethics committee of the authors' university, and written informed consent was obtained from all patients. One hundred forty-seven patients (age range, 11-101 years; mean, 51.4 years +/- 18.7 [standard deviation]) suspected of having urinary stone disease underwent unenhanced multi-detector row CT. CT was performed with four detector rows, a section thickness of 1.0 mm, an effective tube current-time product of 100 mAs, and a tube voltage of 120 kVp (CT dose index, 11.4 mGy). From these data, three sets of transverse images were reconstructed with section widths of 1.5, 3.0, and 5.0 mm and approximately 50% of overlap each. Scans were evaluated in varying random orders by two radiologists for the number, size, and location of uroliths and nephroliths and for the presence of phleboliths, renal cysts, and secondary signs of obstruction. The significance of differences between the numbers of detected calcifications and the numbers of associated abnormalities on the scans obtained with varying section widths was tested with the McNemar test at a P level of less than .05. Spearman rho rank correlation coefficients were calculated to assess the correlation between the presence of uroliths and the presence of secondary signs.

RESULTS

Uroliths were found in 72 of 147 (49.0%) patients, and nephroliths were found in 16 patients (10.9%). There was no significant difference between section widths of 1.5 and 3.0 mm with regard to the number of detected stones (264 uroliths and 61 nephroliths for both protocols). Transverse sections 5.0-mm wide revealed significantly fewer uroliths (n = 231; P < .001) and nephroliths (n = 47; P < .016). The final diagnosis was changed in four of 72 patients. All missed renal and ureteral stones measured less than 3 mm in diameter.

CONCLUSION

Overlapping 3-mm sections are sufficient for the detection of urinary stone disease. Small calculi (<3 mm) may be missed on 5.0-mm-thick sections.

Diagnostic accuracy of ultrasonography compared to unenhanced CT for stone and obstruction in patients with renal failure

Background

To determine accuracy of ultrasound (US) kidney, ureter and bladder (KUB) compared to un-enhanced helical CT (UHCT) in patients with renal failure in the diagnosis of stone and obstruction.

Methods

This is a case controlled study conducted in the period from June 2000 to July 2003 at a university hospital. All patients had both US and UHCT scan. Patients with serum creatinine ≥ 1.8 mg/dl were included in the study. Only direct visualization of stone was considered as confirmatory. In both the studies, UHCT and US, presence of stone and obstruction were noted. The relevant biochemicals, radiological and clinical records of all the patients were analyzed. Data was analyzed using commercially available software.

Results

During the period of study 864 patients had UHCT for evaluation of the urinary tract in patients presenting with flank pain. Out of these 34 patients had both UHCT and US done within a span of one day and had serum creatinine of ≥1.8 mg/dl. Mean age was 48 ±15.8 years and 59% of patients were males. UHCT identified renal stones in 21 (62%), whereas 17 of these were identified on US, with a sensitivity of 81%. Of the four patients with renal stones missed on US, three were identified on plain x-ray; the mean size of stones missed was 6.3 mm. Of the 22 (65%) patients with ureteric stone on UHCT, US could only identify 10; a further 7 were identified on x-ray KUB, giving a sensitivity of 45% (US alone) and 77% (US with x-ray KUB).

Conclusions

US is sensitive and specific for renal stones, 81% and 100% and for hydronephrosis, 93% and 100%, respectively. Its sensitivity to pick ureteric stone (46%) and to identify hydroureter (50%) is low. Addition of x-ray KUB abdomen increases the sensitivity for ureteric stones to 77%.

Multidetector CT urography: techniques, clinical applications, and pitfalls

For two decades, computed tomography (CT) has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, CT is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The last purported advantage of IVU has been its ability to depict subtle and mucosal abnormalities of the urothelium. Now, using multidetector CT (MDCT), this challenge has been overcome. In this article, we review the current role of MDCT urography in the evaluation of the urinary tract.

Multi-detector row CT urography in the evaluation of hematuria

Hematuria can be well evaluated with a comprehensive contrast material-enhanced multi-detector row computed tomography (CT) protocol that combines unenhanced, nephrographic-phase, and excretory-phase imaging. Unenhanced images are obtained from the kidneys to the bladder and allow optimal detection of renal calculi, a common cause of hematuria. Renal parenchymal abnormalities, particularly masses, are best visualized on nephrographic-phase images, which also provide excellent evaluation of the other abdominal organs. Thin-section delayed images obtained from the kidneys to the bladder demonstrate the urinary tract distended with contrast material and are useful in detecting urothelial disease. Intravenous urography, ultrasonography, CT, retrograde ureterography and pyelography, cystoscopy, and ureteroscopy can all be used to evaluate patients with hematuria. In the past, a combination of several of these examinations was necessary to fully evaluate these patients. Now, however, this CT protocol may permit evaluation of hematuria patients with a single comprehensive examination, although more experience and data are needed to determine its efficacy in this setting.

Acute Ureterolithiasis: Incidence of Secondary Signs on Unenhanced Helical CT and Influence on Patient Management

AIM

The purpose of this study was to determine the incidence of secondary signs associated with ureteral stones on unenhanced helical computed tomography (CT) of patients with acute renal colic, and to correlate these with patient management and outcome.

MATERIALS AND METHODS

One hundred and ten patients with ureterolithiasis were evaluated prospectively for the secondary signs of obstruction on unenhanced helical CT. Our attention was focused primarily on the presence or absence of seven secondary signs on unenhanced helical CT, including hydronephrosis, unilateral renal enlargement, perinephric oedema, unilateral absence of the white pyramid, hydroureter, periureteral oedema and lateroconal fascial thickening.

RESULTS

Of the 110 patients, 91 (82.7%) had hydroureter, 88 (80%) had hydronephrosis, 65 (59%) had periureteric oedema and 63 (57.2%) had unilateral renal enlargement. Ninety stones passed spontaneously and 21 required intervention.

CONCLUSION

Secondary signs of urinary tract obstruction are useful and supportive findings in interpretation of the CT examination. In our experience, the most reliable signs indicating ureteral obstruction are hydroureter, hydronephrosis, periureteral oedema and unilateral renal enlargement, respectively. In addition, stones larger than 6 mm, located within the proximal two thirds of the ureter, and seen associated with five or more the secondary signs of obstruction, are more likely to require endoscopic removal and/or lithotripsy.

Hematuria as an indicator for the presence or absence of urinary calculi

The purpose of this study was to determine whether the presence of hematuria or its absence can predict the presence or absence of urinary calculi as determined by computed tomography (CT) scan in patients presenting to the ED with acute abdominal colic. We reviewed the urine analysis and CT scans of all patients presenting to the ED over a 12-month period with acute colic and a clinical suspicion of urinary calculi. Urine samples were drawn on arrival in the ED before CT scanning. Two hundred seventy-seven patients were included in the study. The prevalence of urinary stones as detected by CT was 57.4%. The positive predictive value, negative predictive value, and accuracy for hematuria as a marker for stone disease was 60.9%, 72.4%, and 62.1%, respectively. A total of 3.24% of patients had some degree of obstruction, all of whom had hematuria. The absence of hematuria is not a reliable exclusion criterion for urinary calculi. The detection of urinary stones without hematuria does not imply obstruction.

Evaluation of the patient with flank pain and possible ureteral calculus

Flank pain due to urolithiasis is a common problem in patients presenting to emergency departments. Radiology plays a vital role in the work-up of these patients. Many modalities can be used, including ultrasonography, nuclear medicine, and the traditionally used techniques of intravenous urography and conventional radiography. The development of nonenhanced computed tomography (CT) (single- or multi-detector row helical) has provided a means to enable detection and characterization of urolithiasis with unprecedented sensitivity, specificity, and accuracy while yielding important information for treatment planning, including the size and location of calculi. This technique can also help detect causes for flank pain outside the genitourinary tract. However, close attention must be paid to all aspects of the CT study to prevent misdiagnoses.

Unenhanced helical computed tomography in the evaluation of acute flank pain

OBJECTIVES

The purpose of this study was to determine the value of unenhanced helical computed tomography (UHCT) in the diagnosis of acute flank pain at our institution.

METHODS

Two hundred and thirty-three consecutive UHCT examinations, performed for suspected renal/ureteral colic between July 2000 and August 2001 were reviewed, along with pertinent medical records.

RESULTS

Ureteral calculi were identified in 148 (64%) examinations, evidence of recent passage of calculi was found in 10 (4%) and no calculi were found in 75 (32%). Thirty-two of the conservatively managed patients were excluded for inadequate follow-up. In the remaining 201 patients, sensitivity of UHCT in diagnosing calculi was 99% and specificity was 98%, while the positive predictive value was 99% and negative positive predictive value was 98%. Overall, an alternative or additional diagnosis was established in 28 (12%) patients. Upon diagnosis of ureterolithiasis on UHCT, none of the patients required additional imaging studies for confirmation.

CONCLUSION

UHCT is a highly sensitive imaging modality for the detection of urinary tract calculi and obstruction.

Conspicuity of renal calculi at unenhanced CT: effects of calculus composition and size and CT technique

PURPOSE

To determine the effects of calculus size, composition, and technique (kilovolt and milliampere settings) on the conspicuity of renal calculi at unenhanced helical computed tomography (CT).

MATERIALS AND METHODS

The authors performed unenhanced CT of a phantom containing 188 renal calculi of varying size and chemical composition (brushite, cystine, struvite, weddellite, whewellite, and uric acid) at 24 combinations of four kilovolt (80-140 kV) and six milliampere (200-300 mA) levels. Two radiologists, who were unaware of the location and number of calculi, reviewed the CT images and recorded where stones were detected. These observations were compared with the known positions of calculi to generate true-positive and false-positive rates. Logistic regression analysis was performed to investigate the effects of stone size, composition, and technique and to generate probability estimates of detection. Interobserver agreement was estimated with kappa statistics.

RESULTS

Interobserver agreement was high: the mean kappa value for the two observers was 0.86. The conspicuity of stone fragments increased with increasing kilovolt and milliampere levels for all stone types. At the highest settings (140 kV and 300 mA), the detection threshold size (ie, the size of calculus that had a 50% probability of being detected) ranged from 0.81 mm + 0.03 (weddellite) to 1.3 mm + 0.1 (uric acid). Detection threshold size for each type of calculus increased up to 1.17-fold at lower kilovolt settings and up to 1.08-fold at lower milliampere settings.

CONCLUSION

The conspicuity of small renal calculi at CT increases with higher kilovolt and milliampere settings, with higher kilovolts being particularly important. Small uric acid calculi may be imperceptible, even with maximal CT technique.

The accuracy of noncontrast helical computed tomography versus intravenous pyelography in the diagnosis of suspected acute urolithiasis: a meta-analysis

STUDY OBJECTIVES

We determine the accuracy of noncontrast helical computed tomography (NHCT) compared with that of intravenous pyelography (IVP) in diagnosing acute urolithiasis.

METHODS

Computerized searches of MEDLINE and EMBASE were combined with hand reviews of major journals and of articles from reference lists. Articles were assessed according to a priori criteria for inclusion. Study eligibility was independently assessed by 2 reviewers in a blinded fashion. Test results were combined and analysis of log-transformed data was conducted by using general linear models.

RESULTS

No disagreement was found between the 2 investigators in terms of articles that met the inclusion criteria or between the results of the studies. Four studies involving a total of 296 patients met all of the a priori criteria. The pooled positive likelihood ratios (LR+) for NHCT and IVP are 23.15 (95% confidence interval [CI] 11.53 to 47.23) and 9.32 (95% CI 5.23 to 16.61), respectively. The pooled negative likelihood ratios (LR-) for NHCT and IVP are 0.05 (95% CI 0.02 to 0.15) and 0.33 (95% CI 0.23 to 0.48), respectively. The differences between NHCT and IVP were statistically significant for both LR+ (P =.046) and LR- (P =.013). Differences among trials were not statistically significant in either analysis (P =.125 for LR+; P =.114 for LR-).

CONCLUSION

The studies analyzed consistently demonstrated NHCT to be superior to IVP in accurately diagnosing acute urolithiasis, and differences between the 2 tests for both LR+ and LR- were statistically significant.

Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography

OBJECTIVE

The purpose of this study was to compare the accuracy of unenhanced helical CT with combined sonography and unenhanced radiography in patients with acute flank pain suggestive of ureteral colic.

SUBJECTS AND METHODS

From January 1997 to December 1999, 181 consecutive patients with acute flank pain underwent unenhanced radiography, sonography, and unenhanced helical CT (protocol A). From January 2000 to December 2000, 96 consecutive patients arriving at the emergency department with acute flank pain were alternately submitted either to primary unenhanced helical CT (protocol B, 48 patients) or to unenhanced radiography and sonography with the addition of helical CT in unclear cases (protocol C, 48 patients).

RESULTS

When compared with the diagnostic accuracy for ureterolithiasis of the combined sonography and radiography in the same group of subjects (protocol A), CT had a greater sensitivity (92% vs 77%), negative predictive value (87% vs 68%), and overall accuracy (94% vs 83%). Among patients who underwent primary CT (protocol B), we found three false-negatives (all with spontaneous stone passage) and no false-positives. Among patients initially examined with unenhanced radiography and sonography (protocol C), we found one false-positive (leading to patient admission and needless repeated radiographic and sonographic studies) and six false-negatives (all followed by an uncomplicated course and spontaneous passage); CT depicted four of these stones but did not result in change in treatment. Fourteen percent of the patients in protocol C required invasive treatment, but combined sonography and radiography showed stones and hydronephrosis in all these patients.

CONCLUSION

Unenhanced CT was the most accurate modality for determining the presence of ureterolithiasis. The combination of abdominal radiography and sonography, however, yielded comparable results with no clinically important misdiagnoses and thus can be used as an alternative when CT resources are limited.