Acute ureterolithiasis: nonenhanced helical CT findings of perinephric edema for prediction of degree of ureteral obstruction.

PURPOSE: To determine whether the extent of perinephric edema on helical computed tomographic (CT) images without contrast material enhancement can be used to predict the degree of ureteral obstruction in patients with acute ureterolithiasis. MATERIALS AND METHODS: Nonenhanced helical CT and excretory urographic images in 82 patients with flank pain were retrospectively reviewed. For each patient, a radiologic diagnosis was established, and the degree of ureteral obstruction determined on urograms was compared with the extent of perinephric edema assessed on CT images. RESULTS: None of 29 patients with no abnormalities seen at urography had evidence of perinephric edema at CT. Of six patients with noncalculous disease, two with acute pyelonephritis had perinephric edema at CT. Of 47 patients with acute ureterolithiasis, eight had no perinephric edema at CT and a nonobstructing calculus at urography, 21 had limited edema at CT and low-grade obstruction at urography, and 15 had extensive edema at CT and high-grade obstruction at urography. Three patients had extensive perinephric edema at CT but low-grade obstruction at urography. The extent of edema allowed accurate prediction of the degree of ureteral obstruction in 44 (94%) of 47 patients with acute ureterolithiasis. CONCLUSION: The extent of perinephric edema on nonenhanced helical CT images can be used to predict the degree of ureteral obstruction in acute ureterolithiasis.

Ureterolithiasis: value of the tail sign in differentiating phleboliths from ureteral calculi at nonenhanced helical CT.

PURPOSE: To determine the value of the tail sign in differentiating phleboliths from ureteral calculi at nonenhanced helical computed tomography (CT). MATERIALS AND METHODS: The nonenhanced helical CT scans in 82 patients with a confirmed diagnosis of pelvic ureterolithiasis were retrospectively reviewed. Each calcification along the ureter was classified as a phlebolith or a ureteral calculus on the basis of clinical and imaging findings and was analyzed for the presence of a tail sign. RESULTS: Eighty-two patients each had a single ureteral calculus. None of these calculi were associated with a positive tail sign. Sixty-nine phleboliths were present in 35 patients. Forty-five phleboliths (65%) were associated with a positive tail sign. Of the remaining 24 phleboliths, 17 (25%) were associated with a negative tail sign and seven (10%) were indeterminate. The tail sign has a sensitivity of 65% (45 of 69; 95% CI: 53%, 75%) and a specificity of 100% (82 of 82; 95% CI: 96%, 100%) in differentiating phleboliths from ureteral calculi. CONCLUSION: The tail sign is an important indicator that a suspicious calcification represents a phlebolith. Absence of the tail sign indicates that the calcification remains indeterminate.

Ureterolithiasis: can clinical outcome be predicted with unenhanced helical CT?

PURPOSE: To evaluate the use of helical computed tomography (CT) without contrast material enhancement for prediction of a favorable outcome in ureterolithiasis. MATERIALS AND METHODS: CT studies were reviewed in 69 patients with a single ureteral stone not located at the ureteropelvic junction. CT findings (tissue rim sign, hydronephrosis, perinephric fat stranding, perinephric fluid collections, and thickening of renal fascia) were graded on a scale of 0-3. Stone diameter and renal parenchymal enlargement were also measured. RESULTS: Twenty-two patients had spontaneous passage, 12 did not respond to conservative treatment, and 35 were lost to follow-up. When the latter 35 patients were excluded, perinephric fat stranding (P = .044) and perinephric fluid collections (P = .021) were graded significantly higher in patients with spontaneous stone passage. Mean stone diameter was significantly larger (P < .001) in patients in whom conservative treatment failed (mean, 7.8 mm) than in patients with spontaneous stone passage (mean, 2.9 mm). The presence of a tissue rim sign and the grade of hydronephrosis, renal fascial thickening, and renal parenchymal enlargement were not significantly different between the two groups. CONCLUSION: In addition to stone size, the degree of perinephric fat stranding and the presence of perinephric fluid collections are useful ancillary signs for help in predicting the likelihood of stone passage.

Noncontrast helical CT for ureteral stones.

Noncontrast helical computed tomography (CT) has recently been found to be superior to excretory urography (IVU) in the evaluation of patients with suspected ureterolithiasis. Noncontrast helical CT does not require the use of intravenous contrast material with its associated cost and risk of adverse reactions and can be completed within 5 min, in most cases. Noncontrast CT often detects extraurinary pathology responsible for the patient's symptoms. CT is also more sensitive than IVU in detecting the calculus, regardless of its size, location, and chemical composition. However, confidently differentiating ureteral calculi from phleboliths along the course of the ureter may, at times, be difficult. The "tissue-rim" sign, a rim of soft tissue attenuation around the suspicious calcification, is helpful in making this distinction. Noncontrast CT does not provide physiological information about renal function and the degree of obstruction. A pilot study has suggested a proportional relationship between the extent of perinephric edema and the degree of obstruction. The cost of the examination and the radiation dose delivered to the patient may be higher with CT. Despite these limitations, noncontrast helical CT has quickly become the imaging study of choice in evaluating patients with acute flank pain.

Unenhanced helical CT of ureterolithiasis: value of the tissue rim sign.

OBJECTIVE: The tissue rim sign-a rim or halo of soft-tissue attenuation seen around the circumference of an intraureteral calculus on unenhanced axial CT-has been described as useful in differentiating ureteral calculi from extraurinary abdominal or pelvic calcifications. The purpose of this study was to determine the prevalence of the tissue rim sign in patients with ureterolithiasis and extraurinary calcifications and to determine the relationship between the tissue rim sign, the size of a calculus, and the degree of urinary obstruction. MATERIALS AND METHODS: Unenhanced helical CT studies followed by excretory urography were obtained in 59 patients with suspected acute ureterolithiasis. Each calcification along the expected course of the ureter seen on axial CT scans was categorized as a ureteral calculus or as an extraurinary calcification. Each categorization was based on CT, urographic, and clinical findings and the presence or absence of a tissue rim sign. When the outer wall of the ureter could not be seen because there was no clear fat plane at the level of the calcification on CT, the sign was categorized as "indeterminate." The size of the calculus was measured on CT, and the degree of urinary obstruction was estimated on the basis of the urograms. RESULTS: Thirty-two patients each had a single ureteral calculus. Of these patients, CT revealed a positive tissue rim sign in 16 patients (50%), was negative in five patients (16%), and was indeterminate in 11 patients (34%). In addition, we saw 57 extraurinary calcifications in 18 patients (11 patients with ureteral calculi and seven patients without ureteral calculi). None of the 57 extraurinary calcifications was associated with a positive tissue rim sign. The tissue rim sign was negative in 39 (68%) of the 57 extraurinary calcifications and indeterminate in the remaining 18 (32%). Ureteral calculi with a negative tissue rim sign were larger than ureteral calculi with a positive tissue rim sign (p < .01). A high degree of obstruction was present in four of five patients with ureteral calculi for which CT showed a negative tissue rim sign. Conversely, six of 16 patients in whom CT revealed a positive tissue rim sign also had a high degree of obstruction. Therefore, no clear relationship was found between the degree of obstruction and the presence of a positive tissue rim sign. CONCLUSION: A positive tissue rim sign is specific for the diagnosis of ureterolithiasis. However, a negative tissue rim sign does not preclude such a diagnosis. The presence or absence of this tissue rim sign correlates with the size of a calculus but not with the degree of urinary obstruction. When CT reveals an indeterminate tissue rim sign, careful inspection for other CT findings, such as ipsilateral ureteral dilatation, perinephric edema, dilatation of the intrarenal collecting system, and renal swelling, is necessary.

Suspected urolithiasis in pregnant women: imaging algorithm and literature review.

Urolithiasis during pregnancy is a difficult clinical problem in which carefully selected radiologic studies play an essential role. For years excretory urography has been the standard of care in the radiologic evaluation of urolithiasis in pregnancy. Recently, sonography, particularly Doppler sonography, has evolved as an invaluable tool in the armamentarium of radiologists facing this challenging problem. In experienced hands, the diagnosis of urolithiasis in pregnancy can be made confidently using Doppler sonography and, when necessary, excretory urography.