Relevance of sonographic artifacts observed during in vitro characterization of urocystolith mineral composition

Correlating the Sonographic Finding of Echogenic Debris in the Bladder Lumen With Urinalysis

OBJECTIVES

The purpose of this study was to determine the significance of urinary bladder debris detected by sonography.

METHODS

We conducted a retrospective analysis of urinalysis results in age-matched patients with and without bladder debris detected by transabdominal sonography. Patients were recruited from a radiology database search for bladder sonograms either with words suggesting echogenic debris or by a clinical history suggesting an infectious course. The sonograms were randomized and read by a single radiologist, who was blinded to case versus control. The urinalysis and sonographic results were analyzed by the Fisher exact test.

RESULTS

There was no statistically significant correlation between the finding of debris on sonography and the frequency of abnormal urinalysis results, regardless of the quality of debris (layering versus floating). The only variable that was significantly associated with abnormal urinalysis results was a clinical history suggesting infection.

CONCLUSIONS

A urinalysis should not be routinely recommended to work up the finding of urinary bladder debris on sonography.

Comparative sonographic appearance of nephroliths and associated acoustic shadowing artifacts in conventional vs. spatial compound imaging

Spatial compound sonography improves visualization of tissue details and allows clearer delineation of structural margins. Improved image clarity is due to reduced speckling artifact; however, other types of acoustic shadowing artifacts may be unchanged or variably altered when conventional and spatial compound sonographic images are compared. Because intrarenal distal shadowing artifacts in conventional sonographic images are oftentimes the first or only evidence that a nephroliths is present, we compared the appearance and associated artifacts of nephroliths examined with both imaging modes. Consensus evaluation by two evaluators confirmed differences in appearance of nephroliths based on imaging mode. Nephroliths with conventional imaging mode were less hyperechoic and had better margin delineation while nephroliths were more hyperechoic and had less distinct margins with spatial compound imaging mode. Distal acoustic shadowing artifacts were present in 43% of spatial compound imaging mode vs. 86% of conventional imaging mode. When present in both imaging modes, intensity of these artifacts was weaker and the distance traveled was shorter in spatial compound imaging mode. Multiple diverging acoustic shadowing artifacts originating from a single source, the nephroliths were occasionally noted in spatial compound but not conventional imaging mode. These results demonstrate that the absence of distal acoustic shadowing cannot be used to exclude the presence of a nephrolith in dogs and cats. Optimal diagnosis of nephroliths, margin delineation, and visualization of the distal renal parenchyma requires paired radiography and sonography, and alternating between sonographic imaging modes is therefore suggested.

TWINKLING ARTIFACT IN SMALL ANIMAL COLOR-DOPPLER SONOGRAPHY

Twinkling artifact is a recently described color-Doppler phenomenon that has not been studied in the veterinary field. Our purpose was to assess the grade of the artifact in vitro with varying urolith compositions, and to evaluate its potential role in clinical practice. Five canine and feline uroliths types of 100% mineral composition were studied in vitro with color-Doppler sonography, and a prospective study was performed in 41 patients with renal, bladder, gallbladder, or digestive focal hyperechogenicities. The images were analyzed for the presence and the grade of the artifact. Phantom study demonstrated the constant occurrence of the artifact regardless of the mineral composition of uroliths. Mottled and rough surfaced stones produced higher grades of twinkling artifact. High-grade, color-twinkling artifact generated by stones occured frequently in vivo. Bladder crystalluria was more frequently detected by artifact visualization than sample urinalysis performed by cystocentesis. In veterinary medicine, twinkling artifact may thus be considered an additional sonographic feature of urinary stones, and can lead to a more appropriate management of patients presenting gray-scale sonographic focal hyperechogenicities.

Sonography of a human jackstone calculus

Jackstone calculi are urinary tract stones that have a specific appearance resembling toy jacks. They are almost always composed of calcium oxalate dihydrate and may be found in the urinary bladder or rarely in the upper urinary tract. Their appearance on plain radiographs and computed tomography (CT) in human patients has been well described. They have also been imaged in several species of animals. However, our review of the English medical literature revealed no previous report in which a jackstone calculus had been identified on the sonographic examination of a human patient. We report a case in which a large jackstone calculus was incidentally detected during abdominal sonography in a 75-year-old man.

An integrated epidemiologic and radiographic algorithm for canine urocystolith mineral type prediction

Research involved 2 databases. One database (occurrence frequency) comprised the age, breed, gender and urocystolith mineral type (pure chemical types only) from 2041 canine patients submitted to the Minnesota Urolith Center. The other database (imaging) comprised the maximum size, surface (rough, smooth, and smooth with blunt tips), shape (faceted, irregular, jackstone, ovoid, and round) and internal architecture (lucent center, random-nonuniform, and uniform) from 434 canine patients imaged in a urinary bladder phantom. The imaging database was a partial subset of the occurrence frequency database. Imaging techniques simulated were survey radiography and double contrast cystography. The databases were compared using multivariate analysis techniques. Equations were developed to use clinically-relevant characteristics (age, breed, gender, maximum size, surface, shape, and internal architecture) to predict urocystolith mineral types. The goal was to assess the accuracy of the various techniques in predicting the urocystolith mineral types. The combination of signalment (age, breed, gender) and simulated survey radiographic findings does not improve mineral type prediction accuracy (average across all mineral types is 69.9%) beyond that achievable with signalment alone (average across all mineral types is 69.8%). However, the combination of signalment and double contrast cystography does improve mineral type prediction accuracy (average across all mineral types is 75.3%). For comparison, mineral type prediction accuracy without signalment from survey radiographs only was 65.7% across all mineral types. The clinical utility of the algorithm is the option to distinguish urocystolith mineral types requiring surgical vs. medical treatment.