Sample Teaching Cases

Urinary Imaging

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All modalities are used in imaging of the urinary system. However, with the advent of advanced imaging modalities, fluoroscopy and intravenous pyelography (IVP) play a diminished role. There are instances when these modalities are still the exam of choice.

Case UI.1

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1. What is the most common location for this diagnosis?

2. What complication is demonstrated by this exam?

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Case UI.2

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1. What are the advantages and disadvantages of this study as compared to radionuclide cystogram? To voiding urosonography?

2. What condition is demonstrated?

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Case UI.3

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Questions

1. What criteria are used in the Bosniak classification system of renal masses?

2. What criterion is most concerning for malignancy?

3. In the Bosniak classification system, how would the right renal lesion be classified? The left renal lesion?

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Answers

Case UI.1

Posterior Urethral Valves.pngDiagnosis

Prostatic posterior urethral valve with secondary grade 5 vesiculoureteral reflux.

Findings

Voiding cystourethrogram (VCUG) demonstrates narrowing of the urethra at the level of the prostate with proximal urethral and bladder distention. In addition, left-sided vesiculoureteral reflux is seen with dilatation of the renal calyces.

Answers

1. What is the most common location for this diagnosis?

Occurring exclusively in males, the most common location for a posterior urethral valve is in the prostatic urethra as demonstrated in this voiding cystourethrogram (VCUG) by the dilated proximal urethra. Antenatal ultrasound can identify posterior urethral valves in utero, allowing for early intervention.  Without intervention complications of outflow obstruction will occur.

2. What complication is demonstrated by this exam?

Grade 5 secondary vesiculoureteral reflux (VUR) is the complication demonstrated on this exam. Additional complications can include bladder trabeculation, diverticula, wall thickening and hypertrophy, as well as urinary tract infections, renal function impairment, dysplastic kidneys and urine ascites. Primary VUR is due to inadequacy of the vesiculoureteral valvular mechanism.

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Case UI.2

Vesiculoureteral reflux.pngDiagnosis

Left-sided grade 5 vesicoureteral reflux 

Findings

Retrograde urethrogram (RUG) demosntrates bladder distention with left-sided vesiculoureteral reflux and dilated renal calyces.

Answers

1. What are the advantages and disadvantages of the illustrated study as compared to radionuclide cystogram? To voiding urosonography?

The traditional voiding cystourethrogram (VCUG) produces higher radiation exposure doses than radionuclide cystogram (RNC) and voiding urosonography (VUS), but digital fluoroscopy with screen-save techniques, image coning and pulsed fluoroscopy can reduce this exposure. At the same time, VCUG provides the highest resolution anatomic imaging with real-time visualization. RNC offers reduced radiation but decreased anatomic resolution. While VUS techniques without US contrast have significantly decreased sensitivities and VUS has decrease anatomic resolution, intravesicular US contrast administration allows VUS to approach VCUG in sensitivity and offers real-time visualization and evaluation of renal parenchyma.

2. What condition is demonstrated?

Left-sided grade 5 vesicoureteral reflux is demonstrated by reflux into a tortuous, markedly dilated ureter and pelvicaliceal system with obliteration of the forniceal angles and papillary impressions. The normal anatomy of the ureterovesical wall junction functions as a flap-valve mechanism and prevents urinary reflux. Reflux is associated with an abnormal intramural channel.

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Case UI.3

Renal Cell Carcinoma.png

Diagnosis

Bosniak IV lesion consistent with renal cell carcinoma. Subsequently, histology confirmed the diagnosis of renal cell carcinoma.

Findings

Before contrast is administered, a mass is seen in the medial aspect of the right kidney. Also, smaller low attenuation lesion is seen in the anterolateral aspect of the left kidney. After the administration of contrast the right-sided mass demonstrates significant soft tissue enhancement. The left-sided lesion does not enhance.

Answers

1. What criteria are used in the Bosniak classification system of renal masses?

The Bosniak system is a useful tool in classifying and managing cystic renal masses, requiring assessment of the lesion by computed tomography before and after administration of intravenous contrast. The center of the mass should be characterized by attenuation, and the cyst wall and/or septa should be characterized by thickness, uniformity or irregularity, presence or absence of calcification, presence or absence of soft tissue components, and the degree of enhancement. At least 25% of the wall must be exophytic to be assessable.

  • Type I Bosniak lesions are simple cysts, characterized by internal fluid attenuation (0 – 20 HU) outlined by a hairline-thin wall without septa, calcifications, soft tissue or enhancing components. These are benign and do not require follow-up.
  • Type II Bosniak lesions are minimally complicated cysts, characterized by a few hairline-thin septa without measurable enhancement, fine calcifications or a short segment of thick calcification in the wall or septa. These can also be cystic lesions that are well marginated, non-enhancing, homogeneously high-attenuating (> 20 HU and typically 40 – 90 HU), measuring less than 3 cm. These are benign and do not require follow-up.
  • Type IIF Bosniak lesions may contain multiple hairline-thin septa without measurable enhancement, minimal smooth thickening of wall or septa without measurable enhancement, thick calcification, and/or nodularity without measurable enhancement. Additionally, this category includes intrarenal non-enhancing, high-attenuation renal masses greater than 3 cm. These are probably benign but do require follow-up.
  • Type III Bosniak lesions have thickened walls or septa, which may be irregular or smooth, and have measurable enhancement of greater than 20 HU. These are concerning for malignancy, and tissue diagnosis is required.
  • Type IV Bosniak lesions can be characterized by all the criteria for type III lesions, but also contain enhancing soft-tissue components adjacent to or separate from the wall or septa. These are consistent with malignancy, and tissue diagnosis is required.

2. What criterion is most concerning for malignancy?

The most concerning feature for malignancy is enhancing soft-tissue components adjacent to or separate from the wall or septa on the post-contrast images when compared to the non-contrasted images. This feature categorizes the lesion as Bosniak Type IV.

3. In the Bosniak classification system, how would the right renal lesion be classified? The left renal lesion?

The right renal lesion has thick irregular walls with significant, enhancing soft tissue components; therefore, it would be classified as Bosniak Type IV. Tissue diagnosis revealed renal cell carcinoma. The lesion on the left is less than 1 cm in diameter, does not significantly enhance and would be classified as Bosniak Type 1, a simple cyst. During treatment and surveillance for cancer, the left-sided simple cyst did not change in appearance.

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