Computed Tomography of the Urinary Tract Quiz

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Questions and Answers

When is a scanogram taken during a standard diagnostic computed tomography of the urinary tract?

As the final step of the procedure

After administering i.v. contrast

Before the scan process begins (correct)

Before obtaining venous access

What phase are the scans obtained in approximately 70 seconds after i.v. contrast administration during computed tomography of the urinary tract?

Interstitial phase

Nephrogenic phase

Excretory phase

Arterial phase (correct)

What is one of the indications for performing computed tomography of the urinary tract?

Evaluation of renal stone disease (correct)

Assessment of pulmonary function

Diagnosis of skin infections

Investigation of thyroid nodules

Which of the following is NOT a possible use of computed tomography angiography in the assessment of renal vessels?

Evaluating heart valve functions Signup and view all the answers

When performing computed tomography urinary tract examination, what is used to assess precontrast attenuation and enhancement patterns in the kidneys?

Pre- and post-i.v. contrast scans Signup and view all the answers

In which position does the patient lie during a standard diagnostic computed tomography for renal tract malignancy?

Supine position Signup and view all the answers

Which of the following criteria indicates a benign adrenal lesion on a delayed contrast-enhanced CT scan?

Both an absolute percentage washout (APW) greater than 60% and a relative percentage washout (RPW) greater than 40% Signup and view all the answers

What is the primary purpose of performing an unenhanced CT scan in adrenal lesion characterization?

To measure the attenuation (in Hounsfield units) of any adrenal mass Signup and view all the answers

What is the recommended technique for a CT scan of the kidneys, ureters, and bladder (CT KUB) to assess renal tract calculus disease?

Supine position, no contrast administration, and scanning from the top of the kidneys to the bladder base with a low-radiation-dose technique Signup and view all the answers

In a computed tomography urogram (CTU), what is the purpose of the oral water load given before the intravenous contrast injection?

To induce a diuresis and collect system dilatation for better visualization Signup and view all the answers

During a computed tomography urogram (CTU), at what time point is the nephrographic/parenchymal enhancement phase scan typically acquired?

100 seconds following the start of the bolus intravenous contrast injection Signup and view all the answers

What is the primary limitation of a low-dose CT KUB scan without intravenous or oral contrast?

Limited role in identifying pathology other than renal tract calculus disease Signup and view all the answers

Study Notes

Scanogram timing

A scanogram is taken at the beginning of a standard diagnostic computed tomography (CT) of the urinary tract, before contrast is administered.

Nephrographic Phase

The nephrographic phase of a CT scan of the urinary tract is obtained approximately 70 seconds after intravenous contrast administration.

Indications for CT Urinary Tract

One indication for performing a computed tomography of the urinary tract is to evaluate for suspected renal tract malignancy.

CT Angiography Uses

CT angiography is not used to assess for renal artery stenosis, as it is not as sensitive or specific for this purpose compared to other methods like magnetic resonance angiography (MRA).

CT KUB Assessment

CT KUB examinations use pre-contrast attenuation and enhancement patterns in the kidneys to assess for potential pathologies such as renal masses or cysts.

Patient Position

During a standard diagnostic CT for renal tract malignancy, the patient lies in a supine position on the scanning table.

Benign Adrenal Lesions

On a delayed contrast-enhanced CT scan, a benign adrenal lesion typically demonstrates a low Hounsfield unit (HU) value, indicating a lack of significant contrast enhancement.

Unenhanced CT Scan Purpose

Performing an unenhanced CT scan of adrenal lesions is primarily used to assess the size and density of the lesion, as well as to identify any calcifications within the lesion, aiding in the initial characterization.

Recommended Technique for CT KUB

The recommended technique for a CT KUB scan to assess for renal tract calculus disease involves performing a thin-section (1-2mm) scan through the kidneys, ureters, and bladder, with both pre-contrast and post-contrast image acquisition to optimize visualization of stones.

Oral Water Load in CTU

Providing an oral water load before intravenous contrast injection in a computed tomography urogram (CTU) is essential to distend the urinary bladder, allowing for optimal visualization of the bladder and lower urinary tract, enhancing the diagnostic accuracy for detecting potential issues like bladder stones or tumors.

Nephrographic Phase Acquisition

The nephrographic/parenchymal enhancement phase scan during a CTU is typically acquired around 60-90 seconds after intravenous contrast administration, as this timing provides optimal visualization of the renal parenchyma due to contrast enhancement.

Limitations of Low-Dose CT KUB

A low-dose CT KUB scan without intravenous or oral contrast can be limited in its ability to detect small calculi (stones) or subtle abnormalities in the urinary tract. The lack of contrast limits visualization of the intricate anatomy and subtle pathology.

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Description

Test your knowledge on the indications, techniques, and applications of computed tomography for imaging the urinary tract, including renal colic, renal tumors, renal collections, and more.