Renal Multidector Row CT

The role of diffusion-weighted MRI and contrast-enhanced MRI for differentiation between solid renal masses and renal cell carcinoma subtypes

PURPOSE

To assess the value of diffusion-weighted magnetic resonance imaging (DW-MRI) and contrast-enhanced MRI (CE-MRI) for differentiation between benign and malignant solid renal masses, renal cell carcinoma (RCC) subtypes, oncocytomas, and lipid-poor angiomyolipomas (LP-AML).

METHODS

Minimum or lowest 'apparent diffusion coefficient' (ADC₁) and representative ADC values (ADC₂) of 112 renal masses (n: 46 benign renal mass, n: 66 malignant renal mass) were measured on DW-MRI images (b 50, 400, 800 s/mm²). Signal intensity (SI) measurements were performed in normal renal parenchyma and most avid enhanced area of the renal masses at precontrast, corticomedullary, and nephrographic phases on CE-MRI. Contrast enhancement rate (CER) and contrast enhancement index (CEI) values of renal masses were compared between benign-malignant renal masses and RCC subtypes, oncocytomas, and LP-AMLs.

RESULTS

There was no significant difference between ADC₁, ADC₂ values, and SI of benign and malignant renal masses (p = 0.721, p = 0.255, p = 0.872). Mean ADC₁ and ADC₂ values of clear cell RCCs were significantly higher than nonclear cell RCCs (p = 0.005 p = 0.002). Mean CER value of clear cell RCCs was significantly higher than nonclear cell RCCs in nephrographic phase (p = 0.003). Mean CEI values of clear cell RCCs were significantly higher than nonclear cell RCCs in the corticomedullary and nephrographic phase (p = 0.027 vs. 0.008). LP-AMLs were differentiated from other renal masses with wash-out phenomenon.

CONCLUSION

Combined usage of ADC, SI, CER, and CEI values may be useful for discrimination between RCC subtypes, oncocytomas, and lipid-poor AMLs.

Multiphase renal CT in the evaluation of renal masses: is the nephrographic phase necessary?

The aim of this study is to investigate the feasibility of eliminating the nephrographic phase from the four-phase renal computed tomography (CT) imaging to a three-phase protocol without affecting its diagnostic value. Thirty patients undergoing four-phase renal CT scans for assessment of renal lesions (>10 mm) were included in the study. A three-phase renal CT, without nephrographic phase, had similar diagnostic ability to a four-phase renal CT in the detection and characterization of renal lesions. A three-phase CT (plain, corticomedullary, and excretory phase) is therefore adequate in the clinical diagnosis of renal lesions.

Unusual stent after ureteral substitution. A first case

Background

To the best of our knowledge this is the first case where a Silastic drain is used in ureteral surgery instead of a common urological stent. Patients coming from other institutions, especially in peripheral areas, can be treated with non conventional devices and if traditional imaging is inconclusive, computed tomography (CT) can provide valuable information to make the right diagnosis.

Case presentation

We present the unusual case of a 32F Silastic drain found inside the urinary tract in a female patient who had previously undergone ileal loop replacement of the left ureter for post-hysterectomy stricture at another Institution, and had subsequently repeated surgery due to persistent hydronephrosis. Radiological findings on plain abdominal X-ray were quite misleading, while CT allowed a correct assessment of the drain features.

Conclusion

While double J stents of different lengths, sizes and materials are used in ureteral surgery, the use of Silastic drains has not been previously reported. In light of the present experience we don’t suggest its routinely use.

[Imaging of the kidney]

Imaging of the kidney relies on three main imaging modalities: ultrasound, CT scan and MRI, on one hand, and scintigraphy, on the other hand. First intent ultrasound provides anatomic/vascular and functional information. Tissue perfusion assessment using ultrasound can be improved using contrast agents. Renal ultrasound is particularly useful but remains operator and tumor/patient-dependent (obese, ectopic kidney, type and site of tumor). It is cheap and does not irradiate. Ultrasound contrast agents can improve the sensitivity of ultrasound in many clinical situations. Intravenous urography has been replaced by CT scan. Multi-slice CT scan is indeed the main renal imaging modality: it allows for angiographic and urographic explorations. MRI provides anatomic and functional information. Renal failure must be looked for before performing CT scan or MRI so as to avoid iatrogenic complications. Severe renal failure is a contraindication to both. Each imaging modality has pros and cons and specific indications. CT scan is the mainstay of renal imaging provided that standardized injection protocols are used, that the dose is limited (low-dose protocol) and renal function is assessed. Dynamic renal scintigraphy can be used in situations where information on the function of each kidney is necessary.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

[Multi-detector computed tomography in non-traumatic urologic emergencies]

Today's modern multi-detector computer tomography (MDCT) with its fast gantry rotation enables scanning of large body volumes with high temporal and spatial resolution. The fast acquisition of data and subsequent data reconstruction enables multiphase protocols with short time gaps between consecutive scan series so that large numbers of scans within one respiratory pause are possible and even in cases of non-cooperative patients acceptable quality of image data is provided. The acquired thin-slice raw data with isotropic submillimeter voxels can be visualized with different reconstruction algorithms. The advantages of imaging for diagnostics in urologic emergencies are the excellent visualization of acute arterial and venous pathologies, detailed assessment of renal parenchyma and the precise depiction of the urinary tract. In non-trauma settings this enables detailed visualization of inflammatory diseases and differentiation of obstructive or post-therapeutic pathologies along the upper and lower urinary tract. Based on these MDCT findings adequate therapy planning and planning of interventional or surgical procedures can be carried out.

Imaging of hematuria

Hematuria may have a number of causes, of which the more common are urinary tract calculi, urinary tract infection, urinary tract neoplasms (including renal cell carcinoma and urothelial tumors), trauma to the urinary tract, and renal parenchymal disease. This article discusses the current status of imaging of patients suspected of having urologic causes of hematuria. The role of all modalities, including plain radiography, intravenous urography or excretory urography, retrograde pyelography, ultrasonography, and multidetector computed tomography (MDCT) in evaluation of these patients is discussed. The article highlights the current status of MDCT urography in imaging of patients with hematuria, and discusses various-often controversial-issues, such as optimal protocol design, accuracy of the technique in imaging of the urothelium, and the significant issue of radiation dose associated with MDCT urography.