[Renal ultrasound. Urologic and nephrologic viewpoint]

Renal ultrasound examination is an integral part of urologic and nephrologic clinical examination. It brings very useful information about kidney morphology (B-mode) and haemoperfusion (renal color coded duplex ultrasonography). Standard examination technique is required for recognition of normal findings, urinary transport disturbances of diverse causes (stones, intrinsic or extrinsic compression), kidney tumours and kidney injury. Typical ultrasound findings of these abnormalities were demonstrated. Renal ultrasound with new techniques (sono-CT, harmonic tissue imaging, power mode etc.) is for urology and nephrology an indispensable diagnostic method. In combination with patient history, clinical and laboratory examination takes important part in accomplishing the diagnosis.

[Ultrasound differential diagnosis in renal parenchymal disease]

Ultrasound examination is an integral part of nephrologic differential diagnosis in renal parenchymal disease. A systematic recognition of kidney position, size, shape, contour, structural design and renal perfusion lead together with clinical findings in correct direction of differential diagnosis. Unspecific findings exist in many acute renal diseases (large kidney with prominent pyramids and echogenic cortex). In chronic renal diseases the sonomorphology of chronic glomerulonephritis, pyelonephritis or analgesic nephropathy are more specific. Diagnosis of renal arterial stenosis is almost possible with duplex ultrasonography. Disturbances of kidney perfusion (infection, infarction) are diagnosed with echocontrast-ultrasonography.

Diagnosis of angiomyolipoma using computed tomography—region of interest ≤−10HU or 4 adjacent pixels ≤−10HU are recommended as the diagnostic thresholds

AIM

To study and compare the diagnostic accuracy of region of interest (ROI) density measurement and pixel mapping [computed tomography (CT) density of individual pixels] for the diagnosis of renal angiomyolipoma (AML) using CT.

MATERIALS AND METHODS

A study group of histologically proven AMLs was compared with a control group of histologically proven renal cell cancers, normal renal parenchyma, and simple renal cysts. The mean tissue density (ROI circle) and a pixel density map were recorded. The diagnostic accuracy of various thresholds of ROI and pixel mapping values were compared using receiver operating characteristic curves.

RESULTS

Twenty-two AMLs, 16 renal cell carcinomas (RCCs), 30 simple cysts, and 30 sites of renal parenchyma were evaluated. The mean (+/-1 SD) density of the AMLs was significantly lower [-15.2(20.8) units] than the three control groups [+36.0(8.1) units, +5.4(3.4) units and +22.2(46.5) units for RCC, renal cyst and parenchyma respectively; p < 0.001 (analysis of variance)]. The sensitivities and specificities of the ROI diagnostic thresholds of < or =0 units, < or =-10 units and < or =-20 units were 77 and 97%, 73 and 100% and 50 and 100%, respectively. Using pixel mapping [diagnostic thresholds of either a line of 4 pixels < or =-10 units or a square of 4 pixels < or =-10 units] the sensitivity improves to 86% with a specificity of 97%.

CONCLUSION

Although a ROI threshold value of < or =-10 units has a very high specificity (100% in the present study) the sensitivity is modest at only 73%. Pixel mapping is more sensitive for recognizing small clusters of fat. In practice, both methods can be recommended for the analysis of suspected AMLs. ROI density measurement is convenient when analysing large areas of suspected fat and < or =-10 units should be used as the diagnostic threshold. When faced with small lucent areas or indeterminate values after ROI analysis, pixel mapping is recommended using a line of 4 pixels < or =-10 units or a square of 4 pixels < or =-10 units as the discriminating thresholds.

Imaging characteristics of minimal fat renal angiomyolipoma with histologic correlations

OBJECTIVES

To review our experience with minimal fat angiomyolipomas (AMLs) and correlate the confirmed pathologic diagnosis with preoperative radiologic features to evaluate the feasibility of an accurate diagnosis preoperatively. On rare occasions, renal AMLs contain minimal amounts of fat that are not identified on cross-sectional imaging.

METHODS

From November 1998 to August 2003, 6 patients (seven lesions) underwent renal surgery with the preoperative diagnosis of renal cell carcinoma as determined by preoperative imaging studies, and the finding of AML was unexpected. A single pathologist and radiologist reviewed all pathologic specimens and radiologic examinations. The characteristic findings were recorded and compared with those in published reports.

RESULTS

Pathologic review of the specimens demonstrated microscopic amounts of mature adipocytes, abnormally thickened blood vessels, and smooth muscle cells in all seven lesions. The mean estimated fat content was 4.1% (range 3% to 10%). Hounsfield unit measurement of the lesions on unenhanced computed tomography images revealed all lesions to be hyperdense relative to the normal kidney parenchyma and enhanced by at least 90 Hounsfield units or more with the administration of intravenous contrast. Enhancement was homogenous throughout each of the seven masses.

CONCLUSIONS

Minimal fat renal AML tumors are typically hyperdense relative to the normal kidney parenchyma and demonstrate homogenous enhancement with the administration of intravenous contrast on computed tomography. These results may have important implications when planning partial versus radical nephrectomy by open or minimally invasive techniques.

Spontaneous rupture of renal angiomyolipoma: value of multidetector CT angiography for interventional therapy

Renal angiomyolipomas have a high risk of rupture when they are large and associated with aneurysms. When renal angiomyolipomas rupture, some patients go into shock. Immediate interventional therapies to stop bleeding are required. In the present case, multidetector computed tomographic angiography provided useful information for planning the interventional therapy. Because of the information, transcatheter arterial embolization was safely performed while preserving most renal function.

[Renal giant angiomyolipoma in tuberous sclerosis complex: case report and literature review]

The aim of this paper is to describe a typical clinical case of tuberous sclerosis complex (Bourneville disease) and discuss controversial issues about the management of this rare condition, with a short revision of the literature. Particularly, we define which is the role of the surgeon in the treatment of this very rare condition, that should be primary approached conservatively.

Hepatic angiomyolipoma: identification of an efferent vessel to be hepatic vein by contrast-enhanced harmonic ultrasound

We report two patients with rare hepatic angiomyolipoma and demonstrate the special tumour haemodynamics with contrast-enhanced harmonic ultrasound. This reliably identified the efferent vessel of the hepatic angiomyolipoma to be the hepatic vein in both cases, which corresponded well with that seen on conventional angiography and CT angiography. This haemodynamic finding may be an important characteristic of hepatic angiomyolipoma, and facilitate the differential diagnosis from other benign and malignant hepatic tumours.

Tuberose sclerosis complex: analysis of growth rates aids differentiation of renal cell carcinoma from atypical or minimal-fat-containing angiomyolipoma

AIM

To study the radiological characteristics of renal masses in individuals with tuberous sclerosis complex (TSC) using serial CT, and to examine how renal cell carcinoma (RCC) may be differentiated from indeterminate cysts or masses.

METHODS

This was a retrospective study of 12 cases of TSC in which dedicated renal CT followed after US had demonstrated cystic or sonographically unusual renal masses. The CT density of all masses was measured and the masses categorized as simple cysts, complex cysts, angiomyolipomas or indeterminate solid masses. Subjects were maintained on regular follow-up with repeat CT or MRI and interval renal US. Indeterminate masses that showed rapid growth were considered suspicious for renal cell carcinoma and biopsy or nephrectomy followed.

RESULTS

Comparative data were available for a median of 4 years. In each case the renal masses were multiple and bilateral; mean mass diameter was 3.6 cm. Among a total of 206 masses, 18 were simple cysts and 3 were complex cysts. Of the complex cysts, 1 proved to be an angiomyolipoma on histology and the other 2 showed no growth. Of the solid masses, 133 were typical angiomyolipomas (AMLs) and 52 were indeterminate. On follow-up, only 3 indeterminate masses showed rapid growth (>0.5 cm/year), of which only 1 proved to be an RCC on biopsy. The other 2 were minimal-fat AMLs, and the remainder of the masses showed no or slow growth.

CONCLUSION

Many renal masses associated with TSC are radiologically indeterminate. A growth threshold of >0.5 cm/year identified the only RCC in this study (0.5% of all masses). Yearly radiological follow-up of indeterminate renal masses is recommended for individuals with TSC.

[Renal angiomyolipoma and fever: assessment with isotopic renogram and 67Ga scintigraphy]

A 26 year-old woman with tuberous sclerosis who came to the Emergency Department with high fever, bilious vomit, right hemiabdomen pain and syncope during 2 weeks. Laboratory analyses show hemoglobin 6.7 g/dl, creatinine 1.5 mg/dl and leukocytes 30,000. Abdominal CT is performed because of suspicion of active bleeding in right hemiabdomen, following rupture of right angiomyolipoma, treated by selective arterial embolization. She was referred to the Nuclear Medicine Department to perform a 67Gallium scintigraphy for the detection of infection, and static and dynamic renal scintigraphy for evaluation of the renal morphology and function.

The association of pulmonary lymphangioleiomyomatosis with renal and hepatic angiomyolipomas in a prepubertal girl: a previously unreported entity

Pulmonary lymphangioleiomyomatosis (PLAM) is a rare, diffuse progressive interstitial lung disease that affects females of childbearing age and is characterized by diffuse proliferation of abnormal smooth muscle fibers predominantly developing in the lung and leading to cystic destruction. A prepubertal 13-year-old girl with PLAM associated with renal and hepatic angiomyolipomas who was treated by nephroureterectomy and thoracoscopic pleurodesis is presented. To the best of our knowledge, this is the first reported case of PLAM associated with renal and hepatic angiomyolipomas at the prepubertal age. After evaluating the clinicopathologic features of this rare entity, the authors conclude that PLAM should be considered in the differential diagnosis of cystic pulmonary pathologies in children, particularly teenagers. The most important clinical aid is to bear this rare entity in mind when a child presents with renal and/or hepatic angiomyolipomas. Thoracoscopic pleurodesis is the most effective treatment modality for recurrent pneumothoraces.

Orthostatic hypotension in an octogenarian--an unusual presentation

Orthostatic hypotension is a common problem in older adults and can be associated with falls, dizziness and syncope and their associated consequences. Therefore, it is important to recognise the condition and institute appropriate management. We report an elderly woman who presented with orthostatic hypotension and was found to have a rare, benign yet potentially fatal condition.

Cadaveric kidney transplant complicated by rupture of native kidney angiomyolipoma: a case report and review of the literature

Kidneys with angiomyolipomas have been used for transplantation, but we are unaware of postoperative hemorrhage from a native kidney angiomyolipoma. A 49-year-old male who underwent a cadaveric renal transplant complicated by postoperative hemorrhage from a native kidney angiomyolipoma is presented. Evaluation and current management strategies are discussed.

Perinephric angiomyolipoma: A unique development pattern surrounding the kidney

We report a case of a 31-year-old man with extrarenal angiomyolipoma of the perinephric space. He presented with asymptomatic macrohematuria. Computed tomography of the abdomen revealed a large perinephric mass which was separated from the right kidney and its unique growth appeared to have surrounded the kidney. Extrarenal angiomyolipomas of the perinephric fat are rare and they should be considered in the differential diagnosis of a retroperitoneal mass where asymptomatic macrohematuria was presented at the onset.

[CT differentiation of renal angiomyolipoma and renal cell carcinoma]

OBJECTIVE

To improve the diagnosis of atypical renal angiomyolipoma (RAML) by use of CT to differentiate RAML from renal cell carcinoma (RCC).

METHODS

We retrospectively analyzed the CT manifestations with dual-phase enhanced contrast study in 36 cases of RAML (with 57 lesions) and 46 cases of RCC. 25 lesions of RAML and all RCC were histologically confirmed. Maximum likehood estimator was employed to discriminate all the lesions according to a series of indexes with statistical meanings.

RESULTS

Nine indexes were found to be significant and evident for separating RAML from RCC, namely "single or multiple", border, lobulation, protrusion rate, interface with cortex, angle with cortex, "levering-cortex-up" sign, characters of blood vessel in lesion and calcification. The accuracy rates of discrimination analysis for RAML and RCC were 93.0% and 89.1%, separately.

CONCLUSION

The importance of 4 indexes, including protrusion rate, angle with cortex, "levering-cortex-up" sign and the traits of blood vessel, should be highlighted in the differentiation of RAML and RCC.