Thrombosis of the renal vein is most frequent in left sided advanced renal carcinomas. Contrast enhanced CT with carefully timed venous phase examination is an excellent method to identify venous thrombosis. Color Doppler US is a useful method in cases when the full-length vein can be visualized. The physiological stenoses of the ureters seen at the pyelourteral junction and at the juxtavesical segment are also clinically important as ureter stones are most commonly stuck at these sites. Considering their differential diagnostic and surgical significance it is essential that clinicians and radiologists alike familiarize themselves with these crossing sites.
The ureter crosses superficially to the bifurcation of the iliac arteries. Distal to this point it crosses posterior to the testicular artery in men and the ovarian artery in women. The ureter also passes dorsally to the uterine artery and the spermatic duct. Thus, ligation of these vessels may lead to ureteral injury and potential urinary tract obstruction.
Among the developmental disorders the bifid ureter has to be mentioned.
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In this case the two ureters originate from the duplicated renal pelvis and descend towards the bladder where they enter the lumen through separate orifices. In ureter fissus the two ureters merge proximal to the bladder. Megaloureter is a condition with extreme dilatation of the ureteral lumen due to innervation defect or chronic stricture. Retrocaval ureter is by definition located on the right side. It may lead to urinary retention thus, its detection is clinically important.
Radiologic imaging methods utilize contrast filling of the ureters. In a conventional retrograde pyelogram anterograde or retrograde filling of the ureter is achieved by a catheter insertion. Meanwhile, with cross-sectional imaging techniques CT, MRI timed image acquisition is conducted during the excretory phase approx. Both of the above techniques provide good quality images to assess ureteral patency. With virtual endoluminal reconstructions detailed depiction of the intraluminal lesions is also possible.
For the visualization of intra- or extraluminal ureteral strictures and masses the primary imaging modality is CT with multi-phase contrast enhancement. In addition to detecting nephrolithiasis it is highly sensitive to visualize other GU lesions, congenital and acquired malformations. Due to its restricted use in meteorism and in heavy set patients, US has limited potential in the examination of the proximal collecting system. The bladder can be anatomically divided into a vertex, corpus and fundus. The position of the later one is fixed by the underlying pelvic fascia.
In men the prostate is located right below the fundus, thus prostatic lesions such as prostatic hyperplasia often protrude into the bladder fundus. The ureters enter the bladder through the posterior-caudal part of the fundus. The area bordered by the internal ureteral orifices and origin of the urethra is called the vesical trigone.
Diverticula are the most common congenital malformations of the bladder. These are more frequent in men and tend to occur around the ureteral meatus as the trigone has a different embryologic origin than the rest of the bladder. In addition to dysuria, diverticula, due to prolonged urinary retention, may also lead to pyuria.
Large diverticula can compress the ureteral meatus and cause urinary retention. Ureterocele is the dilatation of the intramuscular ureter segment, which may pose a differential diagnostic problem as it often protrudes into the vesical lumen. When the examination is performed with a right technique, and the lumen is fully distended lesions of the bladder wall can be well detected with US.
Detection of dense urine, which contains hyperechoic particles can also help the examiner. CT and MRI scans also show diffuse wall thickening without any circumscribed lesions. However, in most of the cases this is an accidental finding as these examinations are not indicated in cystitis, except when an emphysematous cystitis is suspected. Bladder cancer is the second most common genitourinary neoplasm after prostate cancer.
Etiological factors include smoking, certain occupations, exposure to chemicals used in rubber and plastic manufacturing, irradiation, prior cyclophosphamide use as well as chronic infections. The primary clinical symptoms are hematuria, urinary frequency and occasional obstructive complications.
Definitive diagnosis can be established with cystoscopy and biopsy. Nevertheless, radiographic imaging plays an essential role in early detection and staging of the disease. When the patient is well prepared and the bladder is full even the very early papillary lesions can be recognized on US.
The papillary form is more common than the muscle invasive type. However, papillary lesions can progress into an invasive type by time. CT and MRI scans provide information on the extent of the parietal and perivesical propagation while, regional and distant lymph node metastases can be also simultaneously identified. When conventional cystoscopy could not be completed due to urethral narrowing or prostate hyperplasia, upon clinical request, similar to other parts of the GU tract, virtual endoluminal images can be reconstructed from the excretory phase series.
According to MacNeal the glandular prostate can be divided into peripheral, preprostatic and central zones. The preprostatic zone also includes the zones of transitional and periurethral glands. Meanwhile, the upper fibromuscular stroma shows a non-glandular structure. The transitional zone is a frequent site of benign prostatic hyperplasia. Importantly, this is the entry point of the ejaculatory duct and the seminal vesicles while, the capsule is absent in this area. Therefore, it is a predilection point where prostate cancer could spread into the periprostatic space.
Prostate cancer is the most common malignant disease in men over Therefore, prostate imaging is an important screening tool. Among the various imaging modalities transrectal US and MRI have a crucial role in primary diagnosis of prostate cancer. CT is used for accurate detection of pelvic and distant metastases. Transabdominal US is only capable to determine the prostate size or extent of the secondary urinary retention and collective system dilatation.
Meanwhile, transrectral US can also be used to guide biopsies from the suspicious hypoechoic areas, which is a significant advancement compared to the blindly performed sextant biopsies. MRI is helpful for the assessment of local invasion and identification of atypical lesions. A highly sensitive MRI technique is spectroscopy, which measures the tissue concentration of metabolites. In prostate carcinomas choline and citrate levels are evaluated. Cancer cells are distinguished by the very low citrate and high choline levels. Diagnosis of inflammatory diseases of the prostate is fundamentally based on clinical methods.
If necessary a transrectal US can be performed, this shows loosened, edematous glandular structure, extracapsular microabscesses and increased flow in the periprostatic veins. Chronic prostatitis is characterized by intraprostatic calcifications although; these can be seen in other conditions as well. Disturbances of testicular descent lead to ectopic testes and cryptorchidism. The ectopic testis is found outside the scrotum and the normal migration route.
In cryptorchidism descent of the testis begins normally but stops uncompleted. Cryptorchidism is associated with increased risk of sterility fibrosing testicular atrophy and malignant transformation, which still remains elevated if the descent is delayed or following surgical orchidopexy. Risk of malignant transformation in these testes is times higher than in the normal population. For US it is important to use high frequency transducers with color Doppler imaging. MRI is particularly important for visualizing defects of testicular descent. In neoplastic diseases, staging for the detection of enlarged pelvic and abdominal lymph nodes and distant metastases can be equally completed with either MRI or CT.
Acute inflammation of the testis or epididymis is most commonly affects the head or the tail of the epididymis. US scanning is highly significant in atypical and therapy resistant cases. In addition to abscess formation, epididymeal enlargement can compress vascular supply of the testis. Chronic inflammations are essentially hydroceles and secondary thickening of the tunica vaginalis testis. In a hydrocele fluid is accumulated between the sheets of the tunica vaginalis. When a hydrocele is detected it is important to exclude potential testicular tumors as well.
Positive family history, Caucasian descent and cryptorchidism are additional risk factors. Metastases, lymphomas and leukemias involve the testicles much less frequently than primary tumors. Seminomas typically occur in years of age. The serum alpha-fetoprotein levels are usually normal while, beta human chorionic gonadotropin beta-hCG is increased.
Seminomas are sensitive for chemo- and radiotherapy.
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Non-seminomas on US have variable echogenicity due to the frequent bleedings, fibrosis and calcifications. Embryonic cell carcinomas arise between years as well as below the age of 2 years; these are very aggressive, with fast spread and distant metastases. Meanwhile, teratomas seen in young boys are benign lesions, which in the adulthood could undergo a malignant transformation.
Choriocarcinomas are most common between years of age. They are typically associated with early metastases to the lungs while, the primary tumor is. In adults testicular metastases most frequently originate from the prostate, lung, kidney, gastrointestinal tract, bladder, thyroid carcinomas and melanomas. In children neuroblastomas give most commonly testicular metastases. These metastases often show multiplex, bilateral distribution, which are frequently hypoechoic on US.
Diffuse or focal hypoechoic areas could also be detected. In leukemias the whole testis may be involved. The basic imaging method used for the examination of the female pelvis and the ovaries is transvaginal US. In malignancies CT is essential to detect local invasion as well as distant metastases. MRI is the preferred method in young or pregnant women as it has similar application spectrum and efficacy to CT; it also has a specific advantage in differential diagnosis of ovarian lesions. Furthermore, it has a great importance in the detection of endometriosis and peritoneal implants.
In addition to clinical and laboratory tests the diagnosis of ovarian inflammatory processes based on US examination. Volume of the inflamed ovary is expanded, vascularity is increased, around the ovaries and in the pelvis, ascites can be detected. In case of a tubo-ovarian abscess, a thick-walled circumscribed fluid collection could be identified in the surroundings.
With US, thick fluid layering and gas formation can be observed inside the lesion.
Diagnostic Imaging: Genitourinary
In undetermined cases an MRI scan must be performed. Ovarian tumors often have an insidious onset with no complaints in the early stage of the disease. Hormone producing tumors can present with irregular bleedings or weight loss, later increased abdominal circumference and ascites could be pathogenic signs. In mucinous cystadenoma the multiplex spaces, which may show differing densities, are separated by vascularized septae.
Adrenal cortical and medullary imaging.
Semin Nucl Med ; Sebastian A, Tait P. Renal imaging. Medicine ; Baxter GM. Ultrasound of renal transplantation. Clin Radiol ; Imaging of hematuria. Multidetector CT urography with abdominal compression and three-dimensional reconstruction. Nolte-Ernsting C, Cowan N. Understanding multislice CT urography techniques: Many roads lead to Rome. Eur Radiol ; Multidetector CT urography in imaging of the urinary tract in patients with hematuria.
Korean J Radiol ; MRI of the kidney-state of the art. Ho VB, Choyke P. MR evaluation of solid renal masses. Renal cancer: Preoperative evaluation with dual-phase three-dimensional MR angiography. Spinal dysraphism at MR urography: Initial experience. MR urography and CT urography: Principles, examination techniques, applications. Rofo ; Prostate cancer staging using imaging.
BJU Int ; The appearance of prostate cancer on transrectal ultrasonography: Correlation of imaging and pathological examinations.
Diagnostic imaging of the genitourinary tract
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