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ANATOMY FOR DIAGNOSTIC IMAGING
The intravesical portion of the ureter has an oblique course of 2 cm through the bladder wall. The vesical muscle has a sphincteric action and the obliquity has a valve-like action. The ureter opens into the bladder at the ureterovesical orifice. Blood supply of the ureter The ureter is supplied by branches of nearby arteries and drains to corresponding veins, that is, the aorta and IVC and the renal, gonadal, internal iliac and inferior vesical vessels. Despite the varied arterial supply, the ureter is prone to vascular injury at surgery, which may lead to stricture formation.
psoas muscle. Prone views aid ureteric filling. Distension of the upper part of the collecting system can also be aided by applying a compression band across the abdomen during the first part of the IVU examination. The ureter enters the posterior part of the bladder, and oblique views are therefore helpful in imaging the ureterovesical junction. Varying degrees of ureteric duplication may be seen with the ureters uniting at any point of their course. Other variants already discussed may also be identified. Ultrasound The proximal and distal ureters may be visible on ultrasound when well distended. Intestinal gas generally obscures the midportion unless it is abnormally dilated.
The development of the ureter The ureter develops as a blind diverticulum from the metanephric duct and grows first posteriorly and then cranially to unite with the developing kidney. Developmental abnormalities and variants Duplication of part or all of the ureter occurs in about 4% of subjects. It is the commonest significant congenital anomaly of the urinary tract. Duplication is two to three times commoner in females. When complete duplication occurs, the ureter serving the upper renal moiety drains fewer calyces and is inserted lower into the bladder than that draining the lower moiety - known as the Weigert-Meyer law. The low insertion may extend to the bladder neck or the urethra or, in females, the vestibule or vagina. Ureteric ectopy is most common in association with duplication, but may occur alone. Ureterocoele is a dilation of the intramural portion of the ureter due to narrowing of its orifice. This is most common in a duplicated system, when it occurs in the ureter draining the upper renal moiety that is usually ectopic. Radiological features of the ureter Plain films of the abdomen The ureter is not visible, but a knowledge of its course in relation to the skeleton is necessary when looking for radio-opaque calculi. The ureters pass anterior to the tips of the transverse processes of L2-L5 lumbar vertebrae and anterior to the sacroiliac joint. They then curve laterally at the ischial spines and medially again to the bladder. Intravenous urography (see Fig. 5.49) The ureters are either completely or partly visible when filled with contrast. Their course is as above. The ureter passes anteriorly from the kidney to its position near the
Computed tomography Ureteric calculi not visible on radiographs are readily visible on CT scans, and non-contrast CT has largely replaced the IVU for diagnosis of ureteric calculi. The normal ureter can be identified on non-contrast scans, although it is easier to identify if it contains contrast medium (see Fig. 5.4). It is visible medial to the lower pole of the kidney, anterior to psoas. More distally the ureter remains anterior to the psoas muscle and is lateral to the great vessels. Having crossed the bifurcation of the common iliac artery, the ureter in the pelvis is medial to the iliac arteries and veins. It enters the bladder posterolaterally. Variants such as duplication are easily identified. MR urography The ureters may be imaged using the same water-sensitive techniques as MR cholangiography (see above). However, because they are intermittently collapsed due to peristalsis parts of the ureter may not be distended with urine and thus not imaged using these techniques. MR urography works well in a distended system. MR contrast urography can be performed where the ureters are imaged during the excretory phase after intravenous gadolinium. MRI tends to be used in cases where irradiation is undesirable, such as during pregnancy. THE ADRENAL GLANDS (see Fig. 5.11) The adrenal glands lie retroperitoneally above each kidney. They are each enclosed within the perirenal fascia but in a separate compartment from the kidney. Each gland is composed of a body and medial and lateral limbs. The adrenal glands have an outer cortex derived from mesoderm and an inner medulla (10% of the weight of the gland), which is derived from the neural crest and is related to the sympathetic nervous system. The right adrenal gland tends to have a consistent location. It lies posterior to the inferior vena cava, medial to the
