Skeletal System: In the second and third trimester, hands (Fig. 72.1) and feet (Fig. 72.2) are checked for complete development of the phalangeal ossification centers (121) and the metatarsal bones (122). In this way, syndactyly as part of other congenital malformation syndromes can be excluded.
Furthermore, supernumerous phalanges can be found, such as hexadactyly as seen in Figure 72.3. A Polydactyly can be associated with shortened ribs and concomitant pulmonary hypoplasia. Not only are the shortened ribs apparent, but also the bell-shaped thorax.
The search for a clubfoot anomaly should not be neglected (Fig. 72.4). The clubfoot does not only appear as a club-like deformity, but also as deviated shortened tubular bones.
Impaired enchondral ossification as part of achondroplasia is frequently recognized only in the 3rd trimester by shortened tubular bones and a head of disproportionately large appearence.
To conclude this section, you can again test how much detail you remember and how much still has to be memorized. The answers to question 1 and questions 3 to 6 can be found in the preceding pages, the answer to the quiz image of question 2 is given on page 77 at the end of the book.
An 18-year-old male patient presents with severe pain in the left scrotum, of sudden onset 3 hours ago and radiating into the left groin. What is your presumptive diagnosis? How much time do you have to proceed? What sonographic method do you select?
9 A 58-year-old female patient is referred to you for a sonographic evaluation of the pelvis. The patient had her menopause at the age of 52 years and currently does not take any hormone preparation. Endovaginal sonography produced the finding illustrated in Figure 73.1. The endometrium measures 18 mm in width. What diagnosis do you suspect and what measures do you initiate?
9 How do you recognize impending ovulation sonographi-cally? What are the postovulatory changes? How many days after the last menstruation/after fertilization can the successful implantation be documented sonographically?
El Write down the six biometric measurements next to this text. Add to each parameter the first and last gestational week of its meaningful application. At what gestational week is one parameter replaced by another parameter?
9 What are the direct and indirect sonographic criteria of spina bifida? Is a blood test of the mother sufficient?
9 What renal malformations do you know? Name at least three sonographic criteria.
Quiz for self-assessment
What is the imaging plane? Try to give a differential diagnosis for both cases. The answers can be looked up on page 77.
The thyroid gland is examined with a 7.5-MHz linear transducer. With the head slightly extended, transverse sections of the entire gland are obtained or, if the entire width of the gland cannot be encompassed, of each lobe separately (Fig. 74.1a). Thereafter, sagittal sections are obtained through each thyroid lobe (Fig. 74.1b). The trachea (84) with its air shadows in the midline and the carotid arteries (82) and jugular veins (83) with their echo-free lumina laterally serve as general orientation on the transverse sections. The thyroid parenchyma (81) is situated between the trachea and the vessels. Anterior to the trachea, a thin parenchymal band (isthmus) connects both thyroid lobes (compare Fig. 75.1)
With the patient performing a Valsalva maneuver (bearing down with the vocal chords closed), the jugular veins distend due to blocked venous drainage (Fig. 74.1c). This makes orientation even easier.
The normal thyroid parenchyma (81) is slightly more echogenic than the anteriorly located sternohyoid muscle
(89) and the more lateral sternocleidomastoid muscle (85). On cross section (Fig. 74.2), the carotid artery (82) is somewhat posteromedial in location and is visualized as a round noncompressible structure. In contrast, the jugular vein (83) runs more anterolateral^, exhibits a typical phasic pulse and can be compressed by applying graded (!) pressure. To assess the size of the thyroid gland, the maximum transverse and sagittal (anteroposterior) diameters of each lobe are measured on transverse sections (Fig. 74.2b). Both values are multiplied by the maximum length as measured on the sagittal sections (Fig. 75.3b) and are divided by two. Within an error range of approximately 10%, the result corresponds to the volume (in ml) of each lobe. Excluding the isthmus, which can be ignored because of its small size, the volume of the thyroid gland should not exceed 25 ml in men and 20 ml in women. Small thyroid cysts (64) might not cause any distal acoustic enhancement (Fig. 74.3) and must be differentiated from hypoechoic nodules (compare p. 75). Intrathyroidal vessels are rarely delineated.
The most common diffuse thyroid condition is iodine deficiency goiter. The thyroid gland (81) is diffusely enlarged and its echogenicity is slightly enhanced (Fig. 75.2). A homogeneous hypoechogenicity (the thyroid gland has become iso-echoic with the musculature) is characteristic of Graves disease or inflammatory conditions such as Hashimoto thyroiditis.
Focal changes have to be separated into benign cysts (64) and solid lesions (Fig. 75.3), by employing the usual criteria that establish a cyst (compare p. 29). Solid lesions comprise adenomas (54) as seen in Figure 75.4 and nodular degenerative changes as well as malignant processes.
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