Metabolic/Endocrine/Reproductive Domain

Radiology Study Guide

 

Metabolic/Endocrine

Evaluation of selected endocrine neoplasms

Thyroid

(Source: Anderson and Wastie. Diagnostic Imaging. 3rd Edition. Page 423.)

  • Either nuclear medicine or ultrasound is typically used to evaluate the thyroid gland. See Thyroid imaging.  Nuclear medicine utilizes an isotope with affinity for the thyroid gland to evaluate the size and uniformity of cell types in the gland.   Technetium 99m sodium pertechnatate or radioactive Iodine tracers are used for this purpose.   Ultrasound utilizes high frequency sound-waves to interrogate the thyroid gland.  Solid structures will be more echoic, less echoic or iso echoic to the normal thyroid.  Cysts will be identified as anechoic areas within the thyroid.  Both studies can be utilized to evaluate thyroid size.
  • Common clinical presentations for thyroid imaging include an enlarged nodular thyroid gland or a solitary thyroid nodule. The former is most commonly associated with multinodular goiter while a solitary nodule may represent thyroid carcinoma.
  • A palpable nodule that does not demostrate uptake of radionuclide on isotope scans is termed a "cold nodule" and is indeterminate in etiology. It can represent a cyst, adenoma or carcinoma. Because of its indeterminate nature, intervention such as biopsy or resection is performed. Conversely a "hot nodule" is usually benign.  Ultrasound can be used to differentiate a "solid" nodule from a "cystic" structure.
  • Multiple thyroid lesions, which can be documented scintigraphically or by ultrasound, are typically associated with a multinodular gland/goiter, which is benign. This is seen scintigraphically as multiple hot and cold nodules in an enlarged gland while on ultrasound is seen as multiple solid lesions of varying echogenicity (the brightness of the lesion) and size.

 

Adrenal

(Source: Anderson and Wastie. Diagnostic Imaging. 3rd Edition. Page 290.)

  • Adrenal masses are best demonstrated with computed tomography or MRI. In Patients who are identified with biochemical evidence for an adrenal lesion, CT or MRI can be used to localize a tumor presurgically. Most functioning lesions are benign adenomas whereas malignant lesions are usually non-functioning. Tumors of the adrenal gland include adenomas (which can cause Cushing’s or Conn’s disease) and pheochromocytomas.  Larger adrenal masses may be identified as well on ultrasonography
  • Hyperplastic conditions rather than actual tumors can cause both Cushing’s or Conn’s disease as well. Hyperplasic adrenal glands are either normal on CT or demonstrate bilateral uniform enlargement.
  • Non-functioning adrenal adenomas are relatively common. These frequently present as an "incidental adrenal mass" on routine abdominal imaging and pose a clinical dilemma in cancer patients, as they must be differentiated from metastatic lesions. Certain malignancies, such as bronchogenic carcinoma, have a tendancy to metastasize to the adrenal glands.

 

Pituitary

(Source: Anderson and Wastie. Diagnostic Imaging. 3rd Edition. Page 405.)

  • Both CT or MRI examinations are used to evaluate the pituitary for lesions.  Those that are identified as macroadenomas are lesions larger than 1cm.  Microadenomas are lesions that are less than 1cm in greatest size.  See Pituitary imaging.
  • Macroadenomas typically demonstrate minimal hormone production. These patients more typically  present with visual symptomatology from mass effect from the lesion effacing optic chiasm rather than from physiological effects from hormone production.
  • Microadenomas commonly produce hormones. Functioning microadenomas can cause elevation in any of the pituitary hormones. For example, women presenting with the most common lesion, the prolactinoma, typically present with galactorrhea.

 

Reproductive

(Source: Anderson and Wastie. Diagnostic Imaging. 3rd Edition. Pages 271-283.)

Ultrasonography of the gravid uterus and fetus- Prenatal Screening

General survey: Number of embryos or fetuses, placenta evaluation, amniotic fluid volume measurement

  • The general survey of a gravid uterus, typically performed at about 18 weeks,  is used to evaluate important features related to the pregnancy such as the number of embryos or fetus’, placenta location, and the amount of amniotic fluid.
  • Measurements of the gestational sac and fetus contribute to accurate dating. The earlier in pregnancy that such measurements are performed, the more accurate and reliable the dating however, the earlier the gestation, the less well fetal anatomic structures are demonstrated. Very early identification of an embryo, at about 5 weeks,  can be made with transvaginal imaging if there is a suspicion for ectopic pregnancy.  Ultrasound can also be used in conjunction with a knowledge of HCG levels, to in many cases exclude the presence of etopic pregnancy.
  • Placenta location and appearance is important in evaluation for placenta previa (where the placenta covers the cervical and can cause life-threatening maternal bleeding) or abruption (where retro placental hemorrhage can contibute to fetal demise).  The relationship of the placenta to the cervix, can change as a pregnancy proceeds.   When placenta previa is suspected, follow-up examination can be beneficial in confirming a persistent relationship of the placenta to the cervical canal.
  • Amniotic fluid quantification is important in that polyhydramnios (too much fluid) is associated with maternal abnormalities such as diabetes and various fetal anomalies. Oligohydramnios (too little fluid) can be associated with fetal anomalies and/or growth retardation.  Tables are available that relate measured fluid levels to gestational age.

Fetal evaluation: Major and most common anomalies.

Neural tube closure and defects- Meningocele, Myleomeningocele, Chiari II malformations and Anencephaly

  • Meningocele is related to a neural tube closing defect and is also known as spina bifida. A meningocele only contains fluid.  The myelomeningocele also contains neural tissue. They can be associated with an elevated AFP (in the maternal serum and amniotic fluid) and is a relatively common anomaly. There is typically a defect of the spine at the level of the meningocele or the Myleomenignocele, especially the lumbosacral region.
  • Anencephaly, also associated with an elevated AFP, can be easily diagnosed at approximately the 12th week by absence of the upper portions of the skull. This particular anomaly is not compatible with life.
  • The Chiari II malformation is a myriad CNS abnormalities, the most important finding of which is hydrocephalus. It is associated with myelomeningocele.

 

Brain anomalies, including hydrocephalus

  • Abnormal dilation of the ventricles of the brain is known as hydrocephalus and can be demonstrated prenatally by ultrasound.  Measurements are taken at the level of the atrium of the lateral ventricles.   Hydrocephalus commonly accompanies spina bifida (as a part of the Chiari II complex) as well as many other congenital anomalies.

 

Urinary tract anomalies, including hydronephrosis, renal agenisis and polycystic kidney disease

  • Renal abnormalities can contribute to decreased amniotic fluid volume as most of the amniotic fluid is produced by the kidneys in the form of fetal urine. Poorly functioning kidneys cause oligohydramnios (decreased amniotic fluid).
  • Congenitally, kidneys may fail to develop (agenesis) or the kidney may be a dysplastic and non-functioning with multiple cysts (multicystic dysplasic kidney).
  • Hydronephrosis (dilated renal collecting system) can be seen when there is renal obstruction.  Tables are used to determine acceptable size for the renal collecting system at differing gestational ages.

 

Abdominal wall defects, including omphalocele and gastroschisis

  • Abdominal wall defects, which are easily demonstrated sonographically, include omphalocele and gastroschises. In these conditions loops of bowel or liver herniate outside of the abdominal cavity.  In opmphalocele, the characteristic finding is a midline lesion with the umbilical cord arising from it's apex.  Gastroschises is a defect of the anterior abdominal wall lateral to the midline.   Gastroschises in general have a better prognosis than omphalocele. 

 

Breast Cancer Screening

(Source: Anderson and Wastie. Diagnostic Imaging. 3rd Edition. Pages 96-97.)

Mammography & Sonography

Epidemiology of cancer detection

  • Breast cancer is the most frequent cancer in women and is diagnosed in approximately 1 our of every 8 women during their lifetime.
  • Screening programs involve women from 40 years and up, depending on the recommending agency. Screening is performed by mammography.  Current recommendations include annual mammograms for all women 40 years and up.  If there is a strong family history of breast cancer (mother or sister), mammographic screening should start earlier.

 

  • Ultrasound is not a screening examination.   The use of ultrasound is restricted to diagnostic evaluations

 

  • Survival has been improved because of mammography by approximately 30%.

Characteristic mammographic and sonographic findings in malignant lesions

  • Mammography uses  low energy, low kilovoltage x-rays to best demonstrate the soft tissues of the breast.  These features accentuate the subtle differences in attenuation between fat and solid structures in the breast.
  • Malignant lesions are commonly seen as ill defined or spiculated soft tissue lesions or irregular clustered calcifications with/or without an associated soft tissue mass.  Nodules associated with malignant lesions tend to have very irregular borders.  Malignant calcifications will frequently be small <1mm calcifications that take on the shape of dots and dashes, or the letters, W, X, Y, Z.

 

Characteristic mammographic and sonographic findings in benign lesions

  • Benign lesions on mammography tend to be spherical and well circumscribed. They may contain calcification.   These calcifications are  larger and courser in appearance than malignant calcifications.
  • Ultrasound is helpful in evaluating breast masses in that it can unequivicolly identify simple cysts, which are benign.  The ultrasonographic features of cysts must include, smooth margins, thin walls, no internal echoes and good through transmission (brighter echoes behind the cyst).
  • Many approaches can be taken to biopsy abnormalities identified by mammogrpahy, palpation and ultrasonograpy.  Needle aspiration or core biopsy, can be guided by stereotactic mammography, ultrasound or palpation of any above lesions can be performed as an outpatient to facilitate diagnosis.

 

Rev 19 January 01

 by Gerald R. Aben, MD