Ch. 19 - US: Understanding the Principles and Recognizing Normal and Abnormal Findings Flashcards
A tissue that reflects many echoes is said to be:
Echogenic (Hyperechoic) –> Usually depicted as bright or white on the sonogram.
A tissue that has few or no echoes is said to be:
Sonolucent (hypoechoic or anechoic) and is usually depicted as being dark or black.
Gallstones:
Characteristically echogenic and produce acoustical shadowing because they reflect most of the signal.
Biliary sludge:
Can be found in the lumen of the gallbladder and is often associated with biliary stasis.
–> May be echogenic - sludge does NOT produce acoustical shadowing like gallstones.
The typical appearance of … is a dilated calyceal system.
Obstructive nephropathy.
In medical renal disease:
Renal parenchyma becomes more echogenic (brighter) that the liver and spleen, the reverse of the normal echo pattern.
US is the screening study of choice when:
An asymptomatic, pulsatile abdominal mass is palpated.
MC MASS in the ovary:
A functional cyst.
Generally, uterine masses are more …, and ovarian masses are more … .
Uterine –> Solid.
Ovarian –> Cystic.
Follicular cysts and corpus luteum cysts are … of the ovary:
Functional cysts.
Functional cysts are characteristically:
- Well-defined.
- Thin-walled.
- Anechoic structures with homogenous internal fluid density.
- They may contain echogenic material if hemorrhage occurs into the cyst.
Non functional cysts of the ovary include:
- Dermoid cysts.
- Endometriomas.
- Polycystic ovaries.
Tumors of the ovaries:
- Most often arise from the surface covering and are either serous or mucinous.
- Most serous tumors + overwhelming number of mucinous tumors are benign.
Acute appendicitis:
Appendix may be blind-ending, aperistaltic tube with a diameter of 6mm or more.
Appendicitis - A fecalith is present in about … of cases:
1/3.
Most ectopic pregnancies are:
Tubal in location and occur near the fimbriated (ovarian) end.
An ectopic pregnancy can be effectively excluded:
If an intrauterine pregnancy is present.
An ectopic pregnancy can be effectively included:
If an extrauterine pregnancy is seen.
Most often, an ectopic pregnancy is diagnosed by a combination of:
Absence of an identifiable intrauterine pregnancy while the β-HCG rises above a certain level.
A molar pregnancy:
Is suggested by a uterine size that is disproportionately large for the dates of gestation and β-HCG levels in excess of 100.000 mIU/mL. (NORMAL –> 60.000mUI/mL).
Carotid stenosis begins to cause changes in the velocity of flow when there is greater than … narrowing of the lumen.
50%.
Sonographic evaluation for DVT of the leg is mainly based on the principle that:
Normal venous structures will be easily compressed and collapsed by the transducer, whereas veins harboring thrombi will NOT compress.
–> Also seeks to visualize the echogenic thrombus itself.
Uses of US during pregnancy:
- Fetal presence and gestational age.
- Fetal abnormalities and viability.
- Presence of multiple pregnancies.
- Placental localization.
- Amniotic fluid volume.
- Intrauterine growth retardation.
- Helping guide invasive studies like:
a. Amniocentesis.
b. Chorionic villus sampling.
c. Intrauterine transfusions.
Advantages of ultrasonography:
- No ionizing radiation.
- No known long-term side effects.
- “Real-time” images.
- Produces little or no patient discomfort.
- Small, portable, inexpensive, ubiquitous.
Disadvantages of US:
- Difficulty penetrating through bone.
- Gas-filled structures reduce its utility.
- Obese patients may be difficult to penetrate.
- Dependent on the skills of the operator scanning.
Types of US - A mode:
- Simplest.
- Spikes along a line represent the signal amplitude at a certain depth.
- Used mainly in ophthalmology.
Types of US - B mode:
- Mode most often used in diagnostic imaging.
- Each echo is depicted as a dot and the sonogram is made up of thousands of these dots.
- Can depict real-time motion.
Types of US - M-Mode:
Used to show moving structures such as blood flow or motion of the heart valves.
Types of US - Doppler:
- Uses the Doppler effect to assess blood flow –> Used for vascular US.
- Pulsed Doppler devices emit short-bursts of energy that allow for an accurate localization of the echo source and has replaces continuous wave Doppler.
Types of US - Duplex US:
Utilized in vascular studies - Refers to the simultaneous use of both gray-scale or color Doppler to visualize the structure of and flow within a vessel and spectral waveform Doppler to quantitate flow.
Creation of a sonographic image (sonogram) depends on 3 major components:
- Production of high-frequency sound wave.
- Reception of a reflected wave or echo.
- Conversion of that echo into the actual image.
By convention sonographic images are viewed …?
With the patient’s HEAD to your LEFT and the patient’s FEET towards your RIGHT; anterior is UP - posterior is DOWN.
Doppler US - By convention, red indicates flow … the transducer, and blue indicates flow … from the transducer.
RED –> TOWARDS.
BLUE –> AWAY.
US is usually the study of 1st choice in imaging …?
- The female pelvis.
- Pediatric patients.
- In differentiating cystic versus solid lesions in ALL patients.
- In non invasive vascular imaging.
- Imaging of the fetus and placenta during pregnancy.
- Real-time, image-guided fluid aspiration biopsies.
Other common uses of US:
- Evaluation of cystic vs solid BREAST masses.
- Thyroid nodules.
- Tendons.
- Assessing the brain, hip, spine in NEWBORNS.
In the fasting patient, the gallbladder is about …?
4x10cm in size and the wall is normally no thicker than 3mm.
What do gallstones produce?
They are echogenic and produce –> Acoustical shadowing –> They reflect most of the signal.
What is the biliary sludge?
An aggregation that may contain CH crystals, bilirubin, and glycoproteins –> Associated with BILIARY STASIS.
While it may be echogenic, sludge …?
DOES NOT produce acoustical shadowing like gallstones.
Signs of acute cholecystitis on US (4):
- Presence of gallstones, possibly impacted in the neck of the gallbladder.
- Thickening of the gallbladder wall >3mm.
- Pericholecystic fluid –> Fluid around the gallbladder.
- Positive Murphy - Pain that is elicited by compression with the US probe).
PPD of US in the presence of gallstones and gallbladder wall thickening?
94%.
Besides US, what is also used in the diagnosis of acute cholecystitis?
HIDA scans.
US can visualize common hepatic duct (CHD), common bile duct (CBD) and pancreatic duct. Diameter?
CHD –> Usually no more than 4mm.
CBD –> Usually no more than 6mm.
PD –>
The renal sinus is the home of …?
- Renal pelvis.
2. Renal artery + vein.
Why does the renal sinus appears brightly echogenic?
Because it contains fat.
The renal calyces are …?
Normally NOT visible.
The medullary pyramids are …?
Hypoechoic.
The renal parenchyma has uniformly …?
LOW ECHOGENICITY –> Usually less than that of the adjacent liver + spleen.
In early stages of medical renal disease, the kidneys may appear normal. Later …?
Changes in the echo architecture occur but these are usually non specific.
–> Renal parenchyma becomes more ECHOGENIC (brighter) than the liver and spleen, the reverse of the normal echo pattern.
Asymptomatic, abdominal, palpable mass?
US is the screening study of choice.
AAA - US?
Blood moves –> Anechoic.
Thrombus does not move –> Echogenic.
AAA - Advantage of unenhanced CT?
Depicts the absolute size of of the aneurysm, but in order to define the extent of MURAL THROMBUS and the presence of dissection, IV contrast must be used.
What is the MC tumor of the uterus?
Leiomyomas confined to the myometrium.
Endometrial carcinomas are usually confined to the …?
Uterus at the time of discovery.
MC mass in the ovary is a …?
Functional cyst.
Generally, uterine masses are … and ovarian masses are …?
Uterine –> Solid.
Ovarian –> Cystic.
Dimensions of the uterus in adult?
Length –> 8cm.
Width –> 5cm.
AP dimension –> 4cm.
The standard transabdominal study of the uterus is done with a …?
FULL BLADDER –> Provides acoustical window by pushing bowel loops out of the pelvis and also helps to delineate the bladder itself.
Transvaginal studies of the uterus are done with …?
HIGHER frequency probes –> Better resolution.
Transvaginal studies of the uterus are done with an …?
EMPTY BLADDER.
What is the sonohysterography?
A procedure in which saline is instilled in the uterine cavity in conjunction with images obtained using transvaginal US.
What is the role of sonohysterography?
Excellent visualization of the uterine cavity + fallopian tubes –> Used to detect small uterine polyps, submucosal myomas, and adhesions.
Uterine leiomyomas (fibroids) - Imaging study of choice?
Transabdominal AND transvaginal.
Uterine leiomyomas - MRI?
Used mainly to evaluate complicated cases or in surgical planning.
Recognizing uterine leiomyomas on US (4)?
- Heterogeneously hypoechoic solid masses.
- Frequently absorb enough sound to produce ACOUSTICAL SHADOWING.
- Necrotic –> Anechoic.
- If they contain calcium –> Acoustical shadowing.
Recognizing uterine leiomyomas on CT?
- Lobulated soft tissue masses that frequently calcify with amorphous/popcorn calcification.
- When large –> Central necrosis –> Low attenuation.
- Myometrium is VERY vascular and markedly enhances on contrast –> Viable portions of uterine myomata also enhance dramatically following injection of IV contrast.
Imaging study of choice for evaluating the ovaries?
US.
In premenopausal women, the ovaries are approximately …?
2x3x4cm in size - Frequently containing cystic follicles.
Under normal hormonal stimulation, one egg-containing follicle becomes dominant and attains a size of about …?
2.5cm at the time of ovulation.
If one of the non dominant follicles fills with fluid and does NOT rupture, … is formed.
A follicular CYST.
A corpus luteum is the structure that forms after expulsion of an egg from the dominant ovarian follicle. If the corpus luteum fills with fluid, a … will develop.
Corpus luteal cyst.
–> Less common than follicular cysts.
Follicular cysts + corpus luteum cysts are called …?
Functional cysts –> Because they occur as a result of the hormonal stimuli associated with ovulation.
US features of functional cysts:
- Well-defined and thin-walled.
- Anechoic structures.
- Homogenous internal fluid density.
- -> May contain echogenic material if hemorrhage occurs into the cyst.
NON functional cysts of the ovary include (3)?
- Dermoid cysts.
- Endometriomas.
- Polycystic ovaries.
Stein-Leventhal syndrome?
PCOS + Oligomenorrhea + Hirsutism + Obesity.
How many cysts in PCOS?
> 12 per ovary.
On US, primary tumors of the ovary are usually … in nature.
CYSTIC.
Keys to differentiating ovarian cysts from tumors include …?
- Thick + irregular walls.
- Internal septations.
which are seen in tumors.
Most cases of PID begin as …?
A transient endometritis –> Ascend to infection of the tubes and ovaries - Patients can have pain, vaginal discharge, adnexal tenderness and elevated WBC count.
3 complications of PID:
- Infertility.
- Ectopic pregnancy.
- Chronic pain.
Recognizing PID in US:
- Enlarged ovaries with multiple cysts and periovarian inflammation.
- Pyosalpinx –> Fluid-filled and dilated fallopian tube.
- Fusion of the dilated fallopian tube and ovary - Tubo-ovarian complex.
- Multiloculated mass with septations - Tubo-ovarian abscess.
Recognizing PID on CT requires the use of …?
IV contrast.
PID on CT(+) - Findings include:
- Haziness of pelvic fat.
- Thickened tubes.
- Enlarged uterus.
- Pyosalpinx + tubo-ovarian abscess - Adnexal mass with focal areas of hypodensity.
- Pelvic ascites.
Ascites - Transudate is …?
SONOLUCENT.
–> Exudates or hemorrhage may contain echoes.
US is frequently used to identify …?
The best location to perform a paracentesis to remove ascitic fluid.
Normal appendix on US?
May NOT be seen - Diameter usually les than 6mm.
In acute appendicitis - US?
May be recognized as a blind-ending, aperistaltic tube with a diameter of 6mm or more –> Appendix is NON COMPRESSIBLE.
–> 1/3 of cases a FECALITH will be present.
The goals of sonography during pregnancy may differ depending on the timing of the scan - 1st trimester?
Goals are:
- To exclude an ectopic prenancy.
- Estimate the age of the pregnancy.
- Determine fetal viability.
- Determine if there are multiple fetuses present.
Goals of US during the 2nd and 3rd trimester may include?
- Estimates of amniotic fluid.
- Detection of fetal abnormalities.
- Determination of placental and fetal positioning.
- Guidance for invasive studies to determine the likelihood of fetal viability in the event of a premature birth.
Ectopic pregnancy - Location?
Tubal - Near the fimbriated (ovarian) end - Classical clinical findings of: 1. Pain. 2. Abnormal vaginal bleeding. 3. Palpable adnexal mass. seen in ONLY HALF of cases.
What US findings can effectively exclude ectopic pregnancy?
- Gestational sac (earliest sonographic finding in pregnancy, appearing at about 4-5 weeks).
- Yolk sac (first structure to be seen normally in gestational sac).
- Viable fetus.
are identified in the UTERINE CAVITY, an ectopic pregnancy can effectively be excluded.
What does heterotopic pregnancy mean?
Simultaneous intrauterine and extrauterine pregnancies –> Extremely rare.
An ectopic pregnancy is also presumed present when there are …?
Large amounts of free fluid (blood) inside the abdominal cavity.
Small amounts of free fluid in the abdomen may occur from other causes such as …?
- Spontaneous abortion.
- Ruptured ovarian cysts.
- Normal ovulation.
Molar pregnancy is the …?
MC of a group of disorders of the PLACENTA that also includes:
- Invasive mole.
- Choriocarcinoma.
Pathologically, molar pregnancies feature …?
Cystic (grapelike or hydatidiform) degeneration of CHORIONIC VILLI + Proliferation of the placental trophoblast.
A molar pregnancy is suggested by …?
- Uterine size that is disproportionately large for the dates of gestation.
- β-hCG in excess of 100.000mIU/mL (normal pregnancies are less than 60.000mIU/mL).
- Vomiting.
- Vaginal bleeding.
- Toxemia.
Sonographic findings of molar pregnancy:
- Enlarged uterus –> Echogenic tissue that enlarges the endometrial cavity.
- Innumerable, uniform-sized cystic spaces that represent HYDROPIC VILLI.
- Enlarged and cyst-filled ovaries.
- -> Complete molar pregnancy = NO FETUS.
The highest yield sonographic exam for DVT using US occurs in the …?
SYMPTOMATIC patient who has symptoms ABOVE THE KNEE –> US has much LOWER sensitivity in ASYMPTOMATIC patients.
