Ultrasonography

·         SONOGRAPHIC FEATURES OF A NORMAL EARLY INTRAUTERINE PREGNANCY

1. Double decidual sac sign present by 5-6 weeks
2. Yolk sac visible by a mean gestational sac diameter of 8 mm transvaginally and 20 mm transabdominally
3. Embryo visible by a mean gestational sac diameter of 16 mm transvaginally and 25 mm transabdominally
4. Embryonic cardiac activity detected by a crown rump length of =5 mm

·         SONOGRAPHIC FINDINGS ASSOCIATED WITH AN ECTOPIC PREGNANCY

1. Extrauterine embryo (100% diagnostic)
2. Complex or solid adnexal mass
3. Moderate to large amount of particulate pelvic free fluid
4. Empty uterus with extrauterine gestational sac

·         An hourglass deformity is a severe form of incompetent cervix that occurs when the internal cervical os is open and the endocervical canal is dilated to the external os. Clinically, the amniotic membranes bulge into the vagina. Spontaneous pregnancy loss usually cannot be avoided

·         The abdominal circumference is measured in the transverse plane at the fetal liver, with the umbilical portion of the left portal vein in the center of the abdomen. The abdominal circumference is not as accurate as the BPD and femur length are for estimating gestational age. Instead, it is commonly used to determine proportionality with the head. A head:abdominal circumference ratio is used for this purpose. Normally, the head is larger than the body in the second and early third trimester, with a reversal of this ratio at term

·         A Dandy-Walker malformation causes an enlarged cisterna magna. From the inside of the occiput to the back of the cerebellar vermis, the cisterna magna normally measures 2-10 mm. Dandy-Walker malformations are caused by dysgenesis (Dandy-Walker variant) or agenesis of the cerebellar vermis and are associated with midline central nervous system abnormalities, including lateral and third ventricle hydrocephalus, encephalocele, and agenesis of the corpus callosum. Additional abnormalities of the body, including cardiac and renal abnormalities, may be found

·         sonographic findings of a pseudoaneurysm (PSA):

1.       Hypoechoic fluid collection immediately adjacent to the injured artery

2.       Variable amount of peripheral thrombus

3.       Swirling color flow (yin-yang) as blood flows in and out of the PSA

4.       "To and fro" pattern of flow at the PSA neck on pulsed Doppler with a normal systolic upstroke as blood enters the PSA

5.       Pandiastolic flow reversal due to the compliant nature of the PSA walls, as blood in the PSA cavity is ejected back into the artery during diastole

·         The liver should normally be equal to or slightly more echogenic than the right kidney and less echogenic than the pancreas.

·         The wall-echo-shadow (WES) sign may be seen when the gallbladder is completely filled with stones. This sign consists of two curvilinear structures followed by a shadow. The first line is hypoechoic and represents the gallbladder wall. The second is echogenic, representing multiple gallstones, with their associated shadowing making up the third portion of the sign. The WES sign may be difficult to differentiate from a gas-filled bowel loop.

·         The top two considerations of a hypoechoic pancreatic mass lesion are pancreatic adenocarcinoma and focal pancreatitis. A helpful finding in differentiating these is the presence of vascular encasement or metastases, which would support the diagnosis of adenocarcinoma. Pancreatic ductal dilation may be seen in either process, although the obstructed pancreatic duct in adenocarcinoma is typically smoothly dilated, whereas the duct in chronic pancreatitis most often has an irregular appearance. Other differential diagnostic considerations include islet cell tumors, pancreatic lymphoma, metastases, and peripancreatic lymph nodes.

·         SOLID RENAL MASS

1.       Renal carcinoma is the most common cause.

2.       Angiomyolipoma (AML) is usually hyperechoic, but some carcinomas mimic AML on ultrasound.

3.       Other neoplasms include oncocytoma, renal lymphoma, transitional cell carcinoma of the renal collecting system, and metastasis to the kidney.