Tag Archives: Incidental findings

Comet tail artefacts from metallic objects

Here are the chest ultrasound images from a cardiac surgery patient. They were obtained from the sternal area and represent comet tail artefacts from sternal wires. They look like B-lines but they are in the black background of sternal shadow rather than hazy background of the lung. Moreover, they are arranged in zig zag pattern unlike B-lines.

Note the chest X-ray from the same patient showing sternal wires.

In terms of mechanism, these are a form of reverberation artefacts where the echoes generated from the main beam are repeatedly reflected, in repeated trips before going back to the transducer. Remember, time = distance in ultrasound language and the machine places echoes making repeated trips one below the other (taking more time to reach the probe = placed below), finally creating a vertical line. On the other hand, lung B-lines are ring-down artefacts. Consider watching my video (20 min-27:30) if you need to review these and other important artefacts.

Early intrauterine pregnancy

While scanning urinary bladder in women, we may occasionally encounter sonographic findings suggestive of pregnancy.  The earliest definitive evidence of pregnancy visible on ultrasonography (typically endovaginal) is the gestational sac appearing as a round, anechoic structure surrounded by thickened decidua without visible contents. At this stage, it might be difficult to distinguish true gestational sac from a pseudosac.

However, by the time it is detectable on transabdominal scans (6-7 weeks’ gestation; better seen when the urinary bladder is full), usually there are visible contents (yolk sac, fetal pole) inside the gestational sac. Visualization of a yolk sac is the first definitive evidence of an ‘intrauterine’ pregnancy. Ectopic pregnancies are rarely visible on transabdominal ultrasound but do watch for free fluid in the Morison’s pouch = could be sign of a ruptured ectopic that will likely require surgical intervention. Following are normal transabdominal images of an early intrauterine pregnancy.

Rarely, you may also find intact intrauterine contraceptive device (IUD) alongside the gestational sac (= contraception failure), which warrants immediate referral to the appropriate specialist. Following 2 cases illustrate this phenomenon.

The TIE fighter sign

These days, portable automated bladder scanners are widely used to check for urinary retention in hospitalized patients. They certainly avoid the need for invasive chatheterizations but cannot differentiate between urine and other fluid collections such as ascites. We recently published a case where bladder scanner falsely read ~800cc of urine but POCUS demonstrated that it actually was pelvic ascites in a patient with cirrhosis. In the transverse plane, uterus was seen floating in the pelvic ascites and together with ovarian ligaments, giving the appearance of a “TIE fighter”. Here is the video abstract:

Cervical mass

The cervix is not well visualized on transabdominal scans in most patients. The endovaginal approach usually results in more optimal visualization because the transducer can be placed closer to the cervix and allows the use of high frequency probes. However, large tumors can be incidentally found while looking for urinary bladder in the suprapubic region. Here is one such case of a huge cervical carcinoma appearing as a heterogeneous irregular structure in the bladder area.  

Double Bladder Sign

In a female patient presenting with lower abdominal pain, abnormal ovarian (cyst) location, that is, in midline above the uterus and adjacent to urinary bladder on transabdominal scan suggests ovarian torsion. As both bladder and the cyst are anechoic structures, it appears as if there are two bladders next to each other. In addition, watch for free fluid in the pouch of Douglas.

Why talking about cyst? Note that torsion is usually associated with an ovarian cyst that twists along the infundibulopelvic ligament and pedicle, subsequently compressing the ovarian vein and artery leading to stromal edema and ovarian enlargement. Presence of the cyst is a clue to ovarian location as the ovarian tissue itself is not clearly visualized on abdominal scans.

Stone-In-Neck phenomenon

Stone-In-Neck or the ‘SIN’ sign is when you see an immobile stone lodged in the gallbladder neck, without any anechoic space between the neck and the stone. It is suggestive of cholecystitis even in the absence of other sonographic signs such as thickened gall bladder wall, Pericholecystic fluid, sonographic Murphy’s sign etc. One small study found that the sensitivity of this sign is 56.5% and the specificity 97% for cholecystitis.

Thickened gall bladder wall: not always acute cholecystitis

In clinical practice, a cut off of 3mm is commonly used to define the upper limit of normal gall bladder wall thickness and acute cholecystitis is one thing that comes to our mind when we see increased wall thickness. Along with a compatible clinical picture, ultrasonographic features that suggest acute cholecystitis are a distended gallbladder, thickened walls, biliary sludge and lithiasis, pericholecystic fluid and the sonographic Murphy’s sign, which is defined as maximal abdominal tenderness from pressure of the ultrasound probe over the visualized gallbladder.

However, this is not the only condition that causes gall bladder wall thickening. As POCUS is not necessarily performed in a fasting patient, we must be aware that the gall bladder wall is thick in non-fasting state. In addition, any systemic disease associated with generalized hypervolemia such as congestive heart failure can lead to gall bladder wall thickening. In these patients, think of alternate etiology if the clinical picture does not fit. The presence of gall stones also does not mean much if there are no symptoms. Following image shows thickened gall bladder wall and ascites in a patient with congestive heart failure exacerbation. Note that the liver floating in ascites appears like a fish with gall bladder as its mouth. Though the wall diameter is measured in transverse plane in this example, it is generally recommended to be measured in long axis, and of the anterior wall (the one on the top).