Tag Archives: Incidental findings

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).

Mirror image artefact

This is one of the commonest artefacts encountered in NephroPOCUS. It is generated by the false assumption that an echo returns to the transducer after a single reflection. In this scenario, the primary beam encounters a highly reflective interface, the reflected echoes then encounter the “back side” of the structure and are reflected back toward the reflective interface before being reflected to the transducer for detection. The display shows a duplicated structure equidistant from but deep to the strongly reflective interface. Remember, time = distance in the ultrasound world, which means if the echoes take longer time to reach back to the probe, that structure is displayed farther from the top of the screen and vice versa. In other words, structures closer to the probe are displayed at the top of the image.

In this example, the diaphragm sitting next to the air-filled lung that is reflective acts as a mirror, and the mirror image artefact appears as hepatic parenchyma (or spleen on the left) in the expected location of lung. However, when there is pleural effusion, this artefact disappears (fluid is an excellent transmitter of ultrasound waves unlike air) and you’ll see an anechoic area above the diaphragm representing the effusion. In these cases, identification of thoracic spine sign confirms the diagnosis of pleural effusion.

You can watch my video 10 ~7:58 for more examples and better understanding of the mechanism of this artefact.

Hepatic Hemangioma

This image demonstrates hepatic hemangioma incidentally found while imaging the kidney. On ultrasound, hepatic hemangiomas appear as well-defined, hyperechoic, homogeneous lesions. Some of them may have posterior acoustic enhancement. The hyperechogenicity probably results from multiple fibrous interfaces between vascular spaces. If the lesion is in a fibrotic liver, that is background echogenicity, it may appear hypoechoic. Lesions >5 cm can have mixed echogenicity because of intratumoral thrombosis and fibrosis.

Ultrasound has a good accuracy in differentiating hepatic hemangioma from malignant hyperechoic masses (sensitivity of 94.1% and specificity of 80.0% for lesions less than 3 cm diameter). The absence of blood flow on Doppler exam is also a reliable sign to differentiate hemangioma from hepatocellular carcinoma, which frequently has intra- or peri-tumoral vascularity. Though the lesion is vascular, the blood flow is too slow to be picked up by Doppler usually. In hypoechoic lesions, a peripheral echogenic rim favors hemangioma, while a perilesional hypoechoic rim, known as the ‘target sign’, strongly suggests malignancy.

Asymptomatic patients with lesions <1.5 cm, but also including those with lesions ≤5 cm, can be reassured and observed without follow-up imaging. On the other hand, close radiologic follow-up of should be considered in patients with lesions >5 cm (e.g. CT scan yearly), particularly those in a subcapsular location. In the absence of symptoms, prophylactic resection is usually not recommended [UpToDate].

This image demonstrates a lesion of mixed echogenicity in a non homogeneous liver (cirrhosis) and ascites. It was diagnosed as HCC.