Monthly Archives: October 2019

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:

Renal abscess

A middle-aged man with diabetes mellitus type 2 presented with fever, chills and malaise. Urinalysis revealed pyuria and was positive for nitrite. Renal sonogram demonstrated a heterogeneous mass-like structure in the mid right kidney extending over the lower pole.

CT scan and MRI with contrast were suggestive of renal abscess. A drainage catheter was placed and patient started on intravenous antibiotics. Fluid culture grew Klebsiella pneumoniae and the therapy was tailored accordingly. 1-week later, a repeat sonogram demonstrated near-complete resolution of the collection.

On a sonogram, renal abscess appears as a well-defined hypoechoic area often with thick walls and internal echoes. Can be associated with surrounding diffusely hypoechoic, enlarged kidney due to pyelonephritis or hydronephrosis interspersed with echogenicities if it ruptures into the collecting system = pyonephrosis. It may appear similar to an organizing hematoma or renal cell carcinoma as in the above case where history becomes crucial and further imaging should be obtained. Small abscesses can be totally missed on ultrasound. Following are two more examples.

For renal abscesses <5 cm in diameter, antibiotic therapy alone without drainage is appropriate initial management. These lesions usually respond well to prolonged antibiotic treatment, and moreover, radiographic localization for drainage can be difficult. If clinical symptoms and radiographic findings persist after several days of antimicrobial therapy, drainage should be considered.

Renal abscesses >5 cm should be managed with percutaneous drainage in addition to antimicrobial therapy.

Am I seeing two urinary bladders?

We previously talked about the double bladder sign in female patients indicative of ovarian torsion. Here are images from a middle-aged gentleman, where the suprapubic scan revealed two anechoic structures, only one of which is the urinary bladder. While pelvic ascites can look similar, the two structures are well defined and moreover, the patient did not have any ascites in other abdominal scan zones.

The diagnosis is penile prosthesis. If you closely observe, one of these structures contains reverberation artefacts. That structure is the reservoir of the inflatable penile prosthesis and the artefacts are from check-valve apparatus. Below is an illustration that helps understand the anatomic relations better.

This case highlights the importance of integrating patients’ history with POCUS findings. In addition, not every anechoic thing in the suprapubic region is urinary bladder. Pelvic ascites, fresh blood, a large ovarian or seminal vesicle cyst, implant reservoir all should be considered depending on the clinical context.

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.  

Lung Mass

Occasionally, you may stumble upon a lung mass while evaluating for B lines or other common pathologies. Particularly, ultrasonography is good at detecting primary and metastatic lung masses adjacent to the pleural surface. They typically appear as hypoechoic areas that are distinct from consolidated or hepatized lung, with normally aerated lung appearing in the scan field with respiration. Consolidation and fluid bronchograms may be been seen adjacent to the mass.

It is interesting to note that ultrasonography has been shown to have better sensitivity and specificity (89% and 95% respectively) for assessing chest wall involvement by a lung tumor compared to CT scan. Extension of the tumor beyond the parietal pleura into the chest wall can be determined if the mass breaches the pleura and stops moving with respiration. If trying to find this, use a high resolution linear probe. Spectral Doppler may be helpful in differentiating malignant versus benign masses but it is beyond the scope of NephroPOCUS.