Tag Archives: Bladder

Ureterovesical junction stone

We have previously talked about ureteral jets and the twinkle artefact. Here is an excellent clip shared by Dr. Robert Jones demonstrating twinkle artefact in the right distal ureter region suggestive of an ureterovesical junction stone. Shadowing from the stone is not always prominent in this region and twinkle artefact on color Doppler helps to make the diagnosis. Note the strong ureteral jet on the left compared to the right corroborating with obstruction on the right.

Take home point: Always look for the cause of hydronephrosis and utilize color Doppler to identify twinkle artefact when you see something suspicious for a stone.

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.

Ureteral jets

The intravesical ureteral jets, or the bladder jets represent the sonographic appearance of discrete boluses of urine entering the bladder, better detected using color Doppler. They are thought to result from autonomic and pressure dependent calyceal and ureteral peristalses.

Most healthy people have a ureteric jet frequency of 2 or more per minute on either side. Absence of ureteric jets during 10 minutes of observation in the steady diuresis phase may indicate complete ureteral obstruction, and the ureteric jet frequency of less than 2 per minute may indicate partial obstruction. In addition, jets may be absent in cases with poor renal plasma flow, or impaired unilateral renal circulation, such as in the case of renal cell carcinoma complicated with renal vein occlusion from tumor invasion or tumor thromboembolism.

However, their practical utility is not well established. In one study, urologists and radiologists disagreed on both the necessity for evaluating ureteral jets and their clinical relevance. In summary, if you see strong jets on both sides, it’s good and if you don’t, it doesn’t mean much unless you have suspicion for unilateral ureteral obstruction and there is no jet on that side after you ‘patiently’ monitored for at least 10 minutes.

Urinary bladder wall thickness: what is the number to remember?

It is not uncommon to see a thickened urinary bladder wall in cases of chronic bladder outlet obstruction. Have you ever wondered how thick is thick? In a study, a bladder wall thickness of 5 mm appeared to be the best cutoff point to diagnose bladder outlet obstruction. Note that we should not comment on the wall thickness or other characteristics when the bladder is empty. In this study for example, the bladder was filled to 150 ml before performing the scan. Prior to that, uroflowmetry and pressure-flow studies were performed.

Bladder ultrasound: calculation of volume

Sonographic evaluation of the urinary bladder should be performed in any patient with dilated collecting system or frequent urinary tract infections, especially in a male. The examination is performed with the patient in supine position with suprapubic area exposed. The probe is placed longitudinally in the mid-line above the pubic symphysis with probe marker towards patient’s head to obtain sagittal view of the bladder. Then it should be angled laterally and ‘swept’ to left and right to examine the lateral borders. The probe is then rotated 90 degrees counter clockwise to obtain the transverse view and swept superior to inferior to image the bladder completely. The volume of the bladder is estimated by orthogonal measurements, assuming it to be an ellipsoid (= 0.52 × the three orthogonal dimensions). Both pre and post-void measurements should be taken to diagnose urinary retention.

Not every anechoic thing in the pelvis is urine!

In this pelvic area sonogram, the Foley balloon (arrow) appears to be located outside the urinary bladder suggesting malposition of the catheter. However, the fluid collection anterior to the Foley is pelvic ascites and the Foley is in appropriate position as shown by the green dot in the illustration. Blood, serous fluid, and urine are all black on ultrasound. Note the margins of this ‘bladder-like’ structure are irregular which should make us suspect something isn’t right. To confirm the diagnosis, we should perform a long axis scan which will show that this fluid collection is in continuity with the peritoneal cavity. Moreover, a patient’s medical history should alert to the presence of pelvic ascites. It’s interesting to note that the bedside bladder scanning devices that are available in most hospitals these days can wrongly display ascitic fluid volume as bladder volume in this scenario.