Monthly Archives: May 2019


On the sonogram, hydronephrosis appears as branching, interconnected areas of decreased echogenicity (anechoic or black in general, indicating the presence of fluid) in the renal collecting system. The source of obstruction is usually located distal to the kidney, for example, a stone in the pelviureteric junction, ureter or ureterovesical junction or bladder outlet obstruction from enlarged prostate, stone or a mass.

On the other hand, the collecting system of a normal kidney is not well-visualized unless distended and is embedded in the surrounding echogenic sinus fat. The renal pelvis area is hypoechoic but not ‘black’ unless there is hydronephrosis.

As the hydronephrosis increases in severity, the urine moves proximally into the kidney exerting pressure on the parenchyma. While there is no universally accepted grading system, hydronephrosis is often classified as mild, moderate or severe in routine clinical practice.

In mild hydronephrosis, there is dilatation of the renal pelvis and calyces but the pelvicalyceal pattern is retained and the cortex remains unaffected. Distinct medullary pyramids may be seen in some cases though not necessary to make a diagnosis as pyramids are not always appreciable even in a normal kidney.

In moderate hydronephrosis, medullary pyramids start to flatten due to back pressure in addition to dilatation of pelvicalyceal system and outpouching of the calyces, which is sometimes referred to as ‘cauliflower appearance’. Cortical thickness is preserved.

In severe cases, renal pelvis and calyces appear ballooned and cortico-medullary differentiation is lost making the cortex thin.

Here is the video form:

Urinary bladder diverticula – The Mickey Mouse sign

A bladder diverticulum is a sac that protrudes out of the bladder wall. Diverticulae may be congenital or acquired and acquired diverticula from chronic bladder outlet obstruction are commonly encountered in adults. They appear as Mickey Mouse ears on bladder ultrasound, with the bladder representing the head.

Here is an example of a large bladder diverticulum. Much larger than a typical Mickey Mouse ear!

The Journey Begins

Following are some of my published articles on POCUS. See the visual abstracts section for other important POCUS-related literature.

Utility of POCUS in volume assessment in ESRD

POCUS curriculum for nephrology fellows

Renal ultrasonography basics: pictorial mini-review

NephroPOCUS program for internal medicine residents

Why should we incorporate POCUS into our practice?

The TIE fighter sign on abdominal POCUS

Emphysematous pyelonephritis versus staghorn calculus

Retroperitoneal lymphoma causing hydronephrosis

Post-kidney biopsy AV fistula

Bladder stone: POCUS signs

Renal AVM mimicking hydronephrosis

Dromedary hump

Parapelvic cysts mimicking hydronephrosis

Twinkle artefact in tumor lysis syndrome

Volume depletion masking hydronephrosis