Kidney

Introduction:

In the setting of suspected renal colic, bedside ultrasound can assist in making the diagnosis by assessing for hydronephrosis. The goals of bedside ultrasound are to look for the presence and extent of hydronephrosis, assess urine volume, and perhaps look for ureteral jets as well. If abdominal aneurysm is in the differential diagnosis, it is important that AAA be assessed as well.  Some aneurysms or other masses can cause hydronephrosis, so it does not exlude the diagnosis of AAA.

Focused Questions:

  1. Is there hydronephrosis?
  2. What is the bladder volume?

Video Overview:

Required Views:

1. Right Kidney (Longitudinal)

 

Probe position Image
RKProbeLong 300x225 Kidney RK2 500x383 Kidney
Notes
  • Try to find a window between the ribs
  • You may need more than one view to see the entire kidney
  • Fan from anterior to posterior to visualize through the entire kidney

2. Right Kidney (Transverse)

Probe position Image
RKProbeTRV 300x225 Kidney RKTRV 500x375 Kidney
Notes
  • Fan superior to inferior

3. Left Kidney (Longitudinal)

Probe position Image
LKprobeLong 300x225 Kidney LK 500x399 Kidney
Notes
  • Try to find a window between the ribs
  • You may need more than one view to see the entire kidney
  • Fan from anterior to posterior to visualize through the entire kidney

4. Left Kidney (Transverse)

Probe position Image
LKProbeTRV 300x225 Kidney LKTRV Kidney
Notes
  • Fan superior to inferior

Abnormal Image Gallery:

5. Bladder (Transverse)

Probe position Image
BladTRVProbe 300x267 Kidney Blad 500x397 Kidney
Notes
  • Fan superior to inferior, including rectum and prostate or vaginal cuff inferiorly

6. Bladder (Longitudinal)

Probe position Image
BladSagProbe 300x253 Kidney BladSag 500x384 Kidney
Notes
  • Fan left to right

Estimating bladder volume

Many machines contain built-in calculators for bladder volume estimation based on measurements. One simple and validated equation is simply:

length x width x height x 0.75

BladTRVvolume 300x248 KidneyStated another way, 75% of the cubic volume of the bladder. To measure all three axis of the bladder you will need a transverse view in largest dimension (for length [anterior-posterior] and width [left-right]) and a sagittal measurement (for length and height [cranial-caudal]).
This estimation can be helpful in determining post-void residual noninvasively, in the evaluation of anuria, renal failure, hydronephrosis, Foley catheter placement, and other renal and bladder anomalies. In infants, measuring the bladder volume prior to catheterization reduced the ‘dry tap’ rate significantly.

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