Abdominal scanning points
7 abdominal scanning points labelled in general order of scanning
Each area of the abdominal ultrasound allows assessment of a different underlying structures.
Scanning areas 1&2 assesses the RUQ of the abdomen and the liver, diaphragm, lung, and right kidney should be identified.
Scanning areas 3&4 assess the LUQ of the abdomen and the spleen, diaphragm, lung, and left kidney should be identified.
Scanning point 5&6 assess the RIF&LIF of the abdomen for free fluid, but may just show bowel.
Scanning point 7 assess the suprapubic region of the abdomen and the bladder and prostate/cervix should be identified if possible.
7 abdominal scanning points and the underlying anatomical structures
Peritoneal free fluid accumulates in potential spaces in the abdomen, it has a low acoustic impedance so it is echo poor and appears dark on ultrasound. Due to it being a good transmitter of ultrasound underlying structures appear bright and well defined.
It is important to be aware that ultrasound does not help identify the source of the free fluid which can be due to ascites or bleeding and the overall clinical picture needs to be taken into account.
The probe is placed in the RUQ of the abdomen in the coronal plane. In this view the liver is the main abdominal organ that can be identified. Superior to this is the diaphragm and below the liver and slightly posteriorly is the right kidney.
Look for peri-hepatic fluid and fluid in the hepatorenal recess (also known as Morrison’s pouch). If fluid is seen above the liver it is important to identify the diaphragm to see if the fluid is pleural (above the diaphragm) or peritoneal (below the diaphragm).
RUQ coronal view showing the liver kidney and Morrison's pouch
Scanning through the RUQ coronal view showing the liver kidney and Morrison's pouch
Fluid shown on ultrasound around the inferior border of the liver and extending into Morrison's pouch
Sub-phrenic fluid shown on ultrasound in the RUQ above the liver. Basal lung collapse/consolidation can also be seen.
In this view assess the spleen, left kidney and the diaphragm. The spleen is smaller than the liver and so can be hard to find. Once found assess for peri-splenic fluid or fluid in the splenorenal recess.
Similarly to the RUQ view if fluid is seen above the spleen it is important to assess whether the fluid is above the diaphragm and therefore pleural fluid or below the diaphragm and therefore peritoneal.
LUQ coronal view showing the spleen and kidney with the spleno-renal recess labelled
Scanning through the LUQ coronal view showing the spleen and kidney with the spleno-renal recess labelled
Sagittal plane of the male lower abdomen - displaying the rectovesical pouch where free fluid can accumulate if present.
Sagittal plane of the female lower abdomen - displaying the pouch of Douglas where free fluid can accumulate if present.
Sagittal plane ultrasound of the bladder in a male - showing the rectum and recto-vesicle pouch. Superior is to the left of the image.
Transverse plane ultrasound of the bladder in a male - showing the recto-vesicle pouch.
Assessment of bladder volume
Bladder volume can be estimated using the formula [½ x width (cm) x height (cm) x depth (cm)]. In the transverse plane measure the width at the largest point, then obtain the sagittal view and measure the height and depth of the bladder at the largest point.
Transverse plane of the bladder with colour flow doppler demonstrating ureteric jets (the normal physiological efflux of urine from the distal ureter into the bladder)
RIF ultrasound demonstrating the presence of ascites. The fluid is seen surrounding the bowel.
[Note that whilst coagulopathy may increase tendency to bleed following the procedure it is not a contraindication in patients with decompensated liver disease because the necessity to confirm and treat SBP if present far outweighs the risks.]
Assess both the right and left iliac fossa with the ultrasound and find the deepest pocket. Measure it with calipers and mark the area, making sure to assess in 2 planes. A depth of 3cm is enough to perform the procedure. With the ultrasound any large abdominal wall vessels can be seen and avoided.
Identification of the bladder has been covered above when also assessing for intra-abdominal free fluid.
It is important to identify whether the bladder is full or empty. On intensive care the majority of patients are catheterised so the bladder should be empty. If a patient is catheterised with evidence of residual volume then the catheter may be blocked.
It is also important to identify the kidneys and assess for any hydronephrosis and whether it is unilateral or bilateral. This will help determine the area causing the obstruction.
The kidneys are found on ultrasound bilaterally beneath the spleen and liver in normal patients. The scanning window is often found postero-laterally in the coronal view. The kidneys cortex appears dark with echo bright fat in the renal sinuses. The medullary pyramids appear triangular, are echo poor and are seen between the renal cortex and renal pelvis.
Labelled ultrasound of the kidney from the RUQ coronal view in longitudinal section
Illustrated anatomy of the kidney
Hydronephrosis is when urinary flow from the kidney is blocked the renal pelvis starts to dilate. The severity of hydronephrosis depends on the extent of the dilatation.
If only the renal pelvis is dilated this is mild hydronephrosis, if the renal pelvis and calyces are dilated this is most likely moderate hydronephrosis. If there is gross renal pelvis and calyces dilatation and there is evidence of this impacting renal architecture/causing cortical atrophy then this is severe hydronephrosis.
If hydronephrosis is found on ultrasound both kidneys should be examined for hydronephrosis and the bladder should be assessed as to whether it is full or empty. This can help determine the level of the obstruction.
If there is unilateral hydroneprosis with an empty bladder the level obstruction is likely in the ureter. If there is bilateral hydronephrosis with a full/distended bladder then the obstruction is likely below the level of the bladder.
The absence of hydronephrosis and an empty bladder make urinary tract obstruction unlikely.
Grading of hydronephrosis
Renal pelvis dilatation
Moderate renal pelvis dilatation
Gross renal pelvis dilatation
No calyceal dilatation
Moderate calyceal dilatation
Gross calyceal dilatation
No parenchymal atrophy
Early parenchymal atrophy may be present
Loss of normal architecture
Ultrasound appearance hydronephrosis
Renal pelvis dilatation is a key feature of all grades of hydronephrosis. This appears as an echo poor area (the dilated renal pelvis) surrounded by echo bright fat from the renal sinuses.
As the hydronephrosis progresses this echo poor area extends into the calyces and becomes larger and in severe cases starts causes loss of normal architecture of the kidney and cortical atrophy.
Ultrasound view of the right kidney in the longitudinal section. The renal pelvis is dilated and this can be extending up into the calyces. There is no obvious cortical atrophy.
Scanning through the right kidney in the longitudinal section. This further demonstrates the dilated renal pelvis extending up into the calyces.
Content created by Ben Stoney
Design by Max Broadbent
The ultrasound images and clips used on this website have be reproduced following the local clinical governance guidance.