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D. N. Suwondo and C. Baloescu
inferiorly using a rocking hand maneuver and the
sound beam is directed into the pelvis. In the sagittal plane, the bladder is scanned from edge-toedge by fanning the transducer left and right. In
males, the prostate is located in the midline at the
posterior-inferior aspect of the bladder and can
often be seen on the transverse view, particularly
when enlarged (Fig.43.2c). In females, the cer-
Fig. 43.2 (a) Normal bladder in transverse plane, from
which two of the three measurements needed to calculate
bladder volume can be obtained, (b) Normal bladder in
sagittal plane, from which the third measurement can be
obtained and the bladder volume calculated, (c) Transverse
view of a severely distended bladder in a patient with urinary retention due to an enlarged prostate (asterisk), with
more than 1L of urine in the bladder, (d) Sagittal view of
a bladder after placement of a urinary catheter, showing
an enlarged prostate (asterisk) at the base of the bladder,
the opening at the tip of the catheter (thin arrow), and the
inated catheter balloon (block arrow) properly located
within the lumen of the bladder, (e) Transverse view of
bladder with color-ow Doppler showing left ureteral jet,
conrming patency of left ureter, (f) Transverse view of
bladder showing hyperechoic stone (arrow) at right ure-
terovesical junction (UVJ) with acoustic shadowing.
Suwondo DN and Baloescu C. Renal and Bladder
Ultrasonography for the Intensivist. In: Lanspa MJ and
Levinson AT, editors. Echocardiography and
Ultrasonography in the ICU: A Comprehensive Text.
Springer; in preparation, 2022
43 Renal andBladder Ultrasonography fortheIntensivist
485
vix is located posterior to the bladder and the
anteverted uterus is located superior to the bladder, and best visualized on the sagittal view. The
presence of intraperitoneal free uid in the pelvis
is typically identied as irregularly shaped,
uncontained anechoic areas tracking between the
bladder wall and surrounding structures such as
bowel. This is unlike urine in the bladder, which
is also anechoic but well-circumscribed and fully
encapsulated in a spherical or cuboid shape.
Bladder Ultrasound
Point-of-care bladder ultrasound can be used by
the intensivist to accurately measure bladder volume, diagnose acute urinary retention, troubleshoot malfunctioning urinary catheters, and
assess ureteral patency via the presence of ureteral jets.
Bladder Volume
Although bladder volume is commonly estimated using commercial handheld bladder scanning devices, these devices may have decreased
accuracy when compared to POCUS-based
measurements, particularly in patients with
morbid obesity or ascites [14, 15]. Using
POCUS, the intensivist can quickly and accurately identify a urine-lled bladder based on
anatomic landmarks and appearance, which
may help differentiate the bladder from other
potential abdominopelvic uid-containing
pathologies such as ascites, distended uidlled loops of bowel, an abdominal aortic aneurysm, or adnexal cysts. To calculate bladder
volume, the maximal length and width of the
bladder lumen are measured in the transverse
plane (Fig. 43.2a), and the maximal height of
the bladder lumen is measured in the sagittal
plane (Fig. 43.2b), yielding three orthogonal
measurements. Most ultrasound machines will
automatically calculate a bladder volume from
these three measurements, although a variety of
formulas for manually calculating the volume
have been described, the simplest of which is
L*W*H*0.75 [7, 16]. As ultrasound vendors
have introduced articial intelligence algo-
rithms into their machines, some devices may
have an automatic feature which calculates
bladder volume without need for manual scan-
ning in different planes.
Urinary Catheters
POCUS can also help the intensivist identify
and troubleshoot problems with urinary cathe-
ters. In catheterized patients who develop
anuria, suprapubic pain, or hematuria, POCUS
can be used to identify signs of urinary catheter
obstruction or malposition and to differentiate
catheter obstruction from true anuria. An
inated Foley balloon typically appears as a
perfectly spherical structure comprising a thin
hyperechoic border with anechoic contents
(Fig.43.2d) near the tip of the catheter [13]. A
distended bladder on ultrasound despite the
presence of a urinary catheter suggests catheter
obstruction or malposition. POCUS can also
reveal hyperechoic debris or clot layering in
dependent areas of the bladder, or a Foley bal-
loon inappropriately positioned within the pros-
tatic urethra. In both non-catheterized and
catheterized patients with decreased output or
hematuria, the presence of a large clot burden
lling the bladder may dissuade blindly per-
forming brisk bladder irrigation.
Ureteral Stones andJets
In patients with known or suspected ureteral
stones, POCUS can help conrm ureteral
patency by visualizing the presence of ureteral
“jets” at the ureterovesical junction (UVJ) using
color- ow Doppler. On a transverse view of the
bladder with color-ow Doppler applied, jets
appear as intermittent streams of color ow
originating from the posterior wall of the blad-
der at the left or right UVJ and angled towards
the center of the bladder lumen (Fig.43.2e). Jets
represent expulsion of urine from the ureter into
the bladder during ureteral peristalsis, and
486
D. N. Suwondo and C. Baloescu
depending on hydration status, may be seen one
or more times per minute, each lasting up to a
second [7, 8]. The presence of bilateral jets
makes complete ureteral obstruction unlikely,
while their unilateral absence can suggest ureteral obstruction. Although ultrasound is generally insensitive for the detection of ureteral
stones, sufciently large UVJ stones may be
identied on ultrasound as an echogenic focus
which may exhibit posterior acoustic shadowing
on B-mode imaging (Fig. 43.2f) or a “twinkling” artifact on color- ow Doppler, which
manifests as a rapidly alternating or shifting
color signal behind the stone surface and which
has been reported to have a 78% positive predictive value for the presence of nephrolithiasis on
unenhanced CT [17]. Large ureteropelvic junction (UPJ) stones may also be visible on ultrasound at the proximal ureter.
Hydronephrosis
Grading ofHydronephrosis
Hydronephrosis in adults is typically graded
as mild, moderate, or severe [7–9]. Mild
hydronephrosis involves mild dilation or
“splaying” of the renal pelvis, without significant distortion of the calyces (Fig. 43.3a).
Moderate hydronephrosis involves significant
renal pelvic dilation that extends into the calyceal system, causing enlargement and blunting
of the calyces; this results in a characteristic
multipronged broccoli-like or claw-like
appearance (Fig. 43.3b), which spares the
renal cortex. In severe hydronephrosis, the
calyceal dilation results in thinning of the
renal parenchyma (Fig.43.3c). Severe hydronephrosis with cortical atrophy may represent
chronic rather than acute etiology [18]. Among
ED patients with suspected renal colic, the
finding of moderate or severe hydronephrosis
on POCUS has a pooled specificity of 94% for
the presence of a renal stone on CT [19].
POCUS may also reveal the presence of other
non-obstructing renal stones, which may
appear as echogenic foci with acoustic shad-
owing. In a critically ill ICU patient with uro-
sepsis, the finding of unilateral hydronephrosis
on POCUS suggests the presence of an
infected obstructing stone and may prompt
urgent procedural intervention. In a patient
with a renal transplant, isolated hydronephro-
sis of the transplanted kidney without bladder
distension can suggest edema or obstruction at
the ureteral anastomosis site [9].
Pitfalls
When evaluating for hydronephrosis in patients
with unilateral symptoms, it may be helpful to
rst scan the unaffected contralateral kidney to
obtain a set of baseline images against which to
compare the renal collecting system of the
affected side, particularly when the degree of
hydronephrosis is mild. Prominent renal vascula-
ture, particularly the veins at the level of the
hilum, can be misidentied as hydronephrosis on
grayscale imaging; applying color-ow Doppler
can rapidly differentiate the renal pelvis from
surrounding vasculature (Fig. 43.3e). A renal
cyst, particularly a parapelvic cyst, may also be
misidentied as hydronephrosis; however, cysts
are fully circumscribed with a smooth rounded
shape, may exhibit posterior acoustic enhance-
ment, and are not associated with dilation of the
renal pelvis or surrounding calyces (Fig.43.3d).
Hydronephrosis, by comparison, manifests as
renal pelvic dilation that extends into all the
calyces.
ab
cd
ef
43 Renal andBladder Ultrasonography fortheIntensivist
487
Fig. 43.3 (a) Mild hydronephrosis, with splaying of the
renal pelvis (arrow), (b) Moderate hydronephrosis, which
extends into the calyces (arrows), and hydroureter (block
arrow), (c) Severe hydronephrosis, with thinning of the
renal cortex (arrow), (d) Simple renal cyst (arrow), which
may be mistaken for hydronephrosis, (e) Color-ow
Doppler can be used to differentiate the renal blood vessels (block arrow) from mild hydronephrosis (arrow), (f)
Pulsed-wave spectral Doppler of a transplanted kidney.
Angle-corrected pulsed-wave spectral Doppler can be
used to measure the peak systolic velocity in the main
renal artery, and can be used to calculate the resistive
index (RI) in the renal parenchymal arteries. Suwondo
DN and Baloescu C.Renal and Bladder Ultrasonography
for the Intensivist. In: Lanspa MJ and Levinson AT, edi-
tors. Echocardiography and Ultrasonography in the ICU:
A Comprehensive Text. Springer; in preparation, 2022
488
D. N. Suwondo and C. Baloescu
Renal Blood Flow
Renal duplex Doppler ultrasound is typically
used in the evaluation of renal transplants and in
cases where renal artery stenosis or renal vein
thrombosis is suspected. An elevated peak systolic velocity of >285 cm/s on angle-corrected
spectral Doppler in the main renal artery and a
delayed acceleration time of >0.1 s from enddiastole to peak-systole in the renal parenchymal
arteries suggest renal artery stenosis [2, 9, 20].
The resistive index (RI), calculated from the peak
systolic velocity (PSV) and end diastolic velocity
(EDV) as (PSV-EDV)/PSV, is normally
0.58±0.10 (Fig.43.3f) [20]. A clinically signicant elevated RI is typically >0.80. This may predict persistent AKI in critically ill patients [21],
but is nonspecic as to the cause of AKI [2, 8, 9]
and represents an area of evolving evidence.
Along with ow pattern assessment of the
hepatic and portal veins, Doppler of the renal vein
plays a role in the Venous Excess UltraSound
(VExUS) score that was developed as an attempt to
detect early congestion and avoid end-organ damage. (Details are discussed in Chap. 54) Intrarenal
venous Doppler demonstrates a steady monophasic
ow beneath the baseline in normal circumstances.
It is considered abnormal if discontinuous ow patterns are seen in systolic and diastolic phases, or in
the diastolic phase alone [22]. This topic is also an
emerging area of evolving evidence.
Summary Points
• Post-renal AKI can be readily diagnosed using
POCUS of the kidneys and bladder
• POCUS of the bladder can be used to more
accurately measure bladder volume and to
troubleshoot problems with urinary catheters
• POCUS of the kidneys can be used to identify
hydronephrosis, particularly moderate or
severe hydronephrosis
• Mild hydronephrosis involves mild dilation or
splaying of the renal pelvis
• Moderate hydronephrosis involves signicant
dilation of the renal pelvis and extends to the
calyces, producing a characteristic multi-
pronged claw-like appearance
• Severe hydronephrosis results in thinning of
the renal cortex
• The presence of bilateral ureteral jets on colorow Doppler of the bladder suggests ureteral
patency
• Spectral Doppler can be used to evaluate for
renal artery stenosis and venous congestion
Pro-Tip (Call-Out)
To calculate bladder volume, the maximal
length and width of the bladder lumen are measured in the transverse plane and the maximal
height of the bladder lumen is measured in the
sagittal plane, yielding three orthogonal
measurements.
Emerging Evidence (Call-Out)
Among ED patients with suspected renal colic,
the nding of moderate or severe hydronephrosis
on POCUS has high (>90%) specicity for the
presence of a renal stone on CT.
Questions
1. On point-of-care ultrasound of the right
kidney, you note a dilated anechoic structure at the renal pelvis which appears to
branch into three dilated rounded structures.
The thickness of the surrounding renal cortex appears similar to the contralateral side.
On color-ow Doppler, there is no ow
within the structure. How would you grade
this nding?
A. Normal nding.
B. Mild hydronephrosis.
C. Moderate hydronephrosis.
D. Severe hydronephrosis.
Answer: (C) Moderate hydronephrosis.
Mild hydronephrosis is primarily limited to
the renal pelvis. This patient has moderate
hydronephrosis, which extends into the calyceal system. Severe hydronephrosis involves
thinning of the renal cortex.
2. You suspect a complete obstruction of the
right ureter. Which of the following ndings,
if present, most suggests patency of the right
ureter?
43 Renal andBladder Ultrasonography fortheIntensivist
489
A. The presence of only mild right hydrone-
phrosis, rather than moderate or severe
hydronephrosis.
B. The presence of a ureteral jet originating
from the right ureterovesical junction on
color-ow Doppler of the bladder.
C. A resistive index of 0.60in the right renal
artery on pulsed-wave spectral Doppler.
D. A distended bladder with a bladder vol-
ume of 550cc.
Answer: (B) Ureteral jet. Recall that the
degree of hydronephrosis does not necessarily
correspond to the acuity or severity of obstruction and may appear falsely minor in hypovolemic patients until adequate uid
resuscitation.
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Gastric, Biliary, andHepatic
Ultrasound intheICU
MahaSalama andAmiraMohamed
44
Learning Objectives
1. Examine POCUS ndings consistent with
liver cirhossis
2. Review the key POCUS ndings associated
with acute cholycystitis
3. Understand the utility of point of care ultrasound in the identication of abdominal
pathology
4. Learn the techniques required in the assessment of stomach, liver, and gallbladder as
well as their associated pathologies using
point of care ultrasound
Indications andLimitations
Gastric and biliary pathologies in the ICU are
common problems and are ones that could be detrimental if missed. US diagnosis of GI dysfunction has been widely used for decades; however,
M. Salama (*)
Cardiothoracic ICU Lenox Hill Hospital NYC,
Emergency Medicine Jacobi Medical Center/North
Central Bronx, Bronx, NY, USA
e-mail: Msalama4@northwell.edu
A. Mohamed
Critical Care Medicine Fellowship Program, Albert
Einstein College of Medicine, Bronx, NY, USA
Division of Critical Care Medicine, Monteore
Medical Center, Bronx, NY, USA
e-mail: ammohamed@monteore.org
it is only recently that it is being utilized by the
intensivist. Free air, free uid, and even biliary
obstruction can be identied on an ultrasound
exam but guidelines regarding the interpretation
and diagnostic utility of these ndings are
lacking.
Patient positioning, surgical incisions, and
other factors may be barriers to obtaining complete studies; however, any information obtained
could be valuable, especially in an ICU.Just as
with other parts of the POCUS (point of care
ultrasound) exam, any images obtained should be
interpreted together with the patient’s overall
clinical picture, and in some cases conrmed
with additional imaging studies prior to making
clinical decisions.
Anatomy andTechnique
Stomach
The stomach is situated in the left upper quadrant
of the abdomen anterior to the spleen. It is divided
into three parts: the antrum, body, and the fundus.
It can be visualized with the patient in multiple
positions: supine, right lateral decubitus, sitting,
and semi sitting, with the antrum being the easiest to visualize in most patients. In the critically
ill patient, only the supine position is usually feasible and therefore we will focus on that position
in this section.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2025
M. J. Lanspa, A. T. Levinson (eds.), Echocardiography and Ultrasonography in the ICU,
Respiratory Medicine, https://doi.org/10.1007/978-3-031-80038-2_44
491
492
M. Salama and A. Mohamed
A low frequency probe is used and placed in
the epigastric area in a longitudinal plane with
the probe marker towards the patient’s right side.
You may be able to see the liver, pancreas, and
antrum in this view (Fig.44.1). Other landmarks
that may be seen include the IVC (Inferior Vena
Cava), the aorta, the superior mesenteric vein,
and the superior mesenteric artery.
The gastric body and fundus are harder to
examine due to their deep location and presence
of air which may obstruct ultrasound waves. The
low frequency probe can be placed in the
subcostal margin or in the left mid-axillary line in
a longitudinal plane to see the gastric body and
fundus, respectively.
A high frequency probe can also be placed in
the epigastric region to assess the ve layers of
the stomach wall which are best seen in the
antrum, especially in thinner patients.
Liver
The liver is divided into the left lobe, the right
lobe, and the caudate lobe. The left and right
lobes are separated by the main lobar ssure
which connects the gallbladder fossa and the
IVC, while the caudate lobe is posteriorly located
between the IVC and the ssure of the ligamentum venosum.
The best location to obtain ultrasound images
of the liver is the right subcostal approach with
the patient in a supine position. If the patient is
awake, asking them to take a deep breath which
will displace the liver downwards, enhancing the
view.
Holding the low frequency probe in a longitudinal plane with the probe marker towards the
patient’s right side left of the midline and moving along the right subcostal margin laterally,
the left lobe of the liver is seen at the same
plane as the aorta followed by the caudate lobe,
then the right lobe and the inferior vena cava in
the same plane (Fig.44.2). Moving further laterally, the gallbladder fossa is seen posterior to
the right lobe, and the kidney inferiorly and
laterally.
The liver is normally homogenous and is
divided into eight segments, each with its own
blood supply, lymphatics, and biliary drainage.
The portal vein branch is centralized and surrounded by the hepatic veins in each segment.
The most common measurement of the liver is in
the midclavicular line and ranges between 12 and
16cm.
Medially at the porta hepatis, the portal vein
can be measured at about 10–15mm and, using
color doppler, the ow is seen with a velocity of
16–40cm/s. The hepatic venous system will be
covered elsewhere.
Fig. 44.1 The left lobe of the liver is seen with the antrum laterally. Stomach contents are seen in the antrum
44 Gastric, Biliary, andHepatic Ultrasound intheICU
Fig. 44.2 A normal homogenous looking liver seen from the subcostal view
493
Fig. 44.3 A normal appearing gall bladder and common bile duct with no obvious stones
Biliary System
normally 1–3 mm. It is recommended that the
patient be fasting for around 6h prior to imaging,
The gallbladder is situated in the gallbladder
fossa of the posterior right hepatic lobe lateral to
the second part of the duodenum and anterior to
the kidney. It is divided into four parts: fundus,
body, infundibulum, and neck. Using a low frequency probe, the biliary system can be visualized with the patient lying supine and the probe
placed in the longitudinal plane in the right subcostal margin moving laterally until the gallbladder is seen.
Normally, the gallbladder will contain bile
which appears anechoic and clear with no echoes.
A normal gallbladder measured longitudinally is
8–12cm, while the gallbladder wall thickness is
otherwise the gallbladder wall may appear thickened due to contraction. However, this is often
not feasible when assessing a patient in the ICU.
Landmarks that help with the identication of
the gallbladder include the portal vein, common
bile duct (CBD), and the hepatic artery or the
portal triad which is also known as the “Mickey
Mouse sign”. Using color doppler to differentiate
between the ow types, the hepatic artery and
portal vein can be easily identied, while the
CBD will not have any ow (Fig.44.3). The main
lobar ssure can be traced from the neck of the
gallbladder to the portal triad which also makes it
a useful landmark.