Ultrasound
Ultrasonographic Localization of the Gallbladder 1 Peter W. Callen, M.D., and Roy A. Filly, M.D.2
A linear echo connecting the gallbladder to the right or main portal vein was seen on ultrasonograms in a high percentage of patients (68 %). This echo represents a portion of the main lobar fissure of the liver and appears to be a reliable anatomical indicator of the location of the gallbladder. The anatomical features responsible for this echo are discussed. (Gallbladder, anatomical detail, 7 [62] .920) • (Gallbladder, normal variant, 7[62] .130) • (Gallbladder, ultrasonography, 7[62J .1298). Gallbladder, ultrasound studies. (Liver, biliary system, ultrasonography,
INDEX TERMS:
7[6] .1298) Radiology 133:687-691 , December 1979
LTRASONOGRAPHY has become valuable for demonstratingthe diseasedgallbladder. Numerousreports validate the diagnostic accuracy and spectrum of appearance of cholelithiasis as seen on ultrasound (1-3). However, despite the obvious success of the technique , some basic problems exist. It is occasionally impossible to demonstrate a bile-filled gallbladder in fasting patients. This observation carries a strong suspicion of gallbladder pathology (4). " Nonvisualization" as an indicator of pathology implies that ultrasonograms have been obtained at sufficiently narrow intervals to ensure visualization of a small, normal gallbladder. Certainty that the appropriate ultrasonic sections have been obtained requires identification of structures which have specific and reliable an-
U
atomical relationships with the gallbladder. Unlike the pancreas, which has multiple highly specific arterial, bil· iary, venous, and gastroenteric relationships (5), the gallbladder possesses few such indicators. One reliable anatomical indicator of the position of the gallbladder, its neck , usually comes in contact with the main segment of the right portal vein or the main portal vein near the origin of the left portal vein (Fig. 1). Additionally, the gallbladder usually resides in a fossa on the medial aspect of the liver (Fig. 2). However, this fossa may be so shallow that it cannot be clearly identified, or it may be absent. These reference points are often insufficient to indicate which location deserves an intensified search.
Fig. 1. a. Parasagittal ultrasonogram of the gallbladder (GB). Note the relat ionship of the neck of the gallbladder to the right portal vein (RPV). b. Parasagittal scan to the right of Figure 1, a. A high-amplitude linear echo joins the right portal vein to the gallbladder (GB). 1 From the Department of Radiology, School of Medicine , University of California , San Francisco , CA. Received Feb. 21, 1979 and accepted May 30 . ;2 Picker Scholar, James Picker Foundation. sb
687
688
PETER W. CALLEN AND ROY
A.
December 1979
FILLY
performed for possible gallbladder pathology, since visualization of the gallbladder is a routine requirement on all upper abdominal ultrasonograms performed in our laboratory. No patients were excluded because of bowel gas or poor physique . All studies were performed on commercially available gray-scale units. Focused transducers of 2.25 or 3.5 mHz were employed. No attempt was made to vary the focal zone of the transducer to optimize visualization of the porta hepatis. The parasagittal ultrasonograms were routinely obtained in the supine position at closely-spaced intervals (usually 1 em), beginning at the right aspect of the patient's abdomen and proceeding medially. Scans in the decubitus position were frequently employed to assist in visualization of specific structures. RESULTS Fig. 2. Subcostal oblique ultrasonogram of a patient with a deep gallbladder fossa. Note how the gallb~ (GB) invaginates the hepatic parenchyma. The duodenum and hepatic flexure cause only slight impressions on the liver . RPV = right portal vein , K = right kidney.
We have observed a linear echo within the liver, seen best on parasagittal planes , which appears to be a useful and reliable indicator of the location of the gallbladder (Fig. 1, band 3). The significance, frequency of identification, and probable origin of this linear echo form the basis of this report.
Of 100 patients, 68 demonstrated a linear echo extending from the gallbladder to the right or main portal vein (Fig. 3). The cephalocaudad length of the linear echo varied on any single parasagittal section. In each instance the reflection was of high amplitude. The cephalic portion of the linear echo was invariably in contact with the right portal vein, main portal vein, or both. Similarly, in all instances the caudal aspect of the linear echo " pointed" directly to or touched the gallbladder. When the gallbladder was not identified on the initial plane, more medial planes identified the gallbladder in the precise location indicated by the linear echo.
MATERIALS AND METHODS
The abdominal ultrasonograms of 100 patients were selected randomly and reviewed retrospectively with attention to the porta hepatis region, right portal vein, and gallbladder. Ultrasonograms were not limited to those
Fig. 3. Parasagiltal ultrasonogram of the right upper abdomen, demonstrating the linear echo (curved arrow) extending from the gallbladder (GB) to the right portal vein (RPV).
DISCUSSION
Although the gallbladder has few specific anatomical indicators of its precise location, the linear echo appears to be a highly reliable indicator of its position. Even when the gallbladder is filled with bile, this linear echo may precisely identify a gallbladder of unusual appearance (Fig. 4, b) or identify pathological conditions on ultrasonograms demonstrating only the gallbladder fundus (Figure 4, a). Additionally, the structure is visible in nearly 70 % of routine scans. This is of considerable significance, since an anatomical indicator, no matter how specific, decreases in value if it is difficult to demonstrate. An example of this is the gastroduodenal artery which is a specific indicator of the position of the pancreatic head, but is a difficult structure to identify routinely (5). The origin of the linear echo has not been absolutely identified, but a number of features lead us and others to believe that it is a portion of the main lobar fissure of the liver (6, 7) which lies between the gallbladder and the right portal vein. The gallbladder lies in the posterior and caudal aspect of the fissure (8). The right portal vein is under the medial segment of the left hepatic lobe before bifurcating and entering the parenchyma of the right hepatic lobe (8). Thus the right portal vein is partially located in the main lobar fissure . Computed tomography (Fig. 5) and ultrasonography (Fig. 6) frequently show a structure which ap-
Vol. 133
UL TRASONOGRAPHIC LOCALIZATION OF THE GALLBLADDER
689
Ultrasound
4a,b
Fig. 4. a. A small f!uid-containing structure (GB) is seen adjacent to the liver in the right upper abdomen, which could be secondary to fluid-filled bowel or the gallbladder. This structure can be ident ified as the gallbladder because of its relationship to the linear echo (curved arrow) extending from it to the right portal vein (RPV) . A stone with posterior shadowing further confirms this structure as the gallbladder. b. Parasagittal ultrasonogram in a patient with a right-upper-quadrant mass and nonvisualization of the gallbladder during oral cholecystography. Although the gallbladder could not be specifically identified during ultrasOnography,a large mass (M) with a necrotic, flu id-filled center was seen emanating from the caudal aspect of the linear echo (curved arrow) and extending anteriorly to involve the liver. As a result of this anatomical relationship, it was suggested that this mass either or iginated from or involved the gallbladder. At surgery , an adenocarcinoma of the gallbladder invading the liver was found . (Courtesy of David Sofia, M.D.)
pears to represent the posterior aspect of the main lobar fissure. Fibro-fatty tissue from the porta hepatis tends to work into this space in patients with large amounts of fat (Fig. 5). Fibro-fatty tissues result in high-amplitude reflections similar to those observed in this study. Finally , this cleft can be seen to " line up" with the ligamentum venosum, another fissure emanat ing from the porta hepatis, which divides the caudate lobe from the lateral segment of the left lobe (Fig. 7). Each of these features tends to indicate that a portion of the main lobar fissure erna-
nating from the porta hepatis is a visible anatomical cleft which may be seen on both ultrasonograms and computed tomograms. Whether our conclusion regarding the origin of this specularly-reflecting interface is correct or not, its value as a reliable indicator of the gallbladder location will not be affected . However, our data strongly support the contention that a cleft in the posteromedial aspect of the main lobar fissure of the liver is the origin of the specular reflection commonly identified coursing from the right portal
Fig. 5. a. CT scan through the midabdomen, demonstrating fat from the porta hepatis extending into the posterior aspect of the main interlobar fissure (arrow) which divides the right (RHL) from the left hepatic lobe (LHL) . b. CT scan at a slightly lower level than Figure 5, a, demonstrating the gallbladder (GB) in its normal position in the posterior and caudal aspect of the main lobar fissure. RHL right hepatic lobe , LHL left hepatic lobe .
=
=
690
PETER
W.
CALLEN AND ROY
A.
December 1979
FILLY
6a,b
LHL
LHL GB
RHL
Fig. 6.
a.
On this limited transverse ultrasonogram, the main lobar fissure (arrow) is seen as a linear echo dividing the right
(RHL) from the left hepatic lobe (LHL).
b. At a lower level than Figure 6, a, the gallbladder (GB) is seen in its normal position in the cleft of the posterior and caudal aspect of the main lobar fissure. 7a,b
Fig. 7. a. Oblique longitudinal ultrasonogram. The linear echo represents a portion of the main lobar fissure (curved arrow) which extends from the gallbladder (GB) to the portal vein (PV) . The echo appears to line up with the fissure of the ligamentum venosum (FL V). CL caudate lobe. ivc = inferior vena cava. b. Oblique longitudinal scan slightly more medial than Figure 7, a; the gallbladder (GB) approaches the portal vein (PV). The fissure for the ligamentum venosum (FLV) extends superiorly from the portal vein and divides the caudate lobe (CL) from the left hepatic lobe (LHL). ivc = inferior vena cava.
=
vein to the gallbladder on parasagittal ultrasonograms of the right upper quadrant.
Department of Radiology M-380 School of Medicine University of California San Francisco, CA 94143
REFERENCES 1. Bartrum RJ Jr, Crow HC, Foote SR: Ultrasonicand radiographic cholecystography . N Engl J Med 296:538-541, 10 Mar 1977 2. Leopold GR, Amberg J, Gosink BB, et al: Gray scale ultrasonic cholecystography : a comparison with conventional radiographic techniques. Radiology 121:445-448, Nov 1976 3. Lawson TL: Gray scale cholecystosonography: diagnostic criteria and accuracy . Radiology 122:247-251 , Jan 1977 4. Crade M, Taylor KJW, Rosenfield AT, et al: Surgical and
Vol. 133
ULTRASONOGRAPHIC LOCALIZATION OF THE GALLBLADDER
pathologic correlation of cholecystosonography and cholecystography. Am J RoentgenoI131:227-229, Aug 1978 5. Sample WF: Techniques for improved delineation of normal anatomy of the upper abdomen and high retroperitoneum with grayscale ultrasound. Radiology 124: 197-202, Jul 1977 6. Marks WM, Filly RA, Callen PW: Ultrasonic anatomy of the liver:
691
Ultrasound
a review with new applications. J Clin Ultrasound 7:137-146, Apr 1979 7. Parulekar SG: Ligaments and fissures of the liver: sonographic anatomy. Radiology 130:409-411, Feb 1979 8. Goss CM, ed: Gray's Anatomy of the HumanBody. Philadelphia, Lea & Febiger, 1966, p 1250
Ultrasonographic Localization of the Gallbladder 1 Peter W. Callen, M.D., and Roy A. Filly, M.D.2
A linear echo connecting the gallbladder to the right or main portal vein was seen on ultrasonograms in a high percentage of patients (68 %). This echo represents a portion of the main lobar fissure of the liver and appears to be a reliable anatomical indicator of the location of the gallbladder. The anatomical features responsible for this echo are discussed. (Gallbladder, anatomical detail, 7 [62] .920) • (Gallbladder, normal variant, 7[62] .130) • (Gallbladder, ultrasonography, 7[62J .1298). Gallbladder, ultrasound studies. (Liver, biliary system, ultrasonography,
INDEX TERMS:
7[6] .1298) Radiology 133:687-691 , December 1979
LTRASONOGRAPHY has become valuable for demonstratingthe diseasedgallbladder. Numerousreports validate the diagnostic accuracy and spectrum of appearance of cholelithiasis as seen on ultrasound (1-3). However, despite the obvious success of the technique , some basic problems exist. It is occasionally impossible to demonstrate a bile-filled gallbladder in fasting patients. This observation carries a strong suspicion of gallbladder pathology (4). " Nonvisualization" as an indicator of pathology implies that ultrasonograms have been obtained at sufficiently narrow intervals to ensure visualization of a small, normal gallbladder. Certainty that the appropriate ultrasonic sections have been obtained requires identification of structures which have specific and reliable an-
U
atomical relationships with the gallbladder. Unlike the pancreas, which has multiple highly specific arterial, bil· iary, venous, and gastroenteric relationships (5), the gallbladder possesses few such indicators. One reliable anatomical indicator of the position of the gallbladder, its neck , usually comes in contact with the main segment of the right portal vein or the main portal vein near the origin of the left portal vein (Fig. 1). Additionally, the gallbladder usually resides in a fossa on the medial aspect of the liver (Fig. 2). However, this fossa may be so shallow that it cannot be clearly identified, or it may be absent. These reference points are often insufficient to indicate which location deserves an intensified search.
Fig. 1. a. Parasagittal ultrasonogram of the gallbladder (GB). Note the relat ionship of the neck of the gallbladder to the right portal vein (RPV). b. Parasagittal scan to the right of Figure 1, a. A high-amplitude linear echo joins the right portal vein to the gallbladder (GB). 1 From the Department of Radiology, School of Medicine , University of California , San Francisco , CA. Received Feb. 21, 1979 and accepted May 30 . ;2 Picker Scholar, James Picker Foundation. sb
687
688
PETER W. CALLEN AND ROY
A.
December 1979
FILLY
performed for possible gallbladder pathology, since visualization of the gallbladder is a routine requirement on all upper abdominal ultrasonograms performed in our laboratory. No patients were excluded because of bowel gas or poor physique . All studies were performed on commercially available gray-scale units. Focused transducers of 2.25 or 3.5 mHz were employed. No attempt was made to vary the focal zone of the transducer to optimize visualization of the porta hepatis. The parasagittal ultrasonograms were routinely obtained in the supine position at closely-spaced intervals (usually 1 em), beginning at the right aspect of the patient's abdomen and proceeding medially. Scans in the decubitus position were frequently employed to assist in visualization of specific structures. RESULTS Fig. 2. Subcostal oblique ultrasonogram of a patient with a deep gallbladder fossa. Note how the gallb~ (GB) invaginates the hepatic parenchyma. The duodenum and hepatic flexure cause only slight impressions on the liver . RPV = right portal vein , K = right kidney.
We have observed a linear echo within the liver, seen best on parasagittal planes , which appears to be a useful and reliable indicator of the location of the gallbladder (Fig. 1, band 3). The significance, frequency of identification, and probable origin of this linear echo form the basis of this report.
Of 100 patients, 68 demonstrated a linear echo extending from the gallbladder to the right or main portal vein (Fig. 3). The cephalocaudad length of the linear echo varied on any single parasagittal section. In each instance the reflection was of high amplitude. The cephalic portion of the linear echo was invariably in contact with the right portal vein, main portal vein, or both. Similarly, in all instances the caudal aspect of the linear echo " pointed" directly to or touched the gallbladder. When the gallbladder was not identified on the initial plane, more medial planes identified the gallbladder in the precise location indicated by the linear echo.
MATERIALS AND METHODS
The abdominal ultrasonograms of 100 patients were selected randomly and reviewed retrospectively with attention to the porta hepatis region, right portal vein, and gallbladder. Ultrasonograms were not limited to those
Fig. 3. Parasagiltal ultrasonogram of the right upper abdomen, demonstrating the linear echo (curved arrow) extending from the gallbladder (GB) to the right portal vein (RPV).
DISCUSSION
Although the gallbladder has few specific anatomical indicators of its precise location, the linear echo appears to be a highly reliable indicator of its position. Even when the gallbladder is filled with bile, this linear echo may precisely identify a gallbladder of unusual appearance (Fig. 4, b) or identify pathological conditions on ultrasonograms demonstrating only the gallbladder fundus (Figure 4, a). Additionally, the structure is visible in nearly 70 % of routine scans. This is of considerable significance, since an anatomical indicator, no matter how specific, decreases in value if it is difficult to demonstrate. An example of this is the gastroduodenal artery which is a specific indicator of the position of the pancreatic head, but is a difficult structure to identify routinely (5). The origin of the linear echo has not been absolutely identified, but a number of features lead us and others to believe that it is a portion of the main lobar fissure of the liver (6, 7) which lies between the gallbladder and the right portal vein. The gallbladder lies in the posterior and caudal aspect of the fissure (8). The right portal vein is under the medial segment of the left hepatic lobe before bifurcating and entering the parenchyma of the right hepatic lobe (8). Thus the right portal vein is partially located in the main lobar fissure . Computed tomography (Fig. 5) and ultrasonography (Fig. 6) frequently show a structure which ap-
Vol. 133
UL TRASONOGRAPHIC LOCALIZATION OF THE GALLBLADDER
689
Ultrasound
4a,b
Fig. 4. a. A small f!uid-containing structure (GB) is seen adjacent to the liver in the right upper abdomen, which could be secondary to fluid-filled bowel or the gallbladder. This structure can be ident ified as the gallbladder because of its relationship to the linear echo (curved arrow) extending from it to the right portal vein (RPV) . A stone with posterior shadowing further confirms this structure as the gallbladder. b. Parasagittal ultrasonogram in a patient with a right-upper-quadrant mass and nonvisualization of the gallbladder during oral cholecystography. Although the gallbladder could not be specifically identified during ultrasOnography,a large mass (M) with a necrotic, flu id-filled center was seen emanating from the caudal aspect of the linear echo (curved arrow) and extending anteriorly to involve the liver. As a result of this anatomical relationship, it was suggested that this mass either or iginated from or involved the gallbladder. At surgery , an adenocarcinoma of the gallbladder invading the liver was found . (Courtesy of David Sofia, M.D.)
pears to represent the posterior aspect of the main lobar fissure. Fibro-fatty tissue from the porta hepatis tends to work into this space in patients with large amounts of fat (Fig. 5). Fibro-fatty tissues result in high-amplitude reflections similar to those observed in this study. Finally , this cleft can be seen to " line up" with the ligamentum venosum, another fissure emanat ing from the porta hepatis, which divides the caudate lobe from the lateral segment of the left lobe (Fig. 7). Each of these features tends to indicate that a portion of the main lobar fissure erna-
nating from the porta hepatis is a visible anatomical cleft which may be seen on both ultrasonograms and computed tomograms. Whether our conclusion regarding the origin of this specularly-reflecting interface is correct or not, its value as a reliable indicator of the gallbladder location will not be affected . However, our data strongly support the contention that a cleft in the posteromedial aspect of the main lobar fissure of the liver is the origin of the specular reflection commonly identified coursing from the right portal
Fig. 5. a. CT scan through the midabdomen, demonstrating fat from the porta hepatis extending into the posterior aspect of the main interlobar fissure (arrow) which divides the right (RHL) from the left hepatic lobe (LHL) . b. CT scan at a slightly lower level than Figure 5, a, demonstrating the gallbladder (GB) in its normal position in the posterior and caudal aspect of the main lobar fissure. RHL right hepatic lobe , LHL left hepatic lobe .
=
=
690
PETER
W.
CALLEN AND ROY
A.
December 1979
FILLY
6a,b
LHL
LHL GB
RHL
Fig. 6.
a.
On this limited transverse ultrasonogram, the main lobar fissure (arrow) is seen as a linear echo dividing the right
(RHL) from the left hepatic lobe (LHL).
b. At a lower level than Figure 6, a, the gallbladder (GB) is seen in its normal position in the cleft of the posterior and caudal aspect of the main lobar fissure. 7a,b
Fig. 7. a. Oblique longitudinal ultrasonogram. The linear echo represents a portion of the main lobar fissure (curved arrow) which extends from the gallbladder (GB) to the portal vein (PV) . The echo appears to line up with the fissure of the ligamentum venosum (FL V). CL caudate lobe. ivc = inferior vena cava. b. Oblique longitudinal scan slightly more medial than Figure 7, a; the gallbladder (GB) approaches the portal vein (PV). The fissure for the ligamentum venosum (FLV) extends superiorly from the portal vein and divides the caudate lobe (CL) from the left hepatic lobe (LHL). ivc = inferior vena cava.
=
vein to the gallbladder on parasagittal ultrasonograms of the right upper quadrant.
Department of Radiology M-380 School of Medicine University of California San Francisco, CA 94143
REFERENCES 1. Bartrum RJ Jr, Crow HC, Foote SR: Ultrasonicand radiographic cholecystography . N Engl J Med 296:538-541, 10 Mar 1977 2. Leopold GR, Amberg J, Gosink BB, et al: Gray scale ultrasonic cholecystography : a comparison with conventional radiographic techniques. Radiology 121:445-448, Nov 1976 3. Lawson TL: Gray scale cholecystosonography: diagnostic criteria and accuracy . Radiology 122:247-251 , Jan 1977 4. Crade M, Taylor KJW, Rosenfield AT, et al: Surgical and
Vol. 133
ULTRASONOGRAPHIC LOCALIZATION OF THE GALLBLADDER
pathologic correlation of cholecystosonography and cholecystography. Am J RoentgenoI131:227-229, Aug 1978 5. Sample WF: Techniques for improved delineation of normal anatomy of the upper abdomen and high retroperitoneum with grayscale ultrasound. Radiology 124: 197-202, Jul 1977 6. Marks WM, Filly RA, Callen PW: Ultrasonic anatomy of the liver:
691
Ultrasound
a review with new applications. J Clin Ultrasound 7:137-146, Apr 1979 7. Parulekar SG: Ligaments and fissures of the liver: sonographic anatomy. Radiology 130:409-411, Feb 1979 8. Goss CM, ed: Gray's Anatomy of the HumanBody. Philadelphia, Lea & Febiger, 1966, p 1250
