Portal Gas
This is a situation where ease of diagnosis and effi- ciency of therapeutic management meet. Portal gas generally requires prompt surgery [2, 3]. In a critical scene, portal gas immediately evokes mesenteric infarction. Ultrasound may give a chance for the patient to benefit from an earlier diagnosis. Portal gas is traditionally considered a pejorative sign [4], but this feeling is based on radi- ographic findings.Yet ultrasound is more sensitive than radiographs [2]. In addition, we have seen surgical success even when ultrasonic portal gas was present.
Portal gas yields numerous punctiform hypere- choic images without acoustic shadow within the liver parenchyma and usually peripheral (Fig. 7.2).
In this case, we speak of static portal gas. In some cases, one can observe a flux of gas particles at the portal vein (Fig. 7.3), a sign we called dynamic por- tal gas. In these cases, when such particles are seen coming from the superior mesenteric vein and not is rarely a target for emergency therapeutic deci-
sions in the ICU.
Mechanical ventilation, which lowers the diaphragm, can make its exploration easier. When the liver is located high, intercostal scans will be taken, provided the probe is small enough. Liver analysis is often not exhaustive in such conditions, but we will see that this limitation is relative in the critically ill patient.
Hepatomegaly
Although some operators can evaluate the weight of each lobe, the subjective feeling that the liver is enlarged is sufficient for others [1]. In the critically ill patient, it is more important to recognize the cause of this enlargement than the exact dimen- sions or weight. Usual causes in the ICU are acute right heart failure and cirrhosis.
The cardiac liver has a homogeneous structure, with dilatation of hepatic veins and vena cava infe- rior (Fig. 7.1). This finding will be accessory: the dilatation of the right heart and the lung disorder will then be recognized at the same time.
A cirrhotic liver will give numerous signs we will not detail here: a coarse pattern, a nodular pat- tern, atrophy or hypertrophy of one lobe with resulting global dysmorphia, absence of supple- ness of the parenchyma, signs of portal hyper- tension (dilatation of the portal vein, ascites, reopening of the umbilical vein, splenomegaly and others). See Fig. 6.7, p 35, for an illustration of esophageal varices.
As regards tumoral or infectious (abscesses) enlargements, the cause will immediately appear on the screen.
Fig. 7.1. Liver in right heart failure. Dilatation of the three hepatic veins, which open into an inferior vena cava (V) also dilated. Note that this scan does not reflect the site where its caliper should be measured (see Chap. 13, p 82). Epigastric subtransverse scan
from the splenic vein, they originate logically from the GI tract.
Volvulus or strangulation, ulcerous colitis, and intra-abdominal abscesses are other causes de- scribed in the adult [4].
Hepatic Abscess
Ultrasound is a quick and user-friendly method of diagnosis, since it spares the highly unpleasant pain caused by liver shaking. Pain is often absent in
a encephalopathic patient in shock, hence the interest of a systematic ultrasound examination in any critically ill new arrival.
Abscess yields an image contrasting with the reg- ular hepatic echostructure. It is generally hypo- echoic, heterogeneous, and roughly round (Fig. 7.4).
A very characteristic sign is sometimes observed:
within the mass, an internal movement is visible, in rhythm with respiration. This is in fact the inertia of the pus caused by the movement (Fig.7.5),the equiv- alent of the plankton sign discussed in Chap. 5. In our observations, it proves the fluid nature of the 42 Chapter 7 Liver
Fig. 7.2. Static portal gas. Numerous hyperechoic punc- tiform opacities, without acoustic shadow, within the liver of a patient with mesenteric infarction. Note that this patient survived, in spite of the classically poor prognosis of portal gas
Fig. 7.3. Dynamic portal gas. A visible flow with hyper- echoic particles (large arrows) is observable in the portal vein. Static portal gas can be seen (small arrows). Obli- que scan of the right hypochondrium, in the axis of the portal vein (large arrows), in a patient with septic shock
Fig. 7.4. Hepatic abscess (Klebsiella). Hypoechoic hete- rogeneous mass within the hepatic parenchyma
Fig. 7.5. Hepatic abscess (Streptococcus milleri). Huge round hypoechoic mass. In real-time, this mass had a characteristic internal motion, which indicated a fluid nature. Percutaneous ultrasound-guided drainage (see Fig. 26.1, p 173) has withdrawn 1,150 cc of frank pus
collection (regardless of the presence or absence of posterior enhancement), and above all it indicates pathological fluid (pus,blood).Highly echoic images are sometimes seen, indicating microbial gas. Pleu- ral effusion (generally radiopaque) is possible.
Amebic abscess yields a hypoechoic, well-limit- ed collection.
Hydatidosis should be evoked before any punc- ture of fluid hepatic mass. This does not cause a problem when the cyst is well defined and anech- oic, since there is no emergency, but it may in the suppurative forms, when the cyst becomes echoic and heterogeneous (Fig. 7.6).
Diffuse Infectious Disorders
Tuberculous hepatic miliary can be missed by ultrasound (Fig. 7.7). In cases where there is strong clinical suspicion, a prompt liver biopsy should provide bacteriological confirmation.
Cholestasis
Ultrasound is a quick and simple way to check for the normal condition of the bile ducts. However, cholestasis occurring in a ventilated patient is very frequent. In our observations, the cause of cholestasis is always medical: sepsis or impairment of venous return. We are still awaiting a surgical cause of cholestasis in a patient initially ventilated for another reason.
This said, in case of an obstacle, ultrasound will detect bile duct dilatation: the intrahepatic duct anterior to the portal bifurcation (Fig. 7.8) or the main duct anterior to the portal vein (Fig. 7.9). The normal caliper of the main bile duct is said to be 7 mm (up to 12 mm in the case of an old cholecystectomy), but some authors have fixed the upper limit at 4 mm [5]. When the com- mon bile duct is dilated, it acquires a tortuous route and cannot be visualized in a single view.
The sensitivity of ultrasound is poor for detection of common bile duct calculi, which rarely produce posterior shadows, even if massive [6].
Fig. 7.6. Hydatid cyst of the liver (arrowheads). The het- erogeneous pattern indicates complication, here sup- puration, which was confirmed at the laparotomy of this patient in septic shock. Longitudinal scan of the liver. L, liver
Fig. 7.7. Diffuse tuberculous miliary. In this longitudinal scan of the liver and the kidney (K), it is hard to detect frank anomalies. Real-time showed that the liver paren- chyma pattern was homogeneously granular, but one can consider it is a subtle sign
Fig. 7.8. Dilatation of intrahepatic bile ducts. Vessels (X) are visible anterior to portal bifurcation (V), producing a double channel pattern
Hepatic Vein Disorders
Ultrasound is an excellent noninvasive method for examining hepatic vein disorders [7]. In the Budd- Chiari syndrome with hepatic veins thrombosis, these veins are filled with echoic material, are fili- form, or are not visible if they have the same echogenicity as the liver. Other signs exist but their description would deviate too far from our initial objectives. Faithful to a maximal use of two- dimensional ultrasound, and regarding the rarity of this disorder (at least in our institutions), we think that two-dimensional ultrasound should be done first. Visualization of anechoic hepatic veins, which can be compressed with the pressure of the probe, indicate patency of these veins. Obviously, the operator should search for more frequent diseases to explain the symptoms bringing suspi- cion of Budd-Chiari syndrome. If the examination remains noncontributory, then and only then should a Doppler study be indicated.
In critically ill patients, mobile gas is sometimes observed in the median and left hepatic veins, which are the non-declive veins (Fig. 7.10). The most logical explanation is that air accidentally coming from perfusions (in the arms, for instance) are trapped in these veins. A tricuspid regurgita- tion, very frequent in the mechanically ventilated patient, may be the cause.
Hepatic Tumors
Recognition of metastases may give a theoretical element of prognosis in the acute phase. They are usually known, but they can be discovered by ultrasound when no anamnesis is available. The pattern is usually characteristic: multiple dissemi- nated images with anarchic distribution, isoechoic, or hyperechoic with a fine hypoechoic stripe, or again hypoechoic images (Fig. 7.11). As regards other tumors, we will be brief, since they do not need particular treatment or reflexion during the stay in the ICU. A round, regular, anechoic image is generally a biliary cyst, sometimes also an uncomplicated hydatid cyst. An echoic heteroge- 44 Chapter 7 Liver
Fig. 7.9. Anterior to the portal vein (V), the common bile duct (arrow) is dilated with a 9-mm caliper. Oblique scan of epigastric area. G, gallbladder
Fig. 7.10. Hyperechoic structure, highly dynamic in real- time, visible at the median hepatic vein (arrows). Trap- ped air in the hepatic venous system. Subtransverse epi- gastric scan acquired with an Ausonics 2000 device
Fig. 7.11. Hypoechoic masses, disseminated in the liver with a multicentric pattern. Hepatic metastases. Perito- neal effusion surrounding the liver (asterisk) secondary to peritoneal metastases
sion in favorable cases (see Fig. 24.1, p 165).
Aerobilia can be pathological, in ileus by impact- ed gallstone, or physiological, after biliary surgery.
Numerous air opacities are visible along the biliary vessels, which converge to the hilum. Thus, the images are more central than in portal gas.
Interventional Ultrasound
Percutaneous Aspiration or Drainage of Liver Abscess
We were able to successfully aspirate hepatic abscesses with the material described in Chap. 26.
Deep locations or locations near the dome can cause technical problems.
Percutaneous or Transjugular Liver Biopsy
The presence of permanent ultrasound assistance means that emergency liver biopsies can be car- ried out. Three indications can be imagined in the ICU:
∑ Documenting diffuse tuberculosis before treat- ment
∑ Proving the malignant nature of liver images, if this finding can modify immediate treatment
∑ Investigating fulminant hepatitis.
In this last case, hemostasis disorders usually require a transjugular approach, which usually
sional image of an area. It accurately steers the material through the inferior vena cava, then the hepatic veins. This visual guidance should decrease the number of incidents that occur with radio- scopic guidance.
References
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331–334
3. Traverso LW (1981) Is hepatic portal venous gas an indication for exploratory laparotomy? Arch Surg 116:936–938
4. Liebman PR, Patten MT, Manny J (1978) Hepatic por- tal veinous gas in adults. Ann Surg 187:281–287 5. Berk RN, Cooperberg PL, Gold RP, Rohrmann CA Jr,
Ferrucci JT Jr (1982) Radiography of the bile ducts. A symposium on the use of new modalities for diagno- sis and treatment. Radiology 145:1–9
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