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Functional segmental liver anatomy by couinaud:
  1. Segment i              : caudate lobe
  2. Segment ii             : left lateral superior
  3. Segment iii            : left lateral inferior
  4. Segment iv            : quadrate lobe
                                     left medial superior
                                     left medial inferior
  5. Segment v             : right anteroinferior
  6. Segment vi            : right posteroinferior
  7. Segment vii           : right posterosuperior
  8. Segment viii          : right anterosuperior
  1. Simple hepatic cysts
    1. These are developmental with their incidence increasing with age.
    2. They may occur in younger patients with polycystic liver disease, ADPKD and (25-33%) Von Hippel Lindao disease (usually >10).Q
    3. USG is investigation of choice.Q
    4. It is usually single an echoic lesion with thin well–defined wall, with out septae or debris in it with posterior acoustic enhancement.Q
  • Hydatid cyst
  1. Radiographic and related imaging studies are important in detecting and evaluating echinococcal cysts. Plain films will define pulmonary cysts of e. Granulosus — usually as rounded masses of uniform density — but may miss cysts in other organs unless there is cyst wall calcification (as occurs in the liver).
  2. MRI, CT, and ultrasound reveal well-defined cysts with thick or thin walls.
  3. The most pathognomonic finding, if demonstrable, is that of daughter cysts within the larger cyst.
  1. Cavernous hemangiomas of Liver
    1. These are the most common benign tumors of the liver, occurring in all age groups but are more common in adults, particularly women.
    2. On USG these are typically small, less than 3 cm sized, well defined, and homogenous and hyperechoic lesions. Mixed echogenicity can, however, be a feature of atypical liver hemangioma.
    3. Hemangiomas are characterized by very slow blood flow that won't routinely be detected by either color or duplex doppler. There are usually incidental findings observed on routinely performed abdominal sonograms and confirmation is costly and unnecessary. However, atypical pattern of hemangioma needs an additional imaging technique to confirm the suspicion of hemangioma.
    4. If the lesion is greater than 2.5 cm in diameter, a TC-99m RBC study with SPECT is recommended.Q
    5. If the lesion is less than 2.5 cm in diameter, MRI is recommended.Q
    6. Dynamic triple-phase contrast enhanced CT scan with delayed sections, although less specific than both hepatic scintigraphy and MRI, can reliably diagnose liver hemangioma and is presently the investigation of choice. CECT characteristically shows delayed enhancement with ‘filling in’ of the hemangiomas centripetally and nodular densities of dilated vascular channels in the vicinity.Q

Almost all hepatic cysts and hemangiomas can be differentiated from malignant liver disease by the use of heavily T2-weighted (>180 msec) images.

  1. Focal nodular hyperplasia
    1. QFNH is the only liver tumor, which consistently contains functioning RE cells and so shows uptake of labeled colloids.
    2. It characteristically shows prolonged retention of IDA on delayed images.
    3. On CT and MRI delayed enhancement of the Qcentral scar is a characteristic which result from the presence of vascularized collagenous tissue, in contrast with the central stellate scar seen in fibrolamellar hepatic carcinoma.
    4. Hemorrhage or presence of capsule is pointer towards hepatic adenoma.
  2. Hepatocellular carcinoma
    1. Vascular invasion is atypical feature of HCC but tends to occur in larger lesions, which can cause portal vein invasion and thrombosis.Q
    2. Doppler study may distinguish tumor from thrombus as presence of arterial signals within the material occluding a portal vein indicates the presence of tumor. However the most sensitive approach for this study is CT in HCTAP phase and biphasic examination.
    3. The CT features of portal venous invasion by HCC include arterioportal fistula, periportal streaks of high attenuation, dilatation of main portal vein and its branches and the ‘straight line sign’ i.e. complete nonenhancement of the affected lobe (seen in HAP phase). Invasion may also be caused by secondaries in liver also.
  3. Liver Metastasis
    1. QLiver is the most common metastatic site after regional lymph nodes.
    2. QMetastases to liver are most common malignant liver lesions.
    3. Organ of origin: QColon (42%), stomach (23%), pancreas (21%), breast (14%), lung(13%).
    4. CT angiography is most sensitive imaging modality.
    5. QExclusion criteria for metastasectomy:
      1. Advanced stage of primary tumor
      2. > 4 metastases
      3. Extra hepatic disease
      4. < 30% normal liver tissue/function available after resection.

Focal hepatic lesions with T1 components that are isointense to mildly hyperintense to the surrounding liver are almost always hepatocellular in origin.

Gallbladder and Billiary Tree
  1. Gallbladder  is supplied by cystic artery, which is usually a branch of right hepatic artery, but may arise from main hepatic artery or left hepatic artery or gastroduodenal artery.
  2. Its function is to store and concentrate bile; capacity is 50 ml and can concentrate 10 times.
  1. Acute cholecystitis
    1. Only about 20% of gallstones contain sufficient calcium to be visible on plain radiographs and in normal state also it is very uncommon to identify a normal sized GB on plain radiographs as it is not surrounded by fat and in acute cholecystitis also it may be completely normal or show only borderline dilatation of small or large bowel.
    2. QUltrasound is widely used for diagnosing acute cholecystitis with features including thickened wall, associated gallstone, pericholecystic collection and distended GB. Contrast examinations like OCG have now been superseded by scintigraphy (HIDA and P-1P-1DA).

QAdenomyosis of GB typically produces COMET-TAIL artefacts on USG

  1. Primary sclerosing cholangitis
    1. It is a disease of unknown etiology characterized by a fibrosing inflammatory process affecting the intrahepatic and/or extrahepatic ducts and causing progressive cholestasis.
    2. Currently its diagnosis is based on radiological findings.
    3. Ultrasound examination is often normal or inconclusive.
    4. CT may show focal areas of mild duct dilatation peripherally.
    5. Scintigraphy (HIDA) may show multiple focal areas of increased uptake corresponding to dilated ducts.
    6. Direct cholangiography is the gold standard investigation to diagnose it and ‘pruned tree’ appearance is characteristic finding on cholangiography. However, similar picture is seen in AIDS related cholangiopathy. Q
    7. AIDS related cholangiopathy is characterized by cholangitis (irregular thickened was of biliary radicals), papillary stenosis and multifocal extrahepatic biliary apparatus strictures with dilatation of CBD in its entire course. Cholangiography provides the most reliable information characterized by multifocal strictures of intra and extrahepatic ducts, which, however, mimics the diffuse form of cholangiocarcinoma and is not absolutely diagnostic.
    8. QERCP is the preferred approach because of greater likelihood of success using this method in the absence of intrahepatic duct dilatation.
  2. Stricture in bile duct:
    1. Trauma (post surgery), pyogenic or parasitic cholangitis, and sclerosing cholangitis in association with inflammatory bowel disease are the most common causes of biliary strictures.
    2. QPost surgery (cholecystectomy) is the most common cause.
    3. Initial tests of choice can be USG and MRCP.
    4. QERCP is gold standard investigation
    5. Acute cholangitis is typically found in patients with obstruction or stone disease. Gram-negative organisms, Q (E. coli is most common) are often responsible.
    6. The disease can become quite severe and life threatening, requiring immediate relief of the obstruction as well as antibiotic therapy.
  3. EHBA
    1. Phenobarbital augmented cholescintingraphy is 90–97% sensitive, 60–94% specific and 75–90% accurate for diagnosis of EHBA. It reveals no visualization of bowel on delayed images at 6 and 24 hrs.
    2. It is impossible to differentiate it from neonatal hepatitis in absence of small bowel activity and requires liver biopsy.
    3. Liver biopsy has 60–97% accuracy.
    4. QPercutaneous / endoscopic / intra-operative cholangiography may be extremely helpful.
  4. Caroli’s Disease
    1. It si type V choedochal cyst, in which there is communicating cavernous ectasia of intrahepatic biliary ducts.

Ultrasound in Caroli's disease (type v choledochal cyst characterized by segmental nonobstructive dilatation or ectasia of IHBRs) shows multiple low reflective cystic areas with a central dot of high reflection activity representing the portal vein branch surrounded by an ectatic bile duct.

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