Postoperative Changes, Liver

Published on 18/07/2015 by admin

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 Consider iatrogenic infarction of hepatic mass or liver parenchyma

image Consider retained absorbable oxidized cellulose (Surgicel)
• Embolized, iodinated, poppyseed oil (Ethiodol, Lipiodol)

image May mimic calcified or hypervascular mass on plain radiography or CT, respectively
• Treated tumor often undergoes progressive volume loss and fibrosis

image May simulate focal confluent fibrosis, peripheral cholangiocarcinoma, or cirrhosis
• Consider prior resection of portions of liver

image May have similar appearance to congenital absence or hypoplasia of hepatic segments
• Iatrogenic arterioportal (AP) fistula

image Complication of percutaneous liver biopsy
image May simulate other vascular lesions, including tumor
• Small peripheral AP shunts are common, spontaneous findings in cirrhotic liver

TOP DIFFERENTIAL DIAGNOSES

• Pyogenic abscess
• Portal venous gas with bowel infarction
• Focal confluent fibrosis
• Cholangiocarcinoma (peripheral)
• Regenerative and dysplastic nodules
• Cirrhosis
• Hepatic angiomyolipoma
• Other causes of transient hepatic attenuation (THADs) and intensity (THIDs) differences
• Congenital absence of hepatic segments
image
(Left) Axial CECT shows several viable enhancing liver metastases image and 2 masses with gas and necrotic debris image that are the result of percutaneous radiofrequency ablation.

image
(Right) Axial CECT shows a collection of gas image but very little fluid in the cholecystectomy bed, mimicking an abscess. Note the surgical clips image. This is bioabsorbable oxidized cellulose (Surgicel), which was used as a hemostatic agent to control bleeding from the operative bed during cholecystectomy.
image
(Left) Axial CECT shows an absence of enhancement of the left lobe with a straight line of demarcation image and portal venous gas image, all due to hepatic arterial ligation during attempted resection of a peripheral cholangiocarcinoma.

image
(Right) Axial CECT shows a metallic coil image in the right hepatic artery, with a wedge-shaped collection image of gas and fluid “downstream.” Needle aspiration and drainage of this collection showed an infected hepatic infarction.

TERMINOLOGY

Definitions

• Iatrogenic changes to hepatic morphology that may cause or simulate pathologic conditions

IMAGING

Imaging Recommendations

• Best imaging tool

image Imaging test that shows morphology and hemodynamic characteristics of hepatic lesion
• Protocol advice

image Correlate with medical records and history of prior intervention

CT Findings

• Gas collection in hepatic or perihepatic lesion

image Abscess is primary concern, but also consider iatrogenic causes
image Iatrogenic infarction of hepatic mass or liver parenchyma

– Sudden death of hepatic (or other) tissue releases gas, ± coexisting infection

image Examples: Radiofrequency ablation, hepatic arterial chemoembolization, hepatic arterial occlusion (intentional or not)
– Gas released from sudden death of tissue

image Does not imply infection of tissue
image Clinical syndrome (fever, pain, leukocytosis) may mimic sepsis
image Retained absorbable oxidized cellulose (Surgicel)

– May be placed intraoperatively and left in place to control bleeding
– Appears as spherical, sponge-like collection of gas bubbles with little or no fluid component

image Tightly packed gas bubbles ± linear arrangement; no enhancing wall
image Fixed location and appearance on sequential exams
image Highly echogenic mass on US with posterior reverberation artifact
• Iatrogenic causes of portal venous gas

image Any procedure resulting in sudden death of hepatic parenchyma may release hepatic parenchymal ± portal venous gas

– Examples: Surgical ligation or transcatheter occlusion of hepatic artery (deliberate or unintentional)
– Might be used to devascularize hypervascular liver mass, benign (e.g., focal nodular hyperplasia or adenoma) or malignant
• Focal hepatic malignancy following chemoembolization

image May be accompanied by embolized, iodinated, poppyseed oil (Ethiodol, Lipiodol)
image → very high (metallic) density within treated lesion on CT

– May mimic calcified mass on plain radiography or NECT
– May mimic hypervascular tumor on arterial phase CECT
image MR will show low-intensity signal within lesion on T2WI

– As opposed to typical appearance of viable tumor (high signal on T2WI)
image Lesions treated with intraarterial chemotherapy or radioactive microspheres (without Ethiodol)

– Effectively treated lesions are hypovascular and nonenhancing on CECT and MR
– Usual appearance on MR: Hyperintense on T1WI, hypointense on T2WI (opposite of usual appearance of viable tumor)
• Consider response to systemic chemotherapy

image Treated tumor often undergoes progressive volume loss and fibrosis

– Appearance may simulate other hepatic lesions with fibrous stroma

image e.g., focal confluent fibrosis or peripheral cholangiocarcinoma
image Appearance may resemble cirrhosis (pseudocirrhosis)

– Volume loss, surface nodularity, multifocal capsular retraction, ± signs of portal hypertension
– Diffuse hepatic metastases from breast cancer are especially prone to pseudocirrhosis
– Even untreated metastases can sometimes elicit fibrotic response mimicking cirrhosis
• Consider prior resection of portions of liver

image May have similar appearance to congenital absence or hypoplasia of hepatic segments

– May also resemble atrophy of anterior and medial segments that occurs with cirrhosis
image Resected focus may be packed with omental fat to control leakage of blood or bile

– Appearance may simulate fat-containing hepatic mass (e.g., angiomyolipoma or hepatocellular carcinoma)
• Iatrogenic arterioportal (AP) fistula

image Common but usually self-limited complication of percutaneous liver biopsy
image Enlarged hepatic arterial branch with early opacification of accompanying portal venous branch and hyperenhancement of subtended segment of liver on arterial phase CECT (or MR)
image May resemble other causes of AP fistulas (e.g., hereditary hemorrhagic telangiectasia [HHT] or transient hepatic attenuation differences [THADs])

– HHT has enlarged hepatic artery, innumerable telangiectasias, and vascular masses in liver with heterogeneous parenchymal enhancement
– Other THAD etiologies usually have occlusion of portal venous branch (e.g., by malignant tumor) or sump effect of hypervascular mass in liver
image Small peripheral AP shunts are common, spontaneous findings in cirrhotic liver

DIFFERENTIAL DIAGNOSIS

Pyogenic Abscess

• Usual appearance is multiloculated collection of fluid ± gas in right lobe of liver
• Almost always contains more fluid than seen with bioabsorbable gelatin sponge

Portal Venous Gas With Bowel Infarction

• Should see gas in bowel wall (pneumatosis) in addition to portal venous gas
• Clinical setting for iatrogenic portal venous gas is usually different than for bowel infarction

Focal Confluent Fibrosis

• Wedge-shaped focus of hepatic volume loss and fibrosis occurs in advanced cirrhosis

image Hepatic capsular retraction is usually more striking than with treated malignancy
• Usually affects anterior and medial segments
• No history of prior treatment for hepatic malignancy

Cholangiocarcinoma (Peripheral)

• Appearance may be identical to focal confluent fibrosis or treated hepatic malignancy
• Look for dilation of bile ducts within affected segment of liver
• Delayed persistent enhancement is more common with cholangiocarcinoma than with treated hepatocellular carcinoma or metastases

Regenerative and Dysplastic Nodules

• Typically hyperintense on T1WI and hypointense on T2WI
• Similar to appearance of successfully treated primary or metastatic hepatic malignancies
• History of prior treatment of tumor is key to diagnosis

Congenital Absence of Hepatic Segments

• Usually affects anterior and medial segments
• May be absent or, more commonly, atrophic
• Appearance may resemble cirrhosis or result from surgical resection of hepatic segments
• Absence of signs of cirrhosis or prior history are key to recognition

Cirrhosis

• Nodular contour, volume loss (usually right anterior and medial segments more than caudate), and widened fissures
• May show signs of portal hypertension (ascites, varices, splenomegaly)
• Etiology is usually known (alcohol, chronic viral hepatitis, etc.)
• No history of prior treated malignancy

Hepatic Angiomyolipoma

• Soft tissue ± fat-density mass in liver
• May occur with angiomyolipomas in kidney, especially in tuberous sclerosis complex
• Iatrogenic placement of fat in surgical defect in liver may show surgical clip ± volume loss, unlike hepatic angiomyolipoma

Other Causes of Transient Hepatic Attenuation and Intensity Differences (THADs and THIDs)

• Most common causes are small, peripheral, AP shunts in cirrhotic patients or occlusion of portal vein branches by tumor or clot
• Iatrogenic arteriovenous fistulas have early opacification of portal vein branch, not occlusion

CLINICAL ISSUES

Demographics

• Age

image More common in elderly; can affect children

DIAGNOSTIC CHECKLIST

Consider

• Knowing history is key to appropriate diagnosis
image
(Left) Axial T1WI MR of a hepatocellular carcinoma (HCC) following arterial chemoembolization shows the mass image as hyperintense, which would be unusual for a viable HCC.

image
(Right) In the same patient, the nonviable HCC lesion image is hypointense on T2WI, which would be atypical for a viable HCC.
image
(Left) Arterial phase CECT of hepatocellular carcinoma shows a subtle, hypervascular, 2 cm nodule image in the right lobe, along with signs of cirrhosis (widened fissures, etc.).

image
(Right) Portal venous phase image in the same patient shows classic washout of contrast medium from the nodule image, essentially diagnostic of hepatocellular carcinoma in this setting. The patient was treated with transarterial chemoembolization, including Lipiodol.
image
(Left) Follow-up NECT in the same patient shows retention of the iodinated Lipiodol image within the tumor. Note the indirect evidence of hepatic injury, with volume loss of the right lobe and ascites.

image
(Right) Arterial phase CECT shows hyperenhancement of a portion of the lateral segment of the liver (THAD) image and early enhancement of the portal vein branch image that drains this segment. This represents an arterioportal shunt and is probably the result of the prior biopsy of the liver at this site.

SELECTED REFERENCES

1. Rajkoviimage, Z, et al. Differential diagnosis and clinical relevance of pneumobilia or portal vein gas on abdominal x-ray. Acta Clin Croat. 2013; 52(3):369–373.

2. Kim, JH, et al. Percutaneous radiofrequency ablation using internally cooled wet electrodes for the treatment of hepatocellular carcinoma. AJR Am J Roentgenol. 2012; 198(2):471–476.

3. Pai, M, et al. Radiofrequency assisted liver resection: analysis of 604 consecutive cases. Eur J Surg Oncol. 2012; 38(3):274–280.

4. Park, SY, et al. Radiofrequency ablation of hepatic metastases after curative resection of extrahepatic cholangiocarcinoma. AJR Am J Roentgenol. 2011 Dec; 197(6):W1129–W1134. [Erratum in: AJR Am J Roentgenol. 198(1):2, 2012].

5. Kim, AY, et al. Venous thrombosis after radiofrequency ablation for hepatocellular carcinoma. AJR Am J Roentgenol. 2011; 197(6):1474–1480.

6. Shah, PA, et al. Hepatic gas: widening spectrum of causes detected at CT and US in the interventional era. Radiographics. 2011; 31(5):1403–1413.

7. Arnold, AC, et al. Postoperative Surgicel mimicking abscesses following cholecystectomy and liver biopsy. Emerg Radiol. 2008; 15(3):183–185.

8. Khankan, AA, et al. Hepatocellular carcinoma treated with radio frequency ablation: an early evaluation with magnetic resonance imaging. J Magn Reson Imaging. 2008; 27(3):546–551.

9. Simon, CJ, et al. Pulmonary radiofrequency ablation: long-term safety and efficacy in 153 patients. Radiology. 2007; 243(1):268–275.

10. Zhang, YJ, et al. Hepatocellular carcinoma treated with radiofrequency ablation with or without ethanol injection: a prospective randomized trial. Radiology. 2007; 244(2):599–607.

11. Ahrar, K, et al. Percutaneous radiofrequency ablation of renal tumors: technique, complications, and outcomes. J Vasc Interv Radiol. 2005; 16(5):679–688.

12. Lencioni, R, et al. Early-stage hepatocellular carcinoma in patients with cirrhosis: long-term results of percutaneous image-guided radiofrequency ablation. Radiology. 2005; 234(3):961–967.

13. Lu, DS, et al. Radiofrequency ablation of hepatocellular carcinoma: treatment success as defined by histologic examination of the explanted liver. Radiology. 2005; 234(3):954–960.

14. Oei, T, et al. Radiofrequency ablation of liver tumors: a new cause of benign portal venous gas. Radiology. 2005; 237(2):709–717.

15. Sandrasegaran, K, et al. Distinguishing gelatin bioabsorbable sponge and postoperative abdominal abscess on CT. AJR Am J Roentgenol. 2005; 184(2):475–480.

16. Wah, TM, et al. Image-guided percutaneous radiofrequency ablation and incidence of post-radiofrequency ablation syndrome: prospective survey. Radiology. 2005; 237(3):1097–1102.

17. Iannitti, DA, et al. Portal venous gas detected by computed tomography: is surgery imperative? Dig Surg. 2003; 20(4):306–315.

18. Rossi, S, et al. Percutaneous radio-frequency thermal ablation of nonresectable hepatocellular carcinoma after occlusion of tumor blood supply. Radiology. 2000; 217(1):119–126.

19. Oto, A, et al. MR characteristics of oxidized cellulose (Surgicel). AJR Am J Roentgenol. 1999; 172(6):1481–1484.

20. Melamed, JW, et al. Sonographic appearance of oxidized cellulose (Surgicel): pitfall in the diagnosis of postoperative abscess. J Ultrasound Med. 1995; 14(1):27–30.

21. Young, ST, et al. Appearance of oxidized cellulose (Surgicel) on postoperative CT scans: similarity to postoperative abscess. AJR Am J Roentgenol. 1993; 160(2):275–277.

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