ouinaud’s system of hepatic nomenclatureprovides the anatomic basis for modernhepatic surgical resections.1,2 In this system,

the liver segments are defined by their relationshipsto vascular structures, hepatic ligaments, and the gall-bladder. The multiplanar imaging capability of ultra-sonography is well suited to the identification ofthese structures and to the precise localization ofmasses to hepatic segments. Accurate preoperativelocalization is essential to surgical planning.

In this paper we present a systematic method forthe segmental localization of liver masses usingultrasonography. With some practice, the techniqueshould be within the capability of most experiencedsonographers. We also review the anatomy of thecommon hepatic resections.

The segmental localization of liver tumors is criticalto planning appropriate resection. Couinaud’snomenclature is a surgically relevant system of hepat-ic segmental anatomy, which defines the liver seg-ments by their relationships to vascular structures,

hepatic ligaments, and the gallbladder. We demon-strate a way to accurately localize hepatic masseswith sonography. KEY WORDS: Liver; Ultrasonography;Couinaud classification.

Received November 27, 1995, from the Department of DiagnosticRadiology and Nuclear Medicine, London Health Sciences Centre,University Campus, University of Western Ontario, London,Ontario. Revised manuscript accepted for publication February 20,1998.

Address correspondence and reprint requests to Dean F. Smith,MD, FRCPC, Department of Diagnostic Radiology and NuclearMedicine, London Health Sciences Centre, University Campus,University of Western Ontario, 339 Windermere Road, London,Ontario, Canada, N6A 5A5.

ABBREVIATIONS

PV, Portal vein; FL, Falciform ligament; RHV, Right hepatic vein;MHV, Middle hepatic vein; LHV, Left hepatic vein; IVC, Inferiorvena cava; GB, Gallbladder; RPV, Right portal vein; MPV, Mainportal vein; LPV, Left portal vein

1998 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 17:375–381, 1998 • 0278-4297/98/$3.50

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Sonographic Demonstration of Couinaud’s Liver Segments

Dean Smith, MD, FRCPC, Donal Downey, MB, BCh, FRCPC, Alison Spouge, MD, FRCPC, Sue Soney, RT, RDMS, RCMS

PICTORIAL ESSAY

Figure 1 Couinaud’s hepatic segments. Diagrammatic repre-sentation of the liver from an anterior perspective (all segmentsnumbered appropriately). The caudate lobe (1) is situated posteriorly.

376 COUINAUD LIVER SEGMENTS J Ultrasound Med 17:375–381, 1998

Procedure for Localizing a Hepatic Mass to One of Couinaud’s Segments with Sonography

1. Image along the plane that separates any two segments.2. Rotate the transducer 90 degrees.3. Keep the separating boundary in the image, and scan through the liver until the mass and the

boundary are seen in the same image.

Which Lobe, Right or Left?

Figure 2 The sagittal plane defined by the MHV and the IVC separates the right and left lobes. A, Transverse subcostal view indeep inspiration through the superior portion of the liver reveals the main fissure separating the right and left lobes (dashed line). In the inferior portion of the liver, a plane connecting the long axis of the gallbladder to the left side of the IVC separates the rightand left lobes. B, Transverse subcostal view in deep inspiration through the inferior portion of the liver; dashed line divides rightand left lobes.

A B

Right Lobe Segments: 5/6 or 7/8?

Figure 3 A transverse plane through the horizontal portion of the RPV separates segments 7/8 superiorly from 5/6 inferiorly. A, Transverse subcostal view in deep inspiration through the right lobe at the level of the RPV branch. B, Turning the transduc-er 90 degrees will obtain a sagittal intercostal view of the right lobe in the left posterior oblique position. The transverse portionof the RPV is shown in cross section. Dashed line separates segments 7/8 superiorly from segments 5/6 inferiorly.

A B

377J Ultrasound Med 17:375–381, 1998 SMITH ET AL

Right Lobe Segments: 5/8 or 6/7?

Figure 4 A, A longitudinal plane defined by the RHV and the IVC separates segments 5/8 medially from segments 6/7 laterally.B, Turning the transducer 90 degrees will obtain a transverse intercostal view of the right lobe in the left posterior obliqueposition. This image shows the descending portion of the RHV and the IVC. Dashed line separates segments 6/7 laterally fromsegments 5/8 medially.

A B

Left Lobe Segments: 4 or 2/3?

Figure 5 A, A longitudinal plane containing the ligamentum teres (lig. teres), the ascending portion of the LPV, and the fissurefor the ligamentum venosum (lig. venosum) separates segments 2/3 laterally from segments 4A/4B medially. B,Turning thetransducer 90 degrees will obtain a transverse scan through the left lobe. Dashed line separates segments 2/3 laterally from segments 4A/4B medially.

A B

378 COUINAUD LIVER SEGMENTS J Ultrasound Med 17:375–381, 1998

Left Lobe: 2 or 3?

Figure 6 A, A longitudinal plane containing the LHV and the IVC separates segment 2 posteromedially from segment 3 antero-laterally. B, Turning the transducer 90 degrees will obtain a transverse image through the lateral portion of the left lobe. Thisimage shows the descending portion of the LHV and the IVC. Dashed line separates segment 2 from segment 3. Confusion existsin the literature regarding the separation of segments 2 and 3. According to Couinaud,1 the LHV is the dividing landmarkbetween these two segments. However, other authors have stated that these segments are separated by an imaginary plane con-taining the transverse portion of the LPV.3–5 This error results in the creation of nonanatomic segments, placing segment 2 supe-rior to segment 3 rather than posteromedial to it.

A B

Left Lobe: 4A or 4B?

Figure 7 A, An oblique transverse plane through the transverse portion of the LPV separates segment 4A superiorly from seg-ment 4B inferiorly. B, Turning the transducer 90 degrees will obtain a sagittal view through the medial portion of the left lobe.This image shows the transverse portion of the LPV; dashed line separates segment 4A from segment 4B.

A B

Caudate Lobe

379J Ultrasound Med 17:375–381, 1998 SMITH ET AL

Figure 8 The caudate lobe (Couinaud’s segment 1) is bordered by the fissure for the ligamentum venosum ante-riorly, the IVC posteriorly, and a line connecting the MHVand the GB laterally. The lobe extends cephalad to junctionof the MHV and the IVC.6 A, Schematic representation oflateral view of caudate lobe. B, Longitudinal midline imageshows caudate lobe relationships. Lig. venosum, Fissure forthe ligamentum venosum. C, Transverse midline imageshows caudate lobe relationships.

B C

A

380 COUINAUD LIVER SEGMENTS J Ultrasound Med 17:375–381, 1998

Figure 10 A, In a left lateral segmentectomy, segments 2 and 3 are removed. Black nodule, Tumor; yellow portion, resected area.B, Postoperative image, left lateral segmentectomy. No liver is seen lateral to segments 4A/4B (arrow).

A

Figure 11 Transverse hepatectomy is performed most oftenfor GB carcinoma. This resection removes segments 1, 4B, 5,and 6. Black nodule, Tumor; yellow portion, resected area.

Figure 9 In a left lobectomy, segments 2, 3, 4A, and 4B areremoved; the caudate lobe (segment 1) and the entire rightlobe are left intact. Black nodule represents tumor; yellow por-tion, resected area.

Patients with primary hepatic neoplasms or fewerthan five metastases are potential candidates forresection. The goal of surgery is to remove the entirelesion or all the lesions with tumor-free margins,while preserving a sufficient quantity of residualliver with intact blood supply and biliary drainage tosustain life. This requires the removal or preserva-tion of entire liver segments. Inoperable tumors arethose involving the MPV, hepatic artery, or both theright and left hepatic ducts.7

B

Hepatic Resections

Conclusion

Advances in hepatic oncologic surgery require thatradiologists specify the location of masses accordingto the segmental anatomy of the liver. The systematicapplication of ultrasonography can accurately local-ize masses to Couinaud’s segments, thereby provid-ing vital information for preoperative planning.

References

1. Couinaud C: Le foie: Etudes anatomiques et chirurgi-cales. Paris, Masson, 1957

2. Bismuth H: Surgical anatomy and anatomical surgery ofthe liver. World J Surg 6:3, 1982

3. Soyer P: Segmental anatomy of the liver: Utility of anomenclature accepted worldwide. AJR 161:572, 1993

4. Mukai JK, Stack CM, Turner DA, et al: Imaging of surgi-cally relevant hepatic vascular and segmental anatomy. I. Normal anatomy. AJR 149:287, 1987

5. Rumack CM, Wilson SR, Charboneau JW: DiagnosticUltrasound. St. Louis, Mosby–Year Book, 1991, p 45

6. Dodds WJ, Erickson SJ, Taylor AJ, et al: Caudate lobe ofthe liver: Anatomy, embryology, and pathology. AJR154:87, 1990

7. Gazelle GS, Haaga JR: Hepatic neoplasms: Surgically rel-evant segmental anatomy and imaging techniques. AJR158:1015, 1992

381J Ultrasound Med 17:375–381, 1998 SMITH ET AL

Figure 12 A, In a right lobectomy, segments 5 through 8 are removed. Black nodule, Tumor; yellow portion, resected area. B, Postoperative image, right lobectomy. Bowel has filled the space previously occupied by the right lobe (arrow).

A B

Figure 13 If a process involves all but the lateral segments ofthe left lobe, a right trisegmentectomy is performed toremove segments 1, 4A, 4B, and 5 through 8. Black nodule,Tumor; yellow portion, resected area.