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Abstract
Objective Liver biopsy is an important tool for the diagnosis and assessment of liver disease. The authors aimed to establish the relationship between biopsy length and the number of total portal tracts.
Methods The authors reviewed 163 16G percutaneous medical liver biopsies taken at a tertiary referral centre over a 14-month period. Haematoxylin and eosin sections were analysed using imaging software and portal tracts were counted.
Results Liver biopsy length correlates with total portal tracts. The median biopsy length was 13.3 mm with a median of six portal tracts. Ninety-five per cent of biopsies measuring at least 15 mm contained six portal tracts or more with a significant difference between total portal tracts when compared with biopsies <15 mm (p<0.0001).
Conclusion To facilitate adequate histological assessment by examining at least six portal tracts, the authors suggest that 16G biopsies should be at least 15 mm long.
- Percutaneous liver biopsy
- length
- portal tract
- liver core biopsies
- length and number of portal tracts
- histopathology
- liver
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- Percutaneous liver biopsy
- length
- portal tract
- liver core biopsies
- length and number of portal tracts
- histopathology
- liver
Introduction
Liver biopsy is an important part of the management of many patients with liver disease.1 Two established approaches to obtaining needle core liver tissue are percutaneous and transjugular biopsy. The latter is preferred if contraindications to percutaneous biopsy are present, the commonest being coagulopathy and presence of moderate or severe ascites. Percutaneous liver biopsy remains the commonest approach, but it is not without its risks. The most frequent complication is pain, with up to 30% of patients experiencing this problem, while mortality can arise from intraperitoneal haemorrhage due to disruption of the Glisson capsule or intrahepatic vessels by the cutting needle at a rate in UK district general hospitals ranging between 0.13 and 0.33%.2 Multiple passes and the use of larger needle sizes are implicated in increasing the risk of complications.3
A typical needle core biopsy samples approximately 1/50 000 of the total liver volume.4 Histological diagnosis is dependent upon adequate tissue sampling with the guidelines of the Royal College of Pathologists (RCPath) advising that liver biopsies should generally be at least 1 cm and contain a minimum of six portal tracts.5 Previous studies have recommended a biopsy length of 20–25 mm with at least 11 portal tracts for accurate evaluation of chronic viral hepatitis.6–8 However, sampling this amount of liver tissue is not always possible in practice. Therefore, percutaneous liver biopsy must balance the risk of the procedure to the patient with the acquisition of sufficient tissue to allow adequate histological assessment.
At Southampton General Hospital, percutaneous liver biopsies are performed under ultrasound guidance by radiologists, predominantly using a 16G (internal diameter 1.6 mm) cutting needle. To provide data on the adequacy of liver sampling with this technique, we performed an audit of archived histological slides. In particular, we aimed to demonstrate the relationship between length of biopsy and the number of portal tracts.
Materials and method
All cases of percutaneous liver biopsy reported between 1 January 2008 and 28 February 2009 were retrieved from the database of Southampton General Hospital. Cases were included only if a 16G needle had been used, the original histological slides were available, and liver tissue was present in the biopsy. Patients aged under 16 years were excluded. We also excluded cases in which the liver was cirrhotic, since it is not possible to give a meaningful count of portal tracts in cirrhotic livers in this context.
The original haemotoxylin & eosin stained sections were scanned at ×200 magnification using an Olympus U-TV1X-2 (Olympus, Tokyo, Japan) microscope and image captured with dotSlide virtual microscopy system software (Olympus Imaging Solution, Tokyo, Japan). The section level with the greatest surface area was selected for analysis with the length (total if fragmented) and surface area measured using the ruler and rhomboid functions.
We counted portal tracts provided at least two of the three main structures (portal vein, hepatic artery and bile duct) could be identified. Complete portal tracts were defined as those in which the connective tissue of the tract was entirely present, whereas partial portal tracts were defined as those in which the connective tissue was incomplete.
The data were anonymised and entered into an Excel (Microsoft, Seattle, Washington) spreadsheet for analysis. The audit was approved by the Clinical Effectiveness Team of Southampton University Hospitals NHS Trust. Statistical comparison was made using the Mann–Whitney U test.
Results
There were 163 patients who fulfilled the inclusion criteria. The median age was 48 years with a range of 17 to 85 years; 53% of the 163 cases were men. The histopathological diagnoses for these cases were: 51 viral hepatitis, 31 steatosis, 23 steatohepatitis, 17 normal or minimal non-specific changes, 10 drug-induced changes, seven autoimmune hepatits, four haemochromatosis and 20 grouped under other diagnoses. The median number of portal tracts identified in the biopsies was six (table 1). The number of portal tracts as a function of biopsy length is shown in figure 1.
Morphological characteristics of the liver biopsies
Scatter plot demonstrating the correlation of total number of portal tracts with length of liver biopsy.
Eighty-eight per cent of the liver biopsies measured 10 mm or more, but only 52% contained at least six portal tracts. There were 42 biopsies 15 mm or longer; 40 of them (95%) contained six or more portal tracts, and the median number of portal tracts was nine. There were 12 biopsies 20 mm or longer; all of them (100%) contained six or more portal tracts, and the median number was 12.5. In the 121 biopsies less than 15 mm long, only 45 (37%) had six or more portal tracts, and the median number of portal tracts was five. There were 20 biopsies less than 10 mm long; only two of them (10%) had six or more portal tracts, and the median number was 3.5.
There was a significant difference between the number of portal tracts found in biopsies measuring 15 mm or longer compared with those less than 15 mm (p<0.0001).
Discussion
It is important to minimise the risks to the patient when a percutaneous liver biopsy is performed,1 and so clinicians would prefer to take the minimum amount of tissue required to make a diagnosis. However, if the biopsy is insufficient, the pathologist may be unable to fully assess the morphological changes. In such an instance, the patient will have been exposed to the risks of liver biopsy without benefitting from the procedure. Some authors suggest that full assessment requires a biopsy length of 20–25 mm and at least 11 portal tracts.6–8 The guidelines of the RCPath in the UK are less than this (ie, at least six portal tracts should be present, and the biopsy should be at least 10 mm long 5), but many of the biopsies in our series did not fulfil even these relatively modest criteria. This did not preclude the formulation of a histological diagnosis in our series; however, the degree of certainty of each diagnosis in biopsies measuring less than 10 mm was not the aim of this study.
We counted portal tracts, whether partial or complete, provided two of the three main portal structures could be identified. Using this protocol, to have a 95% chance of containing six or more portal tracts, biopsies needed to be at least 15 mm long.
In conclusion, liver biopsies in this series often did not meet the guidelines of the Royal College of Pathologists particularly in terms of a minimum of six portal tracts.5 We suggest that in order to have a good chance of containing six or more portal tracts, liver biopsies taken with a 16G needle should be at least 15 mm in length rather than 10 mm.
Take-home messages
A high proportion of percutaneous liver biopsies meeting the RCPath guidelines of 10 mm length do not contain six portal tracts.
When using a 16G biopsy needle, a length of at least 15 mm is recommended to have a high probability of attaining six portal tracts for assessment as recommended by the RCPath.
Footnotes
Competing interests None.
Ethics approval Ethics approval was provided by the Clinical Effectiveness Team of Southampton University Hospitals NHS Trust.
Provenance and peer review Not commissioned; externally peer reviewed.