Improved Tissue Sections for Medical Liver Biopsies
Improved Tissue Sections for Medical Liver Biopsies
Of the 100 biopsies, 10 were excluded because of the needle gauge or transjugular route (2 transjugular 19 g biopsies and 8 biopsies with 18 or 14 g needles from Leeds). The remaining 49 Bradford biopsies were all obtained with an 18 g needle; 30 were taken by consultants and 19 by trainees. There were two passes in 32 cases and one pass in 17 cases. The remaining 41 Leeds biopsies were all obtained with a 16 g needle; 8 were taken by consultants and 33 by trainees. All except one had a single pass. We found no difference in biopsy length when comparing specimens obtained by consultant and trainee radiologists.
The patients were well matched for age, gender and indication for liver biopsy and frequency of cirrhosis (Table 1).
The number of macroscopic pieces of biopsy core on receipt relative to the number of passes is shown in Table 2. This indicates that biopsy cores were already broken when received in the laboratory in 17/49 (35%) of 18 g biopsies and 7/41 (17%) of 16 g biopsies (p=0.06). The number of microscopic pieces counted on image analysis exceeded the number of macroscopic pieces in 35/49 (71%) of 18 g biopsies and 9/41 (22%) of 16 g biopsies (p<0.001). Overall there was more than one piece of microscopic liver tissue per pass (ie, fragmentation of at least one core) in 37/49 (76%) of 18 g biopsies and 12/41 (29%) of 16 g biopsies (p<0.001), with most of the fragmentation occurring during tissue processing or sectioning for 18 g biopsies. The separate fragments seen in tissue sections may be due to either breakage of the biopsy core or to irregular calibre or failure of flat embedding of the tissue resulting in gaps in the tissue section.
Figure 1 shows the annotated virtual slide images of the biopsies with median areas from the 18 and 16 g groups. The total length, maximum width and measured area of tissue per pass of the biopsy needle are shown in Table 3. The median length of the core per pass is similar in the two groups (14.10 mm for 16 g and 14.61 mm for 18 g, p=0.25). The median value for maximum width measured was 0.74 mm (range 0.53–0.93 mm) for the 18 g biopsies and 1.04 mm (range 0.85–1.20 mm) for the 16 g biopsies (p<0.001). The median value for the measured area for the 16 g needle was 11.38 mm (range 5.12–17.42 mm). The median area for cases with one pass of the 18 g needle was 8.34 mm, but for cases with two passes, the median area are was 15.19 mm, exceeding that of the 16 g needle (figure 1).
The average biopsy width in tissue sections was calculated from measured area/length. The median width for 18 g biopsies (0.53 mm) is significantly less than for 16 g biopsies (0.87 mm, p<0.001).
A perfect longitudinal section through the widest part of the biopsy cylinder would have a calculated theoretical maximum area of the length×maximum width (figure 2). The percentage of this achieved in practice (measured area/calculated theoretical maximum area) is also shown in Table 3 and was significantly higher for the 16 g biopsies (median 82%) than for the 18 g biopsies (median 73%).
Five biopsies showed late-stage cirrhosis, and it was not possible to count their portal tracts. The number of complete and incomplete portal tracts in the remaining 85 biopsies and per centimetre length of biopsy is shown in Table 4. There is a wide variation in the number of portal tracts per length of biopsy, and so the portal tract count cannot be predicted by the biopsy length. The wider biopsies contain nearly twice as many complete portal tracts per centimetre of biopsy.
Using the criterion of >10 complete portal tracts per section, only 5/46 (10.8%) of our routine 18 g biopsies (most of which had two passes) and 7/39 (17.1%) of 16 g biopsies would be classed as adequate. To reliably obtain a sample with over 10 complete portal tracts, multiple passes would be needed with either needle.
Based on the number of portal tracts per 10 mm, we have calculated that the number of biopsies that would have met the criterion of ≥6 complete portal tracts in a single 15 mm core is 7/46 (17.9%) for 18 g biopsies and 28/39 (74%) for 16 g biopsies. For two passes, achieving 30 mm of tissue, this would be 70% and 95%, respectively. However, if all portal tracts (complete and incomplete) are included, there would have been ≥6 tracts in 93% of 18 g biopsies and 100% of 16 g biopsies within one 15 mm core biopsy.
Results
Of the 100 biopsies, 10 were excluded because of the needle gauge or transjugular route (2 transjugular 19 g biopsies and 8 biopsies with 18 or 14 g needles from Leeds). The remaining 49 Bradford biopsies were all obtained with an 18 g needle; 30 were taken by consultants and 19 by trainees. There were two passes in 32 cases and one pass in 17 cases. The remaining 41 Leeds biopsies were all obtained with a 16 g needle; 8 were taken by consultants and 33 by trainees. All except one had a single pass. We found no difference in biopsy length when comparing specimens obtained by consultant and trainee radiologists.
The patients were well matched for age, gender and indication for liver biopsy and frequency of cirrhosis (Table 1).
Fragmentation of Needle Biopsies
The number of macroscopic pieces of biopsy core on receipt relative to the number of passes is shown in Table 2. This indicates that biopsy cores were already broken when received in the laboratory in 17/49 (35%) of 18 g biopsies and 7/41 (17%) of 16 g biopsies (p=0.06). The number of microscopic pieces counted on image analysis exceeded the number of macroscopic pieces in 35/49 (71%) of 18 g biopsies and 9/41 (22%) of 16 g biopsies (p<0.001). Overall there was more than one piece of microscopic liver tissue per pass (ie, fragmentation of at least one core) in 37/49 (76%) of 18 g biopsies and 12/41 (29%) of 16 g biopsies (p<0.001), with most of the fragmentation occurring during tissue processing or sectioning for 18 g biopsies. The separate fragments seen in tissue sections may be due to either breakage of the biopsy core or to irregular calibre or failure of flat embedding of the tissue resulting in gaps in the tissue section.
Area of Tissue in Histology Sections
Figure 1 shows the annotated virtual slide images of the biopsies with median areas from the 18 and 16 g groups. The total length, maximum width and measured area of tissue per pass of the biopsy needle are shown in Table 3. The median length of the core per pass is similar in the two groups (14.10 mm for 16 g and 14.61 mm for 18 g, p=0.25). The median value for maximum width measured was 0.74 mm (range 0.53–0.93 mm) for the 18 g biopsies and 1.04 mm (range 0.85–1.20 mm) for the 16 g biopsies (p<0.001). The median value for the measured area for the 16 g needle was 11.38 mm (range 5.12–17.42 mm). The median area for cases with one pass of the 18 g needle was 8.34 mm, but for cases with two passes, the median area are was 15.19 mm, exceeding that of the 16 g needle (figure 1).
The average biopsy width in tissue sections was calculated from measured area/length. The median width for 18 g biopsies (0.53 mm) is significantly less than for 16 g biopsies (0.87 mm, p<0.001).
Percentage of Possible Maximum Area Included in Tissue Sections
A perfect longitudinal section through the widest part of the biopsy cylinder would have a calculated theoretical maximum area of the length×maximum width (figure 2). The percentage of this achieved in practice (measured area/calculated theoretical maximum area) is also shown in Table 3 and was significantly higher for the 16 g biopsies (median 82%) than for the 18 g biopsies (median 73%).
Number of Portal Tracts
Five biopsies showed late-stage cirrhosis, and it was not possible to count their portal tracts. The number of complete and incomplete portal tracts in the remaining 85 biopsies and per centimetre length of biopsy is shown in Table 4. There is a wide variation in the number of portal tracts per length of biopsy, and so the portal tract count cannot be predicted by the biopsy length. The wider biopsies contain nearly twice as many complete portal tracts per centimetre of biopsy.
Using the criterion of >10 complete portal tracts per section, only 5/46 (10.8%) of our routine 18 g biopsies (most of which had two passes) and 7/39 (17.1%) of 16 g biopsies would be classed as adequate. To reliably obtain a sample with over 10 complete portal tracts, multiple passes would be needed with either needle.
Based on the number of portal tracts per 10 mm, we have calculated that the number of biopsies that would have met the criterion of ≥6 complete portal tracts in a single 15 mm core is 7/46 (17.9%) for 18 g biopsies and 28/39 (74%) for 16 g biopsies. For two passes, achieving 30 mm of tissue, this would be 70% and 95%, respectively. However, if all portal tracts (complete and incomplete) are included, there would have been ≥6 tracts in 93% of 18 g biopsies and 100% of 16 g biopsies within one 15 mm core biopsy.
