Glomerular analysis
Seven of 156 renal samples contained no glomeruli (4.49%). Of these, 5 samples were obtained using 18G needles (71.4%), one using a 14G needle (14.3%), and one using a 16G needle (14.3%). The total numbers of glomeruli harvested using 18G, 16G, and 14G needles were 17.5±9.3, 27.1±14.6, and 29.8±26.5, respectively (P = 0.0457), as assessed by light microscopy. However, when the numbers of glomeruli per core were analyzed, there was no statistical difference among specimens harvested using 18G, 16G, and 14G needles (11.9±7.0, 14.1±8.8, and 14.9±12.1, respectively; P = 0.4051).
Weight was not a factor involved with bleeding (P = 0.439), hematuria (P = 0.279), hematoma (P = 0.478), or number of glomeruli (0.6322). Weight was not important for presence of medulla in the cores harvested (P = 0.1043) or number of glomeruli per core (P = 0.8923).
Table 1. Mean number of glomeruli as assessed by light microscopy, and percentages of kidney samples with less than 10 glomeruli.
|
n
|
Light Microscopy
|
< 10 glomeruli LM (%)
|
< 5 glomeruli LM (%)
|
|
Mean number of glomeruli
|
|
Samples with medullar tissue (%)
|
18 Gauge
|
21
|
17.5±9.3a
|
|
33.3
|
9.5
|
9.5
|
16 Gauge
|
25
|
27.1±14.6b
|
|
28.0
|
12.0
|
4.0
|
14 Gauge
|
6
|
29.8±26.5b
|
|
16.0
|
16.7
|
0
|
Mean values followed by different superscript letters in the same columns are statistically different (p<0.05). LM, light microscopy.
Medulla
The percentage of renal biopsy samples that contained renal medulla fragments was similar between specimens harvested using 18G, 16G, and 14G needles (P=0.5862).
Crushes
Kidney biopsies were considered adequate (good or excellent) by the histopathologist after light microscopy examination of the samples in 57.1% (18G), 72.0% (16G), and 66.7% (14G) of the specimens. Although higher amounts of fragmentation and crushing artifacts were observed in specimens harvested with an 18G needle, no statistical difference was observed between the three needle gauges in this regard (P =0.8738).
Material for immunofluorescence was successfully obtained in 90.5%, 96.0%, and 83.3% of the cores harvested using 18G, 16G, and 14G needles, respectively. Material for electron microscopy was successfully obtained in 95.2%, 96.0%, and 100% of the cores harvested using 18G, 16G, and 14G needles, respectively.
Table 2. Complications observed during execution of 156 renal biopsy procedures. Data on hematoma severity, microscopic hematuria, and persistence of microscopic hematuria are expressed as means ± standard deviations. Data on macroscopic hematuria are expressed as percentages.
|
18 Gauge
|
16 Gauge
|
14 Gauge
|
Hematoma severity (0-3)
|
0.82 ± 0.81a
|
0.71 ± 0.78ab
|
1.02 ± 1.08b
|
Microscopic Hematuria (1-6)
|
4.53 ± 1.28
|
4.02 ± 1.45
|
3.58 ± 1.43
|
Macroscopic Hematuria (%)
|
21.7
|
20.0
|
16.7
|
Persistence of microscopic hematuria (days)
|
3.08 ± 1.85a
|
1.28 ± 1.32b
|
1.75 ± 0.96ab
|
Mean values followed by different superscript letters in the same row are statistically different (P < 0.05).
Hematoma
Hematoma was recognized immediately after harvesting the third core using 18G, 16G, and 14G biopsy needles in 57.1% (n=12), 48.0% (n=12), and 83.3% (n=5) of cases, respectively. Hematomas produced by 14G needles were more severe than those produced by 18G or 16G needles (P = 0.019).
Bleeding
Macroscopic hematuria was observed in one dog in the 14G needle group (16.7%), five dogs in the 16G needle group (20%), and five dogs in the 18G needle group (21.7%) (P = 0.858). None of these episodes were associated with clot retention, and all cases subsided spontaneously after 24 hours. There was no requirement for blood transfusion or reoperation in any of the cases.
Microscopic hematuria was the most common consequence of the biopsy procedure (96.1% of cases), and the patient could be followed at home using urinalysis dipsticks during 7 days in 71.2% (n=37) of the cases. The longest case of postbiopsy microscopic hematuria lasted for 5 days. There were no significant differences in number or erythrocytes in the urine immediately after biopsy using any of the needle gauges (P = 0.417), but persistence of postbiopsy microscopic hematuria was statically different after biopsy using the three biopsy needle gauges (P = 0.0264).
Ultrasound
An asymptomatic perirenal hematoma was detected by ultrasound 10 days after renal biopsy in one case (16G needle). Local tissue reaction was recognized nearby the biopsy site in 2 cases (18G and 16G needles), and presence of a small amount of liquid in the subcapsular area was detected in one case (14G needle). All the cases were managed conservatively with ultrasonographic reevaluation within 1 to 3 months.
Figure 1. Microscopic evaluation of renal biopsy using 18G, 16G, or 14G needles in 156 renal samples. Mean ± standard deviation of the number of days of persistence of microscopic hematuria (A), hematuria severity score (B), total number of glomeruli obtained by biopsy (C), and glomerular crushing score (D). Asterisks indicate statistical differences between the groups evaluated.