Native kidney biopsy

Histology is frequently required in order to direct further management of diffuse renal disease. Biopsy of solid renal masses is rarely performed as the diagnosis of renal cell or transitional cell carcinoma is usually clear from imaging. Biopsies are  still performed however in those patients who are not having surgery to confirm the diagnosis; this is often required prior to chemotherapy or new therapeutic regimes. Biopsy of the native kidney is  performed in the majority of centres under ultrasound guidance. Contraindications to biopsy include hydronephrosis, which may be more appropriately treated with catheterization or nephrostomy, or small kidneys, that is < 8 cm longitudinal axis (these appearances being indicative of chronic renal impairment). Kidneys > 9 cm can potentially be biopsied; however other factors, including cortical thickness, age, clinical history and the requirement for definitive diagnosis will all have a bearing on whether biopsy is performed or not. Hydronephrosis and kidney size are easily assessable with a prebiopsy scan.
In most cases the biopsy is performed with the patient prone over a small bolster to maximize access to the kidney. The shortest route, avoiding adjacent structures, is selected; subcostally, traversing the cortex of the lower pole and avoiding the collecting system and major vessels is recommended. With ultrasound guidance, either kidney may be chosen and accessibility will vary between patients. The depth of penetration and angle of approach are carefully assessed. Biopsy is normally with a 16G needle. The patient’s cooperation is required with suspending respiration at the crucial moment. This avoids undue damage to the kidney as the needle is introduced through the capsule. The needle should be positioned just within the capsule prior to biopsy so that the maximum amount of cortical tissue is obtained for analysis, as the throw of the needle may be up to 2 cm.
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