Theoretical calculation of optimal depth in the percutaneous native kidney biopsy to drastically reduce bleeding complications and sample inadequacy for histopathological diagnosis.

BACKGROUND

In recent years percutaneous native kidney biopsy (PNKB) has become of very common use and safe enough for the patient if performed by skilled physicians; nevertheless, haemorrhagic complications or inadequate tissue sample for the diagnosis may occur. We report here the type and the adequacy rate of specimens for diagnosis and complication rate associated with PNKB performed in a single centre from May 2003 to December 2005 using a mathematical formula to determine the depth in centimetre where pushing the trigger.

METHODS

In this prospective study we analysed data from 126 consecutive PNKB performed by the same two skilled nephrologists with the free hand technique using the 14-gauge automated biopsy gun under continuous sonographic control (Group I). The trigger was pushed exactly at the depth previously calculated by a mathematical formula: BW/H (body weight expressed in hectograms divided by patient height expressed in centimetres) less 0.5 (BW/H - 0.5). The type and the adequacy rate of specimens for diagnosis and the associated complication rate were retrospectively compared with data obtained from 123 consecutive PNKB performed from January 2001 to April 2003 by the same operators before using the mathematical formula described earlier (Group II).

RESULTS

Of our series of 126 consecutive PNKD using the mathematical formula (Group I), only four subjects presented post-biopsy gross haematuria (3.2%) and three experienced symptomatic small subcapsular haematoma (2.4%). All biopsy specimens proved to be adequate for diagnosis (100%) with a mean of 22 glomeruli (range 5-60) per specimen. The previous series of 123 consecutive PNKB (Group II) showed gross haematuria (8.4%; P < 0.01 vs Group I) and symptomatic subcapsular haematoma (3.7%) with an adequate sampling of 94.8% (P < 0.01 vs Group I) and a mean glomerular count of 17 (range 4-47) per specimen (P < 0.01 vs Group I). Conclusions. PNKB is an invasive procedure that in spite of progress made in safety, diagnostic adequacy and performing techniques, still involves minor or major risks. The results obtained show that our method is extremely useful to reduce significantly the incidence of bleeding complications and permits us to take enough renal tissue for diagnostic evaluation in all cases.