**3.2 Immunohistochemistry**

*Renal Diseases*

**2.5 Laparoscopic and open biopsy**

before biopsy [12, 13].

technique becomes the preferred option (**Table 1**).

**3. Specimen handling and processing**

red striations representing vasa recta [14].

gist in interpreting the findings.

**3.1 Light microscopy**

lock syringe, is advanced down the catheter to obtain the tissue core (core biopsy technique) [11]. More than one pass is usually possible to improve tissue yield.

Laparoscopic biopsy is usually performed by a urologist mostly via the retroperitoneal approach but can be approached transperitoneally. The patient receives general anaesthesia, is placed in full right or left flank position, prepped and draped. Using a two-port technique, firstly the retroperitoneum is entered in the posterior axillary line, halfway between the ribs and iliac crest [12]. The lower pole of the kidney is then localized by blunt dissection with the laparoscopic lens to create a space posterior to the kidney. Next a 5 mm trochar is inserted under direct vision in the anterior axillary line at the level of the iliac crest to identify the kidney; the biopsy is taken using a laparoscopic biopsy forceps [12]. Multiple biopsies can be taken and thereafter haemostasis is secured. In uncertain cases, intraoperative ultrasonography can be performed via a laparoscopic probe, to confirm renal tissue

Open biopsies can be performed in patients with contraindication to PRB, or during open abdominal surgeries for other renal indications, e.g. taking a biopsy during a partial nephrectomy. Some patients refuse open biopsies on religious grounds (Jehovah's witness refusing blood transfusion) [12], so the laparoscopic

The manner in which the biopsy core collected is handled and processed contributes to the diagnostic and prognostic usefulness. The tissue core should be gently removed from the biopsy needle using an 18G needle, or washed from the needle onto a Petri dish, using a slow jet of normal saline. A magnifying lens or a dissecting microscope should be used immediately to confirm it is kidney tissue, and whether it is cortex or medulla. The renal cortex appears pale pink to tan with reddish blushes depicting the glomeruli, while the medulla usually contains straight

The biopsy operator must be knowledgeable of effective ways of dividing the renal core obtained when needed, and the right fixative to use. This ensures that adequate samples are delivered to the pathologist, for the different processing and fixation methods required for light microscopy (LM), immunohistochemistry (IHC) and electron microscopy (EM). At least three cores are required, one each for LM, IHC and EM. The need for dividing tissue core arises if the number of cores obtained is inadequate, e.g. if only one core is obtained, 1 mm cuts are made from both ends for EM, while the remainder is cut in two, the larger of which is used for LM while the other for IHC [14]. Specimen should be placed quickly in appropriate fixatives and accompanied with adequate clinical information to guide the patholo-

The fixative for LM is buffered 10% aqueous formaldehyde solution. The tissue is examined using a light microscope which employs focused visible light to magnify objects viewed. Stains are used to enhance characterization of the tissue; common stains are H&E, periodic acid-Schiff (PAS), Silver, and Trichrome. Light microscopy (LM) shows predominantly proliferative lesions, and occasionally

**18**

This includes immunofluorescence (IF) and immunoperoxidase (IP). The choice of which to use often depends on the pathologist and resources available. Immunoperoxidase (IP) requires no special fixation, since a tissue pre-fixed in formalin for LM can be used for IP depending on the question to be answered. It produces well-developed antigen retrieval and results are reproducible [14]. Immunofluorescence is the choice of most renal pathologist. The fixation used is Zeus solution (modified Michel's tissue fixative). IF produces accurate location of deposits with the aid of dark field microscopes, and excellent resolution when fluorescence microscopes with epifluorescence attachments are used. Routine examinations during IF include immunoglobulin's (IgG, IgM, IgA), complements (C3, C1q, C4) fibrin, kappa and lambda chains. Other antibodies may be examined depending on the question to be answered, e.g. C4d in allograft biopsies.
