Percutaneous Renal Biopsy

Percutaneous renal biopsy is the needle excision of a core of kidney tissue for histologic examination. This biopsy may help assess histologic changes caused by acute or chronic glomeru­lonephritis, pyelonephritis, renal vein thrombosis, amyloid infiltration, and systemic lupus erythematosus. In the case of a mass, results can differentiate a primary renal cancer from a metastatic lesion.

Complications of percutaneous biopsy include bleeding, hematoma, arteriovenous fistula, and infection. This procedure is safer than open biopsy, which is the preferred method for sampling a solid lesion, but noninvasive procedures, especially renal ultrasonography and computed tomography, have replaced percutaneous renal biopsy in many hospitals.

Purpose

• To obtain information about glomerular and tubular function or to evaluate a solid renal mass
• To aid diagnosis of renal parenchymal disease
• To monitor the progression of renal disease and assess the effectiveness of therapy.
• To determine the histology of a solid mass

Patient preparation

• Explain to the patient that this test is used to diagnose kidney disorders.
• Describe the procedure to the patient, and answer any questions.
• Instruct the patient to restrict food and fluids for 8 hours before the test.
• Tell him who will perform the biopsy and where.
• Ensure that blood samples and urine specimens are collected and tested be fore the biopsy and that results of other tests to determine the biopsy site, such as excretory urography, ultrasonography, and an erect film of the abdomen, are available.
• Check the patient's history for hemorrhagic tendencies and hypersensitivity to the local anesthetic.
• Administer a mild sedative 30 minutes to 1 hour before the biopsy to help the patient relax.
• Inform the patient that he'll receive a local anesthetic but may experience a pinching pain when the needle is inserted through the back into the kidney.
• Check vital signs, and tell the patient to void just before the test.

Procedure and posttest care

• Place the patient in a prone position on a firm surface with a sandbag beneath his abdomen.
• Tell him to take a deep breath while his kidney is being palpated.
• A 7" 20G needle is used to inject the local anesthetic into the skin at the biopsy site. Instruct the patient to hold his breath and remain still as the needle is inserted through the back muscles, the deep lumbar fascia, the perinephric fat, and the kidney capsule. After the needle is inserted, tell the patient to take several deep breaths. If the needle swings smoothly during deep breathing, it has penetrated the kidney capsule. After the penetration depth is marked on the needle shaft, instruct the patient to hold his breath and remain as still as possible while the needle is withdrawn.
• After a small incision is made in the anesthetized skin, instruct the patient to hold his breath and remain still while the Vim-Silverman needle or a Tru-cut needle with stylet is inserted to the measured depth. An 18G springloaded biopsy gun may also be used.
• Tell the patient to breathe deeply. Then tell him to remain still while the tissue specimen is obtained.
• The tissue is examined immediately under a hand lens to ensure that the specimen contains tissue from both cortex and medulla. Then it's placed on a saline-soaked gauze pad and placed in a properly labeled container.
• If an adequate tissue specimen hasn't been obtained, the procedure is repeated immediately.
• After an adequate specimen is secured, apply pressure to the biopsy site for 3 to 5 minutes to stop superficial bleeding. Then, apply a pressure dressing.
• Instruct the patient to lie flat on his back without moving for at least 12 hours to prevent bleeding. Check vital signs every 15 minutes for 4 hours, then every 30 minutes for 4 hours, then every hour for 4 hours and, finally, every 4 hours. Report any changes.
• Examine all urine for blood; small amounts may be present after the biopsy but should disappear within 8 hours. Hematocrit may be monitored after the procedure to screen for internal bleeding.
• Encourage fluid ingestion to minimize colic and obstruction from blood clotting within the renal pelvis.
• Inform the patient that he may resume his normal diet.

Precautions

• Percutaneous renal biopsy is contraindicated in a patient with a severe bleeding disorder, markedly reduced plasma or blood volume, severe hypertension, hydronephrosis, perinephric abscess, advanced renal failure with uremia, or only one kidney.
• Instruct the patient to hold his breath and remain still whenever the needle or prongs are advanced into or retracted from the kidney.
• Send the specimen to the laboratory immediately.

Normal findings

Normally, a section of kidney tissue shows Bowman's capsule - the area between two layers of flat epithelial cells - the glomerular tuft, and the capillary lumen. The tubule sections differ, depending on the area of tubule involved. The proximal tubule is one layer of epithelial cells with microvilli that form a brush border. The descending loop of Henle has flat squamous epithelial cells. The ascending, distal convoluted, and collecting tubules are lined with squamous epithelial cells.

Abnormal findings

Histologic examination of renal tissue can reveal cancer or renal disease. Malignant tumors include Wilms' tumor, which is usually present in early childhood, and renal cell carcinoma, which is most prevalent in people over age 40. Diseases indicated by characteristic histologic changes include disseminated lupus erythematosus, amyloid infiltration, acute or chronic glomerulonephritis, renal vein thrombosis, and pyelonephritis.

Interfering factors

• Failure to obtain an adequate tissue specimen
• Failure to store the specimen properly
• Failure to send the specimen to the laboratory immediately