Renal Venography

Renal venography is a relatively simple procedure allowing radiographic examination of the main renal veins and their tributaries. In this test, contrast medium is injected by percutaneous catheter passed through the femoral vein and inferior vena cava into the renal vein. Indications for renal venography include renal vein thrombosis, tumor, and venous anomalies.

Purpose

• To detect renal vein thrombosis
• To evaluate renal vein compression due to extrinsic tumors or retroperitoneal fibrosis
• To distinguish renal parenchymal disease and aneurysms from pressure exerted by an adjacent mass
• To assess renal tumors and detect invasion of the renal vein or inferior vena cava
• To detect venous anomalies and defects
• To differentiate renal agenesis from a small kidney
• To collect renal venous blood samples for evaluation of renovascular hypertension

Patient Preparation

• Explain to the patient that this test permits radiographic study of the renal veins.
• If prescribed, instruct him to fast for 4 hours before the test.
• Tell him who will perform the test and where and that it takes about I hour.
• Inform him that a catheter will be inserted into a vein in the groin area after he is given a sedative and a local anesthetic.
• Tell him that he may feel mild discomfort during injection of the local anesthetic and contrast medium and that he may feel transient burning and flushing from the contrast medium.
• Warn him that the X-ray equipment may make loud, clacking noises as the films are taken.
• Check his history for hypersensitivity to contrast media, iodine, or iodinecontaining foods, such as shellfish. Mark sensitivities on the chart.
• Check his history and any coagulation studies for indications of bleeding disorders.
• If renin assays will be done, check the patient's diet and medications, and consult with the health care team. As necessary, restrict the patient's salt intake and discontinue antihypertensive drugs, diuretics, estrogen, and oral contraceptives.
• Make sure that the patient or a responsible family member has signed a consent form.
• Just before the procedure, administer a sedative if necessary.

Equipment

Renal venography tray with flexible guide wires, polyethylene radiopaque vascular catheters, needle and cannula or 18G needle, three-way stopcock, and flexible tubing; preparatory tray; syringes and needles; contrast medium; local anesthetic; emergency resuscitation equipment

Procedure And Posttest Care

• The patient is placed in a supine position on the X-ray table, with his abdomen centered over the film. The skin over the right femoral vein near the groin is cleaned with antiseptic solution and draped. (The left femoral vein or jugular veins may be used.)
• A local anesthetic is injected, and the femoral vein is cannulated.
• Under fluoroscopic guidance, a guide wire is threaded a short distance through the cannula, which is then removed. A catheter is passed over the wire into the inferior vena cava.
• When catheterization of the femoral vein is contraindicated, the right antecubital vein is punctured, and the catheter is inserted and advanced through the right atrium of the heart into the inferior vena cava.
• A test bolus of contrast medium is injected to determine that the vena cava is patent. If so, the catheter is advanced into the right renal vein and contrast medium is injected.
• When studies of the right renal vasculature are completed, the catheter is withdrawn into the vena cava, rotated, and guided into the left renal vein.
• If visualization of the renal venous tributaries is indicated, epinephrine can be injected into the ipsilateral renal artery by catheter before contrast medium is injected into the renal vein. Epinephrine temporarily blocks arterial flow and allows filling of distal intrarenal veins. Obstructing the artery briefly with a balloon catheter produces the same effect.
• After anteroposterior films are made, the patient lies prone for posteroanterior films.
• For renin assays, blood samples are withdrawn under fluoroscopy within 15 minutes after venography. After catheter removal, apply pressure to the site for 15 minutes and put on a dressing.
• Check vital signs and distal pulses every 15 minutes for the first hour, then every 30 minutes for the second hour, and then every 2 hours for 24 hours.
• Observe the puncture site for bleeding or hematoma when checking vital signs; if bleeding occurs, apply pressure. Report bleeding as soon as possible.
• Report signs of vein perforation, embolism, and extravasation of contrast medium. These include chills, fever, rapid pulse and respiration, hypotension, dyspnea, and chest, abdominal, or flank pain. Also report complaints of paresthesia or pain in the catheterized limb - symptoms of nerve irritation or vascular compromise.
• Administer prescribed sedatives and antimicrobials.
• Instruct the patient to resume his normal diet and any discontinued medications.

Precautions

• Renal venography is contraindicated in severe thrombosis of the inferior vena cava.
• The guide wire and catheter should be advanced carefully if severe renal vein thrombosis is suspected.
• Watch for signs of hypersensitivity to the contrast medium.

Normal Findings

After injection of the contrast medium, opacification of the renal vein and tributaries should occur immediately.

Normal renin content of venous blood in a supine adult is 1.5 to 1.6 ng/ml/hour.

Abnormal Findings

Occlusion of the renal vein near the inferior vena cava or the kidney indicates renal vein thrombosis. If the clot is outlined by contrast medium, it may look like a filling defect. However, a clot can usually be identified because it's within the lumen and less sharply outlined than a filling defect. Collateral venous channels, which opacify with retrograde filling during contrast injection, often surround the occlusion. Complete occlusion prolongs transit of the contrast medium through the renal veins.

A filling defect of the renal vein may indicate obstruction or compression by extrinsic tumor or retroperitoneal fibrosis. A renal tumor that invades the renal vein or inferior vena cava usually produces a filling defect with a sharply defined border.

Venous anomalies are indicated by opacification of abnormally positioned or clustered vessels. Absence of a renal vein differentiates renal agenesis from a small kidney.

Interfering Factors

• Recent contrast studies or stool or gas in the bowel
• Failure to restrict salt, antihypertensive drugs, diuretics, estrogen, and oral , contraceptives