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Original Report |
1 Department of Radiology, University of Florida College of Medicine, 1600 S.W.
Archer Rd., P. O. Box 100374, Gainesville, FL 32610-0374.
2 Department of Radiology, University of Michigan Health System, 1500 E. Medical
Center Dr., Ann Arbor, MI 48109-0001.
3 Department of Surgery, University of Florida College of Medicine, P. O. Box
110240, Gainesville, FL 32610-0240.
4 Department of Radiology, North Florida Regional Medical Center, I-75 and
Newberry Rd., Gainesville, FL 32614.
Received July 15, 2002;
accepted after revision October 1, 2002.
Address correspondence to I. F. Hawkins, Jr.
Abstract
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CONCLUSION. CO2 splenoportography is safe and expedient and provides adequate visualization of the portal system for surgical planning in selected patients.
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All three adult candidates who were studied for transjugular intrahepatic portosystemic shunt (TIPS) procedures had inconclusive sonographic and MR angiographic findings. Two pediatric patients with biliary atresia (ages, 5 months and 2 years) who were awaiting liver transplantation had no portal vein seen on sonography or CT. A 12-year-old girl with cystic fibrosis and liver and pancreatic transplants, experiencing left upper quadrant pain and massive splenomegaly, had undergone sonography and CT that showed equivocal patent portal and splenic veins. A 4-year-old girl with cavernous transformation had findings of a patent splenorenal shunt on CT but a clinical presentation of shunt occlusion. Sonographic and CT findings in a 2-year-old boy with recurrent hepatoblastoma who had undergone trisegmentectomy showed what appeared to be an occluded portal vein.
Four of the eight patients had coagulopathy as revealed by abnormally elevated prothrombin times (14–16 sec), partial thromboplastin times (34–42 sec), and platelet counts of 55–121 x 103 µL. One adult was given platelets and one child was given fresh frozen plasma during the procedure. Two adults had ascites (one moderate and one massive). Only the five pediatric patients presented with splenomegaly.
In preparation for the procedure, general anesthesia was administered to the five pediatric patients and two of the adult patients. The remaining adult received minimal IV sedation.
The patients were placed in a supine position and evaluated using sonography to locate the position of the spleen and adjacent structures. The site for needle entry was marked on the skin. The left upper quadrant was subsequently prepared and draped in a sterile fashion, and local anesthesia was administered. A 25-gauge spinal needle (Spinocan; Braun Medical, Bethlehem, PA) was advanced into the splenic pulp using direct sonographic guidance during a breath-hold (a 22-gauge needle was used in a 2-year-old girl). The needle was connected to a modified fluid management system that can be used for safe CO2 delivery (Angioflush III Fluid Management System and Angiofill Fluid Collection Bag; Angio Dynamics, Glens Falls, NY) as previously described [5].
The CO2 delivery system was filled with 99.99% laboratory-grade CO2 from a disposable cylinder (CMD, Gainesville, FL). Initially, a test injection of 3–10 mL of CO2 was made using digital subtraction angiography to confirm appropriate placement of the needle. Definitive injections of CO2 (children, 5–20 mL; adults, 30–40 mL) were administered by hand over 1–2 sec with digital subtraction angiography (1024 x 1024) at 3.5 frames per second. All CO2 injections were made with the patient in the supine position except in the case of the infant with suspected portal vein thrombosis; that patient was placed in the Trendelenburg's position during two injections to attempt to fill the superior mesenteric vein. Patients were not placed in the left lateral decubitus position after the procedure to tamponade the needle entrance site.
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One candidate for a TIPS developed transient chest pain and mild to moderate respiratory distress after two injections of 30 mL of CO2; however, no significant changes were noted in blood pressure or ECG findings. The complication was thought to be associated with a reaction caused by platelet infusion.
In both pediatric patients awaiting liver transplantation, splenoportography showed patency of the superior mesenteric vein, which was essential for transplantation evaluation. During liver transplantation in the 2-year-old girl with an apparent occluded portal vein shown on sonography and MR angiography, the portal vein was patent, verifying the splenoportographic findings (Fig. 1). During liver transplantation in the 5-month-old boy, a small patent portal vein was noted that was misinterpreted on the splenoportogram as a collateral vein (Fig. 2A). No portal or splenic veins were imaged with sonography or CT. The retroperitoneal collateral veins that communicated with the inferior vena cava were ligated at surgery, preventing thrombosis of the anastomosed portal vein (Fig. 2B).
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A 12-year-old girl with cystic fibrosis underwent a splenectomy 54 days after the study, which confirmed the patency of the portal and splenic veins as seen on sonography, CT, and splenoportography. Examination of the excised spleen at pathology showed no evidence of trauma. Splenoportography in a 9-year-old girl revealed cavernous transformation and no evidence of the splenorenal shunt, which had appeared to be patent on CT (Fig. 3). A mesocaval shunt was performed better 25 days after splenoportography. A 2-year-old boy with recurrent hepatoblastoma and trisegmentectomy underwent hepatojejunostomy 3 days after splenoportography, which confirmed the splenoportographic, sonographic, and CT findings of portal vein occlusion (Fig. 4).
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No bleeding complications occurred. Surgical follow-up in six patients 3–54 days after splenoportography showed no gross evidence of splenic trauma. The spleen was specifically examined in only one patient; histology of the liver revealed no evidence of trauma. MR angiography after the procedure revealed no evidence of splenic trauma in another adult patient. The remaining adult patient received neither surgical nor imaging follow-up but showed no clinical evidence of splenic bleeding.
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Ironically, many splenoportography studies with no or few bleeding complications have been reported in the past 30 years—even in cases in which 18-gauge needles were used. In fact, 63 patients have been studied as outpatients without complications [8]. Digital subtraction angiography has permitted the use of even smaller needles (21-to 22-gauge) without bleeding complications [9].
We attempted to minimize the risk of splenic hemorrhage by using an ultrafine 25-gauge spinal needle. Our first CO2 splenoportography was performed in a 5-month-old boy who had very poor femoral pulses. Our experience with fine-needle (21-gauge) TIPS [6] caused us to think that the use of an even smaller, flexible 25-gauge needle would be safer than attempting a femoral artery approach. The cross-section area (size of splenic hole) of the 25-gauge needle is one third the size of a "safe" 21-gauge needle and 6.2 times smaller than the most frequently used 18-gauge needle. Fine needles (20-to 22-gauge) are commonly used for biopsies of the liver without significant bleeding complications [10].
In addition, we had previously injected CO2 into the splenic pulp in five swine, incrementally increasing the dose from 10 to 50 mL with a 22-gauge needle (unpublished data, 2001). No histologic evidence was found of intrasplenic hematoma, laceration, or extravasation. The entire portal system was well seen in all animals, with reflux into the superior mesenteric vein with the larger volumes.
Laceration of the spleen during deep aspiration is a potential danger of splenoportography. No lacerations with 21-gauge needles have been reported [9]. We used general anesthesia in all the children and two adults, which provided controlled respiration. We think that the risk is minimal if a flexible 25-gauge needle is used; however, this technique should probably be performed only with anesthesia in potentially uncooperative patients. A disadvantage of using the fine needle is that it does not allow accurate measurement of splenic pulp pressure. The pulp pressure obtained using a larger needle system provides an estimate of the portal pressure, which may be important in equivocal cases of significant portal hypertension.
The use of a 25-gauge spinal needle is made possible by using low-viscosity CO2 as the imaging agent. We think that the very low viscosity of CO2, as compared with iodinated contrast material, increases the portal venous filling with injection into the splenic pulp. This response is similar to the excellent portal filling we have seen when we have injected CO2 into the liver parenchyma via the transjugular route during TIPS procedures. For splenic injections, we chose volumes of CO2 similar to those used for our TIPS intraparenchymal hepatic injections [6]. The small lumen of the 25-gauge needle obviously precluded comparison of CO2 with iodinated contrast material.
An experimental study similar to our procedure was performed by Hipona and Park [11] in 1967. These researchers placed a needle in the surgically exposed spleen of dogs and made multiple injections of CO2 (2–3 mL/kg) into the splenic pulp, filming the portal system with conventional X-ray film. Artificial portal hypertension was created in five dogs. Opacification of the portal vein with CO2 and iodinated contrast material with elevation of the right side of the five dogs showed that CO2 filled the intrahepatic portal vein much better than the iodinated contrast material because of the buoyancy of the CO2. The disadvantage of that buoyancy is that it does not permit accurate hemodynamic evaluation; on the other hand, it allows CO2 to be used to fill veins that are not seen when liquid contrast material is used. In patients with hepatofugal flow, the extrahepatic portal vein may appear to be occluded with liquid contrast material during both contrast-enhanced splenoportography and arterial portography. Although in this study we did not use buoyancy to fill the portal vein, Hipona and Park [11] did improve portal filling by elevating the right side of the dogs they imaged.
When we elevated the patient's feet during CO2 splenoportography, the buoyant CO2 filled the superior mesenteric vein in the first child we examined (Fig. 2A). This imaging does not usually occur with contrast-enhanced splenoportography because the superior mesenteric vein flow is always cephalad. Also in this patient, the low-viscosity CO2 was shunted into the inferior vena cava during splenoportography and provided critical information for the transplant surgeon. If these collateral veins are not ligated, the portal flow may bypass the liver with resulting portal thrombosis. In this initial patient, blood flow ceased after the portal vein was anastomosed; however, the collateral veins were ligated and good hepatopedal portal flow was reestablished.
CO2 digital subtraction angiography has been used safely in a large number of patients for more than 20 years [12]. Its unique combination of properties—very low viscosity, buoyancy, and absence of nephrotoxicity—makes CO2 ideal for improving the safety and efficacy of splenoportography. Although we studied only a small number of patients, we believe that this technique is a safe and effective method for evaluating the portal system.
When splenoportography is performed using an ultrafine needle and CO2, the procedure is simple and of short duration; it presents a minimal risk of bleeding and no risk of renal toxicity or allergic reaction. The buoyant CO2 provides information beyond that which can be obtained using iodinated contrast material. For these reasons, CO2 splenoportography is a viable option for patients who are at risk for arterial injury (primarily pediatric patients), patients who have renal failure, those in whom the patency of the portal vein must be ascertained because splenomegaly or hepatofugal flow is suspected, patients in whom the patency of splenorenal shunts must be evaluated, and those in whom portal vein status must be evaluated during transjugular intrahepatic portosystemic shunt procedures.
Until more clinical experience is obtained, CO2 splenoportography should be used only when noninvasive imaging studies have failed to provide necessary information about portal vein patency.
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