Percutaneous arterial embolization in the kidneys of dogs: a comparative study of eight different materials

Life-Threatening Post-Nephrolithotomy Hemorrhage Resulting in Cessation of Kidney Function, Treated by Transcatheter Arterial Embolization with Subsequent Restoration of Excretory Function

A massive post-nephrolithotomy renal hemorrhage was successfully controlled by selective arterial embolization using Gelfoam particles. Prior to embolization, the kidney showed no excretory function due to complete obstruction of its collecting system by blood clots. Long-term observation revealed restoration of excretory function of the treated kidney and only minimal loss of its parenchyma.

Water-soluble polyvinyl alcohol microspheres for temporary embolization: development and in vivo characteristics in a pig kidney model

PURPOSE

To preliminarily examine whether solubility of water-soluble polyvinyl alcohol (PVA) microspheres in blood plasma changes in proportion to their degrees of saponification. The study also examined their feasibility as a temporary embolic agents in the pig renal artery.

MATERIALS AND METHODS

Three types of PVA microspheres with the degrees of saponification of 97 mol% (S97), 98 mol% (S98), and 99 mol% (S99) were prepared. Seven kidneys in seven miniature pigs were embolized and divided into three groups so there would be at least two kidneys for each type of PVA. One animal in each group was euthanized immediately after angiography at 3 hours after embolization and the other one at 7 days after. In addition, one animal embolized with S99 microspheres was euthanized at 21 days after embolization.

RESULTS

With S97 microspheres, the vascular network had recovered to the preembolic state by 3 hours after embolization. With S98 microspheres, blood flow in the third-order branch had been restored in the same period. With S99 microspheres, the second- and lower order branches remained occluded until 21 days. Histopathologic specimens harvested at 3 hours revealed only a trace of PVA for S97 microspheres. With S98 microspheres, the vascular lumen was still found to be filled with PVA gel. With S99 microspheres, swollen microspheres densely filled the vascular lumen even on day 21.

CONCLUSIONS

Dissolution process in vitro and the duration of arterial occlusion in vivo were possibly related to the degree of saponification of PVA. This result may support feasibility of PVA microspheres as a temporary embolic agent.

A New Porcine Sponge Material for Temporary Embolization: An Experimental Short-Term Pilot Study in Swine

PURPOSE

To evaluate the safety and efficacy of a porcine-derived gelfoam, Curaspon, for the temporary occlusion of the visceral arteries.

METHODS

Curaspon was used for the selective embolization of segmentary hepatic, unilateral polar renal, and single lumbar arteries of 10 pigs under general anesthesia. Sequential angiographic checks were carried out and the pigs killed between 3 days and 2 weeks later. Macroscopic and microscopic studies using standard techniques were used to evaluate the immediate efficacy of embolization, duration of and completeness of recanalization on angiography, macroscopic appearance of target-organ ischemia, and microscopic analysis of inflammatory reaction.

RESULTS

Immediate arterial occlusion was obtained in all cases. Renal arteries showed a total recanalization in 63% of cases on day 7 and 100% on day 14. Total hepatic recanalization was obtained in 100% of animals on day 7. All lumbar arteries were recanalized on day 14. Microscopic analysis in the kidney revealed a mild inflammatory reaction and a progressive lysis of the Curaspon (87% of samples at day 3 showed a persistence of Curaspon and 5% at day 14). In some cases, localized and partial destruction of the arterial wall was visualized. In the liver the same patterns were observed but resolved more completely and more rapidly.

CONCLUSIONS

Curaspon is an efficient material for the temporary occlusion of visceral and parietal arteries in pigs. However, arterial aneurysms were observed and a relationship of these with the material cannot be excluded.

Radiopaque polymeric materials for medical applications. Current aspects of biomaterial research

The aim of this review is to give an overview and some insight into different radiopaque polymeric materials that are currently used as medical implants or inserts. The advantages and limitations of each radiopaque polymeric material are summarized. The main method used to make medical implants radiologically visible is based on blending polymers with conventional radiopaque agents, blends which usually are a physical mixture of acrylic derivatives and inorganic salts. Other methods reported involve either the formation of single-phase radiopaque polymer salt complexes somehow preventing the release of the radiopacifying element by entrapment of the complex in a crosslinked network, or radiopaque polymerized monomers characterized by a radiopacifying element associated with the monomer unit prior to polymerization. In the near future, research will certainly concentrate on biocompatible radiopaque polymers with covalently bound opaque elements leading to stable polymers with properties equivalent to the nonopaque, parent polymer.

Transcatheter arterial renal and adrenal embolization with iohexol-ethanol solutions. Animal experimental study and clinical application

RATIONALE AND OBJECTIVES

The authors compared the embolic effect of radiolucent absolute ethanol (AE) with that of a radiopaque iohexol-ethanol (IES) solution for renal ablation in dogs and for the destruction of human aldosteronomas by the technique of transcatheter arterial embolization (TAE) to test whether IES can be an alternative to AE.

METHODS

The embolic agents were infused through a balloon catheter into the renal arteries of 17 dogs (9 infused with 0.3 mL/kg AE; 8 infused with IES). The immediate and parenchyma were compared between the two groups. Transcatheter arterial embolization with IES also was performed in three humans with unilateral aldosteronoma.

RESULTS

The IES was visualized faintly under fluoroscopy in all dogs. There were no significant differences in embolic effects between the AE and IES. Three patients with aldosteronoma were treated successfully by TAE with IES.

CONCLUSIONS

The IES can be used as a "visible ethanol" to improve the safety and ease of ethanol embolization.

Histopathological follow-up study of 66 cerebral arteriovenous malformations after therapeutic embolization with polyvinyl alcohol

Embolization with polyvinyl alcohol (PVA) is an accepted method of rendering complex arteriovenous malformations (AVM's) more amenable to surgery, but its effects on human vascular tissues have not been adequately documented. The authors reviewed the histopathology of 66 intracranial AVM's resected 1 to 76 days after embolization with PVA. The mean age of the patients was 36 years, and their AVM's were located in the cerebral hemispheres (92%), the cerebellum (6%), or the corpus callosum (2%). In 79% of cases, at least one vessel contained PVA particles; in most cases, the vessel was filled with sharp, angular PVA particles in a serpiginous pattern. Polyvinyl alcohol particles indented the endothelium in 69% of cases but were rarely found subendothelially. Clotted blood and fibroblasts were present among the particles, and abundant intraluminal mononuclear and polymorphonuclear inflammatory cells were found in all vessels containing PVA particles. Foreign-body giant cells appeared 2 to 14 days after embolization in the majority of cases. Patchy mural angionecrosis and necrotizing vasculitis were found in 39% of the cases. Recanalized lumina were seen in 18% of PVA-embolized vessels. Foreign materials resembling cotton fibers and other particulate substances, which were probably contaminants of the contrast solution or the embolic material, were found in 65% of the cases. These findings suggest a specific chain of events in the interaction between PVA and vessel wall components and may explain some important sequelae of embolization therapy.

Longterm histopathologic follow-up of bronchial arteries after therapeutic embolization with polyvinyl alcohol (Ivalon) in patients with cystic fibrosis

We used light microscopy to examine, at autopsy, bronchial arteries in three patients with cystic fibrosis who died, respectively, 10, 16, and 28 months after bronchial artery embolization with barium sulfate-impregnated polyvinyl alcohol (PVA) to control hemoptysis. PVA was not identified beyond the midsegmental bronchus in any patient. Persistent focal fibrovascular occlusion was noted in two patients, and recanalized and/or partially obstructed vessels were associated with PVA in all. The histologic reaction to PVA included fibrosis, mild chronic inflammation, localized foreign body reaction, and, in two patients, focal calcification of PVA spicules. Within the inflammatory milieu were numerous macrophages containing BaSO4. Extensive vascular mural destruction and fibrosis associated with PVA were also observed. Both PVA and BaSO4 were also frequently present in the perivascular connective tissue. These findings indicate that, although longterm occlusion persists after therapeutic arterial embolization with PVA, focal recanalization also occurs. The extent of vascular mural injury following PVA embolization in humans has been previously underestimated by animal experiments. Finally, perivascular deposition of PVA represents a common reaction to diverse foreign body emboli in both systemic and pulmonary arteries.

Tumour infarction after pre-operative embolisation of renal carcinoma

Thirty kidneys containing renal carcinoma became available for complete histological examination 2-8 days after therapeutic embolisation with various combinations of gel-foam, dura mater, steel coils and thrombin. There was extensive tumour infarction (greater than 50%) in 25 kidneys and in the other five kidneys there was no tumour infarction detected histologically. In the 24 kidneys with a single renal artery, the number with tumour infarction exceeding 50% was significantly higher in cases where the post-embolisation arteriogram had shown complete occlusion of the renal artery close to its origin than in cases where the renal artery had been incompletely occluded (P = 0.0016). Fragments of gel-foam or dura mater were significantly less likely to produce complete arterial occlusion on the post-embolisation arteriogram than mixtures of embolic material containing coils (P = 0.016) or thrombin (P = 0.042). In the six kidneys with two renal arteries, tumour infarction exceeded 50% in the five kidneys where the post-embolisation arteriogram had shown complete occlusion of both renal arteries, and there was no tumour infarction in the single case where an accessory renal artery had been left patent. It is concluded that complete occlusion of the renal artery (or arteries) is essential if tumour infarction in excess of 50% is to be guaranteed, and that this is more readily achieved with mixtures of embolic materials containing fragments of gel-foam or dura mater plus coils or thrombin than with fragments of gel-foam or dura mater on their own.