SAT-167 THE CASE OF A NOT SO ABSENT INFERIOR VENA CAVA

Abstract

Background: Congenital absence of the inferior vena cava (IVC) is an extremely rare condition, which may be congenital or due to perinatal thrombosis, is associated with lower limb deep vein thrombosis risk, non-healing venous ulcers and the development of collateral venous drainage systems. We report a case of a congenitally absent IVC in a patient with renal failure and subsequent renal transplantation, with recurrent acute kidney injury (AKI) related to exercise, whom underwent successful IVC stenting with restoration of venous flow. Case: The patient was a 28-year-old female with a diagnosis of congenital absence of her IVC, with venous drainage of her lower limbs achieved by markedly dilated ascending lumbar veins which drained into an enlarged azygous vein. She had a history of chronic kidney disease with renal transplant at age 4, which failed after recurrent unexplained episodes of acute tubular necrosis (ATN). After her second transplant at age 26 she continued to have recurrent episodes of biopsy proven ATN, which were subsequently found to be related to exercise with creatinine levels of more than 300µmol/L from a baseline of 113µmol/L. Pelvic angiography demonstrated abrupt pinching of the enlarged right lumbar vein at the L4/L5 vertebrae with straight leg raise and subsequent flow of blood into the left lumbar vein. The dilated ascending lumbar veins in the retroperitoneum, which drain the renal transplant, course between the psoas muscle and the lumbar vertebral bodies. During exercise, it is hypothesised that there is venous hypertension in the kidney due to outflow obstruction from compression of the ascending lumbar veins (from psoas muscle compression) at the level of L4/L5. There is subsequent decreased venous return, leading to arterial hypotension, poor renal perfusion, and AKI. These episodes recovered with intravenous fluids and bed rest. Botox injections into the psoas muscles were minimally beneficial in reducing exercise related AKI and complicated by a rash. CT venogram identified suggestion of a chronically occluded IVC remnant, with contrast present in the native kidneys, which appeared small and unscarred, as well as a thin (2mm) cord extending from the liver to the transplant kidney (See Image 1). Subsequently, she underwent endovascular balloon recanalization of the right common iliac vein and IVC to 14mm with restoration of antegrade flow. Subsequent venogram demonstrated some elastic recoil and collapse of the recanalized IVC, so she underwent dilatation of the IVC to 18mm with iliocaval segment reconstruction with stents (20mm caval stents and 10mm iliac stents) shown in Image 2. Repeat imaging 2 days later demonstrated patent stenting in the common iliac vein and IVC, with persisting dilated azygous system, however the lumbar veins had decreased in calibre. Post stenting, her creatinine was 115µmol/L increasing to 144µmol/L after walking 20,000 steps/day for two consecutive days. Image 1: CT venogram showing chronically occluded IVC remnant (indicated with arrow). Image 2: Angiography showing successful IVC stent placement. ▪▪▪ ▪▪▪ The aim of iliocaval reconstruction was to provide a low resistance pathway for venous drainage which would not be subject to extrinsic compression. Iliocaval reconstruction appears to have improved the effect of exercise on renal function.