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Friday, September 30, 2016

From the SIR Residents and Fellows Section (RFS)

Teaching Topic: The Use of Denver Shunts to Manage Chylous Ascites.

Yarmohammadi H, Brody LA, Erinjeri JP, et al. Therapeutic Application of Percutaneous Peritoneovenous (Denver) Shunt in Treating Chylous Ascites in Cancer Patients. J Vasc Interv Radiol 2016; 27: 665-673.

Click here for abstract

This manuscript revaluates the safety and efficacy of percuntaneous and peritoneovenous shunt (PPVS) placement in treating intractable chylous ascite (CA) in patients with cancer. The study from Memorial Sloan-Kettering Cancer Center involved 28 patients with refractory CA. The authors report resolution of ascites or symptom relief in 92% of patients with statistically increased levels of serum albumin in the PPVS placement group. The reported complication rate was 37% with shunt malfunction/occlusion being the most common at 22%. Both smaller venous limb size and presence of peritoneal tumor were associated with higher rates of shunt malfunction.

Clinical Pearls

How does chylous ascites (CA) form?

This study focused on CA (milky appearance of the ascites with an ascitic fluid triglyceride concentration > 110 mg/dL) as a complication of surgical therapy for urologic malignancy, which requires retroperitoneal lymph node dissection (LND). Post-surgical CA can form early, due to damage to the lymphatics themselves, or late, due to adhesions and extrinsic compression on the lymphatic system. Other causes include: malignant compression on lymphatic vessels, cardiovascular disease, such as right heart failure, causing increased lymphatic pressure, hepatic cirrhosis causing disruption of serosal lymphatic channels, infections, such as peritoneal tuberculosis and filariasis, congenital conditions, such as primary lymphatic hypoplasia and Klippel-Trenaunay (lymphatic hypoplastic malformations), or inflammatory conditions such as radiation injury and acute or chronic pancreatitis.

What treatment options are available and how does the Denver shunt work?

Traditionally, CA is managed by conservative diet modification, involving a high-protein, low-fat, medium-chain triglyceride (MCT) oral diet or total parenteral nutrition. Dietary restriction of long-chain triglycerides (LCT) avoids their conversion into monoglycerides and free fatty acids (FFA), which require transport as chylomicrons via intestinal lymph ducts. By contrast, MCTs are absorbed directly into intestinal cells and transported as FFA and glycerol directly to the liver via the portal vein. One of the main problems with conservative management and paracentesis is loss of nutrients and the risk of developing malnutrition. Pharmacological agents, such as somatostatin and octreotide, have been shown to be successful in treating chylous ascites. Paracentesis is performed as needed to palliate symptoms. Peritoneovenous shunt (PVS) placement for treatment of refractory ascites was first described by Smith in 1962. The Denver shunt (CareFusion Corporation, San Diego, California) pump is percutaneous PVS (PPVS) that is either single-valved or double-valved. These shunts redistribute ascitic fluid from the abdomen into the central circulation based on a pressure gradient between the abdomen and central venous system and incorporate a compressible valve chamber between the peritoneal limb and the venous limb to prevent reflux of fluid back into the peritoneal cavity, providing unidirectional flow.

Questions to consider

When should PPVS placement and removal be considered?

Persistent or refractory CA not responding to 2 weeks of conservative treatment and repeated paracentesis was the threshold for PPVS placement in this study. Patients’ high-protein, low-fat diet was switched to a regular diet after the procedure. Patients were instructed to pump the shunt 20 times, twice a day, once in the morning and once before bedtime while in the supine position. Initial symptomatic relief (abdominal distention) was evaluated at the 1-week visit and was achieved in 100% of patients. CA permanently resolved in patients with urologic malignancies, whose ascites had resulted from retroperitoneal LND. In the remaining 15 patients, palliation of symptoms until shunt removal or death was achieved in 13 (87%). Based on the results of the present study, the recommendation is that when a patient experiences changes in pump consistency and there is no clinical or radiographic evidence of ascites, the shunt can be removed.

What complications should be considered for PPVS?

Reported complications of PPVS placement include shunt occlusion, gastrointestinal tract (variceal) bleeding, infection, and DIC. The most common complication in this study was PPVS malfunction/occlusion (21%). Using a large venous limb (15.5F) was noted to occlude less than systems using a 11.5F venous limb. Patients with peritoneal tumors (lymphangioleiomyomatosis [LAM] and peritoneal mesothelioma) should be expected to have repeated occlusions. Two patients (7%) developed asymptomatic or subclinical DIC. One proposed reason for development of DIC is rapid introduction of the ascitic fluid containing high levels of fibrin-rich procoagulants, including endotoxin, thromboplastin activated clotting factors, and plasminogen activator, into the central venous system. In CA, the main reason for ascites formation is leakage of chyle secondary to the obstruction or disruption of the lymphatic system and returning the chylous fluid back into the circulation is actually physiologic. The authors have suggested limiting the risk of DIC by draining the ascites to completion at the time of shunt placement and replacing the ascitic fluid with 4L of normal saline to avoid putting into circulation a large amount of potentially DIC-inducing substances.

Post Author:
Rajat Chand, MD
Diagnostic Radiology Resident, R-1
John H. Stroger Jr. Hospital of Cook County

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