ULTRASOUND GUIDED DRAINAGE

ULTRASOUND-GUIDED DRAINAGE
Many fluid collections are the result of surgical intervention and often cannot be differentiated on ultrasound alone. Diagnostic aspiration of fluid collections is used to establish their exact nature: this may include haematoma, lymphocoele, urinoma, biloma, pseudocysts and others. Postoperative haematomas are normally treated conservatively and tend to resolve spontaneously. Insertion of a drain into such a collection is at high risk of converting the collection into an abscess.

Abscess drainage
Ultrasound-guided drainage of abscesses is now the preferred treatment when the collection can be visualized on ultrasound and a safe route chosen. These may result from postoperative infection, inflammatory bowel conditions, such as Crohn’s disease or appendicitis, or other sources of infection, particularly in immunosuppressed patients. Drains come in different sizes and generally the thicker the pus, the larger the bore of drain that is required. Whilst aspiration is initially performed to confirm the nature of the collection, very often a drain is left in situ; together with appropriate antibiotic therapy this is usually effective. At the very least it normally leads to an improvement in the overall clinical condition to allow definitive treatment and can in itself be a definitive cure.
Ultrasound is particularly useful in cases of hepatic abscesses and in draining the subphrenic, pericolic and subhepatic areas. Superficial collections, usually associated with wound sites, are also readily accessible to ultrasound. Collections obscured by bowel gas are best drained under CT guidance.

Gallbladder drainage
Gallbladder drainage under ultrasound control is a temporary, palliative procedure which tends to be reserved for particularly ill patients with septicaemia, as a method of stabilizing their condition prior to surgery. Drainage of, for example, a gallbladder empyema buys useful time, reducing the risk of perforation and subsequent peritonitis and improving clinical status prior to surgical removal.

Although the portable nature of ultrasound allows a bedside procedure to be performed (which is particularly useful in patients under intensive therapy who cannot be moved), these procedures carry a high risk to the patient and full anaesthetic, nursing and medical support is required.

Nephrostomy
Renal obstruction in which the pelvicalyceal system is dilated may be alleviated by the percutaneous introduction of a nephrostomy tube under ultrasound guidance. This procedure relieves pressure in the renal collecting system and avoids potential irreversible damage to the renal parenchyma. Although the procedure may be carried out completely under ultrasound control, it is normally performed in a screening room where a combination of ultrasound and X-ray screening can be used to maximal effect.

Cyst drainage
The percutaneous treatment of renal and hepatic cysts by simple aspiration may afford only temporary relief as they frequently recur, but a more permanent result may be achieved by injecting a sclerosant, for example absolute alcohol or tetracycline into the cyst. In addition, percutaneous treatment of hydatid liver disease (traditionally avoided because of the risk of spreading parasites along the needle track and causing further infection) has been successfully performed by injecting of a scolicidal agent, avoiding the need for surgical removal. Other applications include draining of pancreatic pseudocysts and inserting a cystogastrostomy tube with combined fluoroscopy and ultrasound guidance; the cyst is allowed to drain through this tube into the stomach. This is now better done endoscopically.