Image-Guided Drainage

Drainage under image control is the percutaneous placement of a catheter into a fluid collection (abscess, infected or sterile collection, empyema, pleural effusion, ascites, pericardial effusion, haematoma, biloma, urinoma, lymphocele, cyst, obstructed organ) to remove fluid for diagnosis and treatment.

Ultrasound, CT and fluoroscopy are used to select the safest route and to place the catheter; ultrasound is preferred for real time control of superficial and upper abdominal collections, CT for deep, small or complex collections.

Two techniques are used: the Seldinger technique (a needle enters the collection, a wire is passed, the tract is dilated and a pigtail drain of 6 to 14 French is placed over the wire) and the trocar technique (a catheter on a stiffening cannula and trocar is inserted directly, for superficial large collections).

Drains are sutured or fixed to the skin, connected to a bag or to suction, and flushed with 5 to 10 mL of saline to prevent blockage. Fibrinolytic agents (alteplase) may be instilled into loculated empyema or abscess to break down septa.

Percutaneous drainage has replaced surgery as the first treatment for most abscesses, because success rates are 70 to 90% for simple abdominal abscess and 80 to 90% for empyema with adjunctive treatment, with lower morbidity and shorter hospital stay. Surgery is still needed for failure, a persistent source (for example a leaking anastomosis), necrotic collections (infected necrosis may need a stepped approach), faecal peritonitis, and multiloculated collections that do not drain.

Indications.

• Intra-abdominal and pelvic abscess: appendiceal, diverticular, post-operative, Crohn related, liver (pyogenic, amoebic when large or failing medical treatment), splenic, renal and perinephric, psoas, and tubo ovarian.
• Pleural: empyema and complicated parapneumonic effusion, malignant effusion (diagnostic and therapeutic drainage), and pneumothorax drainage when needed.
• Pericardial effusion with tamponade (pericardiocentesis, often with echocardiographic control), and mediastinal collections.
• Infected pancreatic necrosis and peripancreatic collections (stepped drainage), and pancreatic pseudocysts that are infected or symptomatic.
• Obstructed systems: infected hydronephrosis and pyonephrosis (percutaneous nephrostomy), gallbladder (percutaneous cholecystostomy for acute cholecystitis in patients who cannot undergo surgery), and biliary obstruction (biliary drainage).
• Ascites drainage for relief of symptoms or diagnosis, and lymphocele, seroma, haematoma and biloma after surgery.
• Hydatid cyst (selected cases, with specialist techniques) and large symptomatic cysts.
• Not when the collection is solid or too small and likely to resolve with antibiotics, when there is no safe path, or when the diagnosis is a vascular lesion (aneurysm, pseudoaneurysm) or an unconfirmed hydatid cyst.

Contraindications. Uncorrected coagulopathy (international normalised ratio over 1.5 and platelets under 50 000 in each microlitre, as the local rule sets for the site), no safe window (interposed bowel, vessels or lung), vascular lesions mistaken for collections, an uncooperative patient, and patient refusal.

Hydatid cysts carry a risk of anaphylaxis and spillage and need specialist techniques. Relative: large ascites for deep collections, small collections under 3 cm, and unsafe positioning.

Preparation.

• Informed consent, with an explanation of the drain, its care, expected duration and risks.
• Imaging review (CT or ultrasound) to plan the route and to identify the number, size and loculation of collections.
• Blood tests: full blood count, clotting, renal function, and cultures; broad spectrum intravenous antibiotics are started before the procedure for suspected infection, and covering likely organisms.
• Local anaesthetic with analgesia and sedation as required; monitoring and fasting for 4 to 6 hours.
• Correction of coagulopathy where possible and optimisation of sepsis (fluids, antibiotics, oxygen).

Technique. The shortest safe route is chosen that avoids bowel, large vessels, the pleura and solid organs where possible (transhepatic, transgluteal, transvaginal, transrectal or extraperitoneal routes are used for deep pelvic collections).

After local anaesthesia, an 18 to 22 gauge needle is advanced into the collection under imaging control, and a sample is aspirated for culture and cytology. A wire is coiled in the cavity, the tract is dilated, and a pigtail catheter is inserted, locked, and secured.

The cavity is aspirated to dryness, and a small amount of contrast may be injected under fluoroscopy to check the size, communication with bowel, bile ducts or the urinary tract (fistula), and catheter position (avoid overdistension and bacteraemia). Drains are flushed regularly, and output is recorded.

Repeat imaging (ultrasound or CT) at 48 to 72 hours checks for residual collections; a sinogram checks for fistulae before removal.

Findings.

• Fluid character: serous (clear to straw), pus (thick, turbid, foul smelling), blood, bile (green or brown), urine (clear, with creatinine of fluid higher than serum), chyle (milky), enteric content (faecal, indicating a fistula), and hydatid fluid (clear).
• Laboratory findings: Gram stain and culture (mixed enteric flora in abdominal abscess, streptococci and anaerobes in empyema, Entamoeba histolytica serology in liver abscess), acid fast bacilli, cell count, glucose, protein, lactate dehydrogenase, pH (pleural pH under 7.2 indicates need for drainage), amylase (pancreatic), bilirubin (bile), and cytology.
• Imaging response: reduction of the cavity on follow up imaging, collapse around the catheter, and absence of a fistula on the sinogram.
• Drain output over days: falling output under 10 mL each day suggests resolution, and persistently high output or enteric contents suggest a fistula.

Critical findings needing immediate action. Septic shock after drainage (bacteraemia is common after manipulation: fluids, vasopressors, intravenous antibiotics, and escalate drainage), haemorrhage from the tract (haemodynamic instability, CT, embolisation or surgery), pneumothorax or haemothorax after thoracic drainage, bowel perforation or peritonitis, bile leak,

tension from a blocked drain with recurrent sepsis, unresponsive sepsis with a residual undrained collection (repeat imaging and re-drainage or surgery), anaphylaxis from hydatid spillage (adrenaline, oxygen, resuscitation), and rapid reaccumulation of enteric fluid indicating a fistula.

Complications. Major complications occur in about 5 to 10%: septic shock or bacteraemia (up to 5 to 10% in infected collections), haemorrhage (1 to 2%), bowel injury and fistula, pneumothorax, pleural or peritoneal contamination, injury to adjacent organs, pain, drain blockage, dislodgement, and catheter associated infection.

Failure to drain occurs with viscous pus, multiloculated or necrotic collections, and fungal or tuberculous collections (surgery may be needed). Recurrence occurs in 5 to 20% of cases, and mortality is mostly from the underlying disease, ranging from under 1% in simple abscess to 10 to 20% or more in severe sepsis.

Aftercare.

• Bed rest for several hours, observation of vital signs, drain output, and pain; analgesia and antipyretics.
• Flush the drain with 5 to 10 mL of saline every 6 to 12 hours, record output daily, and keep the bag lower than the collection.
• Continue antibiotics for the duration set by the clinical response and cultures (usually 4 to 7 days after source control for most intra-abdominal abscesses, longer for liver abscess, empyema and bone or joint infection).
• Repeat imaging if the output stops early, the fever persists after 48 to 72 hours, or the patient worsens; a sinogram or CT checks collapse of the cavity before removal.
• Remove the drain when output is under 10 to 20 mL each day, the cavity has collapsed, the fluid is clear, there is no fistula, and the patient is well; a drain can stay for weeks if there is a fistula.
• Return for fever, increasing pain, pus around the site, leaking, a dislodged drain, or bleeding.

Special groups.

• Children: appendiceal abscess, empyema and liver abscess; drainage in a paediatric surgical centre under sedation or anaesthesia.
• Immunosuppressed and diabetic patients: higher risk of failure and fungal infection; broader antibiotic cover.
• Pregnancy: ultrasound control without radiation.
• Crohn disease and diverticulitis: drainage to control sepsis before elective surgery.
• Patients with fistulae: prolonged drainage, nutrition, and specialist surgical review.
• Regions: amoebic and pyogenic liver abscess, tuberculous psoas and spinal abscess, empyema, post-operative abscess, and pyomyositis are common; drainage under ultrasound with a basic machine is the main treatment where surgery or CT is not available.