Radiological intervention in the gastrointestinal tract

As in other subspecialities, gastrointestinal radiology has seen a large increase in "interventional" procedures, used for diagnosis and therapy. These may be broadly classified as follows:

Angiographic interventions
These interventions include:
i) Therapy to arrest bleeding - previously discussed
ii) Thrombolytic therapy to dissolve thrombo-emboli to the major
mesenteric vessels.
iii) Transluminal balloon angioplasty and stenting for stenosing lesions
of the mesenteric vessels.

Percutaneous abscess drainage

Radiologically guided abscess drainage is now a well accepted, safe and effective alternative to surgery in selected cases. It has revolutionised the management of abscesses and usually obviates the need for general anaesthetic and surgery. lmaging guidance may be by ultrasound (which has the advantage of availability, speed and real-time interaction), CT (which is superior in complicated cases and where safe access is potentially difficult), fluoroscopy, or a combination of modalities. Whereas unilocular abscesses are easiest to treat, multilocularity is not necessarily a bar to percutaneous treatment. Loculi may be broken down and multiple catheters may be used. lndications related to the GI tract include diverticular, appendiceal and perianastomotic postsurgical abscesses and those due to Crohn's disease. Percutaneous drainage of such enteric collections of ten allows surgery to be performed, if indicated, on an elective basis. Drainage is best performed under CT guidance since this allows better demonstration of any intervening bowel; the catheter should not traverse the GI tract. Abscesses are often found to communicate with the GI lumen, but even Crohn's collections usually close without fistulas. The technique and catheter equipment used are largely determined by personal preference. Deep pelvic abscesses may be drained transrectally with radiological guidance.

Overseeing post-procedure catheter care should be the responsibility of the radiologist. Usually low-pressure suction and saline irrigation are maintained. Contrast sinography is performed as required, and withdrawal of the catheter determined on conventional surgical principles.

Drainage of abscesses associated with fistulae should be managed so that the communication must be allowed to dose prior to catheter removal. Low-output fistulae nearly always dose. High-output fistulae sometimes close with prolonged drainage provided distal GI tract obstruction, tumour at the fistula site and persistent infection have been excluded.

Enteric stricture dilatation

Balloon catheter dilatation of strictures is now a well-accepted technique. Balloons should be intrinsically safer than bougies since virtually all the dilating force is radially distributed, whereas with bougies there is considerable shearing stress. Gastroenterologists have largely adopted balloon dilatation techniques; there are advantages to both radiological and endoscopic dilatation. The radiologist can assess the length and configuration of the stricture and ensure the instruments remain within the lumen. The endoscopic method allows direct mucosal visualisation and biopsy, but with a tight lesion the view is limited to the proximal end.

The greatest experience is with oesophageal strictures. Post-surgical strictures respond well; those due to repeated insult, such as peptic strictures respond less well. Response of malignant strictures is variable. The complication of significant oesophageal rupture occurs in approximately 0.3%. Most ruptures are seen in malignant strictures. Other strictures amenable to radiological balloon dilatation include pyloric stenosis, stenosed gastroenterostomies and rectal and distal colonic strictures.

Placement of enteric tubes

Radiologists are of ten asked to place nasoenteric tubes for short or long-term feeding and hydration. This is usually straightforward under fluoroscopic guidance.

Percutaneous gastrostomy

For long term feeding, percutaneous gastrostomy may be performed safely and relatively simply by radiological or endoscopic methods. The catheter can be advanced into the jejunum if required.

Fine needle aspiration biopsy (FNAB)

FNAB of bowel-related lesions may be performed under fluoroscopic, US or CT guidance. The technique is safe and cost-effective. Sensitivity for malignancy of around 90% should be achieved. False positives for malignancy are extremely rare.

Richard M. Mendelson