An abscess in the abdomen (intra-abdominal abscess) is diagnosed by correlating findings on imaging studies with the signs and symptoms present. Read more on symptoms of intra-abdominal abscesses. Other laboratory findings will further confirm the diagnosis.
Blood tests may reveal :
- raised white blood cell counts
- abnormal levels of liver enzymes
Absence of these findings, especially in elderly and debilitated patients, does not rule out intra-abdominal abscess completely.
A blood culture is an important investigation in diagnosing intra-abdominal abscess. Multiple bacterial growths found in blood culture or the presence of bacterial species like Bacteroides in a blood culture are highly suggestive of an intra-abdominal abscess. Peritoneal fluid culture and blood culture are also important in choosing the antibiotics for specific antibiotic treatment.
A plain x-ray of abdomen is the simplest radiological investigation that can be of help in intra-abdominal abscess diagnosis. It should be followed up with more detailed radiological investigations like a CT scan to confirm the diagnosis. A plain x-ray may reveal abnormalities like the presence of gas under diaphragm, or air-fluid level in the abscess cavity.
Ultrasonography is another important investigation which is more useful than an x-ray in the accurate diagnosis of an intra-abdominal abscess. These findings should be correlated with the clinical features and the results of laboratory investigations. The accuracy of an ultrasound depends on the radiologist and the efficacy of ultrasonography is limited in obese or post-operative patients.
Computed Tomography (CT) Scan
A CT scan is the best radiological investigation for diagnosis of an intra-abdominal abscess with very high degree of accuracy. In post-operative patients, a CT scan is recommended only one week after the surgery. A hidden abscesses in abdomen can be identified with serial CT images from diaphragm to pelvis. The accuracy of the investigations may be increased with oral or intravenous contrast dye administration.
Treatment of an Intra-Abdominal Abscess
An intra-abdominal abscess is usually treated with drainage supplemented by adequate antibiotic coverage. Drainage may be performed through surgical approach or more commonly by an approach through the skin (percutaneous) with the help of imaging studies like CT or ultrasound.
The treatment of an intra-abdominal abscess begins the with administration of intravenous (IV) antibiotics. The microbes involved in intra-abdominal abscess are usually a mixture of aerobic and anaerobic organisms and combination of antimicrobial agents (empiric therapy) allows for broad spectrum antibiotic coverage. A culture of the pus taken from abscess will provide the antibiotic sensitivity of the organisms in the pus. The culture report usually takes 2 to 3 days. The initiation of empiric antibiotic therapy without waiting for the pus culture results saves precious time. The antibiotic therapy is started before draining the abscess and continued during the drainage of the abscess until the complete resolution of evidence of sepsis.
Intravenous antifungal drugs (like amphotericin B) may be given in some patients (like AIDS patients or chronic diabetics) in whom fungal infection is suspected or detected.
Non-Surgical Drainage of an Abscess
The pus collected in the abscess cavity should be drained to prevent progression of sepsis. The abscess is localized with a CT scan or an ultrasound scan. Aspiration is then performed with a needle to confirm the presence of pus and the aspirated pus is sent for various investigations including culture. The drain is left in place till all the pus is drained out of the abscess cavity. The use of CT for guiding the catheter reduces chance of injury to the surrounding viscera. It also provides the initial control and containment of the infection.
Response to Treatment
Considerable improvement in the patient condition is seen within 2 to 3 days following percutaneous drainage. The signs of sepsis will disappear and the pus drained will be minimal. An ultrasound or CT scan can be done to confirm the resolution of the abscess cavity. Under these circumstances the drain can be removed. Failure to show improvement of symptoms after the drainage of abscess is suggestive of residual pus or additional pus collections that may be present. This should warrant further evaluation with CT-scan and surgical drainage may become necessary.
Sometimes there may be persistent pus drainage despite the signs of clinical improvement. This may be because of an abnormal connection of the abscess cavity with the intestines (fistula). Patients with a single abscess cavity without any fistula respond best to percutaneous drainage. Intra-abdominal abscess with multiple abscess cavities or with an intestinal fistula usually does not respond well to percutaneous drainage. These cases are best managed with surgical drainage.
Surgical Drainage of Abscess
Surgical drainage of the abscess is considered when there is failure of percutaneous drainage. This can be performed by an open surgical approach or by a laparoscopically. Even for larger intra-abdominal abscesses, a laparoscopic approach allows adequate drainage with minimal operative intervention.
Open surgery (laparotomy) is performed after localization of the abscess cavity. It can be performed from behind the peritoneum (retroperitoneal) or through the peritoneum (transperitoeal). The retroperitoneal approach has less risk of injury of the bowel or spread of the infection by contamination during operation. Transperitoneal approach has high risk of contamination. This can be prevented to a large extent by proper antibiotic coverage initiated before the operative procedure. Draining of multiple abscess cavities is best performed with this approach. A drain is usually placed for continuing the drainage from the abscess cavities postoperatively until the cavities get resolved.
Sometimes surgical drainage can be complicated in presence of adhesions of abdominal viscera and in such situations an initial percutaneous drainage can be of use. Improvement can be seen in patients in 2 to 3 days following the surgical drainage and failure to improve suggests incomplete drainage.